It just so happens that the Sun’s diameter is about 400 times larger than the Moon, but the Moon is 400 times closer than the Sun. This makes the Sun and Moon appear to be about the same size in the sky as viewed from Earth. This is also why the eclipse thing is such a big deal for our planet. You’re about to make your own eclipses as you learn about syzygy.


A total eclipse happens about once every year when the Moon blocks the Sun’s light. Lunar eclipses occur when the Sun, Moon, and Earth are lined up in a straight line with the Earth in the. Lunar eclipses last hours, whereas solar eclipses last only minutes.


Materials


  • 2 index cards
  • Flashlight or Sunlight
  • Tack or needle
  • Black paper
  • Scissors

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Download Student Worksheet & Exercises


  1. Trace the circle of your flashlight on the black paper and cut out the circle with paper. This is your Moon. If you are using the Sun instead, cut out a circle about the size of your fist.
  2. Make a tiny hole in one of the index cards by pushing a tack through the middle of the card.
  3. Hold the punched index card a couple inches above the plain one and shine your light through the hole so that a small disk appears on the lower card. Move the cards closer or further until it comes into focus. The disk of light is the Sun.
  4. Ask your lab partner to slowly move the black paper disk in front of your light as you watch what happens to the Sun on the bottom index card.
  5. Continue moving the black paper until you can see the Sun again.
  6. Where does your circle need to be in order to create an annular eclipse? A partial eclipse?
  7. How would you simulate Mercury transiting the Sun? What would you use?
  8. Fill out the table.

What’s Going On?

An eclipse is when one object completely blocks another. If you’re big on vocabulary words, then let the students know that eclipses are one type of syzygy (a straight line of three objects in a gravitational system, like the Earth, Moon, and Sun).


A lunar eclipse is when the Moon moves into the Earth’s shadow, making the Moon appear copper-red.



A solar eclipse is when the Moon’s shadow crawls over the Earth, blocking out the Sun partially or completely. There are three kinds of solar eclipses. A total eclipse blocks the entire Sun, whereas in a partial eclipse the Moon appears to block part, but not all of the Sun’s disk. An annular eclipse is when the Moon is too far from Earth to completely cover the Sun, so there’s a bright ring around the Moon when it moves in front of the Sun.


It just so happens that the Sun’s diameter is about 400 times larger than the Moon, but the Moon is 400 times closer than the Sun. This makes the Sun and Moon appear to be about the same size in the sky as viewed from Earth. This is also why the eclipse thing is such a big deal for our planet.


Transits are where the disk of a planet (like Venus) passes like a small shadow across the Sun. Io transits the surface of Jupiter. In rare cases, one planet will transit another. These are rare because all three objects must align in a straight line.



Astronomers use this method to detect large planets around distant bright stars. If a large planet passes in front of its star, the star will appear to dim slightly.


Note: A transit is not an occultation, which completely hides the smaller object behind a larger one.


Exercises


  1. What other planets can have eclipses?
  2. Which planets transit the Sun?
  3. How is a solar eclipse different from a lunar eclipse?
  4. What phase can a lunar eclipse occur?
  5.  Can a solar eclipse occur at night?

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On a clear night when Jupiter is up, you’ll be able to view the four moons of Jupiter (Europa, Ganymede, Io, and Callisto) and the largest moon of Saturn (Titan) with only a pair of binoculars. The question is: Which moon is which? This lab will let you in on the secret to figuring it out.


You get to learn how to locate a planet in the sky with a pair of binoculars, and also be able to tell which moon is which in the view.


Materials


  • Printout of corkscrew graph
  • Pencil
  • Binoculars (optional)

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Download Student Worksheet & Exercises


  1. Look at your corkscrew satellite graph. These are common among astronomers for both Saturn and Jupiter. Notice how Saturn has a lot more wavy lines than Jupiter. We’re going to focus on Jupiter for the first part of this lab. Jupiter’s graph is the one on the left with Ganymede as one of the moons.
  2. The wavy lines represent four of Jupiter’s biggest moons: Ganymede, Callisto, Europa, and Io. The central two lines for a band is the width of Jupiter itself. If you see any gaps in the wavy lines, those are times when the moon is behind Jupiter. Each bar across that corresponds to a number is an entire day. The width of the column represents how far away each moon is from Jupiter. Notice at the top it says East and West.
  3. Draw a circle that represents Jupiter.
  4. Notice the largest waves are made by Callisto. Who makes the smallest waves? (Io.)
  5. Look at Dec 4th. Which moons are on which side of Jupiter? (Ganymede is the furthest east, and Io is closer to the planet, still on the east side. On the west, Europa is closer to Jupiter than Callisto.)

What’s Going On?

Jupiter’s Rings and Moons


Jupiter’s moons are threadlike when compared with Saturn’s. Also, unlike Saturn’s rings, Jupiter’s rings come from ash spewed out from the active volcanoes of its moons. Since Jupiter is so large, its gravity likes to catch things. When a volcano shoots its ash-snow up, Jupiter grabs it and swirls it in on itself. The moons are constantly replenishing the rings, which is why they are so much smaller than Saturn’s and much harder to detect (you won’t see them with binoculars or a backyard telescope).


moons-jupiterIf you’re doing the binocular portion of this lab in the evening, the numbers on binoculars refer to the magnification and the lens at the end. For example, 7×50 means you’re viewing the sky at 7X, and the lenses are at 50mm. Most people can easily hold up to 10x50s before their arms get tired. Remember, you’re looking up, not out or down as in normal terrestrial daytime viewing.


Saturn’s Rings and Moons


Galileo Galilei was the first to point a telescope at the sky, and the first to glance at the rings of Saturn in 1610. In the 1980s, the Voyager 1 and Voyager 2 spacecraft flew by, giving us our first real images of the rings of Saturn. Some of the biggest mysteries in our solar system are: What are the rings made up of, and why?


The Cassini-Huygens Mission answered the first question: The rings are made of billions of particles ranging from dust-sized icy grains to a couple of mountain-sized chunks. Actually, Saturn’s rings are an optical illusion. They are not solid, but rather a blizzard of water-ice particles mixed with dust and rock fragments, and each piece orbits Saturn like a little a moon. These billions of particles race around Saturn in tracks, and are herded into position by moons that also orbit within the rings (“shepherd” moons). Shepherd moon Pan orbits in the Encke gap, Daphnis orbits in the Keeler gap, Atlas orbits in the A ring, Prometheus in the F ring, and Pandora in the F ring. These moons keep the gaps open with their gravity.


The second question is harder to answer, but the latest news is that the rings are pieces of comets, asteroids or shattered moons that broke apart before they ever reached Saturn. Although each ring orbits at a different speed around the planet, the Cassini spacecraft had to slow down to 75,000 mph before it dropped into the rings to orbit around the planet.


While the rings are wide enough to see with a backyard telescope, the main rings (A, B and C) are paper-thin, only 10 meters (33 feet) thick.


Uranus and Neptune are called ice giants because of the amounts of ice in their atmospheres. Their atmospheres are also made of mostly hydrogen and helium.


Cassini found that a great plume of icy material blasting from the moon Enceladus is a major source of material for the expansive E ring. Additionally, Cassini has found that most of the planet’s small, inner moons appear to orbit within partial or complete rings formed from particles blasted off their surfaces by impacts of micrometeoroids.


Exercises


  1. Find a date that has all four moons on one side of Jupiter.
  2.  When is Callisto in front of Jupiter and Io behind Jupiter at the same time?
  3. Are the images you’ve drawn in the table what you’d expect to see in binoculars, or are they upside down, mirrored, or inverted?

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Jupiter not only has the biggest lightning bolts we’ve ever detected, it also shocks its moons with a charge of 3 million amps every time they pass through certain hotspots. Some of these bolts are cause by the friction of fast-moving clouds. Today you get to make your own sparks and simulate Jupiter’s turbulent storms.


Electrons are too small for us to see with our eyes, but there are other ways to detect something’s going on. The proton has a positive charge, and the electron has a negative charge. Like charges repel and opposite charges attract.


Materials


  • Foam plate
  • Foam cup
  • Wool cloth or sweater
  • Plastic baggie
  • Aluminum pie pan
  • Aluminum foil
  • Film canister or M&M container
  • Nail (needs to be a little longer than the film canister)
  • Hot glue gun or tape
  • Water

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Download Student Worksheet & Exercises


  1. Lay the aluminum pie pan in front of you, right-side up.
  2. Glue the foam cup to the middle of the inside of the pan.
  3. Lay the plate on the table, upside down. Place the pie pan (don’t glue it!) on top of the plate, back-to-back. Set aside.
  4. Insert the nail through the middle of the film canister lid. Wrap the bottom of the film canister with aluminum foil. Tape the foil into place.
  5. Fill the canister nearly full of water.
  6. Snap on the lid, making sure that the nail touches the water.
  7. Rub the foam plate with the wool for at least a minute to really charge it up. Place the plate upside down carefully on the table.
  8. Put the pie pan back on top of the foam plate. The plate has taken on the charge from the foam plate.
  9. Touch the pie pan with a finger… did you feel anything?
  10. Use the cup as a handle and lift the pie pan up.
  11. Touch the pan with your finger, and you should feel and see a spark (turn down the lights to make the room dark).
  12. Charge the foam plate again and set the pie pan back on top to charge it up. (Make sure you’re lifting the pie pan only by the foam cup, or you’ll discharge it accidentally.)
  13. Hold the film canister by the aluminum foil and touch the charged pie pan to the nail.
  14. Rub the foam plate with the wool again to charge it up. Set the pie pan on the foam plate to charge the pan. Now lift the pie pan and touch the pan to the nail. Do this a couple of times to really get a good charge in the film canister.
  15. Discharge the film canister by touching the foil with one finger and the nail with the other. Did you see a spark?
  16. The wool gives the plate a negative charge. You can use a plastic bag instead of the wool to give the foam plate a positive charge.

What’s Going On?

If you rub a balloon on your head, the balloon becomes filled up with extra electrons, and now has a negative charge. Try the following experiment to create a temporary charge on a wall: Bring the balloon close to the wall until it sticks.


Opposite charges attract right? So, is the entire wall now an opposite charge from the balloon? No. In fact, the wall is not charged at all. It is neutral. So why did the balloon stick to it?


The balloon is negatively charged. It created a temporary positive charge when it got close to the wall. As the balloon gets closer to the wall, it repels the electrons in the wall. The negatively charged electrons in the wall are repelled from the negatively charged electrons in the balloon.


Since the electrons are repelled, what is left behind? Positive charges. The section of wall that has had its electrons repelled is now left positively charged. The negatively charged balloon will now “stick” to the positively charged wall. The wall is temporarily charged because once you move the balloon away, the electrons will go back to where they were and there will no longer be a charge on that part of the wall.


This is why plastic wrap, Styrofoam packing popcorn, and socks right out of the dryer stick to things. All those things have charges and can create temporary charges on things they get close to.


If you rub a balloon all over your hair, the Triboelectric Effect causes the electrons to move from your head to the balloon. But why don’t the electrons go from the balloon to your head? The direction of electron transfer has to do with the properties of the material itself. And the balloon-hair combination isn’t the only game in town.


Electrons move differently depending on the materials that are rubbed together. A balloon takes on a negative charge when rubbed on hair. Today, the kids are going to find when a foam plate is rubbed with wool, the plate takes on electrons and creates a negative charge on the plate. To give the plate a positive charge, kids can rub it with a plastic bag.


The Triboelectric Series is a list that ranks different materials according to how they lose or gain electrons. A rubber rod rubbed with wool produces a negative charge on the rod, however an acrylic rod rubbed with silk creates a positive charge on the rod. A foam plate often has a positive charge when you slide one off the stack, but if you rub it with wool it will build up a negative charge.


Near the top of the list are materials that take on a positive charge, such as air, human skin, glass, rabbit fur, human hair, wool, silk, and aluminum. Near the bottom of the list are materials that take on a negative charge, such as amber, rubber balloons, copper, brass, gold, cellophane tape, Teflon, and silicone rubber. Scientists developed this list by doing a series of experiments, very similar to the ones we’re about to do.


Exercises


  1. What happens if you hold the nail and charge the aluminum foil?
  2. Can you see electrons? Why or why not?

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Today you get to learn how to read an astronomical chart to find out when the Sun sets, when twilight ends, which planets are visible, when the next full moon occurs, and much more. This is an excellent way to impress your friends.


The patterns of stars and planets stay the same, although they appear to move across the sky nightly, and different stars and planets can be seen in different seasons.


Materials:


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Download Student Worksheet & Exercises


  1. If your chart comes on two pages, you’ll need to cut the borders off at the top and bottom and tape them together so they fit perfectly.
  2. Use your ruler as a straight edge to help locate items as you read the chart.
  3. Print out copies of the almanac by clicking the image of the Skygazer’s Almanac. You can print it full-size on two pages, or size it to fit onto a single page. Since there’s a ton of information on it, it’s best read over two pages. This is an expired calendar  to practice with.
  4. First, note the “hourglass” shape of the chart. Do you see how it’s skinnier in the middle and wider near the ends? Since it’s an astronomical chart that shows what’s up in the sky at night, the nights are shorter during the summer months, so the number of hours the stars are visible is a lot less than during the winter. You’ll find the hours of the night printed across the top and bottom of the chart (find it now) and the months and days of the year printed on the right and left side.
  5. Can you find the summer solstice on June 20? Use your finger and start on the left side between June 17 and June 24. The 20th is between those two dates somewhere. Here’s how you tell exactly…
  6. Look at the entire chart – do you see the little dots that make up little squares all over the chart, like a grid? Each dot in the vertical direction represents one day. There are eight dots on the vertical side of the box.
  7. Let’s say you want to find out what time Neptune rises on June 17. Go back to June 17, which has its own little set of dots. Follow the dots with your finger until you hit the line that says Neptune Rises. Stop and trace it up vertically to the top scale to read just after 11 p.m.
  8. Look again at the dot boxes. Each horizontal dot is 5 minutes apart, and every six dots there is a vertical line representing the half-hour. The line crosses between the second and third dot, so if you lived in a place where you can clearly see the eastern horizon and looked out at 11:07, you’d see Neptune just rising. Since Uranus and Neptune are so far away, though, you’d need a telescope to see them. So let’s try something you can find with your naked eye.
  9. Look at Oct 21. What time does Saturn set? (5:30p.m.).
  10. What other two planets set right afterward? (Mercury at 6:03 p.m. and Mars sets at 7:12 p.m.).
  11. When does Jupiter rise? (7:32 p.m.).
  12. What is Neptune doing that night of Oct. 21? (Neptune transits, or is directly overhead, at 8:07 p.m. and sets at 1:30 a.m.)
  13. What other interesting things happen on Oct. 21? (Betelgeuse, one of the bright stars in the constellation Orion, rises at 9:23 p.m. Sirius, the dog star, rises at 11:06 p.m. The Pleiades, also known as the Seven Sisters, are overhead at 1:42 a.m.)
  14. Let’s find out when the Moon rises on Oct. 21. You’ll find a half circle representing the Moon centered on 11:05 p.m. Which phase is the Moon at? First or third quarter? (First. You can tell if you look at the next couple of days to see if the Moon waxes or wanes. Large circles indicate one of the four main phases of the Moon.)
  15. When does the Sun rise and set for Oct. 21? First, find the nearest vertical set of dots and read the time (5:30 p.m.). Now subtract out the 5-minute dots until you get to the edge. You should read three dots plus a little extra, which we estimate to be 17 minutes. Sunset is at 5:13 p.m. on Oct 21.
  16. Note the fuzzy, lighter areas on both sides of the hourglass. That represents the twilight time when it’s not quite dark, but it’s not daylight either. There’s a thin dashed line that runs up and down the vertical, following the curve of the hourglass offset by about an hour and 35 minutes. That’s the official time that twilight ends and the night begins.
  17. Can you find a meteor shower? Look for a starburst symbol and find the date right in the center. Those are the peak times to view the shower, and it’s usually in the wee morning hours. The very best meteor showers are when there’s also a new Moon nearby.
  18. Notice how Mercury and Venus stay close by the edges of the twilight. You’ll find a half-circle symbol representing the day that they are furthest from the Sun as viewed from the Earth, which is the best date to view it. For Venus, the * indicates the day that it’s the brightest.
  19. What do you think the open circle means at sunset on May 20? (New Moon)
  20. Students that spot the “Sun slow” or “Sun fast” marks on the chart always ask about it. It’s actually rather complicated to explain, but here’s the best way to think about it. Imagine that the vertical timeline running down the center means noon, not midnight. Do you see a second line weaving back and forth across the noon line throughout the year? That’s the line that shows the when the Sun crosses the meridian. On Feb 5, the Sun crosses that meridian at 12:14, so it’s “running slow,” because it “should have” crossed the meridian at noon. This small variation is due to the axis tilt of the Earth. Note that it never gets much more than 15 minutes fast or slow. The wavy line that represents this effect is called the Equation of Time. We’ll be using that later when we make our own sundials and have to correct for the Sun not being where it’s supposed to be.
  21. Look at Mars and Saturn both setting around the same time on Aug. 14. When two event lines cross, you’ll find nearby an open circle with a line coming from the top right side, accompanied by a set of arrows pointing toward each other. This means conjunction, and is a time when you can see two objects at once. Usually the symbol isn’t right at the intersection, because one of the objects is rising or setting and isn’t clearly visible. On Aug. 14, you’ll want to view them a little before they set, so the symbol is moved to a time where you can see them both more clearly.
  22. Important to note: If your area uses daylight savings time, you’ll need to add one hour to the times shown on the chart.
  23. Time corrections for advanced students: This chart was made for folks living on the 40o north latitude and 90o west longitude lines (which is Peoria, Ill.).
    1. If you live near the standardized longitudes for Eastern Time (75o), Central (90o), Mountain (105o) or Pacific (120o), then you don’t have to correct the chart times you read. However, if you live a little west or east of these standardized locations, you need a correction, which looks like this:
      1. For every degree west, add four minutes to the time you read off the chart.
      2. For every degree east, subtract four minutes from the time.
      3. For example, if you lived in Washington, D.C. (which is 77o longitude), note that this is 2o west of the Eastern Time, so you’d add 8 minutes to the time you read off the chart. Memorize your particular adjustment and always use it.
    2. If your latitude isn’t 40o north, then you need to adjust the rise and set times like this:
      1. If you live north of 40o, then the object you are viewing will be in the sky for longer than the chart shows, as it will rise earlier and set later.
      2. If you live south of 40o, then the object you are viewing will be in the sky for less time than the chart shows, as it will rise later and set earlier.
      3. The easiest way to calculate this is to note what time an object should rise, and then watch to see when it actually appears against a level horizon. This is your correction for your location.

    What’s Going On?

    This is one of the finest charts I’ve ever used as an astronomer, as it has so much information all in one place. You’ll find the rise and set times for all eight planets, peak times for annual meteor showers, moon phases, sunrise and set times, and it gives an overall picture of what the evening looks like over the entire year. Kids can clearly see the planetary movement patterns and quickly find what they need each night. I keep one of these posted right by the door for everyone to view all year long.

Exercises


  1.  Is Mercury visible during the entire year?
  2.  In general, when and where should you look for Venus?
  3.  When is the best time to view a meteor shower?
  4.  Which date has the most planets visible in the sky?

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A meteoroid is a small rock that zooms around outer space. When the meteoroid zips into the Earth’s atmosphere, it’s now called a meteor or “shooting star”. If the rock doesn’t vaporize en route, it’s called a meteorite as soon as it whacks into the ground. The word meteor comes from the Greek word for “high in the air.”


Meteorites are black, heavy (almost twice the normal rock density), and magnetic. However, there is an Earth-made rock that is also black, heavy, and magnetic (magnetite) that is not a meteorite. To tell the difference, scratch a line from both rocks onto an unglazed tile. Magnetite will leave a mark whereas the real meteorite will not.


Materials


  • White paper
  • Strong magnet
  • Handheld magnifying glass (optional)

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Download Student Worksheet & Exercises


  1. Imagine you are going on a rock hunt. You are to find which rocks are meteorites and which are Earth rocks. If you don’t have access to rock samples, just watch the experiment video of the different rock samples. If you’d like to make your own sample collection, here are some ideas:
    1. 8-10 different rocks, including pumice (from a volcano), lodestone (a naturally magnetized piece of magnetite, and often mistaken for meteorites), a fossil, tektite (dry fused glass), pyrite (also known as fool’s gold), marble (calcite or dolomite), and a couple of different kinds of real meteorites (iron meteorite, stony meteorite, etc.) Also add to your bag an unglazed tile and a magnet.
  2. As you watch the experiment video, record your observations on your data sheet.
    1. Since nearly all meteorites have lots of iron, they are usually attracted to a magnet. However, lodestone is an Earth rock that also has a lot of iron. Iron is heavy, and meteorites contain a lot of iron. When looking through the possibilities, remove any lightweight rocks, as they are not usually meteorites.
    2. Meteorites are small. Most never get big enough or hot enough for metal to sink into the core, so the majority are mixed with rock and dust (stony meteorites). The few that do get big and form metal cores are called iron meteorites.
    3. Most meteorites come from the Asteroid Belt. Some meteorites get a dark crust. While others look like splashed metal. They are all dark, at least on the outside. Remove any light-colored rocks.
    4. Rocks that have holes vaporize or explode when they go through the atmosphere, they don’t burn up. Only strong space rocks without holes make it to the ground. Remove any porous rocks.
    5. The ones you have left are either meteorites or lodestone. To tell the difference, scratch a line from both rocks onto an unglazed tile. Magnetite (lodestone) will leave a mark whereas the real meteorite will not.

Finding Meteorites


  1. Place a sheet of white paper outside on the ground. Do this in the morning when you first start up class.
  2. After a few hours (like just before lunchtime), your paper starts to show signs of “dust.”
  3. Carefully place a magnet underneath the paper, and see if any of the particles move as you wiggle the magnet. If so, you’ve got yourself a few bits of space dust.
  4. Use a magnifying lens to look at your space meteorites up close.

What’s Going On?

94% of all meteorites that fall to the Earth are stony meteorites. Stony meteorites will have metal grains mixed with the stone that are clearly visible when you look at a slice.


Iron meteorites make up only 5% of the meteorites that hit the Earth. However, since they are stronger, most of them survive the trip through the atmosphere and are easier to find since they are more resistant to weathering. More than half the meteorites we find are iron meteorites. They are the one of the densest materials on Earth. They stick strongly to magnets and are twice as heavy as most Earth rocks. The Hoba meteorite in Namibia weighs 50 tons.


Since nearly all meteorites have lots of iron, they are usually attracted to a magnet. However, lodestone is an Earth rock that also has a lot of iron. Iron is heavy, and meteorites contain a lot of iron. When looking through the possibilities, remove any lightweight rocks, as they are not usually meteorites.


Meteorites are small. Most never get big enough or hot enough for metal to sink into the core, so the majority are mixed with rock and dust (stony meteorites). The few that do get big and form metal cores are called iron meteorites.


Most meteorites come from the Asteroid Belt. Some meteorites get a dark crust, while others look like splashed metal. They are all dark, at least on the outside.


Rocks that have holes vaporize or explode when they go through the atmosphere, they don’t burn up. Only strong space rocks without holes make it to the ground.


Every year, the Earth passes through the debris left behind by comets. Comets are dirty snowballs that leave a trail of particles as they orbit the Sun. When the Earth passes through one of these trails, the tiny particles enter the Earth’s atmosphere and burn up, leaving spectacular meteor showers for us to watch on a regular basis. The best meteor showers occur when the moon is new and the sky is very dark.


Meteorites are black, heavy (almost twice the normal rock density), and magnetic. However, there is an Earth-made rock that is also black, heavy, and magnetic (magnetite) that is not a meteorite. To tell the difference, scratch a line from both rocks onto an unglazed tile (or the bottom of a coffee mug or the underside of the toilet tank). Magnetite will leave a mark, whereas the real meteorite will not.


If you find a meteorite, head to your nearest geology department at a local university or college and let them know what you’ve found. In the USA, if you find a meteorite, you get to keep it… but you might want to let the experts in the geology department have a thin slice of it to see what they can figure out about your particular specimen.


Exercises


  1.   Are meteors members of the solar system?
  2.  How big are meteors?
  3. Why do we have meteor showers at predictable times of the year?

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mars-retrogradeIf you watch the moon, you’d notice that it rises in the east and sets in the west. This direction is called ‘prograde motion’. The stars, sun, and moon all follow the same prograde motion, meaning that they all move across the sky in the same direction.


However, at certain times of the orbit, certain planets move in ‘retrograde motion’, the opposite way. Mars, Venus, and Mercury all have retrograde motion that have been recorded for as long as we’ve had something to write with. While most of the time, they spend their time in the ‘prograde’ direction, you’ll find that sometimes they stop, go backwards, stop, then go forward again, all over the course of several days to weeks.


Here are videos I created that show you what this would look like if you tracked their position in the sky each night for an year or two.


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Mercury and Venus Retrograde Motion

This is a video that shows the retrograde motion of Venus and Mercury over the course of several years. Venus is the dot that stays centered throughout the video (Mercury is the one that swings around rapidly), and the bright dot is the sun. Note how sometimes the trace lines zigzag, and other times they loop. Mercury and Venus never get far from the sun from Earth’s point of view, which is why you’ll only see Mercury in the early dawn or early evening.




Retrograde Motion of Mars

You’ve probably heard of epicycles people used to use to help explain the retrograde motion of Mars. Have you ever wondered what the fuss was all about? Here’s a video that traces out the path Mars takes over the course of several years. Do you see our Moon zipping by? The planets, Sun, and Moon all travel along line called the ‘ecliptic’, as they all are in about the same plane.



 
Download Student Worksheet & Exercises


Exercises


  1. During which of the months does Mars appear to move in retrograde?
  2.  Why does Mars appear to move backward?
  3. Which planets have retrograde motion?

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Johannes Kepler, a German astronomer famous for his laws of planetary motion. Check out our Johannes Kepler facts page for more information.
Johannes Kepler, a German astronomer famous for his laws of planetary motion. Check out our Johannes Kepler facts page for more information.

Kepler’s Laws of planetary orbits explain why the planets move at the speeds they do. You’ll be making a scale model of the solar system and tracking orbital speeds.


Kepler’s 1st Law states that planetary orbits about the Sun are not circles, but rather ellipses. The Sun lies at one of the foci of the ellipse. Kepler’s 2nd Law states that a line connecting the Sun and an orbiting planet will sweep out equal areas in for a given amount of time. Translation: the further away a planet is from the Sun, the slower it goes.
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Download Student Worksheet & Exercises


What are the planets in our solar system starting closest to the Sun? On a sheet of paper, write down a planet and label it with the name. Do this for each of the eight planets.


  • Mercury is 0.39 AU (in a rocket it would take 2.7 months to go straight to Mercury from the Sun)
  • Venus is 0.72 AU
  • Earth is 1 AU (in a rocket it would take 7 months to go straight to Earth from the Sun)
  • Mars is 1.5 AU
  • Jupiter is 5.2 AU
  • Saturn is 9.6 AU
  • Uranus is 19.2 AU
  • Neptune is 30.1 AU (in a rocket it would take 18 years to go straight to Neptune from the Sun)

Of course, we don’t travel to planets  in straight lines – we use curved paths to make use of the gravitational pull of nearby objects to slingshot us forward and save on fuel.


  1. Now draw the location of the asteroid belt.
  2. Draw the position of the Kuiper Belt” and ask a student to draw and label it (beyond Neptune).
  3. Where are the five dwarf planets? They are in the Kuiper belt and the asteroid belt:
    • Ceres (in the Asteroid belt, closer to Jupiter than Mars)
    • Pluto (is 39.44 AU from the Sun)
    • Haumea (43.3 AU)
    • Makemake (45.8 AU)
    • Eris. (67.7 AU)

Now for the fun part! You’ll need a group of friends to work together for this lab, so you have at least one student for each planet, one for the Sun, and two for the asteroid belts, and five for the dwarf planets. You can assign additional students to be moons of Earth (Moon), Mars (Phobos and Deimos), Jupiter (assign only 4 for the largest ones: Ganymede, Callisto, Io, and Europa), Saturn (again, assign only 4: Titan, Rhea, Iapetus, and Dione), Uranus (Oberon, Titania), and Neptune (Triton). If you still have extra students, assign one to Charon (Pluto’s binary companion) and one each to Hydra and Nix, which orbit Pluto and Charon. While you ask the students to walk around in a later step, the moons can circle while they orbit.


  1. First, walk outside to a very large area.
  2. Hand the Sun student the measuring tape.
  3. Ask Kuiper Belt student(s) to take the end of the measuring tape and begin walking slowly away from the Sun.
  4. With each student assigned to the distance shown, grab the measuring tape and walk along with it. Please be careful – measuring tapes can have sharp edges! You can use gloves when you grab the tape if you’ve got a sharp steel measuring tape to protect your hands. Ask the Sun to call out the distances periodically so the students know when it’s time to come up.
  5. What do you notice about the distances between the planets? The nearest star is 114.5 miles away!
  6. Ask the students to let go of the measuring tape, except for Neptune and the Sun. Everyone else gathers around you (a safe distance away, as Neptune is going to orbit the Sun).
  7. Using a stopwatch, notice how much time it takes Neptune to walk around the Sun while holding the measuring tape taut. How long did it take for one revolution?
  8. Now ask Mercury to take their position on the tape at the appropriate distance. Time their revolution as they walk around the Sun. How long did it take?
  9. How does this relate to the data you just recorded for Neptune and Mercury? You should notice that the speeds the kids were walking at were probably nearly the same, but the time was much shorter for Mercury. If you could swing them around (instead of having them walk), can you imagine how this would make Mercury orbit at a faster speed than Neptune?
  10. If you have it, you can illustrate how Kepler’s 2nd law works and relate it back to this experiment. Tie a ball to the end of a string and whirling it around in a circle. After a few revolutions, let the string wind itself up around your finger. As the string length shortens, the ball speeds up. As the planet moves inward, the planet’s orbital speed increases. The planet’s speed decreases the further from the Sun it is located.
  11. Ask one of the bigger students to take their position with the measuring tape, reminding them to keep the tape taut no matter what happens. When they start to walk around the Sun, have the Sun move with them a bit (a couple of feet is good). Let the students know that the planet also yanks on the Sun just as hard as the Sun yanks on the planet. Since the planet is much smaller than the Sun, you won’t see as much motion with the Sun.
  12. Optional demonstration to illustrate this idea: take a heavy bag (I like to use oranges) and spin it around as you whirl around in a circle. Do you notice the student leans back a bit to balance themselves as they swing around and around? This is the same principle, just on a smaller scale. The two objects (the bag and the student) are orbiting around a common point, called the center of mass. In our real solar system, the Sun has 99.85% of the mass, so the center of mass lies inside the Sun (although not at the exact center).
  13. Look at the length of your measuring tape. Find the data table you need to use in the tables. Circle the one you’re going to use or cross out the ones you’re not.
  14. Using a stopwatch, time Venus as they walk around the Sun while holding the measuring tape taut. How long did it take for one revolution? (Make sure the Sun doesn’t move much during this process like they did for the demonstration. We’re assuming the Sun is at the center.)
  15. Continue this for all the planets.

