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.

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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 130^oF (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?)

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

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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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?

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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?

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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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 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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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. 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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Today you will make a calibrated, or marked, container that you will use to measure your lung capacity. You will fill the calibrated container with water, slide a hose into it, take a really deep breath, and blow in the hose. As the air in your lungs enters the container, it will push out the water inside. Just blow as long and as much as you can, then when you flip the bottle over you will be able to read the amount of water you have displaced. If you will subtract the water displaced from the total amount of water in the bottle, the result is your lung capacity.

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Here’s what you need

• • 1 2-liter soda bottle
  • 1 black marker, permanent
  • 1 12” length of rubber hose
  • 1 large plastic bowl
  • 1 cup measure

Download Student Worksheet & Exercises

Here’s what you do

1. Fill the 1 cup measure with water. Pour this into the 2-liter bottle and mark the water level with a line using the black, permanent marker. Also, write 1 cup next to the line. Keep adding water, one cup at a time, marking each new 1 cup increment until you have filled the bottle with water.
2. Now flip the newly-filled bottle of water over 1 cup measure until the cup is about 1/3 full. Put one end of the rubber hose in the top of the bottle (which should be now under water).
3. Take a really deep breath – as deep as you can – and blow your breath out into the tube. Continue to blow until you can’t push any more air into the bottle. As air goes in the bottle, it pushes an amount of water equal to its volume out and into the bowl.
4. Put the lid on the bottle and turn it over before lifting it out of the water. How much water is left in the bottle? Subtract this amount from 8.5 cups. This should be your lung capacity.
5. Record your lung capacity in your data records as, “My lung capacity is ____________ cups.”  You can convert this number to milliliters by multiplying by 0.24. For example, 19 cups would equal 4.5 liters.

What’s going on?

A person who is 70 years old has breathed about 600,000,000 times in their life. But they have also breathed a lot of air – about 13,000,000 cubic feet. This is enough air to fill 52 blimps!

A man’s lungs have a greater capacity than a woman’s – it’s about 6 liters for a man and 4.2 liters for a woman. And since a grown-up has a greater lung capacity than a kid, it makes sense that a 10-year old might breathe 20 times per minute when a grown-up might breathe only 12 times in a minute.

Exercises

1. Which body system are your lungs a part of?
2. What are some other parts in this system?
3. Explain this system’s major function.

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When you exercise your body requires more oxygen in order to burn the fuel that has been stored in your muscles.  Since oxygen is moved through your body by red blood cells, exercise increases your heart rate so that the blood can be pumped through your body faster. This delivers the needed oxygen to your muscles faster. The harder you exercise, the more oxygen is needed, so your heart and blood pump even faster still.

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Here’s what you need

• 1 clock with a second hand
• 1 pencil

Download Student Worksheet & Exercises

Here’s what you do

1. While sitting quietly, place your first two fingers of one hand onto the wrist of the other hand. Feel for the pulse of your radial artery. Practice taking your pulse in intervals of 6 seconds.
2. After you have had some practice with the 6 second interval, take your pulse for this amount of time and multiply it by 10. The 6-second rate times 10 is your heart rate per minute. Record each for experiment data.
3. Now stand up and do 50 jumping jacks. When done, sit down immediately and check your pulse. Again, record the 6-second pulse rate, multiply it by 10 and also record the pulse rate per minute.
4. Finally, go outside and run around as fast as you can without stopping for 3 minutes. Again, immediately sit and take your pulse. Record the 6-second rate, multiply it by 10 and get your heart rate per minute.

What’s going on?

Exercising means your muscles need more oxygen. They ask your brain to tell your heart and lungs. When your heart gets the message, it starts to beat harder. Your lungs work harder, too. Together, your heart and lungs work as a team to provide the needed oxygen supply to your muscles. You can identify that this process is occurring by your heart rate increase and more rapid breathing rate.

Did you know that your heart is about the size of your fist? It is actually a muscle and it pumps more than a gallon of blood through your body each minute! An average heart rate is 70 beats per minute, but this can vary depending on age and fitness level. Based on 70 bpm, your heart will beat around 100,000 times per day. That’s more than 36 million beats a year!

Exercises

1. Explain how to take a pulse.
2. What units do we use to measure pulse?

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Stethoscopes are instruments used to amplify sounds like your heartbeat. Your doctor is trained to use a stethoscope not only to count the beats, but he or she can also hear things like your blood entering and exiting the heart
and its valves opening and closing. Pretty cool!

Today you will make and test a homemade stethoscope. Even though it will be pretty simple, you should still be able to hear your heart beating and your heart pumping. You can also use it to listen to your lungs, just like your doctor does.

