Atmospheres

Sunday September 1, 2013

Scientists do experiments here on Earth to better understand the physics of distant worlds. We’re going
to simulate the different atmospheres and take data based on the model we use.


Each planet has its own unique atmospheric conditions. Mars and Mercury have very thin atmospheres, while Earth has a decent atmosphere (as least, we like to think so). Venus’s atmosphere is so thick and dense (92 times that of the Earth’s) that it heats up the planet so it’s the hottest rock around. Jupiter and Saturn are so gaseous that it’s hard to tell where the atmosphere ends and the planet starts, so scientists define the layers based on the density and temperature changes of the gases. Uranus and Neptune are called ice giants because of the amounts of ice in their atmospheres.


Materials


  • 4 thermometers
  • 3 jars or water bottles
  • Plastic wrap or clear plastic baggie
  • Wax paper
  • Stopwatch

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>  
Download Student Worksheet & Exercises


  1. Place one thermometer in direct sunlight. This is like the atmosphere of Mercury and Mars.
  2. Place a second thermometer in a jar and cap it. Place this in sunlight. This is the Earth’s, Jupiter’s and Saturn’s atmosphere.
  3. Line the second jar with wax or tissue paper. Place the third thermometer in the jar and cap it. Place it next to the other two in sunlight. This is the atmosphere on Venus.
  4. Insert the fourth thermometer into a plastic baggie, insert it into the bottle and cap it. Make sure the baggie is loose. This is Neptune and Uranus.
  5. Record your data observations in the table, taking data every couple of minutes.

What’s Going On?

Venus is hot enough to melt cannonballs and crush any spaceship that tries to land on the surface. Carbon dioxide is a “greenhouse gas,” meaning that some wavelengths of light can pass through it, but specifically not infrared light, which is also known as heat. Light from the Sun either bounces off the upper cloud layers and back into space, or penetrates the clouds and strikes the surface of Venus, warming up the land. The ground radiates the heat back out, but the carbon dioxide atmosphere is so dense and thick that it traps and keeps the heat down on the surface of the planet. Think of rolling up your windows in your car on a hot day.


The heat is so intense on Venus that the carbon normally locked into rocks sublimated (turned straight from solid to gas) and added to the carbon in the atmosphere, to make even more carbon dioxide.


Mercury doesn’t have much of an atmosphere, which is just like a bare thermometer. There’s nothing to hold onto the heat that strikes the surface. Mars is in a similar situation.


Earth’s atmosphere is simulated by placing the thermometer in a bottle. The Earth has a cloud layer that keeps some of the heat on the planet, but most of it does get radiated back into space. When the clouds are in at night, the planet stays warmer than when it’s clear (and cold).


Venus’s heavy, dense carbon dioxide atmosphere is simulated by using the waxed paper. Venus is the hottest planet in our solar system because of the runaway greenhouse effect that traps most of the heat that makes it through the atmosphere, bouncing it back down to the surface. The average temperature of Venus is over 900oF.


Jupiter and Saturn’s atmospheres are thinner layers of hydrogen and helium than deeper in the core.


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.


Exercises


  1. Which atmosphere reached the highest temperature?
  2. Each of the jars received the same amount of energy from the Sun. Why is this not quite like the real solar system?

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Exercises for Atmosphere

Sunday September 1, 2013

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.
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1. How does radiation travel?
a. As a beam
b. As a wave
c. as a molecule


2. Where does most of the energy on earth come from?
a. Underground
b. The Sun
c. The Oceans


3. What is one way that we use energy from the sun?


4. Which instrument measures humidity?
a. Thermometer
b. Barometer
c. Hygrometer
d. Rain Gauge


5. What is the unit of measurement for temperature here in the USA?
a. Newtons
b. Joules
c. Fahrenheit
d. Celsius


6. What is another unit of measurement used for temperature?
a. Fahrenheit
b. Celsius
c. Joules
d. Newtons


7. What is the science called that investigates the weather and patterns of the Earth’s atmosphere?
a. Zoology
b. Biology
c. Meteorology
d. Nephology


8. What are clouds made of?
a. Nitrogen
b. Water
c. Oxygen
d. Iridium


9. What form of water exists in clouds
a. Water vapor
b. Liquid water
c. Frozen water


10. What is the name of someone who studies the weather?
a. Oncologist
b. Herpetologist
c. Climatologist
d. Meteorologist
e. Asteroidologist


11. What is the type of energy that comes from the sun?
a. Potential
b. Kinetic
c. Electronic
d. Radiation


12. What principle describes how pressure behaves in a moving fluid?
a. Avogadro’s Principle
b. Bernoulli’s Principle
c. Boyle’s Law
d. Pascal’s Wager


13. A higher pressure will ________ an object.


14. An object experiences pressure in the Earth’s atmosphere in which direction more?
a. Upwards
b. Downwards
c. Equally in all directions


15. If an object is higher in altitude above the earth, it experiences which pressure in relationship to an object at sea level?
a. Greater Pressure
b. Less Pressure
c. Equal Pressure


Need answers?
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Answers to Exercises

Sunday September 1, 2013

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!