What’s Going On?

Johannes Kepler, a German mathematician and astronomer in the 1600s, was one of the key players of his time in astronomy. Among his best discoveries was the development of three laws of planetary orbits. He worked for Tycho Brahe, who had logged huge volumes of astronomical data, which was later passed onto to Kepler. Kepler took this information to design and develop his ideas about the movements of the planets around the Sun.


Kepler’s 1st Law states that planetary orbits about the Sun are not circles, but rather ellipses. The Sun lies at one of the foci of the ellipse. Well, almost. Newton’s Laws of Motion state that the Sun can’t be stationary, because the Sun is pulling on the planet just as hard as the planet is pulling on the Sun. They are yanking on each other. The planet will move more due to this pulling because it is less massive. The real trick to understanding this law is that both objects orbit around a common point that is the center of mass for both objects. If you’ve ever swung a heavy bag of oranges around in a circle, you know that you have to lean back a bit to balance yourself as you swing around and around. It’s the same principle, just on a smaller scale.


In our solar system the Sun has 99.85% of the mass, so the center of mass between the Sun and any other object actually lies inside the Sun (although not at the center).


Kepler’s 2nd Law states that a line connecting the Sun and an orbiting planet will sweep out equal areas in for a given amount of time. The planet’s speed decreases the further from the Sun it is located (actually, the speed varies inversely with the square‐root of the distance, but you needn’t worry about that). You can demonstrate this to the students by tying a ball to the end of a string and whirl it around in a circle. After a few revolutions, let the string wind itself up around your finger. As the string length shortens, the ball speeds up. As the planet moves inward, the planet’s orbital speed increases.


Embedded in the second law are two very important laws: conservation of angular moment and conservation of energy. Although those laws might sound scary, they are not difficult to understand. Angular momentum is distance multiplied by mass multiplied by speed. The angular momentum for one case must be the same for the second case (otherwise it wouldn’t be conserved). As the planet moves in closer to the Sun, the distance decreases. The speed it orbits the Sun must increase because the mass doesn’t change. Just like you saw when you wound the ball around your finger.


Energy is the sum of both the kinetic (moving) energy and the potential energy (this is the “could” energy, as in a
ball dropped from a tower has more potential energy than a ball on the ground, because it “could” move if released). For conservation of energy, as the planet’s distance from the Sun increases, so does the gravitational potential energy. Again, since the energy for the first case must equal the energy from the second case (that’s what conservation means), the kinetic energy must decrease in order to keep the total energy sum a constant value.


Kepler’s 3rd Law is an equation that relates the revolution period with the average orbit speed. The important thing to note here is that mass was not originally in this equation. Newton came along shortly after and did add in the total mass of the system, which fixed the small error with the equation. This makes sense, as you might imagine a Sun twice the size would cause the Earth to orbit faster. However, if we double the mass of the Earth, it does not affect the speed with which it orbits the Sun. Why not? Because the Earth is soooo much smaller than the Sun that increasing a planet’s size generally doesn’t make a difference in the orbital speed. If you’re working with two objects about the same size, of course, then changing one of the masses absolutely has an effect on the other.


Exercises


  1.  If the Sun is not stationary in the center but rather gets tugged a couple of feet as the planet  yanks on it, how do you think this will affect the planet’s orbit?
  2.  If we double the mass of Mars, how do you think this will affects the orbital speed?
  3.  If Mercury’s orbit is normally 88 Earth days, how long do you estimate Neptune’s orbit to  be?

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So you've played with lenses, mirrors, and built an optical bench. Want to make a real telescope? In this experiment, you'll build a Newtonian and a refractor telescope using your optical bench.

Materials:

  • optical bench
  • index card or white wall
  • two double-convex lenses
  • concave mirror
  • popsicle stick
  • mirror
  • paper clip
  • flash light
  • black garbage bag
  • scissors or razor
  • rubber band
  • wax paper
  • hot glue

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Download Student Worksheet & Exercises

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When I was in grad school, I needed to use an optical bench to see invisible things. I was trying to ‘see’ the exhaust from a  new kind of F15 engine, because the aircraft acting the way it shouldn’t – when the pilot turned the controls 20o left, the plane only went 10o. My team had traced the problem to an issue with the shock waves, and it was my job to figure out what the trouble was. (Anytime shock waves appear, there’s an energy loss.)


Since shock waves are invisible to the human eye, I had to find a way to make them visible so we could get a better look at what was going on. It was like trying to see the smoke generated by a candle – you know it’s there, but you just can’t see it. I wound up using a special type of photography called Schlieren.


An optical table gives you a solid surface to work on and nails down your parts so they don’t move. This is an image taken with Schlieren photography. This technique picks up the changes in air density (which is a measure of pressure and volume).


The air above a candle heats up and expands (increases volume), floating upwards as you see here. The Schlieren technique shines a super-bright xenon arc lamp beam of light through the candle area, bounces it off two parabolic mirrors and passes it through a razor-edge slit and a neutral density filter before reaching the camera lens. With so many parts, I needed space to bolt things down EXACTLY where I wanted them. The razor slit, for example, just couldn’t be anywhere along the beam – it had to be right at the exact point where the beam was focused down to a point.


I’m going to show you how to make a quick and easy optical lab bench to work with your lenses. Scientists use optical benches when they design microscopes, telescopes, and other optical equipment. You’ll need a bright light source like a flashlight or a sunny window, although this bench is so light and portable that you can move it to garage and use a car headlight if you really want to get creative. Once your bench is set up, you can easily switch out filters, lenses, and slits to find the best combination for your optical designs. Technically, our setup is called an optical rail, and the neat thing about it is that it comes with a handy measuring device so you can see where the focal points are for your lenses. Let’s get started:
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Materials:


  • lenses (glass or plastic), magnifying lenses work also
  • two razor blades (new)
  • index cards (about four)
  • razor
  • old piece of wood
  • single hair from your head
  • tape
  • aluminum foil
  • clothespins (2-4)
  • laser pointer
  • popsicle sticks (tongue-depressor size)
  • hot glue gun
  • scissors and a sharp razor
  • meter sticks (2)
  • bright light source (ideas for this are on the video)

Your lenses are curved pieces of glass or plastic designed to bend (refract) light. A simple lens is just one piece, and a compound lens is like the lens of a camera – there’s lots of them in there. The first lenses were developed by nature – dewdrops on plant leaves are natural lenses. The light changes speed and bends when it hits the surface of the drop, and things under the drop appear larger. (Read more about refraction here.) The earliest written records of lenses are found in the Greek archives and described as being glass globes filled with water.


Concave Lenses

Concave lenses are shaped like a ‘cave’ and curve inward like a spoon. Light that shines through a concave lens bends to a point (converging beam). Ever notice how when you peep through the hole in a door (especially in a hotel), you can see the entire person standing on the doorstep? There’s a concave lens in there making the person appear smaller.


You’ll also find these types of lenses in ‘shoplifting mirrors’. Store owners post these mirrors around help them see a larger area than a flat mirror shows, although the images tend to be a lot smaller.


If you have a pair of near-sighted glasses, chances are that the lenses are concave. Near-sighted folks need help seeing things that are far away, and the concave lenses increase the focal point to the right spot on their retina.


Concave lenses work to make things look smaller, so there not as widely used as convex lenses. You’ll find concave lenses inside camera lenses and binoculars to help clear weird optical problems that happen around the edges of a convex lens (called aberration).


Here’s a video on lenses, both convex and concave:



Convex lenses bulge outwards, bending the light out in a spray (diverging beam). A hand-held magnifying glass is a single concave lens with a handle. These lenses have been used as ‘burning glasses’ for hundreds of years – by placing a small piece of paper at its focal point and using the sun as a light source, you can focus the light energy so intensely that you reach the flash point of the paper (the paper auto-ignites around 450oF).


When you stack a large convex lens above a solar panel, the magnification effect makes it so you can get away with using a smaller photovoltaic cell to get the same amount of energy from the sun. You’ll find convex lenses in telescopes, microscopes, binoculars, eyeglasses, and more.


Mirrors

lenses-part1What if you coat one side of the lens with a reflecting silver coating? You get a mirror!


Stick wooden skewers into a piece of foam to simulate how the light rays reflect off the surface of the mirror. Note that when the mirror (foam) is straight, the light rays are straight (which is what you see when you look in the bathroom mirror). The light bounces off the straight mirror and zips right back at you, remaining parallel.


lenses-part2 copyNow arch the foam. Notice how the light ways (skewers) come to a point (focal point).


After the focal point, the rays invert, so the top skewer is now at the bottom and the bottom is now at the top.  This is your flipped (inverted) image. This is what you’d see when you look into a concave mirror, like the inside of a metal spoon. You can see your face, but it’s upside-down.


Slits

A slit allows light from only one source to enter. If you have light from other sources, your light beam is more scattered and your images and lines become blurry. Thin slits can be easily made by placing the edges of two razor blades very close together and securing into place. We’re going to use an anti-slit using a piece of hair, but you can substitute a thin needle.


Here’s a video on using filters and slits with your laser:



Filters

There are hundreds of different types of filters, used in photography, astronomy, and sunglasses. A filter can change the amount and type of light allowed through it. For example, if you put on red-tinted glasses, suddenly everything takes on a reddish hue. The red filter blocks the rest of the incoming wavelengths (colors) and only allows the red colors to get to your eyeball. There are color filters for every wavelength, even IR and UV.


UV filters reduce the haziness in our atmosphere, and are used on most high-end camera lenses, while IR filters are heat-absorbing filters used with hot light sources (like near incandescent bulbs or in overhead projectors).


A neutral density (ND) filter is a grayish-colored filter that reduces the intensity of all colors equally. Photographers use these filters to get motion blur effects with slow shutter speeds, like a softened waterfall.


Build an Optical Bench

It’s time to put all these pieces together and make cool optical stuff – are you ready?



Download Student Worksheet & Exercises


Click here for more experiments on building your own microscope and telescope.


Cat’s Eyes

Corner reflectors are U-turns for light beams. A corner mirror made from three mirrors will reflect the beam straight back where it came from, no matter what angle you hit it at.  Astronauts placed these types of mirrors on the moon so scientists could easily bounce laser beams off the moon and have them return to the same place on Earth. They used these reflected laser beams to measure the speed of light.


You’ll find corner mirrors in “cat’s eye” reflectors on the road. Car headlights illuminate the reflectors and send the beam straight back the same way – right at the driver.


Exercises


  1. Using only the shape, how can you tell the difference between a convex and a concave lens?
  2.  Which type of lens makes objects viewed through it appear smaller?
  3.  Which type of lens makes the objects viewed through it appear larger?
  4.  How do you get the f number?

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Light acts like both a particle and a wave, but never both at the same time. But you need both of these concepts in order to fully describe how light works.


Energy can take one of two forms: matter and light (called electromagnetic radiation). Light is energy in the form of either a particle (like a marble) or a wave that can travel through space and some kinds of matter (like a wave on the ocean). You really can’t separate the two because they actually complement each other.


Low electromagnetic radiation (called radio waves) can have wavelengths longer than a football field, while high energy (gamma rays) can destroy living tissue. Light has wavelength (color), intensity (brightness), polarization (the direction of the waves that make up the light), and phase.


Materials: sink or bowl of water, glow in the dark toy, camera flash or sunlight


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To show how light acts like a wave, you can pass light through a glass of water and watch the rainbow reflections on the wall. Why does this happen? When the light passes through the glass and the water, it changes wavelength and angle to give different frequencies of light (different colors).


Dip your fingers in a bathtub of water. Can you see the ripples traveling along the top surface? Light travels just like the waves on the surface of the water.


Light also acts like a particle. Use a camera flash to quickly charge a glow-in-the-dark toy in a dark closet. The light particles (photons) hit the electrons in the toy and transfer energy to the electron. The result is that the electron emits another light particle of a different wavelength, which is why glow-in-the-dark toys don’t reflect back the same color light they were charged with.


Learn more about this scientific principle in Unit 9.


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xtal3In addition to laser experiments, I thought you’d like to learn how to pick up sound that’s traveling on a light wave. A crystal radio is among the simplest of radio receivers – there’s no battery or power source, and nearly no moving parts. The source of power comes directly from the radio waves (which is a low-power, low frequency light wave) themselves.


The crystal radio turns the radio signal directly into a signal that the human ear can detect. Your crystal radio detects in the AM band that have been traveling from stations (transmitters) thousands of miles away. You’ve got all the basics for picking up AM radio stations using simple equipment from an electronics store. I’ll show you how…


The radio is made up of a tuning coil (magnet wire wrapped around a toilet paper tube), a detector (germanium diode) and crystal earphones, and an antenna wire.


One of the biggest challenges with detecting low-power radio waves is that there is no amplifier on the radio to boost the signal strength. You’ll soon figure out that you need to find the quietest spot in your house away from any transmitters (and loud noises) that might interfere with the reception when you build one of these.


One of things you’ll have is to figure out the best antenna length to produce the clearest, strongest radio signal in your crystal radio. I’m going to walk you through making three different crystal radio designs.


You’ll need to find these items below.


  • Toilet paper tube
  • Magnet wire
  • Germanium diode: 1N34A
  • 4.7k-ohm resistor
  • Alligator clip test leads
  • 100’ stranded insulated wire (for the antenna)
  • Scrap of cardboard
  • Brass fasteners (3-4)
  • Telephone handset or get a crystal earphone

Here’s what you do:


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ss-laserWhat happens when you shine a laser beam onto a spinning mirror? In the Laser Maze experiment, the mirrors stayed put. What happens if you took one of those mirrors and moved it really fast?


It turns out that a slightly off-set spinning mirror will make the laser dot on the wall spin in a circle.  Or ellipse. Or oval.  And the more mirrors you add, the more spiro-graph-looking your projected laser dot gets.


Why does it work? This experiment works because of imperfections: the mirrors are mounted off-center, the motors wobble, the shafts do not spin true, and a hundred other reasons why our mechanics and optics are not dead-on straight.   And that’s exactly what we want – the wobbling mirrors and shaky motors make the pretty pictures on the wall!  If everything were absolutely perfectly aligned, all you would see is a dot.


Here’s how to do this experiment:


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Materials:


  • AA battery pack with AA batteries
  • two 1.5-3V DC motors OR rip them off old toys or personal fans sold in the summertime
  • keychain laser pointer
  • clothespin
  • two round mirrors (mosaic mirrors from the craft store work great)
  • two alligator clip leads
  • gear that fits onto the motor and has a flat side to attach to the mirror
  • 5-minute epoxy (don’t use hot glue – it’s not strong enough to hold the mirrors on at high motor speeds)

**Note – if this is your very first time wiring up an electrical circuit, I highly recommend doing this Easy Laser Light Show first. It uses a lot of the same parts, but it’s easier to build.**



Here’s what you do:


1. Insert the batteries into their case.


2. Use 5-minute epoxy to secure the gear onto the round mirror.


3. Press-fit the gear-mirror onto the shaft when the epoxy is dry.


4. Make the motor spin using the alligator clips and the battery case.


5. Turn down the lights and fire up the laser, aiming the beam onto the motor.


6. Shine the reflection somewhere easy to see, like the ceiling.


7. Once you’ve got this working, add a second mirror like you did in the laser maze.


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Advanced Two-Axis Laser Light Show

The second part of this experiment is for advanced students. What shapes can you make?  Is it tough to hold it all in place? Then here’s how to create a portable laser light show:


Materials:


  • Red laser pointer
  • 3VDC motors
  • 2 gears or corks (you’ll need a solid way to attach the mirror to the motor shaft tip)
  • two 1” round mirrors (use mosaic mirrors)
  • 2 DPDT switches with center off
  • 20 alligator clip leads  OR insulated wire if you already know how to solder
  • 2 AA battery packs with 4 AA’s
  • Two 1K potentiometers
  • Zip-tie (from the hardware store)
  • ½ ” or ¾ ” metal conduit hangers (size to fit your motors from the hardware store)
  • 3 sets of ¼ ” x 2″ bolts, nuts, and washers
  • 1 project container (at least 7” x 5”) with lid
  • Basic tools (scissors, hot glue gun, drill, wire strippers, pliers, screwdriver)

Click here to download the Schematic Wiring Diagram for the Advanced Laser Light Show.



Download Student Worksheet & Exercises


Exercises


  1. How does the mirror turn a laser dot into an image?
  2.  What happens when you add a second motor? Third?

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Ever notice how BRIGHT your white t-shirt looks in direct sun? That’s because mom washed with fluorescent laundry soap (no kidding!). The soap manufacturers put in dyes that glow white under a UV light, which make your clothes appear whiter than they really are.


Since light is a form of energy, in order for things to glow in the dark, you have to add energy first. So where does the energy come from? There are are few different ways to do this:


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Materials:


  • UV black fluorescent light (check shopping list to find out where to get one)
  • dark evening inside your house

Light bulbs use incandescence, meaning that the tungsten wire inside a light bulb gets so hot that it gives of light. Unfortunately, bulbs also give off a lot of heat, too. Incandescence happens when your electric stove glows cherry red-hot. Our sun gives off energy through incandescence also – a lot of it.


On the other end of things, cold light refers to the light from a glow stick, called luminescence. A chemical reaction (chemiluminescence) starts between two liquids, and the energy is released in the form of light. On the atomic scale, the energy from the reaction bumps the electron to a higher shell, and when it relaxes back down it emits a photon of light.


Phosphorescence light is the ‘glow-in-the-dark’ kind you have to ‘charge up’ with a light source. This delayed afterglow happens because the electron gets stuck in a higher energy state. Lots of toys and stick-on stars are coated with phosphorescent paints.


Triboluminescence is the spark you see when you smack two quartz crystals together in the dark. Other minerals spark when struck together, but you don’t have to be a rock hound to see this one in action – just take a Wint-O-Green lifesaver in a dark closet with a mirror and you’ll get your own spark show. The spark is basically light from friction.


Fluorescence is what you see on those dark amusement-park rides that have UV lights all around to make objects glow. The object (like a rock) will absorb the UV light and remit a completely different color. The light strikes the electron and bumps it up a level, and when the electron relaxed back down, emits a photon.



 
Download Student Worksheet & Exercises


Whew! There’s a lot to know about glow in the dark stuff, isn’t there? Let’s pull all this together and go on a Treasure Hunt. This hunt is best done just before bed, when it’s already dark outside. All you need is 20 minutes and a UV black light. Ready?


Here’s what you do: Shut off all the lights in the house and go around armed with your UV light, finding things that glow both inside and outside the house. I’ve found some surprises, including a batch of screaming yellow masking tape, eye-popping orange near the microwave (someone’s spillover from lunch?), and garishly green rocks just outside. Our teeth, laundry soap, and sneakers were way fun, too! What fluoresces in your house? Have fun!


What kind of stuff glows under a black light?

Loads of stuff! There are a bunch of everyday things that fluoresce (glow) when under a black light. Note – black lights emit UV light, some of which you can’t see (just like you can’t see infrared – the beam emitted from the remote control to the TV). By the way, that’s why “black lights” were named as such. The reason stuff glows is that fluorescent objects absorb the UV light and then spit it back almost instantaneously. Some of that energy gets lost during that process, and that changes the wavelength of the light, which makes this light visible and causes the material to appear to ‘glow’.


Here are some things that glow: white paper (although paper made pre-1950 doesn’t, which is how investigators tell the difference between originals and fakes), club soda or tonic water (it’s the quinine that glows blue), body fluids (yes, blood, urine, and more are all fluorescent), Vitamins (Vitamin A, B, B-12 (crush and dissolve in vinegar first), thiamine, niacin, and riboflavin are strongly fluorescent), chlorophyll (grind spinach in a small amount of alcohol (vodka) and pour it through a coffee filter to get the extract (keep the solids in the filter, not the liquid)), antifreeze, laundry detergents, tooth whiteners, postage stamps, driver’s license, jellyfish, and certain rocks (fluorite, calcite, gypsum, ruby, talc, opal, agate, quartz, amber) and the Hope Diamond (which is blue in regular light, but glows red).


When you purchase your UV fluorescent “black lights”, be sure to get the LONG WAVE version (short wave UV is the kind that causes permanent damage to living things – that’s how they kill the bacteria in water), and it appears that UV fluorescent lamps work better than the UV LEDs currently on the market, usually sold as “UV Flashlights”. We tried both, and the stuff shone brighter with the fluorescent lamps.


Exercises


  1.  Why are incandescent lights less energy-efficient than fluorescent lights?
  2.  What are the two types of fluorescent lights?
  3. What kinds of things did you find that glow on your treasure hunt? Give at least five examples.

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Here’s a trick question – can you make the color “yellow” with only red, green, and blue as your color palette?  If you’re a scientist, it’s not a problem.  But if you’re an artist, you’re in trouble already.


The key is that we would be mixing light, not paint.  Mixing the three primary colors of light gives white light.  If you took three light bulbs (red, green, and blue) and shined them on the ceiling, you’d see white.  And if you could magically un-mix the white colors, you’d get the rainbow (which is exactly what prisms do.)


If you’re thinking yellow should be a primary color – it is a primary color, but only in the artist’s world.  Yellow paint is a primary color for painters, but yellow light is actually made from red and green light.  (Easy way to remember this: think of Christmas colors – red and green merge to make the yellow star on top of the tree.)


As a painter, you know that when you mix three cups of red, green, and blue paint, you get a muddy brown. But as a scientist, when you mix together three cups of cold light, you get white.  If you pass a beam white light through a glass filled with water that’s been dyed red, you’ve now got red light coming out the other side.  The glass of red water is your filter.  But what happens when you try to mix the different colors together?


The cold light is giving off its own light through a chemical reaction called chemiluminescence, whereas the cups of paint are only reflecting nearby light. It’s like the difference between the sun (which gives off its own light) and the moon (which you see only when sunlight bounces off it to your eyeballs). You can read more about light in our Unit 9: Lesson 1 section.


Here’s what you need:


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Download Student Worksheet & Exercises


You can demonstrate the primary colors of light using glow sticks! When red, green, and blue cold light are mixed, you get white light.


Simply activate the light stick (bend it until you hear a *crack* – that’s the little glass capsule inside breaking) and while wearing gloves, carefully slice off one end of the tube with strong cutters, being careful not to splash (do this over a sink).


Cut off the ends for all three light sticks. Pass the contents of the light sticks through a coffee filter (or paper towel) into a disposable cup – this will capture the glass bits. Now your cup should be glowing white.


Sometimes the chemical light sticks contain a glowing green liquid encapsulated within a red or blue plastic tube, so when you slice it open to combine it with the other colors, it isn’t a true red. Be sure that your chemical light sticks contain a glowing RED LIQUID and BLUE LIQUID in a clear, colorless plastic tube, or this experiment won’t work. Order true color glow sticks here.


Exercises


  1.     What color do you get when you mix blue and green liquid lights?
  2.     What happens when you start to add the red light?
  3.     What is your final color result when mixing red, blue, and green lights?
  4.      How would your result differ if you instead mixed red, blue and green paints?

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There are three primary colors of light are red, green, and blue.  The three primary colors of paint are red, yellow, and blue (I know it's actually cyan, yellow, and magenta, which we'll get to in more detail later, but for now just stick with me and think of the primary colors of paint as red-yellow-blue and I promise it will all make sense in the end).

Most kids understand how yellow paint and blue paint make green paint, but are totally stumped when red light and green light mix to make yellow light. The difference is that we're mixing light, not paint.

Lots of science textbooks still have this experiment listed under how to mix light: "Stir together one of red water and one glass of green water (dyed with food coloring) to get a glass of yellow water." Hmmm... the result I get is a yucky greenish-brown color. What happened?

The reason  you can't mix green and red water to get yellow is that you’re essentially still mixing paint, not light. But don’t take our word for it – test it out for yourself with this super-fast light experiment on mixing colors.

Materials:

  • pair of scissors

  • crayons

  • sharp wood pencil or wood skewer

  • index cards

  • drill (optional)


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Download Student Worksheet & Exercises

Here's what you do: use a cup to outline circles on a sheet of stiff white paper (or manila folders). Stack several blank pages together and cut out multiple circles. Color the circles, push a sharp wooden pencil through a hole in the center, and spin! What color does yellow and blue make? Pink and purple? You can also make a button-spinner to really whirl it around by looping a length of string through two holes in the center of the disk circle.

Troubleshooting: These disks needs to spin rapidly in order to trick your eye into blending the colors. If you have a motor, batteries, and wires lying around, you can use them to spin the disks for you. Simply punch the motor’s shaft through the paper (colored-side up).

Turn the motor on by connecting the power and watch the colors mix! Other alternatives include using a drill, hand-held mixer/beaters (not a Kitchen Aid standard mixer!), electric screwdriver, etc.

Alternate Spinning Method: Want to do this project, but you don't have enough speed or a motor?  You can make a 'button spinner' to whirl these things around super-fast.  (Did you know this is how the first circular saws were made?)

Attach your disk to a piece of stiff cardboard (index cards are too flimsy), punch out two holes near the center and thread a loop of string through and tie the ends together to make the old-fashioned “spinning disk”. Using a circling motion with your hands, you can twist up the string with the card in the middle and then pull horizontally outwards to untwist it and watch the cardboard whirl and whip around!!

Click here for the Mixing Cold Light experiment!

Exercises

  1.  What happens when blue and red are mixed on the spinner?

  2.  What happens when red and green are mixed on the spinner?

  3. What colors would you mix to get orange?

  4. What are the primary colors of light, and how do they differ from the primary colors we learn in art class?


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In this experiment, water is our prism. A prism un-mixes light back into its original colors of red, green, and blue. You can make prisms out of glass, plastic, water, oil, or anything else you can think of that allows light to zip through.


What’s a prism? Think  of a beam of light.  It zooms fast on a straight path, until it hits something (like a water drop).  As the light goes through the water drop, it changes speed (refraction). The speed change depends on the angle that the light hits the water, and what the drop is made of.  (If it was a drop of mineral oil, the light would slow down a bit more.) Okay, so when white light passes through a prism (or water drop), changes speed, and turns colors.  So why do we see a rainbow, not just one color coming out the other side?


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The secret is because the light is made up of different wavelengths, and each gets bent by different amounts when they hit a new material. So one wave changes speed to red, another to yellow, another to green, etc. when the beam hits the prism. And water drops are tiny prisms.


The light passing through a water drop gets refracted twice, not once.  The first time is when it enters the water drop, the second when it bounces off the other side of the drop and reflects back through the water drop and out again (some of the light does make it out the other side of the drop, but most of it bounces back).  When the light emerges from the water drop, it changes speed again, and presto! You have a rainbow.


Natural rainbows (the ones that you see after it rains) happen when water drops (tiny prisms) in the air are hit by sunlight from behind you at just the right angle (which is relatively a low angle, near the ground).  The best rainbows can be seen when half of the sky is darkened with rainclouds and you’re in a clear patch with sun behind you. And guess what?  You can even see a nighttime rainbow (called a moonbow), although they’re pretty rare, usually near full moon.


Here’s what you do:


Materials:


  • mirror
  • shallow baking dish
  • water
  • sunlight


 
Download Student Worksheet & Exercises


Set a clear tray of water in sunlight. Lean a mirror against an inside edge and adjust so that a rainbow appears on the wall. You can also use a light bulb shining through a slit in a flat cardboard piece as a light source.


Troubleshooting: This is one of the easiest experiments to do, and the most beautiful. The trouble is, you don’t know where the water shadow will show up, so make sure you point the mirror to the sky and play with the angle of the mirror until you find the wavering rainbow. Because the shadow is constantly moving, you can snap a few pictures when you’ve got it so you can look over the finer details later. If this project still eludes you, take a large sheet and use it instead of the tiny index card.


Exercises


  1.   What serves as the prism in this experiment?
  2.   What property can help make something a good prism material?
  3. What are some other items that could be used as prisms?

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In this lab, we are going to make an eyeball model using a balloon. This experiment should give you a better idea of how your eyes work. The way your brain actually sees things is still a mystery, but using the balloon we can get a good working model of how light gets to your brain.


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Here’s what you need


    • 1 biconvex plastic lens
    • 1 round balloon, white, 9 inches
    • 1 assistant
    • 1 votive candle
    • 1 black marker
    • 1 book of matches
    • 1 metric ruler
    • Adult Supervision!


Download Student Worksheet & Exercises


Here’s what you do


  1. Blow up the balloon until it is about the size of a grapefruit. If it’s difficult to inflate, stretch the material a few times or ask an adult to help you.
  2. You will need an extra set of hands for this portion. Ask your partner to hold the neck of the balloon closed to keep the air in while you insert the lens into the opening. The lens will need to be inserted perpendicularly to the balloon’s neck. It will prevent any air from escaping once it’s in place. Like your eye, light will enter through the lens and travel toward the back of the balloon.
  3. Hold the balloon so that the lens is pointing toward you. Take the lens between your thumb and index finger. Look into the lens into the balloon. You should have a clear view of the inside. Start to twist the balloon a little and notice that the neck gets smaller like your pupils do when exposed to light. Practice opening and closing the balloon’s “pupil.”
  4. Have an adult help you put the candle on the table and light it. Turn out the lights.
  5. Put the balloon about 20 to 30 centimeters away from the candle with the lens pointed toward it. The balloon should be between you and the candle. You should see a projection of the candle’s flame on the back of the balloon’s surface. Move the balloon back and forth in order to better focus the image on the back of the balloon and then proceed with data collection.
  6.  Describe the image you see on the back of the balloon. How is it different from the flame you see with your eyes? Draw a picture of how the flame looks.
  7. The focal length is the distance from the flame to the image on the balloon. Measure this distance and record it.
  8. What happens if you lightly push down on the top of the balloon? Does this affect the image? You are experimenting with the affect caused by near-sightedness.
  9. To approximate a farsighted eye, gently push in the front and back of the balloon to make it taller. How does this change what you see?