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Here’s what you need

• 3 12-inch lengths of rubber hose
• 1 “T” connector
• 1 funnel

Download Student Worksheet & Exercises

Here’s what you do

1. Take two pieces of hose and work them onto the top ends of the “T” connector. Put the remaining piece of hose onto the bottom of the “T.” The tool you have made should look like a simple stethoscope, but there are no super cold metal end pieces to worry about with yours.
2. Put the funnel into the bottom hose – the one hanging from the bottom of the “T” connector. You know have a functioning stethoscope. One word of warning: NEVER YELL INTO THE FUNNEL WHILE THE STETHOSCOPE IS ATTACHED TO SOMEONE’S EARS. THIS COULD DAMAGE EAR DRUMS!
3. Gently insert the side tubes into your ears. Put the funnel on your chest, just to the left of your breastbone. Listen for your heartbeat. If you are in a sufficiently quiet room you may even be able to hear the opening and closing of your heart’s valves.
4. After you’ve found your hear, try moving the stethoscope to various areas of your chest and listen for different sounds made by your heart. Ask if you can listen to a friend or family member’s heart. Are the sounds made by another heart the same or different?
5. Now listen to your lungs, placing the end of the stethoscope just above and to the left of the bottom of your ribcage (Point A), to the right of the bottom of your ribcage (Point B), and just below where your ribs start (point C). Also listen in the middle of your back to the left (point D) and right of your spine (point E). In each spot, take a deep breath and listen for the sound of air entering and exiting the lungs.
6. For your data records, record how many times your heart beats in a minute while you are quiet and sitting.
7. Next, do 100 jumping jacks. Sit down immediately and check your heart. Record the number of beats per minute for jumping jacks in your data.
8. Finally, go outside and run for 3 minutes, non-stop. Then sit and immediately check your heart rate one more time. Record the beats per minute for running in your experiment data.

What’s going on?

Exercise creates a demand for oxygen in your muscles, which is received from work done by your heart and lungs. They get a message from your brain and start to work harder. You can see the proof of their hard work in your recorded data.

Exercises

1. Approximately how big is your heart?
2. Which body system is the heart a part of?
3. What are some of this system’s jobs?
4. How many chambers does your heart have and what are they called?
5. How did the heart rate change when you exercised?

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Did you know that your tongue can taste about 10,000 unique flavors? Our tongues take an organized approach to flavor classification by dividing tastes into the four basic categories of sweet, sour, salty, and bitter.

For this experiment, you will need a brave partner! They will be blindfolded and will be attempting to guess foods. Relying only on their sense of taste, they will try to determine what kind of foods you are giving them.

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Here’s what you need

• 1 partner
• 1 blindfold
• 1 cup of water
• 1 plate
• 1 lemon
• 2 toothpicks
• 1 sugar cube
• 1 salty cracker
• 1 piece of dark chocolate
• 1 pencil

Download Student Worksheet & Exercises

Here’s what you do

1. (NOTE: Make sure your partner is not around for the first step!) Prepare a plate with a piece of lemon on a toothpick, a sugar cube, a really salty cracker, and a piece of dark chocolate, which will also be on a toothpick.
2. Blindfold your partner before they see the plate. Explain that you’re going to give them food samples. Their job is to taste each sample, one at a time, and then determine whether the food is sweet, sour, salty, or bitter. After they have provided a category, see if they can tell you the specific flavor of the food. They should use the water between samples in order to rinse their mouth and prepare for the next food.
3. Record data and observations for each individual food item. Be sure to list each food, your partner’s group classifications (sweet, sour, salty, or bitter) and what specific flavors that they note.

 What’s going on?

When you put food in your mouth, saliva immediately begins to break it down. Saliva mixes with food and makes a solution, which then takes the food (and its flavor) to the taste pores. There, receptors determine the chemical structure and send this information to your brain, which then decodes and categorizes the taste. The exact nature of the secret code relayed between your taste receptors and your brain is still a mystery. Maybe someday you can help to figure out the science behind it!

Did you know that humans have about 7500 taste buds? That’s a lot compared to most chickens, which only have about 24, total. But it’s a pretty small amount compared to catfish. They have over 175,000 taste buds! Can you imagine what your favorite dessert might taste like if you had that many? I wonder if it would be a good thing, or maybe too much information. Perhaps we are better off with our own perfect number of taste buds!

Exercises

1. How does saliva help with tasting?
2. What helps to decode the chemical structure of a food so that the brain can determine its taste type?
3. Why do foods sometimes become less strong as we age?

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The tongue has an ingenious design. Receptors responsible for getting information are separate and compartmentalized. So, different areas on the tongue actually have receptors for different types of tastes. This helps us to separate and enjoy the distinct flavors. In this experiment, you will be locating the receptors for sweet, sour, salty, and bitter on the tongue’s surface.