Here’s printer-friendly versions of the exercises and answers for you to print out: Simply click here.
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Answers:


  1. How does radiation travel? (as a wave)
  2. Where does most of the energy on earth come from? (the Sun)
  3. What is one way that we use energy from the sun? (appropriate energy answer)
  4. Which instrument measures humidity? (Hygrometer)
  5. What is the unit of measurement for temperature here in the USA? (Fahrenheit)
  6. What is another unit of measurement used for temperature? (Celsius)
  7. What is the science called that investigates the weather and patterns of the Earth’s atmosphere? (Meteorology)
  8. What are clouds made of? (Water)
  9. What form of water exists in clouds (Water vapor)
  10.  What is the name of someone who studies the weather? (Meteorologist)
  11. What is the type of energy that comes from the sun? (Radiation)
  12. What principle describes how pressure behaves in a moving fluid? (Bernoulli’s principle)
  13. A higher pressure will ________ an object. (Push on)
  14. An object experiences pressure in the Earth’s atmosphere in which direction more? (Equally in all directions)
  15. If an object is higher in altitude above the earth, it experiences which pressure in relationship to an object at sea level? (Less pressure)

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How Much Energy Does the Sun Produce?

Friday November 4, 2011

Without the sun, there would be no life on Earth. The sun warms the earth, generates wind, and carries water into the air to produce rain and snow. The energy of the sun provides sunlight for all the plant life on our planet, and through plants provides energy for all animals.


The sun is like a giant furnace in which hydrogen nuclei (atoms without electrons) are constantly smashed together to form helium nuclei. This process is called nuclear fusion. In this process, 3.6 billion kilograms (8 billion pounds) of matter are converted to pure energy every second. The temperature in the sun exceeds 15 million degrees.


Nuclear fusion is one kind of energy. Other forms of energy include: mechanical energy, heat, electrical energy, chemical energy, and light. Mechanical energy is the energy of organized motion, such as a turning wheel. Heat is the energy of random motion, such as a cup of hot water. Electrical energy is the energy of moving charged particles or electrons, such as a current in a wire. Chemical energy is the energy stored in bonds that hold atoms together. Light is any form of electromagnetic waves, such as X rays, microwaves, radio waves, ultraviolet light, or visible light.


Energy can be converted from one from to another. For example, the nuclear energy of the sun is converted to light, which goes through space to the earth. Solar collectors of mirrors can be used to focus some of that light to heat water to steam. This steam can be used to turn a turbine, which can power a generator to produce electricity.


Most of our energy needs are met by burning fossil fuels such as coal, oil, gasoline, and natural gas. The chemical energy stored in these substances is released by burning these fuels. When fossil fuels burn, they combine with oxygen in the air and produce heat and light.


Fossil fuels are not renewable. When they are used up, they are gone forever. However, renewable energy sources such as wind, sun, geothermal, biomass and water power are renewable. They can be used over and over to generate the energy to run our society.


Tremendous amounts of renewable energy are available. For example, the solar energy that falls on just the road surfaces in the United States is equal to the entire energy needs of the country. Although there are sufficient amounts of renewable energy, we must improve our methods of collecting, concentrating, and converting renewable energy into useful forms.


In the following experiments, you will learn something about the amount of energy the sun produces at the earth’s surface and how heat energy can be stored.
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Materials


    • Water
    • Disposable, aluminum pie pan
    • Paint brush
    • Measuring cups
    • Watch or clock
    • Newspaper
    • Black paint or spray paint (flat, not shiny)


Procedure


Go outside and spread out a sheet of newspaper. Place an aluminum pie pan on the newspaper. Carefully bend one spot on the edge of the pie pan to make a spout shape. This will allow you to more easily pour water out of the pan. Have an adult help you paint the inside of the aluminum pie pan. You can use a brush and a can of paint or spray paint. Be sure not to get the paint on anything except the disposable pie pan and the newspaper. After painting, set the pie pan where the paint can dry overnight.


You will need to do the rest of this experiment on a warm, sunny day. You do not want the pie pan to be in the shade. Set the aluminum pie pan in a warm, sunny spot. The sun will need to constantly shine on the pie pan. The black color of the pie pan allows it to absorb, rather than reflect, solar energy. You will need to begin the experiment about


11:00 A.M., so the solar heating will be done when the sun is high in the sky.


Add exactly one cup of water to the pie pan. Wait four hours while the sun is shining on the pan of water. After exactly four hours of sunshine, carefully pour the remaining water from the pie pan into a one-half or one-fourth measuring cup. Use these measuring cups to estimate the amount of remaining water to the nearest one-eighth of a cup.


Observations


Is the amount of water in the pie pan less than when you began the experiment? How much water is left in the pie pan after four hours of sunlight?


Discussion


You will probably observe that the amount of water in the pie pan is less after four hours of sunlight exposure. Where did the water go? As the sunlight shines on the dark surface of the painted pie pan, solar energy is absorbed and heats the pan and the water. This energy causes a portion of the water to evaporate. As water evaporates, it leaves the liquid form and goes into the air as a gas (water vapor). You will probably find that some, but not all, of the water evaporated.


Scientists use the unit of joule as a measure of energy. However, you may find it helpful to think in units of dietary calories instead of joules. One dietary calorie is equal to 4,184 joules of energy. One cup of breakfast cereal with one-half cup of milk would have about 240 dietary calories, or approximately 1,000,000 joules of energy. Although the earth receives only a tiny portion of the total energy output of the sun, the earth has a constant supply of 173 million billion (173,000,000,000,000,000) watts of solar power. A watt is a unit of power equal to a joule of energy used per second. For comparison, a typical light bulb to run a lamp in your home might require 100 watts of power. A million watts could supply the energy needs of about 500 average American homes.


Use the table below to determine the solar energy required to evaporate a certain amount of water. The amount of water remaining in the pan will allow you to determine how much energy was used, how much power was used, and the amount of power per area.


Your results will probably be in the middle range of this table. For example, if one-half of your water evaporated, then the water remaining would be one-half cup. Thus, the energy used to evaporate this water would be 289,000 joules of energy. This energy would give a power of 20 watts, and a power per area of 800 watts per square meter (watts / meter2).