What’s going on?


Okay, let’s discuss the part of the balloon that relate to parts of your eye. The white portion of the balloon represents your sclera, which you may have already guessed is also the white part of your eye. It is actually a coating made of protein that covers the various muscle in your eye and holds everything together.


Of course, the lens you inserted represents the actual lens in your eye. The muscles surrounding the lens are called ciliary muscles and they are represented by the rubber neck of your balloon. The ciliary muscles help to control the amount of light entering your eyes.


The retina is in the back of your eye, which is represented by the inside back of your balloon. The retina supports your rods and cones. They collect information about light and color and send it to your brain.


Exercises


  1.      How does your eye work like a camera?
  2.      How can you tell if a lens is double convex?
  3.      What is the difference between convex and concave?
  4.      Can you give an example of an everyday object that has both a convex and a concave side?
  5.      How can you change the balloon to make it like a near-sighted eye?
  6.      How can you change the balloon to make it like a far-sighted eye?

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When light rays strikes a surface, part of the beam passes through the surface and the rest reflects back, like a ball bouncing on the ground. Where it bounces depends on how you throw the ball.


Have you ever looked into a pool of clear, still water and seen your own face? The surface of the water acts like a mirror and you can see your reflection. (In fact, before mirrors were invented, this was the only way people had to look at themselves.) If you were swimming below the surface, you’d still see your own face – the mirror effect works both ways.


Have you ever broken a pencil by sticking it into a glass of water?  The pencil isn’t really broken, but it sure looks like it!  What’s going on?


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Tall glass of water, with a red pensil inside.When a beam of light hits a different substance (like the water), the wavelength changes because the speed of the light changes. If you’re thinking that the speed of light is always constant, you’re right… in a vacuum like outer space between two reference frames.


But here on Earth, we can change the speed of light just by shining a light beam through different materials, like water, ice, blue sunglasses, smoke, fog, even our own atmosphere. How much the light speed slows down depends on what the material is made of.  Mineral oil and window glass will slow light down more than water, but not as much as diamonds do.


How broken the pencil appears also depends on where you look.  In some cases, you’ll see a perfectly intact pencil.  Other times, you’ll guess neither piece is touching.  This is why not everyone can see a rainbow after it rains.  The sun must be at a low angle in the sky, and also behind you for a rainbow to appear.  Most times, you aren’t at the right spot to see the entire arc touch the ground at both ends, either.


Lenses work to bend light the way you want them to. The simplest lenses are actually prisms.  Prisms unmix light into its different wavelengths. When light hits the prism, most of it passes through (a bit does reflect back) and changes speed.  Since the sunlight is made up of many different wavelengths (colors), each color gets bent by different amounts, and you see a rainbow out the other side.


Double Your Money

Here are a few neat activities that experiment with bending light, doubling your money, and breaking objects. Here’s what you do:


Materials:


  • glass jar (or water glass)
  • penny
  • eyeballs


Download Student Worksheet & Exercises


Here’s what you do:


1. Toss one coin into a water glass (pickle jars work great) and fill with an inch of water. Hold the glass up and find where you need to look to see TWO coins. Are the coins both the same size? Which one is the original coin? (Answer at the bottom of this page.)


2. Look through the top of the glass – how many coins are there now? What about when you look from the side?


3. Toss in a second coin – now how many are there?


4. Remove the coins turn out the lights. Shine a flashlight beam through the glass onto a nearby wall. (Hint – if this doesn’t work, try using a square clear container.) Stick a piece of paper on the wall where your light beam is and outline the beam with a pencil.


5. Shine the light at an angle up through the water so that it bounces off the surface of the water from underneath. Trace your new outline and compare… are they both the same shape?


6. Add a teaspoon of milk and stir gently. (No milk? Try sprinkling in a bit of white flour.) Now shine your flashlight through the container as you did in steps 4 and 5 and notice how the beam looks.


7. Use a round container instead of square… what’s the difference?


Answers:
1. The smaller coin is the reflection.
2. One coin when glanced from above, two from the side.
3. Four.
4. Beam is a circle.
5. Beam is an oval.
6. I can see the beam through the water!!
7. The round container distorts the beam, and the square container keeps the light beam straight. Both are fun!


The coin water trick is a neat way for kids to see how refraction works. In optics, refraction happens when light  waves travel from one medium with a certain refractive index (air, for example) to another medium which has a different refractive index (like water).  At the boundary between the two (where air meets water), the wave changes direction.


The wavelength increases or decreases but the frequency remains constant. When you sine light through a prism, the wavelength changes and you see a rainbow as the prism un-mixes white light into its different colors.The light wave changed direction when it traveled from air to glass, and then back to air again as it leaves the backside of the prism.


Did you try the pencil experiment? Did you notice how if you look at the pencil (placed at a slant) partially in the water, it appears to bend at the water’s surface? The light waves bend as they travel from water to air. To further complicate things, the way the eye received information about the position of the pencil actually makes the pencil to appear higher and the water shallower than they really are! Can you imagine how important this is for trying to spear a fish? The fish might appear to be in a different place, so you need to account for this when you take aim!


Click here for the Disappearing Beaker experiment!


Exercises


  1. When one coin is in the water, you can actually see two:  Are the coins both the same size? Which one is the original coin?
  2. In step 2 of the experiment: How many coins are there when viewed from the top of the glass? What about when you look from the side?
  3. What happened when you tossed in a second coin?
  4. How did your outlines compare?

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Ever play with a prism? When sunlight strikes the prism, it gets split into a rainbow of colors. Prisms un-mix the light into its different wavelengths (which you see as different colors). Diffraction gratings are tiny prisms stacked together.

When light passes through a diffraction grating, it splits (diffracts) the light into several beams traveling at different directions. If you've ever seen the 'iridescence' of a soap bubble, an insect shell, or on a pearl, you've seen nature's diffraction gratings.

Scientist use these things to split incoming light so they can figure out what fuels a distant star is burning. When hydrogen burns, it gives off light, but not in all the colors of the rainbow, only very specific colors in red and blue. It's like hydrogen's own personal fingerprint, or light signature.

Astronomers can split incoming light from a star using a spectrometer (you can build your own here) to figure out what the star is burning by matching up the different light signatures.

Materials:

  • feather
  • old CD or DVD

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Here's what you do: Take a feather and put it over an eye. Stare at a light bulb or a lit candle. You should see two or three flames and a rainbow X. Shine a flashlight on a CD and watch for rainbows. (Hint – the tiny “hairs” on the feather are acting like tiny prisms… take your homemade microscope to look at more of the feather in greater detail and see the tiny prisms for yourself!

What happens when you aim a laser through a diffraction grating? Here's what you do:

Materials:

 
Download Student Worksheet & Excercises

Exercises

  1. Which light source gave the most interesting results?
  2. What happens when you aim a laser beam through the diffraction grating?
  3. How is a CD different and the same as a diffraction grating?
  4. Why does the feather work?

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UV (ultra-violet) light is invisible, which means you need more than your naked eyeball to do experiments with it. Our sun gives off light in the UV. Too much exposure to the sun and you’ll get a sunburn from the UV rays.


There are many different experiments you can do with UV detecting materials, such as color-changing UV beads and UV nail polish.


Here are a few fun activities you can do with your UV detecting materials:


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Materials:


  • UV beads
  • sunblock
  • sunglasses
  • sunlight
  • clear plastic bag

Testing Sunblock You can test how effective your sunblock is at stopping harmful rays by slapping a coat of the lotion (or SPF-rated lip balm) on the beads and leaving them out in the sun for a minute. Bring the bead indoors and wipe off… did it change color? If so, then UV rays made it through the sunblock to your bead, and chances are that your sunblock isn’t doing it’s job. Does it matter how thick of a coat you layer on?


You can alternatively place the beads inside a plastic bag and coat the outside of the bag with sunblock. And is the sunblock really waterproof? Meaning that they still are white after dunking the beads underwater while sunblocked…?!


Different Times of Day Stick the UV beads outside and take note how bright the colors are in the morning, noon, and afternoon.  You’ll notice a big difference depending on the sun’s spot in the sky. Does it matter whether it’s sunny or cloudy?


Absorption and Filtration Test out different lenses and filters to see which block UV light.  Lay a handful of beads on the sidewalk and set a pair of sunglasses in top (lenses sitting on the layer of beads).  Did any UV light make it through?  If it didn’t, your beads should stay white. What other things can you test? (Hint: how about inside your car?)



 
Download Student Worksheet & Exercises


Why does that work? UV sensitive materials have a pigment inside that changes color when exposed to UV light from either the sun or lights that emit in the 350nm – 300nm wavelength.  (UVA is high-energy: 400-320nm, and UVB is low energy: 320-280nm).  If you have fluorescent black lights, use them.  (Do regular incandescent bulbs work? If not, you know they emit light outside the range of the beads!)


When light hits the pigment molecule, it absorbs the energy and actually expands asymmetrically (one end of the molecule expands more than the other).  Different expansion amounts will give you a different color. Although it’s a bit more complicated that that, you now have the basic idea. Your beads will change colors thousands of times before they wear out, so enjoy these super-inexpensive UV detectors!


Exercises


  1. What kinds of light sources didn’t work with the UV beads?
  2. Did your sun block really block out the UV rays?
  3. Which was the best protection against UV rays?

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spectrometer2Spectrometers are used in chemistry and astronomy to measure light. In astronomy, we can find out about distant stars without ever traveling to them, because we can split the incoming light from the stars into their colors (or energies) and “read” what they are made up of (what gases they are burning) and thus determine their what they are made of. In this experiment, you’ll make a simple cardboard spectrometer that will be able to detect all kinds of interesting things!


SPECIAL NOTE: This instrument is NOT for looking at the sun. Do NOT look directly at the sun. But you can point the tube at a sheet of paper that has the sun’s reflected light on it.


Usually you need a specialized piece of material called a diffraction grating to make this instrument work, but instead of buying a fancy one, why not use one from around your house?  Diffraction gratings are found in insect (including butterfly) wings, bird feathers, and plant leaves.  While I don’t recommend using living things for this experiment, I do suggest using an old CD.


CDs are like a mirror with circular tracks that are very close together. The light is spread into a spectrum when it hits the tracks, and each color bends a little more than the last. To see the rainbow spectrum, you’ve got to adjust the CD and the position of your eye so the angles line up correctly (actually, the angles are perpendicular).


You’re looking for a spectrum (the rainbow image at left) – this is what you’ll see right on the CD itself. Depending on what you look at (neon signs, chandeliers, incandescent bulbs, fluorescent bulbs, Christmas lights…), you’ll see different colors of the rainbow. For more about how diffraction gratings work, click here.


Materials:


  • old CD
  • razor
  • index card
  • cardboard tube

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Download Student Worksheet & Exercises


Find an old CD and a cardboard tube at least 10 inches long.  Cut a clean slit less than 1 mm wide in an index card or spare piece of cardboard and tape it to one end of the tube.  Align your tube with the slit horizontally, and on the top of the tube at the far end cut a viewing slot about one inch long and ½” inch wide.  Cut a second slot into the tube at a 45 degree angle from the vertical away from the viewing slot.  Insert the CD into this slot so that it reflects light coming through the slit into your eye (viewing slot).


Aim the 1 mm slit at a light source such as a fluorescent light, neon sign, sunset, light bulb, computer screen, television, night light, candle, fireplace… any light source you can find.  Look through the open hole at the light reflected off the compact disk (look for a rainbow in most cases) inside the cardboard tube.


Troubleshooting: This is a quick and easy way to bypass the need for an expensive diffraction grating. Use your spectrometer to look at computer screens, laptops, night lights, neon lights, candles, campfires, fluorescent lights, incandescent lights, LEDs, stoplights, street lights, and any other light sources you can find, even the moon through a telescope.


Exercises


  1. Name three more light sources that you think might work with your spectroscope.
  2.   Why is there a slit at the end of the tube instead of leaving it open?

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Polarization has to do with the direction of the light.  Think of a white picket fence – the kind that has space between each board.  The light can pass through the gaps int the fence but are blocked by the boards.  That’s exactly what a polarizer does.


When you have two polarizers, you can rotate one of the ‘fences’ a quarter turn so that virtually no light can get through – only little bits here and there where the gaps line up. Most of the way is blocked, though, which is what happens when you rotate the two pairs of sunglasses. Your sunglasses are polarizing filters, meaning that they only let light of a certain direction in. The view through the sunglasses is a bit dimmer, as less photons reach your eyeball.


Polarizing sunglasses also reduce darken the sky, which gives you more contrast between light and dark, sharpening the images. Photographers use polarizing filters to cut out glaring reflections.


Materials:


  • two pairs of polarized sunglasses
  • tape (the 3/4″ glossy clear kind works best – watch second video below)
  • window

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Here’s what you do: Stack two pairs of sunglasses on top of each other and look through both sets of lenses… now rotate one pair a quarter turn (90o).  The lenses should block the light completely at 90o and allow light to pass-through when aligned at 0o. These lenses allow some light to pass through but not all. When you rotate the lenses to 90o, you block out all visible light.


You use the “filter” principle in the kitchen. When you cook pasta, you use a filter (a strainer) to get the pasta out of the water. That’s what the sunglasses are doing – they are filtering out certain types of light. Rotating the lenses 90o to block out all light is like trying to strain your pasta with a mixing bowl. You don’t allow anything to pass through.


Astronomers use polarizing filters to look at the moon. Ever notice how bright the moon is during a full moon, and how dim it is near new moon? Using a rotating polarizing filter, astronomer can adjust the amount of light that enters into their eye.



 
Download Student Worksheet & Exercises


Advanced students: Download your Polarization lab here.


Exercises


  1. Why do you need two polarizers to block the light completely?
  2.  How can you tell if your sunglasses are polarized if you only have one pair?

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soapWhen you warm up leftovers, have you ever wondered why the microwave heats the food and not the plate? (Well, some plates, anyway.) It has to do with the way microwaves work.


Microwaves generate high energy electromagnetic waves that when aimed at water molecules, makes these molecules get super-excited and start bouncing around a lot.


We see this happen when we heat water in a pot on the stove. When you add energy to the pot (by turning on the stove), the water molecules start vibrating and moving around faster and faster the more heat you add. Eventually, when the pot of water boils, the top layer of molecules are so excited they vibrate free and float up as steam.


When you add more energy to the water molecule, either by using your stove top or your nearest microwave,  you cause those water molecules to vibrate faster. We detect these faster vibrations by measuring an increase in the temperature of the water molecules (or in the food containing water). Which is why it’s dangerous to heat anything not containing water in your microwave, as there’s nowhere for that energy to go, since the electromagnetic radiation is tuned to excite water molecules.


To explain this to younger kids (who might confuse radio waves with sounds waves) you might try this:


There’s light everywhere, some of which you can see (like rainbows) and others that you can’t see (like the infrared beam coming from your TV remote, or the UV rays from the sun that give you a sunburn). The microwave shoots invisible light beams at your food that are tuned to heat up the water molecule.


The microwave radiation emitted by the microwave oven can also excite other polarized molecules in addition to the water molecule, which is why some plates also get hot. The soap in this experiment below will show you how a bar of Ivory soap contains air, and that air contains water vapor which will get heated by the microwave radiation and expand. Are you ready?


Here’s what you need:


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  • bar of Ivory soap
  • microwave (not a new or expensive one)
  • plate (optional)

The following experiment is a quick example of this principle using a naked bar of Ivory soap. The trick is to use Ivory, which contains an unusually high amount of air. Since air contains water moisture, Ivory also has water hidden inside the bar of soap. The microwave will excite the water molecules and your kids will never look at the soap the same way again.



 
Download Student Worksheet & Exercises


Toss a naked bar of Ivory soap onto a glass or ceramic plate and stick it into the microwave (don’t use a new or expensive microwave!) on HIGH for 2-3 minutes. Watch intently and remove when it reaches a “maximum”. Be careful when you touch it after taking it out of the microwave oven – it may still hold steam inside. You can still use the soap and the microwave after this experiment!


Note: Scientists refer to ‘light’ as the visible part of the electromagnetic spectrum, where radio and microwaves are lower energy and frequency than light (and the height of the wave can be the size of a football field). Gamma rays and x-rays are higher energy and frequency than light (these tend to pass through mirrors rather than bounce off them. More on that in Unit 9.)


Exercises


  1.  What is it in your food (and the soap) that is actually heated by the microwave?
  2.  How does a microwave heat things?
  3.  Touch the soap after it has been allowed to cool for a few minutes and record your observations.

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Do you have thick or thin hair? Let’s find out using a laser to measure the width of your hair and a little knowledge about diffraction properties of light. (Since were using lasers, make sure you’re not pointing a laser at anyone, any animal, or at a reflective surface.)


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Light is also called “electromagnetic radiation”, and it can move through space as a wave, which makes it possible for light to interact in surprising ways through interference and diffraction. This is especially amazing to watch when we use a concentrated beam of light, like a laser.


If we shine a flashlight on the wall, you’ll see the flashlight doesn’t light up the wall evenly. In fact, you’ll probably see lots of light with a scattering of dark spots, showing some parts of the wall more illuminated than the rest. What happens if you shine a laser on the wall? You’ll see a single dot on the wall.


In this experiment, we used a laser to discover how interference and diffraction work. We can use diffraction to accurately measure very small objects, like the spacing between tracks on a CD, the size of bacteria, and also the thickness of human hair.


Here’s what you need:


  • a strand of hair
  • laser pointer
  • tape
  • calculator
  • ruler
  • paper
  • clothespin

WARNING! The beam of laser pointers is so concentrated that it can cause real damage to your retina if you look into the beam either directly or by reflection from a shiny object. Do NOT shine them at others or yourself.



Download Student Worksheet & Exercises


  1. Tape the hair across the open end of the laser pointer (the side where the beam emits from)
  2. Measure 1 meter (3.28 feet) from the wall and put your laser right at the 1 meter mark.
  3. Clip the clothespin onto the laser so that it keeps the laser on.
  4. Where the mark shows up on the wall, tape a sheet of paper.
  5. Mark on the sheet of paper the distance between the first two black lines on either side of the center of the beam.
  6. Use your ruler to measure (in centimeters) to measure the distance between the two marks you made on the paper. Convert your number from centimeters to meters (For me, 8 cm = 0.08 meters.)
  7. Read the wavelength from your laser and write it down. It will be in “nm” for nanometers. My laser was 650 nm, which means 0.000 000 650 meters.
  8. Calculate the hair width by multiplying the laser wavelength by the distance to the wall (1 meter), and divide that number by the distance between the dark lines. Multiply your answer by 2 to get your final answer. Here’s the equation:

Hair width = [(Laser Wavelength) x (Distance to Wall)]  / [ (Distance between dark lines) x 0.5 ]


In the video:


  • wavelength was 650 nm = 0.000 000 650 meters
  • distance from the wall was 1 meter
  • the distance between the dark lines was 8 cm = 0.08 m

Using a calculator, this gives a hair width of 0.000 0162 5meters, or 16.25 micrometers (or 0.000 629 921 26 inches). Now you try!


What’s Going On?


The image here shows how two different waves of light interact with each other. When a single light wave hits a wall, it shows up as a bright spot (you wouldn’t see a “wave”, because we’re talking about light).


When both waves hit the wall, if they are “in phase”, they add together (called constructive interference), and you see an even brighter spot on the wall.


If the waves are “out of phase”, then they subtract from each other (called “destructive interference”) and you’d see a dark spot. In advanced labs, like in college, you’ll learn how to create a phase shift between two waves by adding extra travel length to one of the waves along its path.


So why are there dark lines along the light line when you shine your laser on the hair in this experiment? It has to do with something called “interference”.


One kind of interference happens when light goes through a small and narrow opening, called a slit. When light travels through a single slit, it can interfere with itself. This is called diffraction.


When light travels through one of two slits, it can interfere with light traveling through the other slit, a lot like how water ripples can interfere with each other as they travel over the surface of water.


If you’re wondering where the slit is in this experiment, you’re right! There’s no narrow opening that light it traveling through. in fact, light appears to be traveling around something, doesn’t it? Light from the laser must travel around the hair to get to the wall. The way that light does this has to do with Babinet’s Principle, which relates the opposite of a slit (a small object the size of a slit) to the slit itself.


It turns out amazingly enough that when light hits a small solid object, like a piece of hair, it creates the same interference pattern as if the hair were replaced with a hole of the same size. This idea is called Babinet’s Principle.


By measuring the diffraction pattern on the wall, we can measure the width of a small object that the light had to travel around by measuring the dark lanes in the spot on the wall. In our lab, the small object is a piece of your hair!


Questions to Ask:


  1. What would happen to the diffraction pattern if the hair width was smaller?
  2. Using this experiment, how can you tell if the hair is round or oval?
  3. If we redid these experiments with a different color laser instead of red, what changes would you have needed to make?
  4. How can you modify this experiment to measure the width of a track on a CD? Does the track width change as a function of location on the CD? If so, is it larger or smaller near the outside?

Exercises 


  1.  Which light source gave the most interesting results?
  2. What happens when you aim a laser beam through the diffraction grating?
  3. How is a CD different and the same as a diffraction grating?
  4. Why does the feather work?

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Did you know that you can use a laser to see tiny paramecia in pond water? We’re going to build a simple laser microscope that will shine through a single drop of water and project shadows on a wall or ceiling for us to study.


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Here’s how it works: by shining a laser though a drop of water, we can see the shadows of objects inside the water. It’s like playing shadow puppets, only we’re using a highly concentrated laser beam instead of a flashlight.


If you’re wondering how a narrow laser beam spreads out to cover a wall, it has to do with the shape of the water droplet. Water has surface tension, which makes the water want to curl into a ball shape. But because water’s heavy, the ball stretches a little. This makes the water a tear-drop shape, which makes it act like a convex lens, which magnifies the light and spreads it out:


Here’s how to make your own laser microscope:


Materials:


  • red or green laser (watch video for laser tips)
  • large paperclip
  • rubber band
  • stack of books
  • white wall
  • pond water sample (or make your own from a cup of water with dead grass that’s been sitting for a week on the windowsill)


Download Student Worksheet & Exercises


Exercises


  1. Does this work with other clear liquids?
  2.   What kind of lens occurs if you change the amount of surface tension by using soapy water instead?
  3.   Does the temperature of the water matter? What about a piece of ice?
  4.  Does this work with a flashlight instead of a laser?
  5.  Do lasers hurt your eyes? How?

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By using lenses and mirrors, you can bounce, shift, reflect, shatter, and split a laser beam. Since the laser beam is so narrow and focused, you’ll be able to see several reflections before it fades away from scatter. Make sure you complete the Laser Basics experiment first before working with this experiment.


You’ll need to make your beam visible for this experiment to really work.  There are several different ways you can do this:


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1. Take your laser with you into a steamy bathroom (which has mirrors!) after a hot shower.  The tiny droplets of water in the steam will illuminate your beam. (Psst! Don’t get the laser wet!)


2. If you have carpet, shine your laser under the bed while stomping the floor with your hand.  The small particles (dust bunnies?) float up so you can see the beam. Some parents aren’t going to like this idea, sooo….


3. Drop a chunk of dry ice (use gloves!) into a bowl of water and use the fog to illuminate the beam.  The drawback to this is that you need to keep adding more dry ice as it sublimates (goes from solid to gas) and replacing the water (when it gets too cold to produce fog).


Materials:


  • large paper clips
  • brass fastener
  • index card
  • small mirrors (mosaic-type work well)


Download Student Worksheet & Exercises


Here’s what you do: Open up each paper clip into the “L” shape.  Insert a brass fastener into one U-shape leg and punch it through the card.  Hot glue (or tape) one square mirror to the other end of the L-bracket.  Your mirror should be upright and able to rotate.  Do this with each mirror.  (You can alternatively mount each mirror to a one-inch wooden cube as shown in the video.)


Turn on the laser adjust the mirrors to aim the beam onto the next mirror, and the next!  Turn down the lights first and use any one of the methods mentioned above to make your laser beam visible.


What’s happening? The mirrors are bouncing the laser beam to each other, and the effect shows up when you dim the lights and add fog or dust particles to help illuminate the beam.  A laser beam is a highly focused beam of light, and you can direct that light and bounce it off mirrors!


Why can’t I see the beam normally? The reason you can’t see the laser beam without the help of a steamy room, dirty carpet, or fog machine is that your eyes are tuned for green light, not red (which is why you can see the beam from a green laser at night).


Exercises


  1.   The word LASER is actually an acronym. What does it stand for?
  2. What type of laser did we use in our experiment?
  3. Why can’t we see the laser beams without the help of steam, dirty carpet, etc.?

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Crazy Remote

Want to have some quick science fun with your TV remote? Then try this experiment next time you flip on the tube:


Materials:


  • metal frying pan or cookie sheet
  • TV remote control
  • plastic sheet

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Making IR Visible to the Human Eye

Infra-red light is in the part of the electromagnetic spectrum that isn’t usually visible to human eyes, but using this nifty trick, you will easily be able to see the IR signal from your TV remote, remote-controller for an RC car, and more!


  • TV remote control
  • camera (video or still camera)



 
Download Student Worksheet & Exercises


Exercises


  1. Look over your data table. What kinds of objects (plastic, metal, natural, etc.) allow infrared light to pass through them?
  2.  Why does the camera work in making the infrared light visible?

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This is a super-cool and ultra-simple circuit experiment that shows you how a CdS (cadmium sulfide cell) works. A CdS cell is a special kind of resistor called a photoresistor, which is sensitive to light.


A resistor limits the amount of current (electricity) that flows through it, and since this one is light-sensitive, it will allow different amounts of current through depends on how much light it “sees”.


Photoresistors are very inexpensive light detectors, and you’ll find them in cameras, street lights, clock radios, robotics, and more. We’re going to play with one and find out how to detect light using a simple series circuit.


Materials:


  • AA battery case with batteries
  • one CdS cell
  • three alligator wires
  • LED (any color and type)

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Download Student Worksheet & Exercises


Turn this into a super-cool burglar alarm!


Exercises


  1. How is a CdS cell like a switch? How is it not like a switch?
  2. When is the LED the brightest?
  3. How could you use this as a burglar alarm?

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When you warm up leftovers, have you ever wondered why the microwave heats the food and not the plate? (Well, some plates, anyway.) It has to do with the way microwave ovens work.


Microwave ovens use dielectric heating (or high frequency heating) to heat your food. Basically, the microwave oven shoots light beams that are tuned to excite the water molecule. Foods that contain water will step up a notch in energy levels as heat. (The microwave radiation can also excite other polarized molecules in addition to the water molecule, which is why some plates also get hot.)


One of the biggest challenges with measuring the speed of light is that the photons move fast… too fast to watch with our eyeballs.  So instead, we’re going to watch the effects of microwave light and base our measurements on the effects the light has on different kinds of food.  Microwaves use light with a wavelength of 0.01 to 10 cm (that’s ‘microwave’ part of the electromagnetic spectrum). When designing your experiment, you’ll need to pay close attention to the finer details such as the frequency of your microwave oven (found inside the door), where you place your food inside the oven, and how long you leave it in for.


Materials:


  • chocolate bar (extra-large bars work best)
  • microwave
  • plate
  • ruler
  • calculator
  • pencil and paper

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Download Student Worksheet & Exercises


First, you’ll need to find the ‘hot spots’ in your microwave.  Remove the turntable from your microwave and place a naked bar of chocolate on a plate inside the microwave.  Make sure the chocolate bar is the BIG size – you’ll need at least 7 inches of chocolate for this to work.  Turn the microwave on and wait a few minutes until you see small parts of the chocolate bar start to bubble up, and then quickly open the door (it will start to smoke if you leave it in too long).  Look carefully at the chocolate bar without touching the surface… you are looking for TWO hotspots, not just one – they will look like small volcano eruptions on the surface of the bar.  If you don’t have two, grab a fresh plate (you can reuse the chocolate bar) and try again, changing the location of the place inside the microwave.  You’re looking for the place where the microwave light hits the chocolate bar in two spots so you can measure the distance between the spots. Those places are the places where the microwave light wave hits the chocolate.


Open up the door or look on the back of your microwave for the technical specifications.  You’re looking for a frequency in the 2,000-3,000 MHz range, usually about 2450 MHz.  Write this number down on a sheet of paper – this tells you the microwave radiation frequency that the oven produces, and will be used for calculating the speed of light. (Be sure to run your experiment a few times before taking actual data, to be sure you’ve got everything running smoothly.  Have someone snap a photo of you getting ready to test, just for fun!)


When you’re ready, pop in the first food type on a plate (without the turntable!) into the best spot in the microwave, and turn it on.  Remove when both hotspots form, and being careful not to touch the surface of the food, measure the center-to-center distance using your ruler in centimeters.


TIP: If you’re using mini-marshmallows or chocolate chips (or other smaller foods), you’ll need to spread them out in an even layer on your plate so you don’t miss a spot that could be your hotspot!


How to Calculate the Speed of Light from your Data

Note that when you measure the distance between the hotspots, you are only measuring the peak-to-peak distance of the wave… which means you’re only measuring half of the wave.  We’ll multiply this number by two to get the actual length of the wave (wavelength).  If you’re using centimeters, you’ll also need to convert those to meters by dividing by 100.


So, if you measure 6.2 cm between your hotspots, and you want to calculate the speed of light and compare to the published value which is in meters per second, here’s what you do:


2,450 MHz is really 2,450,000,000 Hz or 2,450,000,000 cycles per 1 second


Find the length of the wave (in cm): 2 * 6.2 cm = (12.4 cm) /(100 cm/m) = 0.124 meters


Multiply the wavelength by the microwave oven frequency:


0.124 m * 2,450,000,000 Hz = 303,800,000 m/s


Published value for light speed is 299,792,458 m/s = 186,282 miles/second = 670,616,629 mph


Click here to learn how to turn this project into a Science Fair Project you can enter!


Exercises


  1. What would happen if you used cheese instead of chocolate?
  2. Does it matter where in the microwave the chocolate is located? Does placement of the chocolate affect the wavelength?
  3. Can you explain what the burn marks on the chocolate bar are from?

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Second Law of Thermodynamics: Heat flows from hot to cold. Heat is the movement of thermal energy from one object to another. Heat can only flow from an object of a higher temperature to an object of a lower temperature. Heat can be transferred from one object to another through conduction, convection and radiation.


Temperature is basically a speedometer for molecules. The faster they are wiggling and jiggling, the higher the temperature and the higher the thermal energy that object has. Your skin, mouth and tongue are antennas which can sense thermal energy. When an object absorbs heat it does not necessarily change temperature.


Materials: hot cup of cocoa


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Leave a cup of hot coffee out on a cold morning. Does the coffee get warmer or cooler over time? Your coffee gets cooler, as heat travels from the coffee to the cool morning.


Learn more about this scientific principle in Unit 13.



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First Law of Thermodynamics: Energy is conserved. Energy is the ability to do work. Work is moving something against a force over a distance. Force is a push or a pull, like pulling a wagon or pushing a car. Energy cannot be created or destroyed, but can be transformed.


Materials: ball, string


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Roll a ball down a hill. The amount of energy the ball had while at rest at the top of the hill (potential energy) turns into kinetic energy while it zips to the bottom.


You can also swing on a swing and see this effect happen over and over again: when you’re at the highest point of your swing, you have the highest potential energy but zero kinetic energy (your speed momentarily goes to zero as you change direction). At the lowest point of your swing (when you’re moving the fastest), all your potential energy has turned into kinetic energy. Why do you eventually stop? The reason you eventually slow down and stop instead of swinging back and forth forever is that you have air resistance and friction where the chain is suspended from the bar.


Learn more about this scientific principle in Unit 4 and Unit 5 and Unit 13.
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This project is for advanced students.This Stirling Engine project is a very advanced project that requires skill, patience, and troubleshooting persistence in order to work right.  Find yourself a seasoned Do-It-Yourself type of adult (someone who loves to fix things or tinker in the garage) before you start working on this project,  or you’ll go crazy with nit-picky things that will keep the engine from operating correctly.  This makes an excellent project for a weekend.


Developed in 1810s, this engine was widely used because it was quiet and could use almost anything as a heat source. This kind of heat engine squishes and expands air to do mechanical work. There’s a heat source (the candle) that adds energy to your system, and the result is your shaft spins (CD).


This engine converts the expansion and compression of gases into something that moves (the piston) and rotates (the crankshaft). Your car engine uses internal combustion to generate the expansion and compression cycles, whereas this heat engine has an external heat source.


This experiment is great for chemistry students learning about Charles’s Law, which is also known as the Law of Volumes, which describes how gases tend to expand when they are heated and can be mathematically written like this:



where V = volume, and T = temperature. So as temperature increases, volume also increases. In the experiment you’re about to do, you will see how heating the air causes the diaphragm to expand which turns the crank.


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Here’s what you need:


  • three soda cans
  • old inner tube from a bike wheel
  • super glue and instrant dry
  • electrical wire (3- conductor solid wire)
  • 3 old CDs
  • one balloon
  • penny
  • nylon bushing (from hardware store)
  • alcohol burner (you can build one out of soda cans or Sterno canned heat)
  • fishing line (15lb. test or similar)
  • pack of steel wool
  • drill with 1/16″ bit
  • pliers
  • scissors
  • razor
  • wire cutters
  • electrical tape
  • push pin
  • permanent marker
  • Swiss army knife (with can opener option)
  • template

The Stirling heat engine is very different from the engine in your car.  When Robert Stirling invented the first Stirling engine in 1816, he thought it would be much more efficient than a gasoline or diesel engine. However, these heat engines are used only where quiet engines are required, such as in submarines or in generators for sailboats.



Download Student Worksheet & Exercises


Here’s how a Stirling engine is different from the internal-combustion engine inside your car. For example, the gases inside a Stirling engine never leave the engine because it’s an external combustion engine. This heat engine does not have exhaust valves as there are no explosions taking place, which is why Stirling engines are quieter. They use heat sources that are outside the engine, which opens up a wide range of possibilities from candles to solar energy to gasoline to the heat from your hand.


There are lots of different styles of Stirling engines. In this project, we’ll learn about the Stirling cycle and see how to build a simple heat engine out of soda cans.  The main idea behind the Stirling engine is that a certain volume of gas remains inside the engine and gets heated and cooled, causing the crankshaft to turn. The gases never leave the container (remember – no exhaust valves!), so the gas is constantly changing temperature and pressure to do useful work.  When the pressure increases, the temperature also increases. And when the temperature of the gases decreases, the pressure also goes down. (How pressure and temperature are linked together is called the “Ideal Gas Law”.)


Some Stirling engines have two pistons where one is heated by an external heat source like a candle and the other is cooled by external cooling like ice. Other displacer-type Stirling engines has one piston and a displacer. The displacer controls when the gas is heated and cooled.


In order to work, the heat engine needs a temperature difference between the top and bottom of the cylinder. Some Stirling engines are so sensitive that you can simply use the temperature difference between the air around you and the heat from your hand. Our Stirling engine uses temperature difference between the heat from a candle and ice water.


The balloon at the top of the soda can is actually the ‘power piston’ and is sealed to the can.  It bulges up as the gas expands. The displacer is the steel wool in the engine which controls the temperature of the air and allows air to move between the heated and cooled sections of the engine.


When the displacer is near the top of the cylinder, most of the gas inside the engine is heated by the heat source and gas expands (the pressure  builds inside the engine, forcing the balloon piston up). When the displacer is near the bottom of the cylinder, most of the gas inside the engine cools and contracts. (the pressure decreases and the balloon piston is allowed to contract).


Since the heat engine only makes power during the first part of the cycle, there’s only two ways to increase the power output: you can either increase the temperature of the gas (by using a hotter heat source), or by cooling the gases further by removing more heat (using something colder than ice).


Since the heat source is outside the cylinder, there’s a delay for the engine to respond to an increase or decrease in the heat or cooling source. If you use only water to cool your heat engine and suddenly pop an ice cube in the water, you’ll notice that it takes five to fifteen seconds to increase speed. The reason is because it takes time for the additional heat (or removal of heat by cooling) to make it through the cylinder walls and into the gas inside the engine. So Stirling engines can’t change the power output quickly. This would be a problem when getting on the freeway!


In recent years, scientists have looked to this engine again as a possibility, as gas and oil prices rise, and exhaust and pollutants are a concern for the environment. Since you can use nearly any heat source, it’s easy to pick one that has a low-fume output to power this engine. Scientists and engineers are working on a model that uses a Stirling engine in conjunction with an internal-combustion engine in a hybrid vehicle… maybe we’ll see these on the road someday!


Exercises


  1. What is the primary input of energy for the Stirling engine?
  2.  As Pressure increases in a gas, what happens to temperature?
    1. It increases
    2. Nothing
    3. It decreases
    4. It increases, then decreases
  3. What is the primary output of the Stirling engine?

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Heat is transferred by radiation through electromagnetic waves. Remember, when we talked about waves and energy? Well, heat can be transferred by electromagnetic waves. Energy is vibrating particles that can move by waves over distances right? Well, if those vibrating particles hit something and cause those particles to vibrate (causing them to move faster/increasing their temperature) then heat is being transferred by waves. The type of electromagnetic waves that transfer heat are infra-red waves. The Sun transfers heat to the Earth through radiation.


If you hold your hand near (not touching) an incandescent light bulb until you can feel heat on your hand, you’ll be able to understand how light can travel like a wave. This type of heat transfer is called radiation.


Now don’t panic. This is not a bad kind of radiation like you get from x-rays. It’s infra-red radiation. Heat was transferred from the light bulb to your hand. The energy from the light bulb resonated the molecules in your hand. (Remember resonance?) Since the molecules in your hand are now moving faster, they have increased in temperature. Heat has been transferred! In fact, an incandescent light bulb gives off more energy in heat then it does in light. They are not very energy efficient.


Now, if it’s a hot sunny day outside, are you better off wearing a black or white shirt if you want to stay cool? This experiment will help you figure this out:


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You need:


  • 2 ice cubes, about the same size.
  • A white piece of paper
  • A black piece of paper
  • A sunny day


 


Download Student Worksheet & Exercises


1. Put the two pieces of paper on a sunny part of the sidewalk.


2. Put the ice cubes in the middle of the pieces of paper.


3. Wait.


What you should eventually see, is that the ice cube on the black sheet of paper melts faster then the ice cube on the white sheet. Dark colors absorb more infra-red radiation then light colors. Heat is transferred by radiation easier to something dark colored then it is to something light colored and so the black paper increased in temperature more then the white paper.


So, to answer the shirt question, a white shirt reflects more infra-red radiation so you’ll stay cooler. White walls, white cars, white seats, white shorts, white houses, etc. all act like mirrors for infra-red (IR) radiation. Which is why you can aim your TV remote at a white wall and still turn on the TV. Simply pretend the wall is a mirror (so you can get the angle right) and bounce the beam off the wall before it gets to your TV. It looks like magic!


Click over to this experiment to learn how to make Liquid Crystals.


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This experiment is for advanced students. Did you know that eating a single peanut will power your brain for 30 minutes? The energy in a peanut also produces a large amount of energy when burned in a flame, which can be used to boil water and measure energy.


Peanuts are part of the bean family, and actually grows underground (not from trees like almonds or walnuts).  In addition to your lunchtime sandwich, peanuts are also used in woman’s cosmetics, certain plastics, paint dyes, and also when making nitroglycerin.


What makes up a peanut?  Inside you’ll find a lot of fats (most of them unsaturated) and  antioxidants (as much as found in berries).  And more than half of all the peanuts Americans eat are produced in Alabama. We’re going to learn how to release the energy inside a peanut and how to measure it.


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Materials:


  • raw peanuts
  • chemistry stand with glass test tube and holder (watch video)
  • flameproof surface (large ceramic tile or cookie sheet)
  • paper clip
  • alcohol burner or candle with adult help
  • fire extinguisher


Download Student Worksheet & Exercises


What’s Going On? There’s chemical energy stored inside a peanut, which gets transformed into heat energy when you ignite it. This heat flows to raise the water temperature, which you can measure with a thermometer.  You should find that your peanut contains 1500-2100 calories of energy!  Now don’t panic…  this isn’t the same as the number of calories you’re allowed to eat in a day.  The average person aims to eat around 2,000 Calories (with a capital “C”).  1 Calorie = 1,000 calories.  So each peanut contains 1.5-2.1 Calories of energy (the kind you eat in a day). Do you see the difference?


But wait… did all the energy from the peanut go straight to the water, or did it leak somewhere else, too?  The heat actually warmed up the nearby air, too, but we weren’t able to measure that. If you were a food scientist, you’d use a nifty little device known as a bomb calorimeter to measure calorie content.  It’s basically a well-insulated, well-sealed device that catches nearly all the energy and flows it to the water, so you get a much more accurate temperature reading. (Using a bomb calorimeter, you’d get 6.1-6.8 Calories of energy from one peanut!)


How do you calculate the calories from a peanut?

Let’s take an example measurement.  Suppose you measured a temperature increase from 20 °C to 100 °C for 10 grams of water, and boiled off 2 grams.  We need to break this problem down into two parts – the first part deals with the temperature increase, and the second deals with the water escaping as vapor.


The first basic heat equation is this:


Q = m c T


Q is the heat flow (in calories)
m is the mass of the water (in grams)
c is the specific heat of water (which is 1 degree per calorie per gram)
and T is the temperature change (in degrees)


So our equation becomes: Q = 10 * 1 * 80 = 800 calories.


If you measured that we boiled off 2 grams of water, your equation would look like this for heat energy:


Q = L m


L is the latent heat of vaporization of water (L= 540 calories per gram)
m is the mass of the water (in grams)


So our equation becomes: Q = 540 * 2 = 1080 calories.


The total energy needed is the sum of these two:


Q = 800 calories + 1080 calories = 1880 calories.


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There are lots of different kids of heat engines, from stirling engines to big jet turbines to the engine in your car. They all use clever ways to convert a temperature difference into motion.


Remember that the molecules in steam move around a lot faster than in an ice cube. So when we stick hot steam in a container, we can blow off the lid (used with pistons in a steam engine). or we can put a fan blade in hot steam, and since the molecules move around a lot, they start bouncing off the blade and cause it to rotate (as in a turbine). Or we can seal up hot steam in a container and punch a tiny hole out one end (to get a rocket).


One of the first heat engines was dreamed up by Hero of Alexandria called the aeolipile. The steam is enclosed in a vessel and allowed to jet out two (or more) pipes. Although we’re not sure if his invention ever made it off the drawing board, we do know how to make one for pure educational (and entertainment) purposes.  Are you ready to have fun?


THIS EXPERIMENT USES FIRE AND STEAM…GET ADULT HELP BEFORE YOU OPERATE THE ENGINE.

Here’s what you do:


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Materials:


  • soda can
  • fishing line
  • razor
  • stand
  • drill or large nail and hammer
  • adult help
  • candle


IMPORTANT NOTE: As the water boils, your can will spin. The hot steam shoots out the sides, so take care not to get burned. As the can spins, it may wobble and shake, especially if it’s off-center.  Be careful not to get shot with boiling water!!


What’s going on? When the water boils, the molecules inside are turning into hot steam and moving very quickly, bouncing off the can and out the pipes. Rockets and balloons use this same principle – the pressurized air shoots out the open end and the balloon (or rocket)  moves in the opposite direct.  Newton’s third law in motion! The two jets at an angle work together to spin the can.


  1. Do you think the size of the hole matters?
  2. Does it matter how many candles you use?
  3. What if you used four holes instead of two? Six? Twenty?
  4. Are beer cans better?

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The Drinking Bird is a classic science toy that dips its head up and down into a glass of water. It’s filled with a liquid called methylene chloride, and the head is covered with red felt that gets wet when it drinks. But how does it work? Is it perpetual motion?


Let’s take a look at what’s going on with the bird, why it works, and how we’re going to modify it so it can run on its own without using any water at all!


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The bird needs a temperature difference between the head and tail. Since water needs heat in order to evaporate, the head cools as the water evaporates.  This temperature decrease lowers the pressure inside the head, pushing liquid up the inner tube. With more liquid (weight in the head), the bird tips over. The bird wets its own head to start this cycle again.


The trick to making this work is that when the bird is tipped over, the vapor from the bottom moves up the tube to equalize the pressure in both sides, or he’d stay put with his head in the cup.  Sadly, this isn’t perpetual motion because as soon as you take away the water, the cycle stops. It also stops if you enclose the bird in a jar so water can longer evaporate after awhile. Do you think this bird can work in a rainstorm? In Antarctica?


What’s so special about the liquid? Methylene chloride is made of carbon, hydrogen, and chlorine atoms. It’s barely liquid at room temperature, having a boiling point of 103.5° F, so it evaporates quite easily. It does have a high vapor pressure (6.7 psi), meaning that the molecules on the liquid surface leave (evaporate) and raise the pressure until the amount of molecules evaporating is equal to the amount being shoved back in the liquid (condensed) by its own pressure. (For comparison, water’s vapor pressure is only 0.4 psi).


Note that the vapor pressure will change with temperature changes. The vapor pressure goes up when the temperature goes up. Since the wet head is cooler than the tail, the vapor pressure at the top is less than at the bottom, which pushes the liquid up the tube.


It really does matter whether the bird is operating in Arizona or the Amazon.  The bird will dip more times per minute in a desert than a rain forest!


Let’s find out how to modify the bird so it’s entirely solar-powered… meaning that you don’t have to remember to keep the cup filled with water.  Here’s what you need:


  • drinking bird
  • silver or white spray paint
  • black spray paint
  • razor
  • mug of hot water
  • sunlight or incandescent light


 
Download Student Worksheet & Exercises


In this modification, you completely eliminated the water and converted the bird to solar, using the heat of the sun to power the bird. Now your bird bobs as long as you have sunlight!


How does that work? Since the bottom of the bird is now black, and black absorbs more energy and heats up the tail of the bird. Since the tail section is warmer, the pressure goes up and the liquid gets pushed up the tube. By covering the head with white (or silver) paint, you are reflecting most of the energy so it remains cool. Remember that white surfaces act like mirrors to IR light (which is what heat energy is).


Questions to Ask: Does it work better with hot or cold water? Does it work in an enclosed space, such as an inverted aquarium? On a rainy day or dry? In the fridge or heating pad?


Exercises Answer the questions below:


  1. Where does most of the energy on earth come from?
    1. Underground
    2. The sun
    3. The oceans
  2. What is one way that we use energy from the sun?
  3. What is the process by which the liquid is being heated inside the bird?
    1. Precipitation
    2. Pressure
    3. Evaporation
    4. Transpiration

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Every time I’m served a hot bowl of soup or a cup of coffee with cream I love to sit and watch the convection currents. You may look a little silly staring at your soup but give it a try sometime!


Convection is a little more difficult to understand than conduction. Heat is transferred by convection by moving currents of a gas or a liquid. Hot air rises and cold air sinks. It turns out, that hot liquid rises and cold liquid sinks as well.


Room heaters generally work by convection. The heater heats up the air next to it which makes the air rise. As the air rises it pulls more air in to take its place which then heats up that air and makes it rise as well. As the air get close to the ceiling it may cool. The cooler air sinks to the ground and gets pulled back near the heat source. There it heats up again and rises back up.


This movement of heating and cooling air is convection and it can eventually heat an entire room or a pot of soup. This experiment should allow you to see convection currents.


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You need:


  • A pot
  • A stove with adult help
  • Pepper
  • Ice cubes
  • Food Coloring (optional)


1. Fill the pot about half way with water.


2. Put about a teaspoon of pepper into the water.


3. Put the pot on the stove and turn on the stove (be careful please).


4. Watch as the water increases in temperature. You should see the pepper moving. The pepper is moving due to the convection currents. If you look carefully you many notice pepper rising and falling.


5. Put an ice cube into the water and see what happens. You should see the pepper at the top of the water move towards the ice cube and then sink to the bottom of the pot as it is carried by the convection currents.


6. Just for fun, put another ice cube into the water, but this time drop a bit of food coloring on the ice cube. You should see the food coloring sink quickly to the bottom and spread out as it is carried by the convection currents.


Did you see the convection currents? Hot water rising in some areas of the pot and cold water sinking in other areas of the pot carried the pepper and food coloring throughout the pot. This rising and sinking transferred heat through all the water causing the water in the pot to increase in temperature.


Heat was transferred from the flame of the stove to the water by convection. More accurately, heat was transferred from the flame of the stove to the metal of the pot by conduction and then from the metal of the pot throughout the water through convection.


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If you’ve ever had a shot, you know how cold your arm feels when the nurse swipes it with a pad of alcohol. What happened there? Well, alcohol is a liquid with a fairly low boiling point. In other words, it goes from liquid to gas at a fairly low temperature. The heat from your body is more then enough to make the alcohol evaporate.


As the alcohol went from liquid to gas it sucked heat out of your body. For things to evaporate, they must suck in heat from their surroundings to change state. As the alcohol evaporated you felt cold where the alcohol was. This is because the alcohol was sucking the heat energy out of that part of your body (heat was being transferred by conduction) and causing that part of your body to decrease in temperature.


As things condense (go from gas to liquid state) the opposite happens. Things release heat as they change to a liquid state. The water gas that condenses on your mirror actually increases the temperature of that mirror. This is why steam can be quite dangerous. Not only is it hot to begin with, but if it condenses on your skin it releases even more heat which can give you severe burns. Objects absorb heat when they melt and evaporate/boil. Objects release heat when they freeze and condense.


Do you remember when I said that heat and temperature are two different things? Heat is energy – it is thermal energy. It can be transferred from one object to another by conduction, convection, and radiation. We’re now going to explore heat capacity and specific heat. Here’s what you do:


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You Need:


  • Balloon
  • Water
  • Matches, candle, and adult help
  • Sink


Download Student Worksheet & Exercises


1. Put the balloon under the faucet and fill the balloon with some water.


2. Now blow up the balloon and tie it, leaving the water in the balloon. You should have an inflated balloon with a tablespoon or two of water at the bottom of it.


3. Carefully light the match or candle and hold it under the part of the balloon where there is water.


4. Feel free to hold it there for a couple of seconds. You might want to do this over a sink or outside just in case!


So why didn’t the balloon pop? The water absorbed the heat! The water actually absorbed the heat coming from the match so that the rubber of the balloon couldn’t heat up enough to melt and pop the balloon. Water is very good at absorbing heat without increasing in temperature which is why it is used in car radiators and nuclear power plants. Whenever someone wants to keep something from getting too hot, they will often use water to absorb the heat.


Think of a dry sponge. Now imagine putting that sponge under a slowly running faucet. The sponge would continue to fill with water until it reached a certain point and then water started to drip from it. You could say that the sponge had a water capacity. It could hold so much water before it couldn’t hold any more and the water started dripping out. Heat capacity is similar. Heat capacity is how much heat an object can absorb before it increases in temperature. This is also referred to as specific heat. Specific heat is how much heat energy a mass of a material must absorb before it increases 1°C.


Exercises Answer the questions below:


  1. What is specific heat?
    1. The specific amount of heat any object can hold
    2. The amount of energy required to raise the temperature of an object by 1 degree Celsius.
    3. The type of heat energy an object emits
    4. The speed of a compound’s molecules at room temperature
  2. Name two types of heat energy:
  3. What type (or types) of heat energy is at work in today’s experiment?
  4. True or False: Water is poor at absorbing heat energy.
    1. True
    2. False

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Is it hot where you live in the summer? What if I gave you a recipe for making ice cream that doesn’t require an expensive ice cream maker, hours of churning, and can be made to any flavor you can dream up? (Even dairy-free if needed?)


If you’ve got a backyard full of busy kids that seem to constantly be in motion, then this is the project for you.  The best part is, you don’t have to do any of the churning work… the kids will handle it all for you!


This experiment is simple to set up (it only requires a trip to the grocery store), quick to implement, and all you need to do guard the back door armed with a hose to douse the kids before they tramp back into the house afterward.


One of the secrets to making great ice cream quickly is [am4show have=’p8;p9;p11;p38;p92;p23;p50;p80;p88;p101;’ guest_error=’Guest error message’ user_error=’User error message’ ] to be sure that the milk and cream is COLD.  I will make this particular recipe, it’s usually with hundreds of kids, and our staff will stuff the milk products in the freezer for an hour or two or under hundreds of pounds of ice to make sure it’s super-cold.


If you’re going for the dairy-free kind, simply skip the milk and cream and add a bit of extra time to the chill time of your substitute ‘milk’.  We’ve had the best luck with almond and soy milk. Are you ready?


Here’s what you need:


Materials:


  • 1 quart whole milk (do not substitute, unless your child has a milk allergy, then use soy or almond milk)
  • 1 pint heavy cream (do not substitute, unless your child has a milk allergy, then skip)
  • 1 cup sugar (or other sweetener)
  • 1 tsp vanilla (use non-alcohol kind)
  • rock salt (use table salt if you can’t find it)
  • lots of ice
  • freezer-grade zipper-style bags (you’ll need quart and gallon sizes)


Download Student Worksheet & Exercises


How does that work? Ice cream is basically “fluffy milk”. You need to whip in a lot of air into the milk fat to get the fluffy pockets that make this stuff worthwhile. The more the kids shake the bag, the faster it will turn into ice cream.


Why do we put salt on the ice?


If you live in an area where they put salt on the roads, you already know that people do this to melt the ice. But how does salt melt ice? Think about the chemistry of what’s going on. Water normally freezes at zero degrees Celsius. But salt water presses lower than zero, so the freezing point of salt water is lower than fresh water. By sprinkling salt on the roads, you’re lowering the point at which water freezes at. When you add a solute (salt) to the solvent (water) to alter the freezing point of the solution, it’s known as the “freezing point depression”.


Tips: Don’t use nonfat milk – it won’t work with this style of ice-cream making.  if you’re adding fruit or chocolate bits, make sure you get those cold in advance too, or they will slow down your process as they heat your milk solution. (We usually add those bits last after the ice cream is done.)


IMPORTANT: Do NOT substitute dry ice for the water ice – the carbon dioxide gases build quickly and explode the bag, and now you have flying bits of dry ice that will burn skin upon contact.  That’s not the biggest issue, though… the real problem is that now animals (like your dog) and small children pop a random piece of dry ice into their mouths, which will earn your family a visit to the ER. So stick with the regular ice from your fridge.


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If you’ve completed the Soaking Up Rays experiment, you might still be a bit baffled as to why there’s a difference between black and white. Here’s a great way to actually “see” radiation by using liquid crystal thermal sheets.


You’ll need to find a liquid crystal sheet that has a temperature range near body temperature (so it changes color when you warm it with your hands.)


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The liquid crystal sheet is temperature-sensitive. When the sheet received heat from the bulb, the temperature goes up and changes color. The plastic sheets remain black except for the temperature range in which they display a series of colors that reflect the actual temperature of the crystal.


Materials:



1. Color half of the back side of the thermal paper (the side that doesn’t change color) with the highlighter (or cover half of it with foil).


2. Hold it in a position where you can easily see the color-changing side while keeping the light source on the back side.


3. Which side changes color? Is there a difference between the silver and black halves?


You’ll notice that the black half almost immediately changes color, while the silver side stays black.  The silver coating reflects the heat, keeping it cool. The black side absorbs the heat and raises its temperature.


Why do liquid crystals change color with temperature? Your liquid crystal sheet is not just one sheet, but a stack of several sheets that are slightly offset from each other. The distance between each layer changes as the sheet warms up – the hotter the temperature, the closer the stacks twist together. The color they emit depends on the distance between the sheets.


The molecules that make up the sheets are long and thin, like hot dogs. When the sheets are cooler, these molecules move around less and don’t twist up as much, which corresponds to reflecting back a redder light.  When the temperature rises, the molecules move around more and twist together, and they reflect a bluer light. When the liquid crystal sheet is black, all the light is absorbed (no light gets reflected).


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Fire is a chemical reaction (combustion) involving hot gases and plasma. The three things you need for a flame are oxygen, fuel, and a spark. When the fuel (gaseous wax) and oxygen (from the air) combine in a flame, one of the gases produced is carbon dioxide.


Most people think of carbon dioxide as dry ice, and are fascinated to watch the solid chunk sublimate from solid straight to gas, skipping the liquid state altogether. You’ve seen the curls of dry ice vapor curl down and cover the floor in a thick, wispy fog. Is carbon dioxide always more dense than air, or can we get it to float?


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The answer is… yes! Here’s an experiment that will walk you through how to create a hot, invisible cloud of carbon dioxide and detect where that cloud is.


Materials:


  • three candles
  • adult help
  • blocks or stones
  • LARGE jar that fits over all three candles (watch video)


Download Student Worksheet & Exercises


Carbon dioxide changes volume when you heat or cool it. When you heat the CO2, the volume expands, lowering the density to less than that of air. When the CO2 cools, the cloud contracts (gets smaller), and the density increases as it falls to the floor.


Remember density is mass per unit volume. So it’s an inverse relationship – when volume goes up, density goes down. In this experiment, when the temperature goes up, the volume goes up, and the density goes down.
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The triple point is where a molecule can be in all three states of matter at the exact same time, all in equilibrium. Imagine having a glass of liquid water happily together with both ice cubes and steam bubbles inside, forever! The ice would never melt, the liquid water would remain the same temperature, and the steam would bubble up. In order to do this, you have to get the pressure and temperature just right, and it’s different for every molecule.


The triple point of mercury happens at -38oF and 0.000000029 psi. For carbon dioxide, it’s 75psi and -70oF. So this isn’t something you can do with a modified bike pump and a refrigerator.


However, the triple point of water is 32oF and 0.089psi. The only place we’ve found this happening naturally (without any lab equipment) is on the surface of Mars.


Because of these numbers, we can get water to boil here on Earth while it stays at room temperature by changing the pressure using everyday materials. (If you have a vacuum pump, you can have the water boil at the freezing point of 32oF.)


Here’s what you need to do:


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Materials:


  • plastic syringe (no needle)
  • room temperature water


Bonus Idea: Do this experiment first with water, then with carbonated water.


Why does that work? How did you get the pressure to decrease? Easy – when you pulled on the plunger and increased the volume inside the syringe. Since your finger covered the hole, no additional air was allowed in when you did this (which is why it was probably a little tough to do), so the number of molecules inside the syringe stayed the same, but the space they had to wiggle around got a lot bigger, meaning that the pressure decreased.


The air inside the syringe isn’t just plain old air… it has water vapor inside, too. And that’s not all – the water from your sink isn’t just plain old water, it has air bubbles mixed in with it. When you brought down the pressure (by pulling the plunger), you are forcing the air bubbles to come out of the water, which makes it boil. When you shove the plunger back in and increase the pressure, you’ll find that the air bubbles mix back into the water and disappears.


Did you try the soda water yet? Soda has carbon dioxide already mixed in for you, which is under pressure. You can release this pressure by opening the bottle (you’ll hear a PSSST!), which is the carbon dioxide bubbles coming out of the soda. Go ahead and try that now before reading further…


When you place the soda water into the syringe and decrease the pressure, the carbon dioxide comes out quickly Try tapping the syringe to make all the tiny bubbles combine into one larger bubble. When you increase the pressure (push the plunger back in), some of the bubbles will redissolve back into the soda.


If you’ve ever had a glass of hot water suddenly erupt in an explosion of bubbles, you’ve experienced superheated water (water that’s above it’s normal boiling point) that hasn’t been able to form bubbles yet. By adding a tea bag or simply just jiggling it around is usually enough to cause the bubbles to start, which often splatters HOT HOT water everywhere. (This isn’t something you want to try without adult help.)


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Indoor Rain Clouds

Making indoor rain clouds demonstrates the idea of temperature, the measure of how hot or cold something is. Here’s how to do it:


Take two clear glasses that fit snugly together when stacked. (Cylindrical glasses with straight sides work well.)