Solar Energy Required to Evaporate Water

Water Remaining


(cup)

Water Evaporated (cup)

Energy


Used


(joules)

Power


Used


(watts)

Power per


Area


(watts / meter2)

1

0

0

0

0

7/8

1/8

72,250

5

200

3/4

1/4

144,500

10

400

5/8

3/8

216,750

15

600

1/2

1/2

289,000

20

800

3/8

5/8

361,250

25

1000

1/4

3/4

433,500

30

1200

1/8

7/8

505,750

35

1400

0

1

578,000

40

1600

The following procedure was used to generate the numbers in the Table. It is known that it takes 578,000 joules of energy to evaporate one cup of water. This known energy per cup is multiplied by the fraction of a cup that was evaporated. This gives the solar energy used to evaporate the water in the pie pan. The energy is divided by the number of seconds in four hours (14,400 seconds). This gives the power of the solar energy striking the pie pan, since a watt is equal to a joule per second. Finally, the power (in watts) is divided by the surface area of the pie pan (0.025 square meters) to give the power per area.


When the sun is overhead, the intensity of solar energy can be as much as 1,000 watts per square meter. If all of this energy could be converted to electricity, one square meter of sunshine would be enough to run ten 100-watt light bulbs. However, our current solar cells that convert sunlight to electricity are able to change only about 15 percent of the light to electricity.


You can see from this experiment that there is tremendous energy available from our sun. Most of this energy warms our planet or is reflected back into space. Among other things, the remaining portion of energy powers our water cycle, producing rain and snow, or provides plants with the energy they need to live.


Scientists and engineers are learning more about trapping solar energy and converting it to useful power. It has been estimated that all forms of potentially available renewable energy (wind, water, biomass, and direct solar) have an energy equivalent to 80 trillion barrels of oil. In other words, one year of renewable solar energy is 5,000 times greater than the current yearly energy needs of the United States. In comparison, it has been estimated that all the remaining coal, oil, natural gas, and other potential nonrenewable energy reserves of the United States are equal to about 8 trillion barrels of oil.


Since we do not yet know how to use a significant portion of this renewable energy, much work remains to be done. In the remainder of this book you will learn more about our current ability to use renewable energy and the promise it may hold for the future.


Other Things to Try


Repeat this experiment using different amounts of water on different days and compare the solar power you find.


Repeat this experiment in the late afternoon, when the sun is lower in the sky. How do your result compare to this experiment?
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How Can Water Be Used to Store Heat Energy?

Friday November 4, 2011

Temperature is a measure of the average hotness of an object. The hotter an object, the higher its temperature. As the temperature is raised, the atoms and molecules in an object move faster. The molecules in hot water move faster than the molecules in cold water. Remember that the heat energy stored in an object depends on both the temperature and the amount of the substance. A smaller amount of water will have less heat energy than a larger amount of water at the same temperature.


Increasing the temperature of a large body of water is one way to store heat energy for later use. A large container filled with salt water, called brine, may be used to absorb heat energy during the day when it is warm. This energy will be held in the salt water until the night when it is cooler. This stored heat energy can be released at night to warm a house or building. This is one way to store the sun’s heat energy until it is needed.


Solar ponds are used to store energy from the sun. Temperatures close to 100°C (212°F) have been achieved in solar ponds. Solar ponds contain a layer of fresh water above a layer of salt water. Because the salt water is heavier, it remains at the bottom of the pond-even as it gets quite hot. A black plastic bottom helps absorb solar energy from sunlight. The water on top serves to insulate and trap the heat in the pond.


In a fresh water pond, as the water on the bottom is heated from sunlight, the hot water becomes lighter and rises to the top of the pond. This convection or movement of hot water to the top tends to carry away excess heat. However, in a salt water pond, there is no convection so heat is trapped. In Israel a series of salt water, solar ponds were developed around the Dead Sea. The heat stored in these solar ponds has been used to run turbines and generate electricity.
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Materials


  • Two paper cups
  • Measuring cups
  • Hot water
  • Watch or clock
  • Sink
  • Refrigerator (with freezer compartment)


Download Student Worksheet & Exercises


Procedure


Turn on the hot water faucet of a sink and wait several minutes until the water is hot. Be careful not to burn yourself with this hot water. Add one-fourth cup of this hot water to the first paper cup. Add one cup of hot water to the second paper cup. Place both of these cups in the freezer compartment of a refrigerator.


After thirty minutes check the water in each cup.  Return the cups to the freezer compartment and check them again after fifteen minutes. Keep checking the cups each fifteen minutes until the water in one of the cups is frozen.


Observations


Does the water in the cups freeze at the same time? Does the water in one of the cups freeze first? How long does it take for the water to freeze?


Discussion


You will probably observe that the smaller amount of water in the first cup freezes prior to the larger amount of water in the second cup. Both cups were filled with the same hot water. However, even though the water in both cups was at the same temperature, they did not freeze at the same time. The amount of heat energy stored by the water depends on both the temperature and the amount of water.


We expect that the more heat energy stored in the cup, the longer it takes the water in the cup to freeze. Since one cup of water has more heat energy than one-fourth cup of water, it takes the larger amount of water longer to freeze.


Other Things to Try


Place one-half cup of hot tap water in one cup.  Place one-half cup of cool tap water in a second cup. Put both cups in the freezer compartment of a refrigerator and check them every fifteen minutes until the water freezes solid. Which cup of water do you think has more heat energy? Which cup of water do you think will freeze first?