Fill one glass half-full with ice water and the other half-full with very hot water (definitely an adult job – and take care not to shatter the glass with the hot water!). Be sure to leave enough air space for the clouds to form in the hot glass.


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Place the cold glass directly on top of the hot glass and wait several minutes. If the seal holds between the glasses, a rain cloud will form just below the bottom of the cold glass, and it actually rains inside the glass! (You can use a damp towel around the rim to help make a better seal if needed.)


Materials:


  • glass of ice water
  • glass of hot water (see video)
  • towel
  • adult help


Download Student Worksheet & Exercises


Bottling Clouds

On a stormy, rainy afternoon, try bottling clouds — using the refrigerator! Here’s what you do: Place an empty, clean 2-liter soda bottle in the fridge overnight. Take it out and get an adult to light a match, letting it burn for a few seconds, then drop it into the bottle. Immediately cap the bottle and watch what happens (you should see smoke first, then clouds forming inside). Squeeze the sides of the bottle. The clouds should disappear. When you release the bottle, the clouds should reappear. Materials:


  • 2L soda bottle
  • rubbing alcohol
  • bicycle pump
  • car tire valve (drill a 1/2 inch hole through a 2L soda bottle cap and pull the valve gently through with pliers)


Advanced Idea: You can substitute rubbing alcohol and a bicycle pump for the matches to make a more solid-looking cloud.  Swirl a bit of rubbing alcohol around inside the bottle, just enough to coat the insides, and then pour it out.  Cap your bottle with a rubber stopper fitted with a needle valve (so the valve is poking out of the bottle), and apply your pump.  Increase the pressure inside the bottle (keep a firm hand on the stopper or you’ll wind up firing it at someone) with a few strokes and pull out the stopper quickly.  You should see a cloud form inside.


What’s going on? Invisible water vapor is all around us, all the time, but they normally don’t stick together. When you squeezed the sides of the bottle, you increased the pressure and squeezed the molecules  together.  Releasing the bottle decreases the pressure, which causes the temperature to drop. When it cools inside, the water molecules stick to the smoke molecules, making a visible cloud inside your bottle.


Did you know that most drops of water actually form around a dust particle?  Up in the sky, clouds come together when water vapor condenses into liquid water drops or ice crystals. The clouds form when warm air rises and the pressure is reduced (as you go up in altitude). The clouds form at the spot where the temperature drops below the dew point.


The alcohol works better than the water because it evaporates faster than water does, which means it moves from liquid to vapor more easily (and vividly) than regular old water.


Questions to ask:


  • How many times can you repeat this?
  • Does it matter what size the bottle is?
  • What if you don’t chill the bottle?
  • What if you freeze the bottle instead?

Exercises


  1. Which combination made it rain the best? Why did this work?
  2. Draw your experimental diagram, labeling the different components:
  3. Add in labels for the different phases of matter. Can you identify all three states of matter in your experiment?

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When something feels hot to you, the molecules in that something are moving very fast. When something feels cool to you, the molecules in that object aren’t moving quite so fast. Believe it or not, your body perceives how fast molecules are moving by how hot or cold something feels. Your body has a variety of antennae to detect energy. Your eyes perceive certain frequencies of electromagnetic waves as light. Your ears perceive certain frequencies of longitudinal waves as sound. Your skin, mouth and tongue can perceive thermal energy as hot or cold. What a magnificent energy sensing instrument you are!


Let’s find out how to watch the hot and cold currents in water. Here’s what you need to do:


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Materials:


  • two bottles of water
  • food coloring
  • bathtub or sink
  • index card or business card


 
You need:


Two empty bowls (or water bottles)
Food coloring
Hot water (Does not need to be boiling.)
Cold water


1. Put about the same amount of water into two bowls. One bowl should be filled with hot water from the tap. If you’re careful, you can put it in the microwave to heat it up but please don’t hurt yourself. The other bowl should have cold water in it. If you’re using water bottles, pour the hot and cold water into each bottle.


2. Let both bowls sit for a little bit (a minute or so) so that the water can come to rest.


3. Put food coloring in both bowls (or bottles) and watch carefully.


The food coloring should have spread around faster in the hot water bowl than in the cold water bowl. Can you see why? Remember that both bowls are filled with millions and millions of molecules. The food coloring is also bunches of molecules. Imagine that the molecules from the water and the molecules from the food coloring are crashing into one another like the beans on the plate. If one bowl has a higher temperature than the other, does one bowl have faster moving molecules? Yes, the higher temperature means a higher thermal energy. So the bowl with the warmer water has faster moving molecules which crash more and harder with the food coloring molecules, spreading them faster around the bowl.


If you’re using a bottle, you can do an extra step: For bottles, place a business card over the cold bottle and invert the cold bottle over the hot. Remove card.


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This spooky idea takes almost no time, requires a dime and a bottle, and has the potential for creating quite a stir in your next magic show.  The idea is basically this: when you place a coin on a bottle, it starts dancing around. But there’s more to this trick than meets the scientist’s eye.


Here’s how you do it:


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Materials:


  • coin
  • freezer
  • plastic bottle (NOT glass)


Download Student Worksheet & Exercises


Remove the cap of an empty plastic water or soda bottle and replace it with a dime and stick the whole things upright in the freezer overnight. First thing in the morning, take it out and set it on the table. What happens?


Attention:  Magicians

If you’re a budding magician, here’s how to modify this experiment to use in your next show.  Get a glass container of soda and stick it in the coldest part of your fridge overnight. I know they are getting harder to find these days, but the glass will keep its temperature longer than plastic and enable you to do this trick.  In a pinch, you can refill a cleaned glass bottle from a previous use if you can’t locate a fresh glass soda bottle.


As soon as you’re ready to do your trick (practice first!), take it out of the fridge (have it in an ice chest if you’re on stage) and chug the whole thing. (You can ask your audience for help on this – you just want an empty cold bottle for the next part.)


When the bottle is empty but still cold, cap it with a wet dime. Place both hands on the bottle while you “wax eloquent” (make up an engaging story, like “North Winds, come have a taste of soda…”) but be sure to keep your hands on the bottle to warm it up. In about 20 seconds or so, the dime will click up and down, dancing around mysteriously.  Keep your hands on the bottle for another 20 seconds or so, and then set it gently on the table with it still dancing, and you’ll find it dancing right on without your hands being there.


How does that work? Was the bottle really empty when you placed it in the freezer? Actually, no… it had air inside of it. The air in the bottle shrank down a bit as it cooled, allowing more air to go into the bottle. When you remove the bottle from the freezer and cap it with the coin, you now have a bottle with more air in it than you started. The air warms and expands, pushing the excess air out the top, making the coin dance. Learn more about air with this Air Expands experiment.


Variations to try:

  • Is a plastic bottle or glass bottle better for this experiment?
  • What if you get the coin wet first?
  • Does a cold or warm coin work better?
  • What about a penny? Quarter?
  • Does the size of the bottle matter?

Exercises


  1. When a gas turns into a liquid, this is called:
    1. Convection
    2. Conduction
    3. Absorption
    4. Condensation
  2. When water boils, what happens to the bonds between its molecules?
  3. What is the best way to describe how the bonds between water molecules behave when in a liquid state?
    1. Solid bridges
    2. Rubber bands
    3. No bonds
    4. Brittle like chalk
  4. The crystalline shape of a solid is referred to as:
    1. a matrix
    2. a vortex
    3. a crystal
    4. a cube

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If you can remember thermostats before they went ‘digital’, then you may know about bi-metallic strips – a piece of material made from of two strips of different metals which expand at different rates as they are heated (usually steel and copper). The result is that the flat strip bends one way if heated, and in the opposite direction if cooled.


Normally, it takes serious skill and a red-hot torch to stick two different metals together, but here’s a homemade version of this concept that your kids can make using your freezer.  Here what you do:


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Materials:


  • foil wrapper from a stick of gum or candy bar
  • index card
  • scissors
  • tape


Since gum wrappers are paper on one side and foil on the other, you can use one to make your own bi-metallic strip. Flatten out the wrapper into a sheet and find a way fasten the wrapper so it sits upright on an index card (we used the bubble gum itself as the adhesive). Stick it in the freezer overnight and check it in the morning! Where can you place it to flex the other direction?


How does that work? A bimetallic strip is a stack of two metals stuck together. The metal with the higher expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled. The bi-metallic strip was invented by the eighteenth century clockmaker John Harrison to compensate for temperature-induced changes his clock springs.


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Is it warmer upstairs or downstairs? If you’re thinking warm air rises, then it’s got to be upstairs, right? If you’ve ever stood on a ladder inside your house and compared it to the temperature under the table, you’ve probably felt a difference.


So why is it cold on the mountain and warm in the valley? Leave it to a science teacher to throw in a wrench just when you think you’ve got it figured out. Let’s take a look at whether hot air or cold air takes up more space. Here’s what you do:


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Materials:


  • water
  • plastic bottle
  • balloon
  • stove top and saucepan or the setup in the video


Download Student Worksheet & Exercises


1. Pour a couple of inches of water into an empty soda bottle and cap with a 7-9″ balloon. You can secure the balloon to the bottle mouth with a strip of tape if you want, but it usually seals tight with just the balloon itself.


2. Fill a saucepan with an inch or two of water, and add your bottle. Heat the saucepan over the stove with adult help, keeping a close eye on it. Turn off the heat when your balloon starts to inflate. Since water has a high heat capacity, the water will heat before the bottle melts. (Don’t believe me? Try the Fire-Water Balloon Experiment first to see how water conducts heat away from the bottle!)


3. When you’re finished, stick the whole thing in the freezer for an hour. What happened to the balloon?


What’s going on? So now what do you think? Does the same chunk of air take up more or less space when it’s hot? Cold? When you heat air, it expands because the air molecules move around a lot more when you add energy. The molecules zip around and wiggle like crazy, bouncing off each other more often than when they are cooler.


Getting back to our original question, the upstairs in a house is warmer because the pockets of warm air rise because they are less dense than cool air. The more the molecules move around, the more room they need, and the further they get spaced out. Think of a swimming pool and a piece of aluminum foil. If you place a sheet of foil in the pool, it floats. If you take the foil and crumple it up, it sinks. The more compactly you squish the molecules together, the more dense it becomes. You can read more about density in Unit 3.


As for why mountains and valleys are opposite, it has to do with the Earth being a big massive ball of warm rock which heats up the lower atmosphere in addition to winds blowing on mountains and changes in pressure as you gain altitude… in a nutshell, it’s complicated! What’s important to remember is that the Earth system is a lot bigger than our bottle-saucepan experiment, and can’t be represented in this way.


Exercises


  1. Draw a group of molecules at a very cold temperature in the space below. Use circles to represent each molecule.
  2. True or False: A molecule that heats up will move faster.
    1. True
    2. False
  3. True or False: A material will be less dense at lower temperatures.
    1. True
    2. False

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Temperature is a way of talking about, measuring, and comparing the thermal energy of objects.


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The words “hot” , “cold”, “warm” and so forth describe what scientists call thermal energy. Thermal energy is how much the molecules are moving inside an object. The faster molecules move, the more thermal energy it has.


Objects that have molecules moving very quickly are said to have high thermal energy or high temperature. Like a cloud of steam, for example. The higher the temperature, the faster the molecules are moving inside that steam cloud.


Temperature is just a speedometer for molecules. The speed of the molecules in ice cream is way slower than it is in a hot shower.


If everything is made of molecules, and these molecules are speeding up and slowing down, what do you think happens if they change speed a lot? Do you think my kitchen table will start vibrating across the room if the table somehow gets too hot?


No, probably not, my table will not start jumping around the room, no matter how hot it gets.  It would melt down into a mush first! But some interesting things do happen when molecules change speeds.


There are three common states of matter – I bet you know what they are already: solid, liquid, and gas.  Water is really special because it can a solid, liquid or gas state pretty normal temperatures. You don’t need a mad scientist lab to get it to go into any of these three states.


Water is one of the only substances that expands instead of shrinks when it freezes. It’s also a polar molecule, meaning that if you stick a static charge next to it, like a balloon you rubbed on your head, you can get the water to move.


Imagine an icicle. The water is in a solid state when it’s an icicle. It’s holding its shape. The molecules in the water are held together by strong, stiff bonds. These bonds hold the water molecules in a tight pattern called a matrix. This matrix holds the water molecules in a crystalline pattern.


Can you imagine breaking off an icicle and sticking it in a tea kettle on the stove? Now, let’s pretend to turn on the heat. The heat is transferred from the stove to the kettle to the icicle.


What happens to our icicle?


As the icicle absorbs the heat, the molecules begin to vibrate faster (the temperature is increasing). When the molecules vibrate at a certain speed (they gain enough thermal energy) they stretch those strong, stiff matrix crystalline bonds enough that the bonds become more like rubber bands or springs and they stretch and get all loose-goosey.


That’s when the icicle becomes liquid. There are still bonds between the molecules, but they are a bit loose, allowing the molecules to move and flow around each other.


The act of changing from a solid to a liquid is called melting. The temperature at which a substance changes from a solid to a liquid is called its melting point. For water, that point is 32° F or 0° C. (Remember those numbers from the slide with all the temperature scales?)


Now if we continue heating, we see our icicle go from solid to completely liquid, and now we notice bubbling. What’s going on now?


Now the temperature is at 212° F or 100° C and the water is going from a liquid state to a gaseous state. This means that the loosey goosey bonds that connected the molecules before have been stretched as far as they go, can’t hold on any longer and “POW!” they snap.


Those water molecules no longer have any bonds and are free to roam aimlessly around the room (think toddlers). Gas molecules move at very quick speeds as they bounce, jiggle, crash and zip around any container they are in (kind of like toddles on sugar). The act of changing from a liquid to a gas is called evaporation or boiling and the temperature at which a substance changes from a liquid to a gas is called its boiling point.


Now if we turn off the stove, what do you think happens?


Our gaseous water molecules get close to something cool, they will combine and turn from gaseous to liquid state.  This is what happens to your bathroom mirror during a shower or bath. The gaseous water molecules that are having fun bouncing and jiggling around the bathroom get close to the mirror. The mirror is colder than the air. As the gas molecules get close they slow down due to loss of temperature. If they slow enough, they form loosey goosey bonds with other gas molecules and change from gas to liquid state.


The act of changing from gas to liquid is called condensation. The temperature at which molecules change from a gas to a liquid is called the condensation point. Clouds are made of hundreds of billions of tiny little droplets of liquid water that have condensed onto particles of some sort of dust.


Now let’s turn the heat down a bit more and see what happens. Imagine we stick the tea kettle in the freezer. As the temperature drops and the molecules continue to slow, the bonds between the molecules can pull them together tighter and tighter.


Eventually the molecules will fall into a matrix, a pattern, and stick together quite tightly. This would be the solid state. The act of changing from a liquid to a solid is called freezing and the temperature at which it changes is called (say it with me now) freezing point.


Think about this for a second – is the freezing point and melting point of an object at the same temperature? Does something go from solid to liquid or from liquid to solid at the same temperature?


If you said yes, you’re right!


The freezing point of water and the melting point of water are both 32° F or 0° C. The temperature is the same. It just depends on whether it is getting hotter or colder as to whether the water is freezing or melting.


The boiling and condensation point is also the same point.


Crazy Temperatures

Here’s an experiment you can do to baffle your senses: Fill one glass with hot water (not boiling), another with ice water, and a third with room temperature water. Place a finger in the hot water and a finger in the ice cold water for a minute or two. Then stick both fingers in the room temperature cup.


How does that feel?


Did it seem that each finger detected a different temperature when placed in the room temperature cup? Weird! So what gives?


Materials:


  • 3 cups of water (see video)
  • your hands


Download Student Worksheet & Exercises


Your skin contains temperature sensors that work by detecting the direction heat flow (in or out of your body), not temperature directly. These sensors change temperature depending on their surroundings. So when you heated up one finger, and then placed it in cooler water, the heat flowed out of your body, telling your brain it was getting cooler. The ice water finger was detecting a heat flow into your body… and presto! You have one confused brain.


In order for heat to flow, you need to have a temperature difference. Did you notice how your fingers weren’t good thermometers with this experiment? This is why scientists had to invent the thermometer, because the human body isn’t designed to detect temperature, only heat flow. 


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This is a nit-picky experiment that focuses on the energy transfer of rolling cars.  You’ll be placing objects and moving them about to gather information about the potential and kinetic energy.


We’ll also be taking data and recording the results as well as doing a few math calculations, so if math isn’t your thing, feel free to skip it.


Here’s what you need:


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  • a few toy cars (or anything that rolls like a skate)
  • a board, book or car track
  • measuring tape

The setup is simple.  Here’s what you do:


1. Set up the track (board or book so that there’s a nice slant to the floor).


2. Put a car on the track.


3. Let the car go.


4. Mark or measure how far it went.



Download Student Worksheet & Exercises


As you lifted the car onto the track you gave the car potential energy. As the car went down the track and reached the floor the car lost potential energy and gained kinetic energy. When the car hit the floor it no longer had any potential energy only kinetic.


If the car was 100% energy efficient, the car would keep going forever. It would never have any energy transferred to useless energy. Your cars didn’t go forever did they? Nope, they stopped and some stopped before others. The ones that went farther were more energy efficient. Less of their energy was transferred to useless energy than the cars that went less far.


Where did the energy go? To heat energy, created by the friction of the wheels, and to sound energy. Was energy lost? NOOOO, it was only changed. If you could capture the heat energy and the sound energy and add it to the the kinetic energy, the sum would be equal to the original amount of energy the car had when it was sitting on top of the ramp.


For K-8 grades, click here to download a data sheet.


For Advanced Students, click  here for the data log sheet. You’ll need Microsoft Excel to use this file.


Exercises


  1. Where is the potential energy greatest?
  2. Where is the kinetic energy greatest?
  3. Where is potential energy lowest?
  4. Where is kinetic energy lowest?
  5. Where is KE increasing, and PE is decreasing?
  6. Where is PE increasing and KE decreasing?

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We’re going to build monster roller coasters in your house using just a couple of simple materials. You might have heard how energy cannot be created or destroyed, but it can be transferred or transformed (if you haven’t that’s okay – you’ll pick it up while doing this activity).


Roller coasters are a prime example of energy transfer: You start at the top of a big hill at low speeds (high gravitational potential energy), then race down a slope at break-neck speed (potential transforming into kinetic) until you bottom out and enter a loop (highest kinetic energy, lowest potential energy). At the top of the loop, your speed slows (increasing your potential energy), but then you speed up again and you zoom near the bottom exit of the loop (increasing your kinetic energy), and you’re off again!


Here’s what you need:


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  • marbles
  • masking tape
  • 3/4″ pipe foam insulation (NOT neoprene and NOT the kind with built-in adhesive tape)

To make the roller coasters, you’ll need foam pipe insulation, which is sold by the six-foot increments at the hardware store. You’ll be slicing them in half lengthwise, so each piece makes twelve feet of track. It comes in all sizes, so bring your marbles when you select the size. The ¾” size fits most marbles, but if you’re using ball bearings or shooter marbles, try those out at the store. (At the very least you’ll get smiles and interest from the hardware store sales people.) Cut most of the track lengthwise (the hard way) with scissors. You’ll find it is already sliced on one side, so this makes your task easier. Leave a few pieces uncut to become “tunnels” for later roller coasters.


Read for some ‘vintage Aurora’ video? This is one of the very first videos ever made by Supercharged Science:



 
Download Student Worksheet & Exercises


Tips & Tricks

Loops Swing the track around in a complete circle and attach the outside of the track to chairs, table legs, and hard floors with tape to secure in place. Loops take a bit of speed to make it through, so have your partner hold it while you test it out before taping. Start with smaller loops and increase in size to match your entrance velocity into the loop. Loops can be used to slow a marble down if speed is a problem.


Camel-Backs Make a hill out of track in an upside-down U-shape. Good for show, especially if you get the hill height just right so the marble comes off the track slightly, then back on without missing a beat.


Whirly-Birds Take a loop and make it horizontal. Great around poles and posts, but just keep the bank angle steep enough and the marble speed fast enough so it doesn’t fly off track.


Corkscrew Start with a basic loop, then spread apart the entrance and exit points. The further apart they get, the more fun it becomes. Corkscrews usually require more speed than loops of the same size.


Jump Track A major show-off feature that requires very rigid entrance and exit points on the track. Use a lot of tape and incline the entrance (end of the track) slightly while declining the exit (beginning of new track piece).


Pretzel The cream of the crop in maneuvers. Make a very loose knot that resembles a pretzel. Bank angles and speed are the most critical, with rigid track positioning a close second. If you’re having trouble, make the pretzel smaller and try again. You can bank the track at any angle because the foam is so soft. Use lots of tape and a firm surface (bookcases, chairs, etc).


Troubleshooting Marbles will fly everywhere, so make sure you have a lot of extras! If your marble is not following your track, look very carefully for the point of departure – where it flies off.


-Does the track change position with the weight of the marble, making it fly off course? Make the track more rigid by taping it to a surface.
-Is the marble jumping over the track wall? Increase your bank angle (the amount of twist the track makes along its length).
-Does your marble just fall out of the loop? Increase your marble speed by starting at a higher position. When all else fails and your marble still won’t stay on the track, make it a tunnel section by taping another piece on top the main track. Spiral-wrap the tape along the length of both pieces to secure them together.


HOT TIPS for ULTRA-COOL PARENTS: This lab is an excellent opportunity for kids to practice their resilience, because we guarantee this experiment will not work the first several times they try it. While you can certainly help the kids out, it’s important that you help them figure it out on their own. You can do this by asking questions instead of rushing in to solve their problems. For instance, when the marble flies off the track, you can step back and say:


“Hmmm… did the marble go to fast or too slow?”


“Where did it fly off?”


“Wow – I’ll bet you didn’t expect that to happen. Now what are you going to try?”


Become their biggest fan by cheering them on, encouraging them to make mistakes, and try something new (even if they aren’t sure if it will work out).


Check out this cool roller coaster from one of our students!


Exercises 


  1. What type of energy does a marble have while flying down the track of a roller coaster?
  2. What type of energy does the marble have when you are holding it at the top of the track?
  3. At the top of a camel back hill, which is higher for the marble, kinetic or potential energy?
  4. At the top of an inverted loop, which energy is higher, kinetic or potential energy?

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Bobsleds use the low-friction surface of ice to coast downhill at ridiculous speeds. You start at the top of a high hill (with loads of potential energy) then slide down a icy hill til you transform all that potential energy into kinetic energy.  It’s one of the most efficient ways of energy transformation on planet Earth. Ready to give it a try?


This is one of those quick-yet-highly-satisfying activities which utilizes ordinary materials and turns it into something highly unusual… for example, taking aluminum foil and marbles and making it into a racecar.


While you can make a tube out of gift wrap tubes, it’s much more fun to use clear plastic tubes (such as the ones that protect the long overhead fluorescent lights). Find the longest ones you can at your local hardware store. In a pinch, you can slit the gift wrap tubes in half lengthwise and tape either the lengths together for a longer run or side-by-side for multiple tracks for races. (Poke a skewer through the rolls horizontally to make a quick-release gate.)


Here’s what you need:


  • aluminum foil
  • marbles (at least four the same size)
  • long tube (gift wrapping tube or the clear protective tube that covers fluorescent lighting is great)

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bobsledsIf you’re finding that the marbles fall out before the bobsled reaches the bottom of the slide, you need to either crimp the foil more closely around the marbles or decrease your hill height.


Check to be sure the marbles are free to turn in their “slots” before launching into the tube – if you’ve crimped them in too tightly, they won’t move at all. If you oil the bearings with a little olive oil or machine oil, your tube will also get covered with oil and later become sticky and grimy… but they sure go faster those first few times!



 
Download Student Worksheet & Exercises


Exercises Answer the questions below:


  1. Potential energy is energy that is related to:
    1. Equilibrium
    2. Kinetic energy
    3. Its system
    4. Its elevation
  2. If an object’s energy is mostly being used to keep that object in motion, we can say it has what type of energy?
    1. Kinetic energy
    2. Potential energy
    3. Heat energy
    4. Radiation energy
  3. True or False: Energy is able to remain in one form that is usable over and over again.
    1. True
    2. False

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This is a simple, fun, and sneaky way of throwing tiny objects. It’s from one of our spy-kit projects. Just remember, keep it under-cover. Here’s what you need:


  • a cheap mechanical pencil
  • two rubber bands
  • a razor with adult help

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Advanced students: Download your P-Shooter Lab here.


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This experiment is for Advanced Students.There are several different ways of throwing objects. This is the only potato cannon we’ve found that does NOT use explosives, so you can be assured your kid will still have their face attached at the end of the day. (We’ll do more when we get to chemistry, so don’t worry!)


These nifty devices give off a satisfying *POP!!* when they fire and your backyard will look like an invasion of aliens from the French Fry planet when you’re done. Have your kids use a set of goggles and do all your experimenting outside.


Here’s what you need:


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  • potatoes
  • an acrylic tube (clear is best so you can see what’s happening inside!)
  • wooden dowel
  • washer (this is your ‘hand-saver’)


 
Where is the potential energy the greatest? How much energy did your spud have at this point? Hmmm… let’s see if we can get a few actual numbers with this experiment. In order to calculate potential energy at the highest point of travel, you’ll need to figure out how high it went.


Here are instructions for making your own height-gauge:



Once you get your height gauge working right, you’ll need to track your data. Start a log sheet in your journal and jot down the height for each launch. Let’s practice a sample calculation:


If you measured an angle of 30 degrees, and your spud landed 20 feet away, we can assume that the spud when highest right in the middle of its flight, which is halfway (10 feet). Use basic trigonometry to find the height 45 degrees up at a horizontal distance ten feet away to get:


height = h = (10′) * (tan 30) = 5.8 feet
(Convert this to meters by: (5.8 feet) * (12 inches/foot) / (39.97 inches/meter) = 1.8 meters)

I measured the mass of my spud to be 25 grams (which is 0.025 kg).


Now, let’s calculate the potential energy:


PE = mgh = (0.025 kg) * (1.8 meters) * (10 m/s2) = 0.44 Joules


How fast was the spud going before it smacked into the ground? Set PE = KE to solve for velocity:


mgh = 0.5 mv2 gives v = (2gh)1/2


Plug in your numbers to get:


v = [(2) * (10) * (1.8)]2 = 6 m/s (or about 20 feet per second). Cool!


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When you drop a ball, it falls 16 feet the first second you release it. If you throw the ball horizontally, it will also fall 16 feet in the first second, even though it is moving horizontally… it moves both away from you and down toward the ground. Think about a bullet shot horizontally. It travels a lot faster than you can throw (about 2,000 feet each second). But it will still fall 16 feet during that first second. Gravity pulls on all objects (like the ball and the bullet) the same way, no matter how fast they go.


What if you shoot the bullet faster and faster? Gravity will still pull it down 16 feet during the first second, but remember that the surface of the Earth is round. Can you imagine how fast we’d need to shoot the bullet so that when the bullet falls 16 feet in one second, the Earth curves away from the bullet at the same rate of 16 feet each second?


Answer: that bullet needs to travel nearly 5 miles per second. (This is also how satellites stay in orbit – going just fast enough to keep from falling inward and not too fast that they fly out of orbit.)


Catapults are a nifty way to fire things both vertically and horizontally, so you can get a better feel for how objects fly through the air. Notice when you launch how the balls always fall at the same rate – about 16 feet in the first second.  What about the energy involved?


When you fire a ball through the air, it moves both vertically and horizontally (up and out). When you toss it upwards, you store the (moving) kinetic energy as potential energy, which transfers back to kinetic when it comes whizzing back down. If you throw it only outwards, the energy is completely lost due to friction.


The higher you pitch a ball upwards, the more energy you store in it. Instead of breaking our arms trying to toss balls into the air, let’s make a simple machine that will do it for us. This catapult uses elastic kinetic energy stored in the rubber band to launch the ball skyward.


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Here’s what you need:


  • 9 tongue-depressor size popsicle sticks
  • four rubber bands
  • one plastic spoon
  • ping pong ball or wadded up ball of aluminum foil (or something lightweight to toss, like a marshmallow)
  • hot glue gun with glue sticks


 
Download Student Worksheet & Exercises


catapult1What’s going on? We’re utilizing the “springy-ness” in the popsicle stick to fling the ball around the room. By moving the fulcrum as far from the ball launch pad as possible (on the catapult), you get a greater distance to press down and release the projectile. (The fulcrum is the spot where a lever moves one way or the other – for example, the horizontal bar on which a seesaw “sees” and “saws”.)


Troubleshooting: These simple catapults are quick and easy versions of the real thing, using a fulcrum instead of a spring so kids don’t knock their teeth out. After making the first model, encourage kids to make their own “improvements” by handing them additional popsicle sticks, spoons, and glue sticks (for the hot glue guns).


If they get stuck, you can show them how to vary their models: glue a second (or third, fourth, or fifth) spoon onto the first spoon for multi-ammunition throws, increase the number of popsicle sticks in the fulcrum from 7 to 13 (or more?), and/or use additional sticks to lengthen the lever arm. Use ping pong balls as ammo and build a fort from sheets, pillows, and the backside of the couch.



Want to make a more advanced catapult? 

This catapult requires a little more time, materials, and effort than the catapult design above, but it’s totally worth it. This device is what most folks think of when you say ‘catapult’. I’ve shown you how to make a small model – how large can you make yours?


This project lends itself well to taking data and graphing your results: you and your child can jot down the distance traveled along with time aloft with further calculations for high school students for velocity and acceleration. My university students would also calculate statistics, percent error, and more. My students also mapped out the material properties of the ‘cantilevered beam’ as well as model the popsicle stick as a spring (to determine the spring constant (k) for your calculations from Hooke’s Law). You can take this project as far as you want, depending on the interest and ability of kids.


Materials:


  • plastic spoon
  • 14 popsicle sticks
  • 3 rubber bands
  • wooden clothespin
  • straw
  • wood skewer or dowel
  • scissors
  • hot glue gun


Try different ball weights (ping pong, foil crumpled into a ball, whiffle balls, marshmallows, etc) and chart out the results: make a data table that shows what ball you tried and how far it went. You can also use a stopwatch to time how long your ball was in the air.