Place one cup of water in one paper cup and one-fourth cup of water in a second paper cup. Put both cups in the freezer of a refrigerator and leave overnight. The next day remove both cups of frozen water. Set the two cups out in the room. Observe the time it takes each piece of ice to melt. Which piece of ice do you think will melt first? Which piece will require more heat energy to cause it to melt?


Exercises


  1. What type of heat transfer is at work in a solar pond?
    1. Kinetic
    2. Conduction
    3. Potential
    4. Convection
    5. Radiation
  2. What units do we use to measure energy?
    1. Kilowatts
    2. Joules
    3. Newtons
    4. Kilowatt-hours
  3. Draw a diagram of a solar pond in the space below:

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Can Wind Be Used as a Source of Energy?

Friday November 4, 2011

The United States has large reserves of coal, natural gas, and crude oil which is used to make gasoline. However, the United States uses the energy of millions of barrels of crude oil every day, and it must import about half its crude oil from other countries.


Burning fossil fuels (oil, coal, gasoline, and natural gas) produces carbon dioxide gas. Carbon dioxide is one of the main greenhouse gases that may contribute to global warming. In addition, burning coal and gasoline can produce pollution molecules that contribute to smog and acid rain.


Using renewable energy-such as solar, wind, water, biomass, and geothermal-could help reduce pollution, prevent global warming, and decrease acid rain. Nuclear energy also has these advantages, but it requires storing radioactive wastes generated by nuclear power plants. Currently, renewable energy produces only a small part of the energy needs of the


United States. However, as technology improves, renewable energy should become less expensive and more common.


Hydropower (water power) is the least expensive way to produce I electricity. The sun causes water to evaporate. The evaporated water falls to the earth as rain or snow and fills lakes. Hydropower uses water stored in lakes behind dams. As water flows through a dam, the falling water turns turbines that run generators to produce electricity.


Currently, geothermal energy (heat inside the earth), biomass (energy from plants), solar energy (light from concentrated sunlight), and wind are being used to generate electricity. For example, in California there are more than sixteen thousand (16,000) wind turbines that generate enough power to supply a city the size of San Francisco with electricity.


In addition to producing more energy, we can also help meet our energy needs through conservation. Conservation means using less energy and using it more efficiently.


In the following experiments, you will use wind to do work, examine how batteries can store energy, and see how insulation can save energy.
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Materials


  • Pinwheel (can be purchased or madefrom construction paper)
  • Paper clips
  • Tape
  • Small shoe box  (children’s size)
  • Electric fan
  • Lightweight string  (about 4 feet long)
  • Plastic straw (longer than the width of the shoe box)
  • Hole punch


Download Student Worksheet & Exercises


Procedure


In this activity, you will try to use the energy in the wind to lift a set of six paper clips. You will first need to construct your windmill.


Use a hole punch to punch holes in the opposite sides across the width of a small, cardboard shoe box. Use the narrow sides of the box so the two holes are less than six inches (15 centimeters) apart. Make sure the holes are directly opposite each other. Place a plastic straw through the two holes. You may need to use the hole punch to enlarge the holes so the straw can rotate within the holes. The ends of the straw should extend out either side of the box.


Use the blades from a purchased pinwheel, or cut and fold a square piece of construction paper into the shape of a pinwheel. Next you will need to attach the pinwheel blades to one end of the straw. Partially unfold a small paper clip and insert the larger end into the straw. Push the straightened end of the paper clip through the center of the pinwheel. Bend this end of the paper clip and tape it to the outside of the pinwheel.


Set the electric fan on a table or countertop. Hold the shoe box so that the pinwheel is free to turn. HAVE AN ADULT PLUG IN AND TURN ON THE FAN. Move the windmill box to direct the breeze from the fan toward the blades of the pinwheel. Move the box until you find the best angle of the fan to the pinwheel so that the pinwheel turns freely and rapidly.


Turn off the fan. Now tape one end of the string to the side of the straw with no pinwheel just outside the box, and wrap the string around the straw a few times. Tie the other end of the string to a paper clip. Attach five other paper clips to the paper clip tied to the string. Allow the string to hang down so that the paper clips on the end of the string rest on the floor.


Now, you will test to see if your windmill can convert wind power to do work and lift the paper clips off the ground. Turn on the fan and hold the box where you did before to make the pinwheel turn.


Observations


Does the windmill turn the straw? Does the string wrap around the straw as the straw turns? What happens to the paper clips?


Discussion


You should observe the straw shaft turning as the wind from the fan is directed toward the blades of the pinwheel. As the pinwheel turns, it should wrap the string around the straw and lift the paper clips into the air. Your windmill converts the energy of the wind to work and lifts the weight of the paper clips. If your windmill is not working, then examine all the parts.


Compare your setup to the drawing, and see if any changes need to be made in your construction.


One way to store the energy produced by a windmill is to lift a weight. When the weight is allowed to fall, work can be produced. Weights in a grandfather clock are used to store energy and can run a clock for a week or longer. A windmill’s energy can be used to pump water to a storage area at a higher elevation. Later, this water can be allowed to fall through a turbine which turns a generator and produces electricity.


Electricity can also be produced directly from wind power. The shaft, or rod to which the windmill blades are attached, can be used to turn a generator. A generator or dynamo is used to convert mechanical energy into electrical energy. Power conversion units can change the direct current that wind generates to an alternating current. The alternating current can be fed directly into utility lines and used in our homes.


The sun is the original source of wind power. Without the sun to heat the earth, there would be no wind. The energy of the sun heats the earth, but all parts of the earth are not at the same temperature. These differences in temperature are responsible for global and local patterns of wind. For example, during the day a constant wind blows from the sea toward the land along coastal regions. Air above the hotter land rises and cooler, heavier air above the ocean moves in to take its place.