You can also graph your results: make a chart where you plot each data point on a graph that has distance on the vertical axis and time on the horizontal axis.


Advanced Teaching Tips: For high school and college-level physics classes, you can easily incorporate these launchers into your calculations for projectile motion. Offer students different ball weights (ping pong, foil crumpled into a ball, and whiffle balls work well) and chart out the results.


Exercises Answer the questions below:


  1. How is gravity related to kinetic energy?
    1. Gravity creates kinetic energy in all systems.
    2. Gravity explains how potential energy is created.
    3. Gravity pulls an object and helps its potential energy convert into kinetic energy.
    4. None of the above
  2. If you could use your catapult to launch your ball of foil into orbit, how high would it have to go?
    1. Above the atmosphere
    2. High enough to slingshot around the moon
    3. High enough so that when it falls, the earth curves away from it
    4. High enough so that it is suspended in empty space
  3. Where is potential energy the greatest on the catapult?

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This is a very simple yet powerful demonstration that shows how potential energy and kinetic energy transfer from one to the other and back again, over and over.  Once you wrap your head around this concept, you’ll be well on your way to designing world-class roller coasters.


For these experiments, find your materials:


  • some string
  • a bit of tape
  • a washer or a weight of some kind
  • set of magnets (at least 6, but more is better)

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Here’s what you do:


1. Make the string into a 2 foot or so length.


2. Tie the string to the washer, or weight.


3. Tape the other end of the string to a table.


4. Lift the weight and let go, causing the weight to swing back and forth at the end of the pendulum.



Download Student Worksheet & Exercises


Watch the pendulum for a bit and describe what it’s doing as far as energy goes. Some questions to think about include:


  • Where is the potential energy greatest?
  • Where is the kinetic energy greatest?
  • Where is potential energy lowest?
  • Where is kinetic energy lowest?
  • Where is KE increasing, and PE is decreasing?
  • Where is PE increasing and KE decreasing?
  • Where did the energy come from in the first place?

Remember, potential energy is highest where the weight is the highest.


Kinetic energy is highest were the weight is moving the fastest. So potential energy is highest at the ends of the swings. Here’s a coincidence, that’s also where kinetic energy is the lowest since the weight is moving the least.


Where’s potential energy the lowest? At the middle or lowest part of the swing. Another coincidence, this is where kinetic energy is the highest! Now, wait a minute…coincidence or physics? It’s physics right?


In fact, it’s conservation of energy. No energy is created or destroyed, so as PE gets lower KE must get higher. As KE gets higher PE must get lower. It’s the law…the law of conservation of energy! Lastly, where did the energy come from in the first place? It came from you. You added energy (increased PE) when you lifted the weight.


(By the way, you did work on the weight by lifting it the distance you lifted it. You put a certain amount of Joules of energy into the pendulum system. Where did you get that energy? From your morning Wheaties!)


Chaos Pendulum

For this next experiment, we’ll be using magnets to add energy into the system by having a magnetic pendulum interact with magnets carefully spaced around the pendulum. Watch the video to learn how to set this one up.  You’ll need a set of magnets (at least one of them is a ring magnet so you can easily thread a string through it), tape, string, and a table or chair. Are you ready?



Exercises


  1. Why can we never make a machine that powers itself over and over again?
    1. Energy is mostly lost to heat.
    2. Energy is completely used up.
    3. Energy is unlimited, but is absorbed by neighboring air molecules.
    4. None of these
  2. In the pendulum, as kinetic energy increases, potential energy ______________.
    1. Increases
    2. Decreases
  3. As potential energy decreases, kinetic energy _________________.
    1. Increases
    2. Decreases

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There are many different kinds of potential energy.  We’ve already worked with gravitational potential energy, so let’s take a look at elastic potential energy.


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Materials: a rubber band


A simple way to demonstrate elastic energy is to stretch a rubber band without releasing it.  The stretch in the rubber band is your potential energy. When you let go of the rubber band, you are releasing the potential energy, and when you aim it toward a wall, it’s converted into motion (kinetic energy).



Here’s another fun example:  the rubber band can also show how every is converted from one form to another.  If you place the rubber band against a part of you that is sensitive to temperature changes (like a cheek or upper lip), you can sense when the band heats up.  Simply stretch and release the rubber band over and over, testing the temperature as you go. Does it feel warmer in certain spots, or in just one location?


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When you toss down a ball, gravity pulls on the ball as it falls (creating kinetic energy) until it smacks the pavement, converting it back to potential energy as it bounces up again. This cycles between kinetic and potential energy as long as the ball continues to bounce.


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But note that when you drop the ball, it doesn’t rise up to the same height again. If the ball did return to the same height, this means you recovered all the kinetic energy into potential energy and you have a 100% efficient machine at work. But that’s not what happens, is it? Where did the rest of the energy go? Some of the energy was lost as heat and sound. (Did you hear something when the ball hit the floor?)



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In this experiment, you’re looking for two different things:  first you’ll be dropping objects and making craters in a bowl of flour to see how energy is transformed from potential to kinetic, but you’ll also note that no matter how carefully you do the experiment, you’ll never get the same exact impact location twice.


To get started, you’ll need to gather your materials for this experiment. Here’s what you need:


[am4show have=’p8;p9;p11;p38;p92;p15;p42;p88;’ guest_error=’Guest error message’ user_error=’User error message’ ]


  • several balls of different weights no bigger then the size of a baseball (golf ball, racket ball, ping pong ball, marble etc. are good choices)
  • fill a good size container or mixing bowl with flour or corn starch (or any kind of light powder)
  • If you’re measuring your results, you’ll also need a tape measure (or yard stick) and a spring scale (or kitchen scale).

Are you ready?


1. Fill the container about 2 inches or so deep with the flour.


2. Weigh one of the balls (If you can, weigh it in grams).


3. Hold the ball about 3 feet (one meter) above the container with the flour.


4. Drop the ball.


5. Whackapow! Now take a look at how deep the ball went and how far the flour spread. (If all your balls are the same size but different weights it’s worth it to measure the size of the splash and the depth the ball went. If they are not, don’t worry about it. The different sizes will effect the splash and depth erratically.


6. Try it with different balls. Be sure to record the mass of each ball and calculate the potential energy for each ball.



Each one of the balls you dropped had a certain amount of potential energy that depended on the mass of the ball and the height it was dropped from. As the ball dropped the potential energy changed to kinetic energy until, “whackapow”, the kinetic energy of the ball collided with and scattered the flour. The kinetic energy of the ball transferred kinetic energy and heat energy to the flour.


For Advanced Students:

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Calculate the gravitational potential energy of the ball. Take the mass of the ball, multiply it by 10 m/s2 and multiply that by 1 meter. For example, if your ball had a mass of 70 grams (you need to convert that to kilograms so divide it by 1000 so that would be .07 grams) your calculation would be


PE=.07 x 10 x 1 = .7 Joules of potential energy.


So, how much kinetic energy did the ball in the example have the moment it impacted the flour? Well, if all the potential energy of the ball transfers to kinetic energy, the ball has .7 Joules of kinetic energy.


Create a table in your science journal or use ours. (You’ll need Microsoft Excel to use this file.)


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Note: Do the pendulum experiment first, and when you’re done with the heavy nut from that activity, just use it in this experiment.


You can easily create one of these mystery toys out of an old baking powder can, a heavy rock, two paper clips, and a rubber band (at least 3″ x 1/4″).  It will keep small kids and cats busy for hours.


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Here’s what you get:


  • can with a lid
  • heavy rock or large nut
  • two paper clips
  • rubber band

You’ll need two holds punched through your container  – one in the lid and the bottom. Thread your rubber band through the heavy washer and tie it off (this is important!).  Poke the ends of the rubber band through one of the holes and catch it on the other side with a paper clip.  (Just push a paper clip partway through so the rubber band doesn’t slip back through the hole.)  Do this for both sides, and make sure that your rubber band is a pulled mildly-tight inside the can.  You want the hexnut to dangle in the center of the can without touching the sides of the container.



 
Download Student Worksheet & Exercises


Now for the fun part… gently roll the can on a smooth floor away from you.  The can should roll, slow down, stop, and return to  you!  If it doesn’t, check the rubber band tightness inside the can.


The hexnut is a weight that twists up the rubber band as the can rolls around it.  The kinetic energy (the rolling motion of the can) transforms into potential (elastic) energy stored in the rubber band the free side twists around. The can stops (this is the point of highest potential energy) and returns to you (potential energy is being transformed into kinetic). The farther the toy is rolled the more elastic potential energy it stores.


Exercises


  1. Explain in your own words two types of energy transfer:
  2. True or false: All energy in a system is lost to heat.
    1. True
    2. False

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Are you curious about pulleys? This set of experiments will give you a good taste of what pulleys are, how to thread them up, and how you can use them to lift heavy things.


We’ll also learn how to take data with our setup and set the stage for doing the ultra-cool Pulley Lift experiments.


Are you ready?
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For this experiment, you will need:


  • One pulley (from the hardware store… get small ones that spin as freely as possible. You’ll need three single pulleys or if you can find one get a double pulley to make our later experiment easier.)
  • About four feet of string
  • 2 paper cups
  • many little masses (about 50 marbles, pennies, washers etc.)
  • Yardstick or measuring tape
  • A scale (optional)
  • 2 paper clips
  • Nail or some sort of sharp pokey thing
  • Table


 
Download Student Worksheet & Exercises


Advanced students: Download your Simple Pulley Experiments


1. Take a look at the video to see how to make your “mass carriers”. Use the nail to poke a hole in both sides of the cup. Be careful to poke the cup…not your finger! Thread about 4 inches of string or a pipe cleaner through both holes. Make sure the string is a little loose. Make two of these mass carriers. One is going to be your load (what you lift) and the other is going to be your effort (the force that does the lifting).


2. Dangle the pulley from the table (check out the picture).


3. Bend your two paper clips into hooks.


4. Take about three feet of string and tie your paper clip hooks to both ends.


5. Thread your string through the pulley and let the ends dangle.


6. Put 40 masses (coins or whatever you’re using) into one of the mass carriers. Attach it to one of the strings and put it on the floor. This is your load.


7. Attach the other mass carrier to the other end of the string (which should be dangling a foot or less from the pulley). This is your effort.


8. Drop masses into the effort cup. Continue dropping until the effort can lift the load.


9. Once your effort lifts the load, you can collect some data. First allow the effort to lift the load about one foot (30 cm) into the air. This is best done if you manually pull the effort until the load is one foot off the ground. Measure how far the effort has to move to lift the load one foot.


10. When you have that measurement, you can either count the number of masses in the load and the effort cup or if you have a scale, you can get the mass of the load and the effort.


11. Write your data into your pulley data table in your science journal.


Double Pulley Experiment

You need:


Same stuff you needed in Experiment 1, except that now you need two pulleys.


1. Attach the string to the hook that’s on the bottom of your top pulley.


2. Thread the string through the bottom pulley.


3. Thread the string up and through the top pulley.


4. Attach the string to the effort.


5. Attach the load to the bottom pulley.


6. Once you get it all together, do the same thing as before. Put 40 masses in the load and put masses in the effort until it can lift the load.


7. When you get the load to lift, collect the data. How far does the effort have to move now in order to lift the load one foot (30 cm)? How many masses (or how much mass, if you have a scale) did it take to lift the load?


8. Enter your data into your pulley table in your science journal.


Triple Pulley Experimentitem7

You Need


Same stuff as before


If you have a double pulley or three pulleys you can give this a shot. If not, don’t worry about this experiment.


Do the same thing you did in experiments 1 and 2 but just use 3 pulleys. It’s pretty tricky to rig up 3 pulleys so look carefully at the pictures. The top pulley in the picture is a double pulley.


1. Attach the string to the bottom pulley. The bottom pulley is the single pulley.item8


2. Thread the string up and through one of the pulleys in the top pulley. The top pulley is the double pulley.


3. Take the string and thread it through the bottom pulley.


4. Now keep going around and thread it again through the other pulley in the top (double) pulley.


5. Almost there. Attach the load to the bottom pulley.


6. Last, attach the effort to the string.


7. Phew, that’s it. Now play with it!


Take a look at the table and compare your data. If you have decent pulleys, you should get some nice results. For one pulley, you should have found that the amount of mass it takes to lift the load is about the same as the amount of mass of the load. Also, the distance the load moves is about the same as the distance the effort moves.


All you’re really doing with one pulley, is changing the direction of the force. The effort force is down but the load moves up.


Now, however, take a look at two pulleys. The mass needed to lift the load is now about half the force of the load itself! The distance changed too. Now the distance you needed to move the effort, is about twice the distance that the load moves. When you do a little math, you notice that, as always, work in equals work out (it won’t be exactly but it should be pretty close if your pulleys have low friction).


What happened with three pulleys? You needed about 1/3 the mass and 3 times the distance right? With a long enough rope, and enough pulleys you can lift anything! Just like with the lever, the pulley, like all simple machines, does a force and distance switcheroo.


The more distance the string has to move through the pulleys, the less force is needed to lift the object. The work in, is equal to the work out (allowing for loss of work due to friction) but the force needed is much less.


Exercises Answer the questions below:


  1. What is the load and effort of a pulley? Draw a pulley and label it.
  2. What is the best way to say what a simple machine helps us do?
    1. Do work without changing force applied
    2. Change the direction or strength of a force
    3. Lift heavy shipping containers
    4. None of these
  3.  Name one other type simple machine and an example:

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We're going to be using pulleys to pull two (or more) kids with one hand. You will be using something called ‘Mechanical Advantage’, which is like using your brains instead of brute strength. When you thread the rope around the broom handles, you use 'mechanical advantage' to leverage your strength and pull more than you normally could handle.

How can you possibly pull with more strength than you have? Easy - you trade ‘force’ for ‘distance’ - you can pull ten people with one hand, but you have to pull ten feet of rope for every one foot they travel.

Here's what you do: [am4show have='p8;p9;p11;p38;p92;p14;p41;p88;' guest_error='Guest error message' user_error='User error message' ]
  • nylon rope (at least 50')
  • two strong dowels (like the handle from a broomstick)
  • friends and you

Download Student Worksheet

Have two people face each other and each hold a smooth pipe or strong dowel (like a mop or broom) horizontally straight out in front of their chest.   Tie a length of strong nylon rope (slippery rope works best to minimize friction) near the end of the mop.

Drape the rope over the second handle (broom), loop around the bottom, then back to the top of the broom.  You're going to zigzag the rope back and forth between the mop and broom until you have four strings on each handle.

Attach a third person to the free end of the rope.  Make a quick handle for a third person: Thread a 6" length of PVC pipe onto the end and tie the rope back onto itself to form a handle.

The two people hold the dowels will not be able to resist the pull you give when pulling on the end of the rope! Be careful with this one - there's a lot of force going through your rope, and that's usually the first thing to break. If everyone pulls gently, you don't have to worry.

Troubleshooting Tip: If you’re finding there’s just too much friction between the rope and the broomstick (meaning that the rope doesn’t slide smoothly over the broom handles, then click here to learn how to upgrade to pulleys. [/am4show]

Simple machines make our lives easier. They make it easier to lift, move and build things. Chances are that you use simple machines more than you think. If you have ever screwed in a light bulb, put the lid on a jam jar, put keys on a keychain, pierced food with a fork, walked up a ramp, or propped open a door, you've made good use of simple machines. A block and tackle setup is also a simple machine.

Block and tackle refers to pulleys and rope (in that order). One kid can drag ten adults across the room with this simple setup – we've done this class lots of times with kids and parents, and it really works! Be careful with this experiment - you'll want to keep your fingers away from the rope and don't pull too hard (kids really get carried away with this one!)

If you haven't already, make sure you try out the broomstick version of this activity first.

[am4show have='p8;p9;p11;p38;p92;p14;p41;p88;' guest_error='Guest error message' user_error='User error message' ] Materials:
  • Rope
  • pulleys
  • chain link fence (or a broom)
  • three people
Cut off about 12" of rope and circle a loop around a strong support, like a chain link fence. Before you tie a knot, thread three pulleys onto the rope… and now tie it off.

Make another circle of rope and add three more pulleys onto it. Loop the rope over the handle of a mop or broom. Thread the rest of the nylon rope through zigzag fashion first through one pulley on the fence, then through a pulley on the mop, then to an open pulley back on the fence, then another free pulley on the mop, etc… Knot the end of the rope to the mop. You should have one free end of rope left.

Attach a kid to the free end of the rope by adding a handle.  You can thread a rope through a 6" piece of PVC pipe and tie the rope back on itself.  Attach adults to the mop, holding it straight out in front of their chest.  The adults' job is to resist the pull they will feel as the kid pulls with his end of the rope.



Download Student Worksheet [/am4show]

Silly as our application for this experiment may sound, we use this system to keep pens handy near the shopping list on the fridge.  It’s saved us from many pen-searches over the years!

We install these at various places around the house (by the telephone, fridge, front door, anywhere that you usually need a pen at the last minute), and have even seen them at the counters of local video-rental stores.

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Download Student Worksheet

Troubleshooting: It’s important to note that the weight needs to slide freely both up and down the length of the cord (which is why fishing line is a great choice – the surface of the line is very low friction). Another important tip: the weights you use must weigh more than the object at the end of the string plus the force of friction in the lines (and the pulley).  Hollow, metal objects work great like nuts (for bolts).

You’ll need to practice to find just the right balance point: where the pen flies up to its resting position when you let go of the pen.

This is a great addition to any tree house or playground structure!  Hang a loop of rope from a tree branch (don't forget to thread the pulleys onto the rope before you tie the knot!  Connect one pulley to the basket handle made from a circle of short rope.  Tie a length of rope to the basket handle, then up through one tree pulley, down through the basket pulley, and up through the second tree pulley. Thread a 6" length of PVC pipe onto the end and tie the rope back onto itself to form a handle.

[/am4show]

These homemade pulleys work great as long as they glide freely over the coat hanger wire (meaning that if you give them a spin, they keep spinning for a few more seconds).  You can adjust the amount of friction in the pulley by adjusting the where the metal wire bends after it emerges from the pulley.

[am4show have='p8;p9;p11;p38;p92;p14;p41;p88;' guest_error='Guest error message' user_error='User error message' ] All you need is a wire coathanger, a thread spool, and a pair of vice grips... and the video below.


Download Student Worksheet

Cut a wire coat-hanger at the lower points (at the base of the triangular shape) and use the hook section to make your pulley. Thread both straight ends through a thread spool, crossing in the middle, and bend wire downwards to secure spool in place. Be sure the spool turns freely. Use hook for easy attachment. (These pulleys work well for the return-pulley system experiment in this section.)
If you still have trouble, you can purchase pulleys from the hardware store, or more inexpensively, from a farm supply store. (We get ours from the chicken coup section – no kidding!) If you really want to go hog-wild with pulleys, get a bunch and clip them onto climbing-rated carabineer. [/am4show]

trebuchet23This experiment is for Advanced Students. For ages, people have been hurling rocks, sticks, and other objects through the air. The trebuchet came around during the Middle Ages as a way to break through the massive defenses of castles and cities. It’s basically a gigantic sling that uses a lever arm to quickly speed up the rocks before letting go. A trebuchet is typically more accurate than a catapult, and won’t knock your kid’s teeth out while they try to load it.


Trebuchets are really levers in action. You’ll find a fulcrum carefully positioned so that a small motion near the weight transforms into a huge swinging motion near the sling. Some mis-named trebuchets are really ‘torsion engines’, and you can tell the difference because the torsion engine uses the energy stored in twisted rope or twine (or animal sinew) to launch objects, whereas true trebuchets use heavy counterweights.


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This is a serious wood-construction project. If you have access to scrap wood and basic tools (and glue!), you have everything you need to build this project. You will need to find heavy objects (like rocks or marbles) for the weights.


We want kids to discover that science isn’t in the special parts that come with a kit, but rather in the imagination and skill of the kid building it. We strive to avoid parts that are specially made just for a kit, molded plastic pieces, etc. and instead use parts that any kid could buy from the store. This means that kids can feel free to change things around, use their own ideas to add improvements and whatever else their imagination can come up with. So on this note, let’s get started.


WARNING: This project requires the use of various hand tools. These tools should only be used with adult supervision, and should not be used by children under 12 years of age.


Tools you’ll need:


  •   Hammer
  •   Electric drill with ¼” bit
  •   Hot glue gun & glue sticks
  •   Measuring tape or ruler
  •   Hand saw & clamp (or miter box)
  •   Scissors
  •   Screwdriver (flathead) or wood chisel

Materials:


  • 7 pieces of ½” x ½” x 24″ pieces of wood stock
  • 2 pieces of ¾” x 24″ wood
  • 1 piece of 3″ x 24″ wood
  • 18″ Wooden dowel
  • Screw eye
  • Nails
  • String
  • Clear tube
  • Rubber mesh

Note: wood pieces may be slightly larger or smaller than specified. Just use your best judgment when sizing.


From ½” x ½” x 24″ pieces of wood stock cut:


  • 3 pieces 5″ long
  • 2 pieces 9″ long
  • 3 pieces 3-1/2″ long
  • 4 pieces 5-1/2″ long

From the dowel cut:


  • 2 pieces 7″ long
  • 1 piece 4″ long

From the 3″ x 24″ flat piece of wood cut:


  • 2 pieces 3″ long (one of these has a 1″ square notch in it)
  • 2 pieces 5″ long
  • 1 piece 4-1/2″ long

AND…


  • String should be cut into 2 pieces 14-16″ long
  • The pouch is cut from the rubber mesh and is 5″ x 1-1/2″


 


Advanced Students: Download your Student Worksheet Lab here!


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We’re going to practice measuring and calculating real life stuff (because science isn’t just in a textbook, is it?) When I taught engineering classes, most students had never analyzed real bridges or tools before – they only worked from the textbook. So let’s jump out of the words and into action, shall we? This experiment is for Advanced Students.


Before we start, make sure you’ve worked your way through this experiment first!


[am4show have=’p8;p9;p11;p38;p92;p41;p85;p88;’ guest_error=’Guest error message’ user_error=’User error message’ ]
For this experiment, you need:


  1. Meter or yard stick
  2. A stopwatch or timer
  3. Object

Here’s what you do:



Download Student Worksheet & Exercises


1. Grab your 100 gram object, put it on a table.


2. Now lift it off the table straight up until you lift it one meter (one yard).


3. Start the timer and at the same time start lifting the object up and down 20 times.


4. Stop the timer when you’re done with the 20 lifts.


So, do you have the power of the Dodge Viper? Hmmm, probably not but let’s take a look.


First of all figure out how much work you did. Work = force x distance so take the force you used and multiply that by the distance you moved it. In this case, you can multiply 1 Newton x 20 meters and get 20 Joules of work.


Now figure out how much power you used. Power is work divided by time so take your work (20 Joules) and divide it by how much time it took you to do that work.


For example, if you lifted the block 20 times (doing 20 Joules of work) in 5 seconds, you did 20 Joules/5 seconds = 4 Watts of power. To convert Watts to horsepower we multiply by .001 so in this example, you did 4 x .001 = .004 horsepower. Not exactly vroom vroom!


Exercises


  1. What is work?
    1. Force divided by distance
    2. Force times distance
    3. Energy required for power
    4. Kinetic and potential energy
  2. What is power?
    1. Work divided by time
    2. Work multiplied by time
    3. Energy used in an exercise
    4. Calories over time
  3. How do we measure work? Name one unit.
  4. How do we measure power? Name one unit.

[/am4show]


This experiment is for Advanced Students. We’re going to really get a good feel for energy and power as it shows up in real life. For this experiment, you need:


  • Something that weighs about 100 grams or 4 ounces, or just grab an apple.
  • A meter or yard stick

This might seem sort of silly but it’s a good way to get the feeling for what a Joule is and what work is.
[am4show have=’p8;p9;p11;p38;p92;p41;p85;p88;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Download Student Worksheet & Exercises


1. Grab your 100 gram object, put it on a table.


2. Now lift it off the table straight up until you lift it one meter (one yard).


3. Lift it up and down 20 times.


A 100 gram object takes about one Newton of force to lift. Since it took one Newton of force to lift that object, how much work did we do? Remember work = force x distance so in this case work = 1 Newton x 20 meters or work = 20 Joules.


You may ask “but didn’t we move it 40 meters, 20 meters up and 20 down?” That’s true, but work is moving something against a force. When you moved the object down you were moving the object with a force, the force of gravity. Only in lifting it up, are you actually moving it against a force and doing work. Four Joules are about 1 calories so we did 5 calories of work.


“Wow, I can lift an apple 20 times and burn 5 calories! Helloooo weight loss!” Well…not so fast there Richard Simmons. When we talk about calories in nutrition we are really talking about kilo calories. In other words, every calorie in that potato chip is really 1000 calories in physics. So as far as diet and exercise goes, lifting that apple actually only burned .005 calories of energy,…rats.


It is interesting to think of calories as the unit of energy for humans or as the fuel we use. The average human uses about 2000 calories (food calories that is, 2,000,000 actual calories) a day of energy. Running, jumping, sleeping, eating all uses calories/energy. Running 15 minutes uses 225 calories. Playing soccer for 15 minutes uses 140 calories. (Remember those are food calories, multiply by 1000 to get physics calories). This web site has a nice chart for more information: Calories used in exercise.


Everything we eat refuels that energy tank. All food has calories in it and our body takes those calories and converts them to calories/energy for us to use. How did the food get the energy in it? From the sun! The sun’s energy gives energy to the plants and when the animals eat the plants they get the energy from the sun as well.


So, if you eat a carrot or a burger you are getting energy from the sun! Eating broccoli gives you about 50 calories. Eating a hamburger gives you about 450 calories! We use energy to do things and we get energy from food. The problem comes when we eat more energy than we can use. When we do that, our body converts the energy to fat, our body’s reserve fuel tank. If you use more energy then you’ve taken in, then your body converts fat to energy. That’s why exercise and diet can help reduce your weight.


Let’s take the concept of work a little bit farther. If Bruno carries a 15 pound bowling ball up a 2 meter (6 foot) flight of stairs, how much work does he do on the bowling ball? It takes 66 Newtons of force to lift a 15 pound bowling ball 1 meter. Remember work = force x distance.


So, work = 66 Newtons x 2 meters. In this case, Bruno does 132 Joules of work on that bowling ball. That’s interesting, but what if we wanted to know how hard poor Bruno works? If he took a half hour to go up those stairs he didn’t work very hard, but if he did it in 1 second, well then Bruno’s sweating!


That’s the concept of power. Power is to energy like miles per hour is to driving. It is a measure of how much energy is used in a given span of time. Mathematically it’s Power = work/time. Power is commonly measured in Watts or Horsepower. Let’s do a little math and see how hard Bruno works.


In both cases mentioned above Bruno, does 132 Joules of work, but in the first case he does the work in 30 minutes (1800 seconds) and in the last case he does it in 1 second. Let’s first figure out Bruno’s power in Watts. A Watt is 1 Joule/second so:


For the half hour Bruno’s Power = 132 Joules/1800 seconds = .07 Watts


For the second Bruno’s Power = 132 joules/1 second = 132 Watts


You can see that the faster you exert energy the more power you use. Another term for power is horsepower. You may have heard the term horsepower in car ads. The more powerful car can exert more energy faster, getting the car moving faster. A Dodge Viper has 450 horsepower which can accelerate a 3,300 pound car from 0 to 60 mph in 4.1 seconds…WOW!


One horsepower is 745 Watts or one Watt is .001 horsepower. So converting Watts to horsepower poor Bruno exerts:


.07 x .001 = .00007 horsepower over the half hour


132 x .001 = .132 horsepower over the second (not exactly a Dodge Viper!)


Exercises


  1. If something has a weight of 2 Newtons and is moved half a meter, how many Joules of energy are used? Show your work.
  2. What is the source of all this energy we’re working with here?
  3. It doesn’t count as work when you move the apple back down. Why not?

[/am4show]


We’re going to use everyday objects to build a simple machine and learn how to take data. Sadly, most college students have trouble with these simple steps, so we’re getting you a head start here. The most complex science experiments all have these same steps that we’re about to do… just on a grander (and more expensive) scale. We’re going to break each piece down so you can really wrap your head around each step. Are you ready to put your new ideas to the test?


This experiment is for Advanced Students.


[am4show have=’p8;p9;p11;p38;p92;p41;p75;p85;p88;’ guest_error=’Guest error message’ user_error=’User error message’ ]
You need:


  • A wooden ruler or a paint stick for the lever
  • Many pennies, quarters, or washers (many little somethings of the same mass)
  • A spool, eraser, pencil (anything that can be your fulcrum)
  • A ruler (to be your um….ruler)
  • Paper cups
  • Optional: A scale that can measure small amounts of mass (a kitchen scale is good)


Download Student Worksheet & Exercises


1. Tape one paper cup to each end of lever. (This allows for an easy way to hold the pennies on the lever.)


2. Set your fulcrum on the table and put your lever (ruler or paint stick) on top of it. Try to get the ruler to balance on the fulcrum.


3. Put five pennies on one side of your lever.


4. Now, put pennies, one at a time on the other side of your lever, this is your effort. Keep adding pennies until you get your lever to come close to balancing. Try to keep your fulcrum in the same place on your lever. You may even want to tape it there.


5. Count the pennies on the effort side and count the pennies on the load side. If you have a scale, you can weigh them as well. With the fulcrum in the middle you should see that the pennies/mass on both sides of the lever are close to equal.


6. This part’s a little tricky. Measure how high the lever was moved. On the load side, measure how far the lever moved up and on the effort side measure how far the lever moved down. Be sure to do the measuring at the very ends of the lever.


7. Write your results in your science journal as shown in the video.


8. Remove the pennies and do it all over again, this time move the fulcrum one inch (two centimeters) closer to the load side.


9. Continue moving the fulcrum closer to the load until it gets too tough to do. You’ll probably be able to get it an inch or two (two to four centimeters) from the load.


10. If you didn’t use a scale feel free to stop here. Don’t worry about the “work in” and “work out” parts of the table. Take a look at your table and check out your results. Can you draw any conclusions about the distance the load moved, the distance the effort moved, and the amount of force required to move it?