The power of the wind can be harnessed to do work. For at least 4,000 years, the wind has been used to move sailing ships. The wind has enough power to move ships across oceans and around the world.


For at least 1,000 years, windmills have been used for pumping water and turning


stones to grind grain. Millions of windmills have been used on the plains of America, Africa, and Australia to pump water from deep wells for livestock and humans.


In this century, windmills or wind engines have been used to generate electricity. Over 15,000 wind engines were installed in California in the 1980s. These wind engines have the capability to produce up to 1.5 billion watts of electricity. In California in 1987, wind was used to produce as much electricity as the city of San Francisco uses in an entire year.


 


Other Things to Try


Repeat this experiment and find the maximum weight you can lift with your windmill. Try more paper clips or try a heavier weight such as a pen.


List some of the problems associated with using windmills. What happens when the wind is blowing too gently? What happens if the wind blows strongly, such as in a storm? Do you think the area where you live is windy enough for wind engines to produce electricity?


Exercises


  1. Name three sources of renewable energy:
  2. What does the sun have to do with wind?
  3. Name three examples of wind power in historical or current usage:

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Cartesian Diver

Sunday October 23, 2011

Rene Descartes (1596-1650) was a French scientist and mathematician who used this same experiment show people about buoyancy. By squeezing the bottle, the test tube (diver) sinks and when released, the test tube surfaces. You can add hooks, rocks, and more to your set up to make this into a buoyancy game!
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The test tube sinks because the when you squeeze the bottle, you increase the pressure of the water and this forces water up into the test tube, which then compresses the air inside the tube. When this happens, it adds enough mass to cause it to sink. Releasing the squeeze on the bottle means that you decrease the pressure and the water is forced back out of the tube.


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Instant Ice

Thursday June 30, 2011

Supercooling a liquid is a really neat way of keeping the liquid a liquid below the freezing temperature. Normally, when you decrease the temperature of water below 32oF, it turns into ice. But if you do it gently and slowly enough, it will stay a liquid, albeit a really cold one!


In nature, you’ll find supercooled water drops in freezing rain and also inside cumulus clouds. Pilots that fly through these clouds need to pay careful attention, as ice can instantly form on the instrument ports causing the instruments to fail. More dangerous is when it forms on the wings, changing the shape of the wing and causing the wing to stop producing lift. Most planes have de-icing capabilities, but the pilot still needs to turn it on.


We’re going to supercool water, and then disturb it to watch the crystals grow right before our eyes! While we’re only going to supercool it a couple of degrees, scientists can actually supercool water to below -43oF!


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Materials:


  • water
  • glass
  • bowl
  • ice
  • salt


Download Student Worksheet & Exercises


Don’t mix up the idea of supercooling with “freezing point depression”. Supercooling is when you keep the solution a liquid below the freezing temperature (where it normally turns into a solid) without adding anything to the solution. “Freezing point depression” is when you lay salt on the roads to melt the snow – you are lowering the freezing point by adding something, so the solution has a lower freezing point than the pure solvent.


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Hot Ice Sculptures

Thursday June 30, 2011

Did you know that supercooled liquids need to heat up in order to freeze into a solid? It’s totally backwards, I know…but it’s true! Here’s the deal:


A supercooled liquid is a liquid that you slowly and carefully bring down the temperature below the normal freezing point and still have it be a liquid. We did this in our Instant Ice experiment.


Since the temperature is now below the freezing point, if you disturb the solution, it will need to heat up in order to go back up to the freezing point in order to turn into a solid.


When this happens, the solution gives off heat as it freezes. So instead of cold ice, you have hot ice. Weird, isn’t it?


Sodium acetate is a colorless salt used making rubber, dying clothing, and neutralizing sulfuric acid (the acid found in car batteries) spills. It’s also commonly available in heating packs, since the liquid-solid process is completely reversible – you can melt the solid back into a liquid and do this experiment over and over again!


The crystals melt at 136oF (58oC), so you can pop this in a saucepan of boiling water (wrap it in a towel first so you don’t melt the bag) for about 10 minutes to liquify the crystals.


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Materials:


  • Sodium Acetate
  • Disposable aluminum pie plate


Download Student Worksheet & Exercises


You have seen this stuff before – when you combined baking soda and vinegar in a cup, the white stuff at the bottom of the cup left over from the reaction is sodium acetate. (No white stuff? Then it’s mixed in solution with the water. If you heat the solution and boil off all the water, you’ll find white crystals in the bottom of your pan.) The bubbles released from the baking soda-vinegar reaction are carbon dioxide.


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Cloud Tracker Weather Instrument

Wednesday June 29, 2011

One of the most remarkable images of our planet has always been how dynamic the atmosphere is a photo of the Earth taken from space usually shows swirling masses of white wispy clouds, circling and moving constantly. So what are these graceful puffs that can both frustrate astronomers and excite photographers simultaneously?


Clouds are frozen ice crystals or white liquid water that you can see with your eyes. Scientists who study clouds go into a field of science called nephology, which is a specialized area of meteorology. Clouds don’t have to be made up of water – they can be any visible puff and can have all three states of matter (solid, liquid, and gas) existing within the cloud formation. For example, Jupiter has two cloud decks: the upper are water clouds, and the lower deck are ammonia clouds.


We’re going to learn how to build a weather instrument that will record whether (weather?) the day was sunny or cloudy using a very sensitive piece of paper. Are you ready?


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Materials:


  • Sun print paper or other paper sensitive to light
  • Film canister or soup can
  • Drill with drill bit
  • Scissors
  • Sunlight


The paper from a sun print kit has a very special coating that makes the paper react to light. Most sun print kits use set of light-sensitive chemicals such as potassium ferricyanide and ferric ammonium citrate to make a cyanotype solution. The paper changes color when exposed to UV light. In fact, you can try exposing the paper to different colors and see which changes the paper the most over a set amount of time!


The last step of this chemical process is to ‘set’ the reaction by washing it in plain water – this keeps the image on the paper so it doesn’t all disappear when you hang it on the wall. After the paper dries, the area exposed to UV light turns blue, and everything shaded turns white.


You can use sun print paper to test how well your sunblock works – just smear your favorite sunscreen over a sheet (or put a couple dabs of each kind) and see how well the paper stays protected: if it turns white, the light is getting through. If it stays blue, the sunscreen blocked the light!


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Thermometer

Wednesday June 29, 2011

First invented in the 1600s, thermometers measure temperature using a sensor (the bulb tip) and a scale. Temperature is a way of talking about, measuring, and comparing the thermal energy of objects. We use three different kinds of scales to measure temperature. Fahrenheit, Celsius, and Kelvin. (The fourth, Rankine, which is the absolute scale for Fahrenheit, is the one you’ll learn about in college.)


Mr. Fahrenheit, way back when (18th century) created a scale using a mercury thermometer to measure temperature. He marked 0° as the temperature ice melts in a tub of salt. (Ice melts at lower temperatures when it sits in salt. This is why we salt our driveways to get rid of ice). To standardize the higher point of his scale, he used the body temperature of his wife, 96°.


As you can tell, this wasn’t the most precise or useful measuring device. I can just imagine Mr. Fahrenheit, “Hmmm, something cold…something cold. I got it! Ice in salt. Good, okay there’s zero, excellent. Now, for something hot. Ummm, my wife! She always feels warm. Perfect, 96°. ” I hope he never tried to make a thermometer when she had a fever.


Just kidding, I’m sure he was very precise and careful, but it does seem kind of weird. Over time, the scale was made more precise and today body temperature is usually around 98.6°F.


Later, (still 18th century) Mr. Celsius came along and created his scale. He decided that he was going to use water as his standard. He chose the temperature that water freezes at as his 0° mark. He chose the temperature that water boils at as his 100° mark. From there, he put in 100 evenly spaced lines and a thermometer was born.


Last but not least Mr. Kelvin came along and wanted to create another scale. He said, I want my zero to be ZERO! So he chose absolute zero to be the zero on his scale.


Absolute zero is the theoretical temperature where molecules and atoms stop moving. They do not vibrate, jiggle or anything at absolute zero. In Celsius, absolute zero is -273 ° C. In Fahrenheit, absolute zero is -459°F (or 0°R). It doesn’t get colder than that!


As you can see, creating the temperature scales was really rather arbitrary:


“I think 0° is when water freezes with salt.”
“I think it’s just when water freezes.”
“Oh, yea, well I think it’s when atoms stop!”


Many of our measuring systems started rather arbitrarily and then, due to standardization over time, became the systems we use today. So that’s how temperature is measured, but what is temperature measuring?


Temperature is measuring thermal energy which is how fast the molecules in something are vibrating and moving. The higher the temperature something has, the faster the molecules are moving. Water at 34°F has molecules moving much more slowly than water at 150°F. Temperature is really a molecular speedometer.


Let’s make a quick thermometer so you can see how a thermometer actually works:


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Materials:


  • plastic bottle
  • straw
  • hot glue or clay
  • water
  • food coloring
  • rubbing alcohol
  • index card and pen


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!


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Hygrometer

Wednesday June 29, 2011

Hygrometers measure how much water is in the air, called humidity. If it's raining, it's 100% humidity. Deserts and arid climates have low humidity and dry skin. Humidity is very hard to measure accurately, but scientists have figured out ways to measure how much moisture is absorbed by measuring the change in temperature (as with a sling psychrometer), pressure, or change in electrical resistance (most common).

The dewpoint is the temperature when moist air hits the water vapor saturation point. If the temperature goes below this point, the water in the air will condense and you have fog. Pilots look for temperature and dewpoint in their weather reports to tell them if the airport is clear, or if it''s going to be 'socked in'. If the temperature stays above the dewpoint, then the airport will be clear enough to land by sight. However, if the temperature falls below the dewpoint, then they need to land by instruments, and this takes preparation ahead of time.

A sling psychrometer uses two thermometers (image above), side by side. By keeping one thermometer wet and the other dry, you can figure out the humidity using a humidity chart. Such as the one on page two of this document. The psychrometer works because it measures wet-bulb and dry-bulb temperatures by slinging the thermometers around your head. While this sounds like an odd thing to do, there's a little sock on the bottom end of one of the thermometers which gets dipped in water. When air flows over the wet sock, it measures the evaporation temperature, which is lower than the ambient temperature, measured by the dry thermometer.

Scientists use the difference between these two to figure out the relative humidity. For example, when there's no difference between the two, it's raining (which is 100% humidity). But when there's a 9oC temperature difference between wet and dry bulb, the relative humidity is 44%. If there's 18oC difference, then it's only 5% humidity.

You can even make your own by taping two identical thermometers to cardboard, leaving the ends exposed to the air. Wrap a wet piece of cloth or tissue around the end of one and use a fan to blow across both to see the temperature difference!

One of the most precise are chilled mirror dewpoint hygrometers, which uses a chilled mirror to detect condensation on the mirror's surface. The mirror's temperature is controlled to match the evaporation and condensation points of the water, and scientists use this temperature to figure out the humidity.