11. If you used a scale to get the masses you can find out how much work you did. Remember that work=force x distance. The table will tell you how to find work for the effort side (work in) and for the load side (work out). You can multiply what you have or if you’d like to convert to Joules, which is a unit of work, feel free to convert your distance measurements to meters and your mass measurements to Newtons. Then you can multiply meters times Newtons and get Joules which is a unit of work.


1 inch = .025 meters


1 cm = .01 meter


1 ounce =0.278 Newtons


1 gram = 0.0098 Newtons


By taking a look at your data and by all the other work we did this lesson, you can see the beautiful switcheroo of simple machines. Simple machines sacrifice distance for force. With the lever, the farther you had to push the lever, the less force had to be used to move the load.


The work done by the effort is the same as the work done on the load. By doing a little force/distance switcheroo, moving the load requires much less force to do the work. In other words, it’s much easier. Anything that makes work easier gets a thumbs up by me! Hooray for simple machines!


Exercises


  1. What is work?
    1. Force against an object
    2. Force over distance
    3. 9 hours and sweat
    4. Energy applied to an object
  2. What is the unit we use to measure energy?
    1. Newton
    2. Watt
    3. Joule
    4. Horsepower
  3. Describe a first class lever using one example.

[/am4show]


When people mention the word “hydraulics”, they could be talking about pumps, turbines, hydropower, erosion, or river channel flow.  The term “hydraulics” means using fluid power, and deals with machinesand devices that use liquids to move, lift, drive, and shove things around.

Liquids behave in certain ways: they are incompressible, meaning that you can’t pack the liquid into a tighter space than it already is occupying.

If you've ever filled a tube partway with water and moved it around, you've probably noticed that the water level will remain the same on either side of the tube.

However, if you add pressure to one end of the tube (by blowing into the tube), the water level will rise on the opposite side. If you decrease the pressure (by blowing across the top of one side), the water level will drop on the other side.

In physics, this is defined through Pascal's law, which tells us how the pressure applied to one surface can be transmitted to the other surface. As liquids can't be squished, whatever happens on one surface affects what occurs on the other.  Examples of this effect include siphons, water towers, and dams. Scuba divers know that as they dive 30 feet underwater, the pressure doubles. This effect is also show in hydraulics - and more importantly, in the project we're about to do!

But first, let's understand what's happening with liquids and pressure:

Here’s an example: If you fill a glass full to the brim with water, you reach a point where for every drop you add on top, one drop will fall out.  You simply can’t squish any more water molecules into the glass without losing at least the same amount. Excavators, jacks, and the brake lines in your car use hydraulics to lift huge amounts of weight, and the liquid used to transfer the force is usually oil at 10,000 psi.

Air, however, is compressible.  When car tires are inflated, the hose shoves more and more air inside the tire, increasing the pressure (amount of air molecules in the tire).  The more air you stuff into the tire, the higher the pressure rises.  When machines use air to lift, move, spin, or drill, it’s called “pneumatics”. Air tools use compressed air or pure gases for pneumatic power, usually pressurized to 80-100 psi.

Different systems require either hydraulics or pneumatics.  The advantage to using hydraulics lies in the fact that liquids are not compressible. Hydraulic systems minimize the “springy-ness” in a system because the liquid doesn’t absorb the energy being transferred, and the working fluids can handle much heavier loads than compressible gases.  However, oil is flammable, very messy, and requires electricity to power the machines, making pneumatics the best choice for smaller applications, including air tools (to absorb excessive forces without injuring the user).

We're going to build our own hydraulic-pneumatic machine.  Here's what you need to do: [am4show have='p8;p9;p11;p38;p92;p14;p41;p75;p88;' guest_error='Guest error message' user_error='User error message' ] Materials:
  • plastic cup
  • 20 tongue-depressor-size popsicle sticks
  • 6 syringes (anything in the 3-10mL size range will work)
  • 6 brass fasteners
  • 5’ of flexible tubing (diameter sized to fit over the nose of your syringes)
  • four wheels (use film canister lids, yogurt container lids, milk jug lids, etc.)
  • 4 rubber bands
  • two naked (unwrapped) straws
  • skewers that fit inside your straws
  • hot glue gun (with glue sticks)
  • sharp scissors or razor (get adult help)
  • drill with small drill bits (you’ll be drilling a hole large enough to fit the stem of a brass fastener)
earthmover Let’s play with these different ideas right now and really “feel” the difference between hydraulics and pneumatics. Connect two syringes with a piece of flexible tubing.  Cut the tubing into three equal-sized pieces and use one to experiment with.  Shove the plunger on one syringe to the “empty”, and leave the other in the “filled” position before connecting the tubing.  What happens when you push or lift one of the plungers? Is it quick to respond, or is there “slop” in the system?

Now remove both plungers and, leaving the tubing attached, fill the system with water to the brim on both ends (this is a good bath-time activity!).  Keep the open ends of the syringes at the same level as you fill them.  What happens if you lower one of the syringes? What happens when you raise it back up?  Is there now air in your system?

Fill your syringe-tube system up with water again, keeping the plungers at the same height as you work.  Insert one of the plungers into one of the syringes and play with the levels of the syringes again, lifting one and lowering the other.  Now what happens, or doesn’t happen?

Why does that work? Because both syringes are open to the atmosphere, they both have equal amounts of air pressure pushing down on the surface of the water.  When you raise one syringe higher than the other, you have increased the elevation head of higher syringe, which works to equalize the water levels in the two syringes (thus shoving water out of the lower syringe).  Elevation head is due to the fluid’s weight (gravitational force) acting on the fluid and is related to the potential energy of the raised syringe (which increased with elevation).

Now connect your plungers into a fully hydraulic system:  Push the plunger all the way down to expel the water from one of the syringes (water should leak all over the place from the open syringe).  Now add the second plunger to the open syringe and push the plunger down halfway.  What happens?  You have just made a hydraulic system!

Are you ready to build it into a three-axis machine?  Then click the play button below:


Download Student Worksheet [/am4show]

This isn't strictly a 'levers' experiment, but it's still a cool demonstration about simple machines, specifically how pulleys are connected with belts.

Take a rubber band and a roller skate (not in-line skates, but the old-fashioned kind with a wheel at each corner.) Lock the wheels on one side together by wrapping the rubber band around one wheel then the other.  Turn one wheel and watch the other spin.

Now crisscross the rubber band belt by removing one side of the rubber band from a wheel, giving it a half twist, and replacing it back on the wheel.  Now when you turn one wheel, the other should spin the opposite direction. Here's a quick video on what to expect:

[am4show have='p8;p9;p11;p38;p92;p14;p41;p88;' guest_error='Guest error message' user_error='User error message' ]


Download Student Worksheet [/am4show]

Parts of the Lever

Levers, being simple machines, have only three simple parts. The load, the effort, and the fulcrum. Let’s start with the load. The load is basically what it is you’re trying to lift. The books in the last experiment where the load. Now for the effort. That’s you. In the last experiment, you were putting the force on the lever to lift the load. You were the effort. The effort is any kind of force used to lift the load. Last for the fulcrum. It is the pivot that the lever turns on. The fulcrum, as we’ll play with a bit more later, is the key to the effectiveness of the lever.

There are three types of levers. Their names are first-class, second-class and third-class. I love it when it’s that simple. Kind of like Dr. Seuss’s Thing One and Thing Two. The only difference between the three different levers is where the effort, load and fulcrum are.

[am4show have='p8;p9;p11;p38;p92;p14;p41;p88;p92;' guest_error='Guest error message' user_error='User error message' ] Are you ready for some 'vintage Aurora' video? We thought you'd want to check out one of the first videos she ever made (in her basement with the auto-focus stuck in the ON position). Enjoy!



Download Student Worksheet & Exercises

Advanced students: Download your First, Second, and Third Class Levers"

First-Class Leveritem7

A first-class lever is a lever in which the fulcrum is located in between the effort and the load. This is the lever that you think of whenever you think of levers. The lever you made in Experiment 1 is a first-class lever. Examples of first-class levers are the see-saw, a hammer (when it’s used to pull nails), scissors (take a look, it’s really a double lever!), and pliers (same as the scissors, a double lever).

First Class Lever Experiment

For this experiment, you'll need:
  1. A nice strong piece of wood. 3 to 8 feet long would be great if you have it.
  2. A brick , a thick book or a smaller piece of wood (for the fulcrum)
  3. Books, gallons of water or anything heavy that’s not fragile
Be careful with this. Don’t use something that’s so heavy someone will get hurt. Also, be sure not to use something so heavy that you break the wooden lever. Last but not least, be sure to keep your head and face away from the lever. I’ve seen folks push down on the lever and then let go. The lever comes up fast and can pop you pretty hard.

1. Put your fulcrum on the ground.

2. Put your lever on the fulcrum. Try to get your fulcrum close to the middle of the lever.

3. Put some weight on one end of the lever.

4. Now push down on the other side of the lever. Try to remember how hard (how much force) you needed to use to lift the heavy object.

5. Move the fulcrum under the lever so that it is closer to the heavy object.

6. Push down on the other side of the lever again. Can you tell the difference in the amount of force?

7. Move the fulcrum closer still to the heavy object. Feel a difference now?

8. Feel free to experiment with this. Move the fulcrum farther away and closer to the object. What conclusions can you draw?

What you may have found, was that the closer the fulcrum is to the heavy object, the less force you needed to push with to get the object to move. Later we will look at this in greater detail, but first let me tell you about the other types of levers.

Second-Class Lever

item8The second-class lever is a little strange. In a second-class lever, the load is between the fulcrum and the effort. A good example of this, is a wheel-barrow. The wheel is the fulcrum, the load sits in the wheel-barrow bucket and the effort is you. Some more examples would be a door (the hinge is the fulcrum), a stapler, and a nut-cracker.

Second-class Lever Experiment

You need:
  1. A nice strong piece of wood. 3 to 8 feet long would be great if you have it.
  2. A brick, a thick book or a smaller piece of wood (for the fulcrum)
  3. Books, gallons of water or anything heavy that’s not fragile
Again, be careful with this. Don’t use something that’s so heavy someone will get hurt. Also, be sure not to use something so heavy that you break the wooden lever. Last but not least, be sure to keep your head and face away from the lever. I’ve seen folks push down on the lever and then let go. The lever comes up fast and can pop you pretty hard.

1. Put your fulcrum, the book or the brick, whatever you’re using on a nice flat spot.

2. Put the end of your lever on the fulcrum.

3. Put the books or gallon jugs or whatever you’re using for a load, in the middle of the lever.

4. Now, put yourself (the effort) on the opposite end of the lever from the fulcrum.

5. Lift

6. Experiment with the load. Move it towards the fulcrum and lift. Then move it toward the effort and lift. Where is it harder(takes more force) to lift the load, near the fulcrum or far? Where does the load lift the greatest distance, near the fulcrum or far?

Third-Class Lever

This fellow is the oddest of all. The third-class lever has the effort between the load and the fulcrum. Imagine Experiment 1 but this time the fulcrum is at one end of the board, the books are on the other item9end and you’re in the middle. Kind of a strange way to lift books huh? A few examples of this are tweezers, fishing rods (your elbow or wrist is the fulcrum), your jaw (the teeth crush the load which would be your hamburger), and your arm (the muscle connects between your elbow (fulcrum) and your load( the rest of your arm or whatever you’re lifting)). Your skeletal and muscular system are, in fact, a series of levers!

Third-class Lever Experiment

You need:
  1. A nice strong piece of wood. 3 to 8 feet long would be great if you have it.


  2. A brick , a thick book or a smaller piece of wood (for the fulcrum)


  3. Books, gallons of water or anything heavy that’s not fragile


Again, be careful with this. Don’t use something that’s so heavy someone will get hurt. Also, be sure not to use something so heavy that you break the wooden lever. Last but not least, be sure to keep your head and face away from the lever. I’ve seen folks push down on the lever and then let go. The lever comes up fast and can pop you pretty hard.

1. Put your fulcrum on the ground in a nice flat place.

2. Put your lever on the fulcrum so that the fulcrum is at the very end of the lever.

3. Put your load on the lever at the end farthest from the fulcrum.

4. Now, put yourself (the effort) in the middle of the lever.

5. Lift. You may need someone to hold down the lever on the fulcrum

6. Experiment with the effort (you). Move towards the fulcrum and lift the load Then move toward the load and lift. Where is it harder(takes more force) to lift the load, near the fulcrum or far? Where does the load lift the greatest distance, near the fulcrum or far?

We’ve had a lot of fun levering this and levering that but now we have to get to the point of all this simple machine stuff. Work equals force times distance, right? Well, what have you been doing all this time with these levers? You’ve been moving something (the load) a distance against a force (gravity). You’ve been doing work. You’ve been exerting energy. See how it all ties in nicely?

In experiment 1,2 and 3, I wanted you to notice how much force you exerted and how much the load moved. You may have noticed that when the force was small (it was very easy to lift) the load moved a very small distance. On the other hand, when the force was large (hard to lift), the load moved a greater distance. Let me point your attention to one more thing and then we’ll play with this.

When the force used to lift the load was small, you moved the lever a large distance. When the force used to lift the load was great you moved the lever a small distance. Remember, work=force x distance. There is work done on both sides of the lever. The effort (you in this case) pushes the lever a distance against a force...work is done. The load also moves a distance against a force so there too...work is done.

Now, here’s the key to this that I hope you can see in the next experiment. Work in is equal to work out. The work you do on one side of the lever (work in), is equal to the work that happens to the load (work out). Let’s do a quick bit of math for an example. Phillip wants to move a 10 kg (22 lb.)box. He uses a lever and notices that when he lifts the box .1meter (4 inches) item10he has to push the lever down 1 meter with a force of 1 kg. Now let’s do some math. (Officially we should convert kilograms (a unit of mass) to Newtons (a unit of force) so that we can work in Joules which is a unit of work. However, we’ll do it this way so you can see the relationship more easily.)

Phillip’s work (the work in) = 1 kg x 1 m = 1

Work on the bowling ball (the work out) = 10 kg x .1 m = 1

Work in equals work out! Later in this energy unit, you’ll learn about energy efficiency. At that point, you’ll see that you never get all the energy you want from the energy you put in. Some is lost to sound and some to heat. A lever is incredibly efficient but you may still see, in your measurements, that the energy in is greater than the energy you get out.

For Advanced Students:

[/am4show][am4show have='p9;p41;' guest_error='Guest error message' user_error='User error message' ] Speaking of your measurements...let’s make some. Open up your science journal and record the type of lever, weight, and location information for your different trial runs. Take a look at your data - can you figure out how much weight you'd need to lift your parents?

Let's see if we can figure this out. For a 10' long beam with the fulcrum in the exact center, you can lift as much as you weigh. For example, if you weigh 100 pounds, you can lift some sitting on the other end, as long as they weigh 100 pounds or less. If you slide the beam and move the fulcrum so that the longer end is on your side, you can lift more than you weigh.

So if there's 7 feet of beam on Alice's side and only 3 feet on Bob's end, you can easily figure this out with a little math (and principles of torque). Here's what you do:

(Alice's Weight) * (Distance from Alice to the Fulcrum) = (Alice's Lifting Ability) * (Distance from Bob to the Fulcrum)

If Alice weighs 100 pounds and when standing on the 7-foot end of the see saw, she barely can lift Bob, let's find out how much Bob weighs.

(100 pounds) (7 feet) = (Alice's Lifting Ability) * (3 feet) 700 / 3 = Alice's Lifting Ability, and since she can just barely lift Bob... Bob weighs 233 pounds!

Now can you figure out how much lever arm distance you need to lift your parents? If Mom and Dad together weigh 300 pounds, and you have a 10' long beam and you weigh 100 pounds, let's find the fulcrum distance you'd need to lift them. Let's put your algebra to use here:

Let's make 'x' the distance from you to the fulcrum. This makes the distance from your parents to the fulcrum 10' - x. (If you're 4 feet from the fulcrum, that means your parents are 6', right?)

(100 pounds) (x) = (300 pounds) (10' - x) 100 x = 3000 - 300 x 400 x = 3000 x = 3000 / 400 Solve for x and you'll find that the distance from you to the fulcrum is 7.5 feet!

Exercises Answer the questions below:
  1. What is the best definition for a simple machine?
    1. A machine with less than three parts
    2. A machine with a simple name
    3. A machine that changes the direction or amount of a force
    4. A machine that helps you do work quickly
  2. What are the three parts of a lever? Circle all that apply:
    1. Fulcrum
    2. Weight
    3. Load
    4. Effort
  3. Name two examples of levers that you could find in your house:
  4. What are the types of levers called?
    1. Three tiers
    2. First, second, and third class
    3. Poor, rich, and middle
    4. Forty-five and ninety-nine percenters
    [/am4show]

What’s an inclined plane? Jar lids, spiral staircases, light bulbs, and key rings. These are all examples of inclined planes that wind around themselves.  Some inclined planes are used to lower and raise things (like a jack or ramp), but they can also used to hold objects together (like jar lids or light bulb threads).


Here’s a quick experiment you can do to show yourself how something straight, like a ramp, is really the same as a spiral staircase.


[am4show have=’p8;p9;p11;p38;p92;p14;p41;p151;p75;p85;p88;p92;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Here’s what you need to find:


  • sheet of paper
  • short dowel or cardboard tube from a coat hanger
  • tape
  • ruler

Cut a right triangle out of paper so that the two sides of the right angle are 11” and 5 ½” (the hypotenuse – the side opposite the right angle – will be longer than either of these). Find a short dowel or use a cardboard tube from a coat-hanger.  Roll the triangular paper around the tube beginning at the short side and roll toward the triangle point, keeping the base even as it rolls.


Notice that the inclined plane (hypotenuse) spirals up as a tread as you roll. Remind you of screw threads?  Those are inclined planes. If you have trouble figuring out how to do this experiment, just watch the video clip below:



 
Download Student Worksheet & Exercises


Inclined planes are simple machines. It’s how people used to lift heavy things (like the top stones for a pyramid).


Here’s another twist on the inclined plane: a wedge is a double inclined plane (top and bottom surfaces are inclined planes). You have lots of wedges at home: forks, knives, and nails just name a few.


When you stick a fork in food, it splits the food apart. You can make a simple wedge from a block of wood and drive it under a heavy block (like a tree stump or large book) with a kid on top.


Exercises


  1. What is one way to describe energy?
    1. The amount of atoms moving around at any given moment
    2. Electrons flowing from one area to another
    3. The ability to do work
    4. The square root of the speed of an electron
  2. Work is when something moves when:
    1. Force is applied
    2. Energy is used
    3. Electrons are lost or gained
    4. A group of atoms vibrate
  3. Name two simple machines:
  4. Name one example of a simple machine:

[/am4show]


Although urine is sterile, it has hundreds of different kinds of wastes from the body. All sorts of things affect what is in your urine, including last night’s dinner, how much water you drink, what you do for exercise, and how well your kidneys work in the first place. This experiment will show you how the kidneys work to keep your body in top shape.


[am4show have=’p8;p9;p11;p38;p92;p29;p56;p81;p87;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Materials


  • 1 liter of water per student
  • 1 can of soda per student
  • 1 sports drink, like Gatorade, per student
  • Red food dye
  • Chalk (or a handful of sand)
  • Coffee filter or cheesecloth
  • pH paper strips
  • Disposable cups
  • Clean glass jar
  • Rubber band
  • Measuring cups

If you are doing the optional Third Bonus Experiment:


  • solution your teacher has prepared for you
  • pipe cleaners
  • cleaned out jar or bottle (pickle, jam, or mayo jar)
  • water
  • borax

Download Student Worksheet & Exercises


Experiment

First Experiment: How Quickly Do the Kidneys Process Fluids?


  1. Drink a liter of water quickly (in less than five minutes).
  2. Wait 20 minutes (you can start on the second part of this lab while you wait) and then collect your urine in a disposable cup in the bathroom and use a pH testing strip to test the pH by dipping it in the cup.
  3. Repeat four times so that you have four samples collected 20 minutes apart.
  4. Repeat steps 1-3  for two different liquids, such as a sports drink and a soda.
  5. Complete the data table for all three liquids.

Second Experiment: Kidney Filtration


  1. Crush a piece of chalk and place it in a clean glass jar. (You can alternatively use a handful of sand from the playground if you don’t have chalk.)
  2. Fill the jar partway with water.
  3. Add a few drops of red food coloring to the water.
  4. The chalk (or sand) represents toxins in the blood. The water represents the blood.
  5. Place a coffee filter (or cheesecloth) on top of the jar and secure with a rubber band. This coffee filter is your kidney.
  6. Tip the jar over a disposable cup and pour the contents into the disposable cup. This is the kidney filtering the blood.
  7. Observe what the filter traps and what it doesn’t and record your observations in the data table.

BONUS Third Experiment: Kidney Stones


  1. A kidney stone is something that develops in the urinary tract from a crystal. Crystals start from “seed crystals” that grow when placed in the right solution.
  2. Use a pipe cleaner to create a shape for crystals to cling to (suggestion: cut into 3 lengths and wrap around one another). Curl the top pipe cleaner around a pencil, making sure the shape will hang nicely in the container without touching the sides.
  3. Add 2 cups of water and 2 cups of borax (sodium tetraborate) into a pot. Heat, stirring continuously for about 5-10 minutes. Do not boil, but only heat until steam rises from the pan.
  4. When the borax has dissolved, add more, and continue to do so until there are bits of borax settling on the bottom of the pan that cannot be stirred in (It may be necessary to stop heating and let the solution settle if it gets too cloudy). You’ll be adding in a lot of borax!  You have now made a supersaturated solution. Make sure your solution is saturated, or your crystals will not grow.
  5. Wait until your solution has cooled to about 130oF (hot to the touch, but not so hot that you yank your hand away). Pour this solution (just the liquid, not the solid bits) into the jar, and add the pipe cleaner shape. Make sure the pipe cleaner is submerged in the solution. Put the jar in a place where the crystals can grow undisturbed overnight, or even for a few days. Warmer locations (such as upstairs or on top shelves) are best.
  6. NOTE: These crystals are NOT edible! Please keep them away from small children and pets!

 


Kidneys Process Fluids Data Table

Record the pH and volume (did you urinate a lot, medium, or little?)


Drink Type


20 min


40 min


60 min


80 min


 


Urine tests look at different components of urine. Most urine tests are done to get information about the body’s health and clarify problems that it might be having.  There are over 100 different kinds of urine tests that can be done. Depending on the test, scientists look for different things.


The most obvious, and the one you can do yourself at home, is to look at the color of urine, which is normally clear. Many different things affect urine color, and the darker it is, the less water there is in it. Vitamin B supplements can turn it bright yellow. If you like to eat blackberries, beets or rhubarb, then your urine might be red-brown.


The next thing to check is smell. Since urine doesn’t smell much, it’s a signal if it suddenly takes on an unusual odor. For example, if you have an E. coli infection, your urine will take on a bad odor.


Scientists also check the specific gravity, which is a measure of the amount of substances in the urine. The higher the specific gravity number measures, the more substance is in the urine. For example, when you drink a lot of water, your kidneys add that water into the urine, which makes for a lower the specific gravity number. This test shows how well the kidneys balance the amount of water in urine. The specific gravity for normal urine is between 1.005-1.030.


pH is a measure of how basic or acidic something is, and for a urine test, it’s the pH of the urine itself.  A pH of 7 is neutral, a 9 is strongly basic, and a 4 is strongly acidic. Using a strip of pH paper will tell you how basic or acidic your urine is. Normally, pH is between 4.6-8.0 for urine.


Protein is not supposed to be in the urine, unless you’re sick with a fever, just had a hard workout session, or are pregnant. Scientists look for protein to be present in the urine to detect certain kinds of kidney diseases.


Glucose is sugar in the blood, and usually there’s no glucose in urine, or if there is, it’s only a tiny bit. When scientists detect glucose in the urine, it means that the body’s blood sugar levels are very high, and they know they need to look into things further.


When scientists find nitrites, they know that bacteria are present, especially the kind that cause a urinary tract infection because bacteria make an enzyme that changes nitrates to nitrites in the urine.


Strong, healthy people will have a couple of small crystals in their urine. If scientists find a large number of crystals, then they start looking for kidney stones. If they don’t find kidney stones, then they start looking at how the body metabolizes food to see if there’s a problem.


Most adults make about 1-2 quarts of urine each day, and kids make about 0.6-1.6 quarts per day


Kidneys Filtration Data Table

Amount of Chalk or Sand


Amount of Water


Color of Water after Mixed


Amount of Solids Filtered
Out by Cheesecloth


 


Questions:


  1. Which fluid produced more urine for the first experiment?
  2. Did the caffeine solutions cause the calcite stones to shrink or have no effect?
  3. What does pouring the chalky water through a coffee filter show?
  4. What are kidney stones and how are they formed?

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Our sense of touch provides us with information that helps us to process and explore our world. Nerves play an important part in the sense of touch by being the wires that carry signals from the skin to the brain. But the body has a plan in place so that our brains don’t get overwhelmed with too much information. This plan is a lot like a blueprint for wiring a house. Just like a house has light switches and electrical outlets in strategic locations, our bodies have touch receptors of various numbers based on their location. In this lab, we will explore an arm to determine where the highest concentrations of nerves are in that limb.


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Here’s what you need


    • 1 large paper clip
    • 1 metric ruler
    • 1 partner


Download Student Worksheet & Exercises


Here’s what you do


  1. Unfold a paperclip so that it has two open ends. The ends should be about a centimeter apart.
  2. Have your partner uncover their arm up to the shoulder. They should place this arm on the table, palm up, but it is also important that they face away from you. They shouldn’t be able to see the test.
  3. GENTLY touch one or both of the open paperclip ends to your partner’s fingertip. Ask your partner to determine how many points you used to touch them (one or two). Then record their response as (Y) for a correct answer or (N) for incorrect.
  4. Continue testing based on the numbered points in the diagram. Randomly vary the points used to touch your subject’s skin, recording their Y (correct) or N (incorrect) response for each individual area.
  5. Repeat steps 3 and 4, with the paperclip ends separated at a distance of 3 cm, 5 cm, and 10 cm.
  6. Your turn! Switch places and have your partner test you and record your responses.
  7. Finally, use the diagram and your data to design a map of nerve concentrations in the arm and hand. What are some of the advantages of this nerve placement?

 What’s going on?


Endings are nerves are located so that we can use them to collect data. The highest concentrations of nerves are in our hands, feet and mouths. We use our hands to gather a lot of data, our feet for moving around, and our mouths for speaking. Luckily, the areas of our bodies that are more likely to be bumped and the ones we use to help protect ourselves have fewer nerve endings. Areas of particularly low concentration include our backs, rear ends, and arms.


Our tongues have the highest nerve concentration of all. In fact, nerve mapping researchers have learned that over half of our brain’s sensory nerves are connected to our tongues. It makes sense when you realize that we taste, talk, and feel with this relatively small organ. It really needs to connect to so many places in the brain!


Exercises


  1. Where is the highest concentration of nerve endings in the body?
  2. What are nerve ends used for?
  3. Where do you think the least amount of nerve ends should be in the body?

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How do you think animals know we’re around long before they see us? Sure, most have a powerful sense of smell, but they can also hear us first. In this activity, we are going to simulate enhanced tympanic membranes (or ear drums) by attaching styrofoam cups to your ears. This will increase the number of sound waves your ears are able to capture.


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Here’s what you need


    • 2 styrofoam cups, 12 oz.
    • 2 styrofoam cups, 32 oz.
    • 1 pair of scissors
    • 1 kitchen timer


Download Student Worksheet & Exercises


Here’s what you do


  1. Set the timer and put it on a table or desk. Walk about 6 feet away and face the timer. Listen for the ticking sound. Now, turn your back on the clock so that you are facing the other direction. How has your ability to hear the ticking changed? We can increase the sounds you hear by using the cups.
  2. Get an adult to help with cutting the cups. They will hold one of the smaller cups with one hand and make a cut about an inch (3 cm) from the rim toward the bottom of the cup.
  3. Draw a circle at the end of the cut that is about the size of your ear where it attaches to your hear. Cut out the circle.
  4. Repeat steps 2 and 3 with the other 12 oz. cup. Carefully put them on your ears with their openings pointing forward. You have just added to the size of your ears and they should be able to collect more sound vibrations. Try listening to the timer now with the cups on your ears.
  5. Now repeat steps 2 through 4 with the larger cups. Set the timer one more time and listen to the timer. Compare what you hear with what you heard with your unenhanced ears, and what you hear with the 12 oz. ears.
  6.  On a scale of 0-10, how much did the cups improve what you were able to hear? Note where you would place both the 12 oz. cups and the 32 oz. cups on the scale if 0 is the starting point equal to what you can hear with your own ears.
  7. Repeat step 5 with the bag of water and again with the baggie of air. Note the clarity of the speech you hear through each bag. Rank each bag from loudest, to medium, to quietest.

What’s going on?


Hearing is based on movement. The initial process involves the actual waves coming toward your ear, which are funneled inside to your tympanic membrane.


In this experiment we focused on the initial funneling process. This is done by the visible, external part of your ear, known as the pinna. By making the pinna larger, you also increased their ability to pick up sound vibrations. This enabled you to hear much more, and at louder levels.


The pinna also help to determine the direction from which sound is coming. If a sound is coming from the left, your left ear hears it a little bit before the right. This lets your brain know where the sound originates.


Exercises


  1. Which part of the ear is this experiment testing?
  2. What happens when you change your variable in this experiment?
  3. Did this experiment change your ability to detect which direction a sound came from?

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Have you ever held a plastic ruler over the edge of a desk or table and whacked the end of it? If so, you would notice a funny sound. This sound changes if you change the length of the ruler that is hanging over the edge. The sound you hear is made by the ruler’s vibrations.


In this lab, we begin to learn about sound. You know it is collected and deciphered by your ears, but did you also know that all sound is made when something vibrates? It could be a guitar string, vocal chords in your throat, or a plastic ruler that is hanging over the edge of the desk: vibrations make sound.


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Here’s what you need


  • 1 desk
  • 1 metric ruler


Download Student Worksheet & Exercises


Here’s what you do


  1. Place the ruler on the desk at the 20 centimeter mark. Hold the portion of the ruler that’s still on the desk down very firmly with one hand. Press down the portion of the ruler hanging off the desk with the other hand. Now let it go. The ruler should begin to vibrate up and down while producing a strange sound.
  2. Now rearrange the ruler so that it is placed at the 15 centimeter mark and give it a thump. What happens to the pitch this time? Is it higher or lower now that the overhanging portion is shorter?
  3. Make sure you try the ruler at 5 centimeters, 10 centimeters, 15 centimeters, 20 centimeters, and 25 centimeters. Listen each time and place the lengths in order from highest to lowest pitch.
  4. Finally, put the ruler at the 25 centimeter mark, with just 5 centimeters on the table and the rest hanging over the edge. Give it a whack and while it’s vibrating, slide the ruler back across the edge of the table to make the overhanging portion shorter and shorter. What happens to the sound?

What’s going on?


The overhanging portion of the ruler is the portion allowed to vibrate. This determines the sound’s pitch. When a short piece is hanging over the edge, a high pitch is made. And when the length is longer, the pitch is lower. This is what happens with all vibrating objects and is a function of their wavelengths.


Did you know that the tiniest bones in your body are found in your ear? They are called ossicles and include the hammer, anvil, and stirrup. They are located just behind your eardrum and collect the vibrations that come into the ear canal and hit your ear drum. When your ear drum begins to vibrate, the tiny bones vibrate as well. This causes your cochlea to vibrate as well, and it sends a signal to your brain for it to interpret.


Exercises


  1. How is sound made?
  2. How do you change the pitch of the ruler?

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You know that sound comes from vibration which are picked up by the pinna (external part of the ears). Then the vibrations vibrate your tympanic membrane, which in turn vibrates the ossicles and then the cochlea. The cochlea sends information through the auditory nerve and sends it to the brain, which recognizes it as sound.


In this lab, you will testing your ability to sort and match different sounds.


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Here’s what you need


    • 10 film canisters (for 53 mm film rolls)
    • beans
    • rice
    • sawdust (or pencil shavings)
    • paperclips
    • pennies
    • 1 black, felt marker
    • assistant


Download Student Worksheet & Exercises


Here’s what you do


  1. Take the caps off the canisters. Number half of them 1 to 5 and mark the others with A through E.
  2. Prepare your experiment while your partner is out of the room. Fill five of the numbered containers with one of the materials. Note which canister contains each material for data records.
  3. Next fill the lettered containers. Be sure to record which container contains which material for reference.
  4. When the contents have been noted and the lids all replaced, bring in your partner into the room. Ask them to match the sound of the item in the first canister with one of the lettered containers. They can shake, roll, and even drop the containers, but they can’t take off the lid. Note the answer they give.
  5. Repeat step 4 for the rest of the numbered containers. Remember to record the responses.  When the canisters have all been matched, take off the lids and see how well they did.

What’s going on?


Objects produce distinct sounds when they vibrate. These differences can sometimes be distinguished by your ears. If you partner has good ears, listening closely and then correctly matching the contents was probably an easy task.


Now to share a little more about the cochlea: you know it ultimately receives sounds and sends signals to the brain. It is a small organ shaped like a spiral. It’s filled with fluid and tiny cells which are shaped like hairs. These hairlike cells convert the vibrations from sound into signals that can travel the auditory nerve up to the brain. The tiny cells are quite sensitive. They can actually be damaged by extremely loud noises, so remember to protect them with earplugs if you will be exposed to very loud sounds.


Exercises


  1. What are the tiny bones in the ear called?
  2. Name some other parts of the ear.

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Sound has the ability to travel through the states of matter: solids, liquids, and gases. In this experiment we will study the movement of sound through these three states.


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Here’s what you need


    • 3 baggies, resealable
    • sand
    • water
    • air
    • 1 desktop
    • 1 spoon
    • 1 partner


Download Student Worksheet & Exercises


Here’s what you do


  1. Fill each bag two-thirds of the way full with each material. You should have one bag with sand, one with water, and one with air. Seal each baggie well.
  2. Put the baggies on the desk or on a table. Note the density of the materials. Which is most dense, medium, and least dense?
  3. Place your ear down on the first baggie that is filled with sand. Have your partner use the spoon to tap the table. Listen for the sound through the bag of sand.
  4. Repeat step 3 with the baggie full of water and then the bag of air. Compare what you hear through each state of matter. Rank the tapping you hear through the solid, liquid and gas in order from loudest, to medium, to quietest.
  5. When you have completed the tapping portion of the experiment, hold the bag of sand up to your ear. Have your partner speak to you through the baggie.
  6. Repeat step 5 with the bag of water and again with the baggie of air. Note the clarity of the speech you hear through each bag. Rank each bag from loudest, to medium, to quietest.

What’s going on?


Sound is made by waves travelling through the air. They pass their energy along to the matter through which they are traveling. But now you know that sound doesn’t just travel through the air. Molecules in water are closer together than air molecules, which makes it much easier for them to bump into one another. So the speed that sounds travel through liquid is actually faster than it travels through the air, and the sounds travel further as well. Sound travels fastest of all in solids because the molecules in this state of matter are very densely packed together. Solids pass sound much farther and at much greater speeds.


If there is no matter to bounce their energy along, sound waves can’t really form. So once you leave earth’s atmosphere, there isn’t any sound!


Exercises


  1. What is density?
  2. Put these in their general order of density: liquid, gas, solid.
  3. Which material passes sound waves along farther and faster?

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Levers are classified into three types: first class, second class, or third class. Their class is identified by the location of the load, the force moving the load, and the fulcrum. In this activity, you will learn about the types of levers and then use your body to make each type.


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Here’s what you need


    • 1 body


Download Student Worksheet & Exercises


Here’s what you do


  1. In a first class lever, the fulcrum is in the middle. The load and effort are on opposite sides with the fulcrum between them. A familiar example of a first class lever is a see saw.
  2. A second class lever has the fulcrum on one end, the load in the middle, and the force on the end opposite the fulcrum. A wheelbarrow is a good example of a second class lever.
  3. Lastly, a third class lever has a fulcrum on one end and the load on the opposite end. The force is applied in the middle in this type of lever. A golf club is an example of a third class lever.
  4. Use the photos to identify the levers of each type in your body.

What’s going on?


Only read further if you have had an opportunity to identify the levers in the pictures. Spoilers below!


Your head moving up and down on your spine is an example of a first class lever. Your neck joint in the middle is the fulcrum, with load and effort on either side. In this example, load and effort switch depending on whether you are moving your head up or down.


Standing on tiptoe is an example of a second class lever where your toes are the fulcrum. The effort, or force, is in your heels – they are lifting your body up. And the resistance is located between your toes and heels.


This leaves us with bicep curls, which are an example of a third class lever. Your elbow serves as the fulcrum, the bicep is the force, and the weight in your hand on the end is the load.


Just for fun, did you know your knee is the largest joint in your whole body? It connects your femur, the largest bone, to the bones of your lower leg. Your smallest joints are the anvil, hammer, and stirrup in your inner ear.


Exercises


  1. Draw a diagram of a first-class lever. Where in your body is this type of lever?
  2. Draw a diagram of a third-class lever. Where will you find this?
  3. Draw a diagram of a second-class lever. Can you give an example of this type of lever in the real world?

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Your eyes have two different light receptors located on the back of the eyeball. These are the rods, which see black, white and grays, and the cones, which see color. In order to adapt to the dark, our eyes make a chemical called visual purple. This helps the rods to see and transmit what you see in situations where there is little light.


Your pupils also increase in diameter in the darkness. This allows for a slight increase in the amount of light entering your eye. This combination of visual purple and more light makes it possible for you to see in darker situations.


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Here’s what you need


    • 1 dark room
    • 1 light switch
    • 1 partner
    • 1 pencil


Download Student Worksheet & Exercises


Here’s what you do


  1. Turn out the light in a darkened room and give your eyes about 5 minutes to get used to the darkness.
  2. After your eyes have had a chance to acclimate to the low-light conditions, it’s time to get to work. Try to draw a picture of your assistant’s eye. Pay particular attention to how the pupil looks in the darkness.
  3. Now turn on the light while still observing your partner’s eye. What happens to their pupil?
  4. Draw another picture of your partner’s eye with the lights on. Again, pay special attention to the pupil.

What’s going on?


As you flip the light switch on, your partner’s brain realizes that there is a lot of light entering the rods and cones, so it restricts the size of the opening (your partner’s pupil) in order to limit the light. You might notice this on a sunny day if you go from a dark movie theater into the bright sun. It can actually hurt for moment, and makes you squint until your eyes have a chance to adjust to the brightness by reducing the size of your pupils.


Exercises


  1. How does the pupil adapt to light conditions?
  2. What are the two special photoreceptors called and where are they located?
  3. Which photoreceptor is used to help us see in the dark?

[/am4show]


Voluntary nerves are the ones that are under our direct control. Others, called involuntary nerves, are under the control of our brains and create involuntary reactions.


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Here’s what you need


    • 1 metric ruler
    • 5 volunteers


Download Student Worksheet & Exercises


Here’s what you do


  1. You will begin by testing your visual reflexes with the help of an assistant.
  2. Hold your right elbow at your waist. Position your arm so that it is parallel to the floor. Make a space of about an inch by holding your thumb and forefinger apart. Ask your assistant to hold the ruler vertically, above your thumb and finger.
  3. Your job is to focus on the ruler. Your partner will unexpectedly release it so that it begins to fall. You will attempt to catch the ruler as soon as you possibly can.
  4. Repeat the experiment 5 times, recording the time it takes to catch the ruler each time for your data. Use the times you record to find your average time.
  5. Try this experiment for 5 additional people. Find the average reaction speed of each person and the average speed of the group as a whole.

What’s going on?


This experiment is an example of a voluntary response. Your eyes see the ruler moving and tell your brain, which then tells your fingers to close quickly. This all happens very fast, but involuntary reflexes can be much faster! You may notice in this activity that the ruler falls over half of the way through your fingers before you can stop it. This is partly because of the communication from eyes to brain to fingers. Although the nerves transmit very quickly, the transmission time can still take a little while.


There are two separate systems at work here: the central nervous system is your brain and spinal column and the longer nerves branching out from the spinal cord to every part of your body is the peripheral nervous system. They work in conjunction to coordinate your actions.


If you lines up all of your nerves, end to end, they would stretch for miles and miles: an average length is about 47 miles of nerves. The longest is the sciatic nerve. It goes from the bottom of your spine to the bottom of your foot.


Exercises


  1. What is the voluntary response in this experiment?
  2. What is an involuntary response in your body?  Give an example.

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Your optic nerve can be thought of as a data cord that is plugged in to each eye and connects them to your brain. The area where the nerve connects to the back of your eye creates a blind spot. There are no receptors in this area at all and if something is in that area, you won’t be able to see it. This experiment locates your blind spot.


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Here’s what you need


    • 1 frog and dot printout
    • 1 meter stick
    • 1 scrap piece of cardboard


Download Student Worksheet & Exercises


Here’s what you do


  1.  Print out the frog and dot and remove the dotted portion. Attach it to the piece of cardboard, which should have a matching portion removed. You can place the paper and cardboard on the meter stick at the notched area.
  2. Now to locate blind spots. First, close your left eye. Look at the frog with your right eye. Can you see the dot and the frog? You should be able to see both at this point, but concentrate on the frog.  Now slowly move the stick toward you so that the frog is coming toward your eye. Pay attention and stop when the dot disappears from your peripheral vision. At this point, the light hitting the dot and reflecting back toward your eye is hitting the blind spot at the back of your right eyeball, so you can’t see it. Record how far your eye is from the card for your right eye.
  3. Continue to move the stick toward your face and at some point you will notice that you are able to see the dot again. Keep moving the stick forward and back. What happens to the dot?
  4.  Repeat steps 2 and 3 with your left eye, keeping your right eye closed. This time, stare at the dot and watch for the frog to disappear. Move the paper on the stick back and forth slowly until you notice the frog disappears. You have found the blind spot for your left eye. Be sure to note the distance the paper is from your eye.

What’s going on?


There are no light receptors in the area of your eye where the optic nerve attaches to your eyeball. This is your blind spot and if an image is in this spot, the light reflected off of it doesn’t get perceived by your eye. So you don’t see it!


Exercises


  1. What did you notice about the vision of the student and the blind spot that you measured?
  2. Why do you think it’s important to know where your blind spot is?

[/am4show]


Like sound, light travels in waves. These waves of light enter your eyes through the pupil, which is the small black dot right in the center of your colored iris. Your lens bends and focuses the light that enters your eye. In this experiment, we will study this process of bending light and we will look at the difference between concave and convex lenses.


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Here’s what you need


    • 1 washer, 3/8 inch inside diameter
    • 1 microscope slide
    • 1 container of petroleum jelly
    • 1 piece of newsprint with a lot of type
    • 1 pipette, 1 mL
    • water



Download Student Worksheet & Exercises


Here’s what you do


  1. Apply a little petroleum jelly on the washer’s flat side. NOTE: washers have flat and founded sides, so be sure you are putting the petroleum jelly on the flat side of the washer.
  2. Put the washer, petroleum jelly side down, on the middle of the microscope slide. Twist the washer a bit to seat it on the slide and make a seal. This should keep the water in place.
  3. Put the washer and slide on the newsprint. Fill the pipette with water. Use the pipette to slowly place water in the washer. Fill the washer until the water makes a domed shape. You have just made a convex lens!
  4. Find a letter e on the newspaper and put the lens over it. Draw a diagram of what the e looks like through the convex lens.
  5. Now use the pipette to remove water from the washer. Your goal is to create a dip in the surface of the water. Now find the same e and place your new concave lens over the letter. Draw a picture of what the e  looks like through the new lens.

What’s going on?


You can see that a convex lens bends outward and a concave lens bends inward. What does this do to light?


In a convex lens, the domed surface means that if light waves come in through the flat bottom surface, they will be spread out, or refracted, as they exit the curved portion of the lens. But since a concave lens dips inward it creates the opposite effect. When light waves exit the concave surface, they are brought together. This makes images appear smaller.


The lens does all the focusing work but it is actually the shape of the eye that determines what you see. If you have a tall, oblong eye, you are far-sighted. And conversely, if your eyes are short and fat, you are near-sighted. In either case, the lenses are functioning properly but the actual shape of the eye needs a slight adjustment.


Exercises


  1. What are the two main types of lenses?
  2. How are the two main types of lenses shaped
  3. How do the two main types of lenses work?

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In this lab, we are going to make an eyeball model using a balloon. This experiment should give you a better idea of how your eyes work. The way your brain actually sees things is still a mystery, but using the balloon we can get a good working model of how light gets to your brain.


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Here’s what you need


    • 1 biconvex plastic lens
    • 1 round balloon, white, 9 inches
    • 1 assistant
    • 1 votive candle
    • 1 black marker
    • 1 book of matches
    • 1 metric ruler
    • Adult Supervision!


Download Student Worksheet & Exercises


Here’s what you do


  1. Blow up the balloon until it is about the size of a grapefruit. If it’s difficult to inflate, stretch the material a few times or ask an adult to help you.
  2. You will need an extra set of hands for this portion. Ask your partner to hold the neck of the balloon closed to keep the air in while you insert the lens into the opening. The lens will need to be inserted perpendicularly to the balloon’s neck. It will prevent any air from escaping once it’s in place. Like your eye, light will enter through the lens and travel toward the back of the balloon.
  3. Hold the balloon so that the lens is pointing toward you. Take the lens between your thumb and index finger. Look into the lens into the balloon. You should have a clear view of the inside. Start to twist the balloon a little and notice that the neck gets smaller like your pupils do when exposed to light. Practice opening and closing the balloon’s “pupil.”
  4. Have an adult help you put the candle on the table and light it. Turn out the lights.
  5. Put the balloon about 20 to 30 centimeters away from the candle with the lens pointed toward it. The balloon should be between you and the candle. You should see a projection of the candle’s flame on the back of the balloon’s surface. Move the balloon back and forth in order to better focus the image on the back of the balloon and then proceed with data collection.
  6.  Describe the image you see on the back of the balloon. How is it different from the flame you see with your eyes? Draw a picture of how the flame looks.
  7. The focal length is the distance from the flame to the image on the balloon. Measure this distance and record it.
  8. What happens if you lightly push down on the top of the balloon? Does this affect the image? You are experimenting with the affect caused by near-sightedness.
  9. To approximate a farsighted eye, gently push in the front and back of the balloon to make it taller. How does this change what you see?

What’s going on?


Okay, let’s discuss the part of the balloon that relate to parts of your eye. The white portion of the balloon represents your sclera, which you may have already guessed is also the white part of your eye. It is actually a coating made of protein that covers the various muscle in your eye and holds everything together.


Of course, the lens you inserted represents the actual lens in your eye. The muscles surrounding the lens are called ciliary muscles and they are represented by the rubber neck of your balloon. The ciliary muscles help to control the amount of light entering your eyes.


The retina is in the back of your eye, which is represented by the inside back of your balloon. The retina supports your rods and cones. They collect information about light and color and send it to your brain.


Exercises


  1.      How does your eye work like a camera?
  2.      How can you tell if a lens is double convex?
  3.      What is the difference between convex and concave?
  4.      Can you give an example of an everyday object that has both a convex and a concave side?
  5.      How can you change the balloon to make it like a near-sighted eye?
  6.      How can you change the balloon to make it like a far-sighted eye?

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This experiment not only explains how your body uses oxygen, but it is also an experiment in air pressure circles – bonus!  You will be putting a dime in a tart pan that has a bit of water in it. Then you will put a lit candle next to the dime and put a glass over the candle with the glass’s edge on the dime. Once all of the air inside the glass is used up by the candle, the dime will be easy to pick up without even getting your fingers wet! Ready to give it a try?


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Here’s what you need


    • 1 aluminum tart pan
    • 1 votive candle
    • 1 box of matches
    • 1 clear drinking glass, 12 or 16 oz.
    • 1 dime
    • water
    • 1 pair of goggles
    • Adult supervision!


Download Student Worksheet & Exercises


Here’s what you do


  1. Pour about ¼ inch of water in the pan and place the dime right in the middle.
  2. Position the candle next to the dime and ask an adult to light it for you
  3. Put the drinking glass over the candle with its edge resting on the dime. Watch closely to observe what happens.
  4. Once the water is inside the glass, you can carefully remove the dime from under its edge. If done properly, the water will stay in the glass.

What’s going on?


When you put the glass over the candle, you created a closed system. The candle only had the gas trapped inside the air beneath the glass to burn. As the candle burned, the gases in the glass burned as well. They were transformed from a state of gas to a very compact solid state that stuck to the wick of the candle (this is why the wick gets black when a candle burns).


An important thing to note is that as the air was removed, the pressure inside the glass was reduces. Lower air pressure inside your closed system created an imbalance with the regular air pressure on the outside of the glass. Since there was more pressure on the outside, the water was pushed inside the glass. The dime helped to make a gateway for the water to be more easily pushed into the glass.


This lab serves to illustrate that oxygen is consumable. It’s the same thing that happens inside your body, but at a much slower rate that what you witnessed with the candle. Your lungs contain about 1,490 miles (2,400 km) of air passages to help absorb oxygen. If they could be spread out flat, an average set of lungs have a surface area of approximately 650 square feet.  The sheer size of this system gives you the chance to absorb all the oxygen that your body needs.


Exercises


  1. What do we mean when we say that oxygen is consumable?
  2. What is the difference between an open and a closed system?
  3. Where is the higher pressure in this experiment?
  4. Why does water rise inside the glass?

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Everything living produces some sort of odor. Flowers use them to entice bees to pollinate them. We know that the tastes of foods are enhanced by the way that they smell. As humans, each of us even has own unique odor.


In this lab, we look at the diffusion of scents. They start in one place, but often end up spread around the room and can be detected by many people.


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Here’s what you need


    • 1 onion
    • 1 lemon
    • 1 bottle of ground cinnamon
    • 1 clove of fresh garlic
    • 1 garlic press
    • 1 pile of fresh coffee grounds
    • 1 kitchen knife
    • 1 cutting board
    • 1 variable-speed fan
    • 1 clock with a second hand


Download Student Worksheet & Exercises


Here’s what you do


  1. Start in a room big enough so that you can prepare the foods at one end and your friends or family members can be at the other end, but positioned so they can’t see what you’re doing.
  2. You will need a simple map of the room showing the locations of your partners, the source of the odor, and the fan (which will help with the scent diffusion). Create a new map for each smell.
  3. Turn on the fan and begin with the onion. Ask an adult to help you with cutting the onion into several small pieces. Be sure to hold the chopped pieces up in front of the fan. Ask your partners to raise their hands when they smell the onion. If they don’t smell it, they can leave their hands down. Note on the onion map where its smell is detected. Indicate with a line the farthest area where the onion is smelled. This is its leading edge.
  4. Check in with your partners once per minute for five minutes. Ask them to raise their hands and repeat the process of noting the areas where the smell is detected. Each time you check, draw a line to indicate the farthest area the smell reaches. This will give you an idea of how fast and how far the smell diffused.
  5.  Repeat steps 3 and 4 with each item: cut and smash the lemon and press the garlic. Which odors travel the farthest? Which ones travel the fastest?

What’s going on?


Many factors affect how quickly odors diffuse. First, the air is constantly moving. As the air molecules in the room are colliding with each other (and with the odor molecules) they help to move the smells farther through the room. Second, the fan makes a huge difference. It accelerates the natural process of air and odor molecules and moves them much farther and faster than they would go otherwise. Finally, the air temperate plays an important role. If the temperature is higher, the air and odor molecules will move faster.


As humans, we can boast about 10,000,000 smell cells in our noses. This seems pretty impressive…unless you compare us to canines. Dogs have over 200,000,000 smelling cells in their nasal cavities!


Exercises


  1. Which odors travel the farthest?
  2.  Which ones travel the fastest?
  3. Why do we use the fan?
  4. Does air temperature matter?

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Peristalsis is the wavelike movement of muscles that move food through your gastrointestinal tract. The process of digestion begins with chewing and mixing the food with saliva. From there, the epiglottis opens up to deposit a hunk of chewed food (called bolus) into your esophagus – this is the tube that runs from your mouth to your stomach. Since the esophagus is so skinny, the muscles along it must expand and contract in order to move food down. In this activity we will examine that process.


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Here’s what you need


    • 1 tennis ball
    • 1 pair of old nylons
    • 1 pair of scissors


Download Student Worksheet & Exercises


Here’s what you do


  1. Cut away the control top portion of the nylons and remove the toe part as well (have an adult help you, if needed). You should now have a long piece of nylon.
  2. Put the tennis ball in one end of the nylon “esophagus.” Start using both hands to move the ball down the nylon tube until it arrives at the other end.

What’s going on?


The esophagus is lined with muscles that work in waves, expanding and contracting to move food along it down into the stomach. These are very strong muscles: even if you ate upside down they would work!


In the grand scheme of the digestion process, the role of the esophagus is important, but relatively short. It takes about 10 seconds to move food from the mouth to the stomach, but the entire process of digestion can take up to 2 and a half days to finish!


Exercises


  1. What is the tube called that connects the mouth and stomach?
  2. What is the process called that moves food along the digestive tract and how does it work?
  3.  How long is food in the esophagus?

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We now know that odor molecules are diffused throughout a room by the motion of air molecules, which are constantly moving and bumping into them.  We also know that warm air moves faster than cold air, and that increasing the movement of the air (like with a fan) will increase the diffusion process.


In this experiment, we look at what happens when the odor molecules find their way into your nose. Your nose has smell cells located in a small area called the olfactory epithelium. We will use them here to match smells with other smells.


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Here’s what you need


    • 10 small containers with lids
    • 10 cotton balls
    • 1 bottle of lemon juice
    • 1 cup of black coffee
    • 1 bottle of vanilla extract
    • 1 bottle of cinnamon oil
    • 1 bottle of soy sauce
    • 1 black felt marker
    • 1 assistant


Download Student Worksheet & Exercises


Here’s what you do


  1. Take the lids off of the containers and number the first five with a 1 through 5. Mark the other five with A through E.
  2. Put a cotton ball into each container. Start with the numbered containers and add some lemon, coffee, cinnamon, soy sauce, and vanilla. Record the smell for each number for reference.
  3. Fill the lettered containers with the same liquids, but not in the same order. Be sure to record the material you have used for each letter.
  4. Take the closed containers to your assistant. Ask them to match the scent in the first canister with the proper lettered container without opening the container. Given them permission to roll, drop, and shake the containers, but they can’t be opened. Note their response – are they correct?
  5. Repeat step 4 for each of the containers until they all have been matched. Then check your recorded data and see how well your assistant did with matching.

What’s going on?


Everything here produces a distinct odor. The smells go into your nose where they are interpreted by the tiny hair-like smell cells in your olfactory epithelium. The smell cells work together to distinguish smells and then send the interpreted information to the brain for recognition.


We previously noted that humans have an average of 10,000,000 smell cells, but they aren’t all the same. You have about 20 different types and each detects a specific type of odor. The types work together and your brain translates their signals as a unique odor.


Exercises


  1. What is the scientific name for sense of smell?
  2. What is the name of the tissue which helps the brain to distinguish between smells?

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An oxygen and carbon dioxide exchange takes place in your bloodstream. When you breathe air into your lungs it brings in oxygen, which is carried from your lungs by red blood cells in your bloodstream. Cells of your body use the oxygen and carbon dioxide is produced as waste, which is carried by your blood back to your lungs. You exhale and release the C02. You will study this exchange in today’s lab.


You will be using a pH indicator known as bromothymol blue. When you exhale into a baggie, the carbon dioxide will react with water in the bag. This reaction produces carbonic acid, which starts to acidify the water. More breathes in the bag equal more carbon dioxide, which equal a lower (more acidic) pH. You will notice the bromothymol will turn green when the pH of the water is right about 6.8 and it will turn yellow when the pH drops further to 6.0 and lower.


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Here’s what you need


    • 1 1 oz. bottle of bromothymol blue
    • 1 straw
    • 1 resealable baggie
    • 1 bottle of ammonia
    • 1 pipette
    • water


Download Student Worksheet & Exercises


Here’s what you do


  1. Pour about 2 ounces of water into the baggie and add two capfuls of the bromothymol blue into it. Close the baggie well and swish the solution around inside it gently to mix. Note the color of the solution for your data record.
  2. Open the baggie a tiny bit and put the straw inside, but DO NOT drink the solution! It could make you sick. Close the bag tightly around the straw and gently blow into the solution. Again, be careful not to suck on the straw.
  3. Watch the color of the solution closely as you continue to blow into the solution and create bubbles of carbon dioxide gas. The color will change to a sea green color and then eventually it will change to bright yellow. Note each color change in your records.
  4. You can return the solution to blue by slowly adding a base – such as ammonia – to the solution in the bag. Bleach will also work. Please ask an adult to help with this. Add one drop at a time, shaking after each addition to mix the solution. You will be able to observe when the pH starts to change back by the color of the solution. It should turn back to green and then to blue.

What’s going on?


Bromothymol blue will change color in a pH range from 6.0 to 7.6.  It is an acid/base indicator. Its basic solution is at a pH of 7.6 or above – this is when it is blue. In acidic conditions, it will turn yellow – this is a pH of 6.0 or below. And when it’s in between the two, it will be the sea green color that you observed in your baggie.


Because carbon dioxide is a little acidic, when we breathe it out into the water and bromothymol blue solution its bubbles start to lower the pH. You saw a small change in pH with the sea green color, but as you continued to exhale and add carbon dioxide, the solution became more and more acidic. This eventually resulted in a pH at or below 6.0 and a bright yellow solution.


In order to exchange oxygen with carbon dioxide in your lungs, they have over 300,000,000 teeny little air sacs calls alveoli. In one minute, you breathe approximately 13 pints of air.


Exercises


  1. What is pH and how it is useful?
  2. What does a yellow color indicate with bromothymol blue?
  3. Is CO2 acidic or basic?

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Food and air both enter your body through your mouth, diverging when they reach the esophagus and trachea. Food goes to the gastrointestinal tract through your esophagus and air travels to your lungs via the trachea, or windpipe.


You will be making a model of how your lungs work in this lab. It will include the trachea, lungs, and the diaphragm, which expands and contracts as it fills and empties your lungs.


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Here’s what you need


    1. 1 2-liter soda bottle, emptied and cleaned
    2. 1 pair of scissors
    3. 1”Y” valve hose connector
    4. 3 round, 9-inch balloons
    5. 1 #3 one-hole stopper
    6. 1 length of hose, 8-inch
    7. 2 rubber bands
    8. 1 jar of petroleum jelly


Here’s what you do


  1. Cut off the bottom of the 2-liter bottle. Ask an adult for help.
  2. Take the “Y” valve and secure the two balloons to the top branches with the rubber bands.
  3. Put a tiny bit of petroleum jelly on the end of the hose to make it easier to insert into the #3 stopper. Pull 6 inches of hose through the stopper and then thread the hose through the bottle’s neck. Insert the stopper into the top of the bottle.
  4. Put the end of the hose (that is now inside the bottle) into the base of the “Y” valve (which now has balloons on its other branches). Pull the hose through the stopper a bit. Also, pull the lungs up toward the top of the bottle.
  5. Tie a knot in the third, unused balloon. Cut it in half and stretch the part with the knot over the open bottom of the soda bottle. Make sure the bottom balloon is as tight as it can be.
  6. Grab the bottle with one hand, the knot at the bottom of the balloon with the other. Carefully pull the knot on the balloon down. What happens to the balloons in the bottle? Now let go of the knot and observe how this affects the balloons. Note your observations in the experiment’s data.
  7. Sketch your model and label its trachea, lungs, and diaphragm.

What’s going on?


By placing a stopper in the top of the bottle and putting the stretched rubber balloon on the bottom, you have created an enclosed system. The tube at the top of the bottle is the only way for air to enter or exit the model’s lungs. Pulling down on the balloon’s knot reduced the air pressure inside the lungs. As compensation, air was pushed down into the tube to equalize the pressure. This caused the balloon lungs to expand. When you released the knot, the air pressure forced the air out of the balloons.


If you need more help with identification, the tube acts as the trachea, the balloons are the lungs, and the balloon with the knot at the bottom is the diaphragm.


Did you know that an average person breathes about 24,000 times each day? If you live to be 70 years old, that means about 600,000,000 breaths. Make them count!


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