We're going to make a very simple hygrometer so you get the hand of how humidity can change daily. Be sure to check this instrument right before it rains. This is a good instrument to read once a day and log it in your weather data book.

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Materials:

  • single hair
  • index card
  • tack
  • cardboard
  • tape
  • scissors
  • dime


 

This device works because human hair changes length with humidity, albeit small. We magnify this change by using a lever arm (the arrow and mark the different places on the cardboard to indicate levels of humidity. Does all hair behave the same way? Does it matter if you use curly or straight hair, or even the color of the hair? Does gray work better than blonde?

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Anemometer

Wednesday June 29, 2011

Most weather stations have anemometers to measure wind speed or wind pressure. The kind of anemometer we’re going to make is the same one invented back in 1846 that measures wind speed. Most anemometers use three cups, which is not only more accurate but also responds to wind gusts more quickly than a four-cup model.


Some anemometers also have an aerovane attached, which enables scientists to get both speed and direction information. It looks like an airplane without wings – with a propeller at the front and a vane at the back.


Other amemometers don’t have any moving parts – instead they measure the resistance of a very short, thin piece of tungsten wire. (Resistance is how much a substance resists the flow of electrical current. Copper has a low electrical resistance, whereas rubber has a very high resistance.) Resistance changes with the material’s temperature, so the tungsten wire is heated and placed in the airflow. The wind flowing over the wire cools it down and increases the resistance of the wire, and scientists can figure out the wind speed.


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Scientists also use sonic anemometers, which use ultrasonic waves to detect wind speed. The great thing about sonic anemometers is that they can measure speed in all three directions, which is great for studying wind that is not all moving in the same direction (like gusts and hurricanes).


Sonic anemometers send a sound wave from one side to the other and measure the time it takes to travel. Which means that these can also be used as thermometers, as temperature will also change the speed of sound. Since there are no moving parts, you’ll find these types of anemometers in harsh conditions, like on a buoy or in the desert, where salt disintegrates and dust gets in the way of the cup-style anemometer. The big drawback to sonic anemometers is water (like dew or rain): if the transducers get wet, it changes the speed of sound and gives an error in the reading.


The quickest anemometer to make is to attach the end of a string (about 12″ long) to a ping pong ball. Suspend the string in the wind, like from a fan or hair dryer (use the ‘cool’ setting). Since the ball is so lightweight, it’s quite responsive to wind speed.


Add a protractor flipped upside down (so you can measure the angle of the string). Use the measurements below to figure out the wind speed. For example, mark the 90o angle with “0 mph”. This is your ping pong ball at rest in no wind. Use the numbers below to make the rest:



Angle Wind Speed
degrees mph
90 0
80 8
70 12
60 15
50 18
40 21
30 26
20 33

Now let’s make a four-cup anemometer. Here’s what you need to do:


Materials:


  • four lightweight cups
  • two sticks or popsicle sticks
  • tape or hot glue
  • tack or pin
  • pencil with eraser on top
  • block of foam (optional)


How steady was the wind that you measured? If you place your anemometer next to a door or a window, is there wind? How fast? Where could you place your anemometer so you can quickly read it each day?


By making two anemometers, one that you already know what the wind speed is, you can easily figure out how to calibrate the other. For example, how fast do the cups fly around when the ping pong ball anemometer indicates 12 mph? Can you see each cup, or are they a blur? You’ll get a feel for how to read the four-cup model by eye once you’ve had practice.


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Barometer

Wednesday June 29, 2011
French physicist Blaise Pascal. He developed work on natural and applied sciences as well being a skilled mathematician and religious philosopher.
French physicist Blaise Pascal. He developed work on natural and applied sciences as well being a skilled mathematician and religious philosopher.

A barometer uses either a gas (like air) or a liquid (like water or mercury) to measure pressure of the atmosphere. Scientists use barometers a lot when they predict the weather, because it’s usually a very accurate way to predict quick changes in the weather.


Barometers have been around for centuries – the first one was in the 1640s!


At any given momen, you can tell how high you are above sea level by measure the pressure of the air. If you measure the pressure at sea level using a barometer, and then go up a thousand feet in an airplane, it will always indicate exactly 3.6 kPa lower than it did at sea level.


Scientists measure pressure in “kPa” which stands for “kilo-Pascals”. The standard pressure is 101.3 kPa at sea level, and 97.7 kPa 1,000 feet above sea level. In fact, every thousand feet you go up, pressure decreases by 4%. In airplanes, pilots use this fact to tell how high they are. For 2,000 feet, the standard pressure will be 94.2 kPa. However, if you’re in a low front, the sea level pressure reading might be 99.8 kPa, but 1000 feet up it will always read 3.6 kPa lower, or 96.2 kPa.


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Materials:


  • balloon
  • straw or stick
  • water glass or clean jam jar
  • index card
  • tape


At standard pressure, depending on the kind of barometer you have, you’ll find they all read one of these: 101.3 kPa; 760 mmHg (millimeters of mercury, or “torr”); 29.92 inHg (inches of mercury); 14.7 psi (pounds per square inch); 1013.25 millibars/hectopascal. They are all different unit systems that all say the same thing.


Just like you can have 1 dollar or four quarters or ten dimes or 20 nickels or a hundred pennies, it’s still the same thing.


Why does water boil differently at sea level than it does on a mountain top?


It takes longer to cook food at high altitude because water boils at a lower temperature. Water boils at 212oF at standard atmospheric pressure. But at elevations higher than 3,500 feet, the boiling point of water is decreased.


The boiling point is defined when the temperature of the vapor pressure is equal to the atmospheric pressure. Think of vapor pressure as the pressure made by the water molecules hitting the inside of the container above the liquid level. But since the saucepan of water is not sealed, but rather open to the atmosphere, the vapor simply expands to the atmosphere and equals out. Since the pressure is lower on a mountaintop than at sea level, this pressure is lower, and hence the boiling point is lowered as well.


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Rain Gauge

Wednesday June 29, 2011

Also known as an udometer or pluviometer or ombrometer, or just plan old ‘rain cup’, this device will let you know how much water came down from the skies. Folks in India used bowls to record rainfall and used to estimate how many crops they would grow and thus how much tax to collect!


These devices reports in “millimeters of rain” or “”centimeters of rain” or even inches of rain”.  Sometimes a weather station will collect the rain and send in a sample for testing levels of pollutants.


While collecting rain may seem simple and straightforward, it does have its challenges! Imagine trying to collect rainfall in high wind areas, like during a hurricane. There are other problems, like trying to detect tiny amounts of rainfall, which either stick to the side of the container or evaporate before they can be read on the instrument. And what happens if it rains and then the temperature drops below freezing, before you’ve had a chance to read your gauge? Rain gauges can also get clogged by snow, leaves, and bugs, not to mention used as a water source for birds.


So what’s a scientist to do?


Press onward, like all great scientists! And invent a type of rain gauge that will work for your area. We’re going to make a standard cylinder-type rain gauge, but I am sure you can figure out how to modify it into a weighing precipitation type (where you weigh the amount in the bottle instead of reading a scale on the side), or a tipping bucket type (where a funnel channels the rain to a see-saw that tips when it gets full with a set amount of water) , or even a buried-pit bucket (to keep the animals out).
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Materials:


  • two water bottles
  • scissors
  • rainy day (or use water)


 
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Desalination

Sunday October 31, 2010

This experiment is for advanced students.


Lewis and Clark did this same experiment when they reached the Oregon coast in 1805. Men from the expedition traveled fifteen miles south of the fort they had built at the mouth of the Columbia River to where Seaside, Oregon now thrives.


In 1805, however, it was just men from the fort and Indians. They built an oven of rocks. For six weeks, they processed 1,400 gallons of seawater, boiling the water off to gain 28 gallons of salt.


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Lewis and Clark National Historic Park commemorates the struggles of the expedition. (The reconstructed fort is also there to visit.) It is Fort Clatsop National Memorial, and is quite an experience to go through the fort.


Lewis and Clark went to great lengths to obtain salt. The men had been complaining that fish without salt had become something to avoid. Salt is important to us as well. It is a condiment, an addition to food that brings out the food’s natural flavor. Besides its food value, salt is used as a food preservative. It destroys bacteria in food by removing moisture from their “bodies” and killing them.


Sodium chloride, table salt, NaCl….they’re all acceptable names for salt. If NaCl is broken down into its component elements, the elements don’t act like our friend salt. Its components are sodium and chlorine.


Sodium is a highly reactive alkali metal, element #11 on the periodic table. It is exothermic in water, which means that is gives of heat as it reacts with water. Small pieces tossed into water will react with it. The sodium particles give off heat that melts them into round balls. The sodium particles bounce and scurry around the surface at a high rate of speed. If you ever get the chance to observe this, do it. The reaction continues until the sodium is gone. Sodium, as it reacts with the water, changes chemically into sodium hydroxide. These cool things that sodium does are also dangerous. Sodium and sodium hydroxide are caustic…they are so pH basic that they will burn you.


Chlorine is a halogen, group 17, element #17. Chlorine is used in bleach, disinfectants, and in swimming pool maintenance. It seems that anywhere you want to remove color or life, chlorine is your element. This property of chlorine to kill was used in war. (It would react with the mucous linings in their throat, undergoing a chemical reaction to turn into hydrochloric acid in their throats. Hydrochloric acid is a very dangerous acid, usually fatal once inside you.) Chlorine is known as bleach at home. Never, never, drink it or breathe its fumes.


Materials:


  • Goggles
  • Gloves
  • Jar or glass
  • 2 90o glass tubes
  • Chemistry stand
  • Rubber tubing
  • Test tube clamp
  • Erlenmeyer flask
  • One-hole rubber stopper
  • Wire screen
  • Alcohol burner
  • Lighter
  • Test tube
  • Water
  • Saltwater
  • Heating rod

Look out for the hot flask and other glassware. Allow everything to cool before cleaning.


When done heating, move the rubber tubing out of the water. There is a difference in pressure between the heated glassware and the water bath. That difference in pressure will cause the water to enter the tubing and cool water will flow into the hot glassware and could cause catastrophic damage to the glassware.


Never…Never!….drink the results of an experiment. Yeah, I know that plain old water is supposed to be in the test tube, but follow the experiment’s safety guidelines. You’ve had other stuff in that test tube, too.


C3000: Experiment 83


Here’s what’s going on in this experiment:


That flask of saltwater will start to boil, and water vapor will leave the flask and travel to the test tube. There is no chemical change occurring in this experiment, but a physical one. A physical change involves a change in state (melting, freezing, vaporization, condensation, sublimation). Physical changes are things like crushing a can, melting an ice cube, breaking a bottle, or boiling saltwater until there is nothing left but salt and steam.


Cleanup: Clean everything thoroughly after you are finished with the lab. After cleaning with soap and water, rinse thoroughly. Chemists use the rule of “three” in cleaning glassware and tools. After washing, chemists rinse out all visible soap and then rinse three times more.


Storage: Place cleaned tools and glassware in their respective storage places.


Disposal: Liquids can be washed down the drain


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Convection Currents

Sunday September 5, 2010

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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