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Here’s what you need

• 4 cotton swabs
• 5 wax cups
• 1 bag of black tea
• 1 bottle of red vinegar
• 2 packages of sugar
• 2 packages of salt
• 1 microwave
• water
• 1 spoon
• 1 partner
• 1 blindfold

Download Student Worksheet & Exercises

Here’s what you do

1. Put 3 ounces of water into the first of the wax cups. Bring it to a boil in the microwave and have an adult help you add a teabag. This will make your bitter cup. Let it sit for 5 minutes. While it is steeping, you can prepare the other cups.

2. Fill the remaining cups with 2 ounces of water each. Prepare them as follows:

A.      For the sweet cup, add two packages of sugar to the warm water in one of the cups. Stir until well dissolved.
B.      For the sour cup, add 2 ounces of red vinegar to another cup and stir well.
C.      For the salty cup, put two packages of salt into the final cup. Stir until dissolved.
D.      The last step in cup preparation is to discard the tea bag that has been steeping in the first cup.

3. Now put the blindfold on your partner and have them stick out their tongue.  Dip the first swab into the tea. Using the diagram as a guide, swab each area one at a time: A, B, C, and D.  Ask your partner to identify the flavors as sweet, sour, salty, bitter, or can’t tell  as you swab each individual area. Record your partner’s response for each area.

4.Your partner should rinse out their mouth with water after testing the bitter tea. Then test each of the remaining solutions, one at a time in the same manner.

What’s going on?

Humans can identify thousands of distinct tastes, but we only have four types of taste receptors. When you take a bite of something flavorful, your saliva starts to dissolve it immediately. This solution of flavor and saliva goes to your taste buds and is then interpreted by your brain as sweet, sour, salty, or bitter.

The taste buds have taste receptors which bind to the structure of certain molecules: sweet receptors recognize hydroxyl groups (OH) in sugars, sour receptors find acids (H+, such as the citric acid in a lemon), salt receptors respond to metal ions (like Na+ in table salt), and bitter receptors are triggered by alkaloids. These are bases which contain nitrogen.  It’s interesting to note the location of the bitter taste buds – they are on the back of the tongue.  Since many poisons are alkaloids, their bitter taste may actually trigger vomiting.

Anyone who’s had a stuffy nose can tell you that smell plays a big role in our ability to taste. This makes sense because we know that we can only really taste the 4 distinct true flavors of sweet, sour, salty, and bitter. Our nose works in partnership with our tongue to allow us to identify more complex flavors.

Exercises

1. How many different types of taste receptors do we have? What are they?
2. Can you still taste food when you have a stuffy nose?
3. Which taste receptors recognize the hydroxyl group?

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Digestion starts in your mouth as soon as you start to chew. Your saliva is full of enzymes. They are a kind of chemical key that unlock chains of protein, fat, and starch molecules. Enzymes break these chains down into smaller molecules like sugars and amino acids.

In this experiment, we will examine how the enzymes in your mouth help to break down the starch in a cracker. You will test the cracker to confirm starch content, then put it in your mouth and chew it for a long time in order to really let the enzymes do their job. Finally you will test the cracker for starch content and see what has happened as a result of your chewing.

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Here’s what you need

1. 1 package of soda crackers
2. 1 5” pie tin
3. 1 craft stick
4. 1 0.5 oz bottle of iodine
5. 1 pre-form tube
6. 1 1 mL plastic pipette
7. water

Download Student Worksheet & Exercises

Here’s what you do

1. Take a cracker from the package and put it in the pie tin. Use your thumb to mash it up, making the pieces as small as possible. Add a small amount of water with the pipette. Mix everything up with the craft stick to make a mash of cracker.
2. Now fill the pipette with iodine. When iodine comes in contact with starch, it changes in color from reddish-brown to a dark blueish-black. Take the pipette and squeeze a few drops onto the cracker mash in various spots. Record what you see in your experiment data.
3. Take another cracker and chew it up for about 2 minutes. Do you notice any flavor changes as you are chewing? If so, note this. Be particularly aware of any sweet flavors.
4. Spit the mash into the pre-form tube once you have chewed for 2 minutes. Use the pipette of iodine to add a few drops of iodine to the chewed mash. Note any change in color. If there is no starch, the iodine will stay reddish-brown in color. If starch is present, you will see the color change to a very dark blue-black as it did in step 2. Record what you see in your data.

What’s going on?

This lab gives you a good idea of what happens in digestion, which starts as soon as food enters your mouth. Actually, the process can start even before this as your body prepares for food. Have you ever had a wonderful smell make your mouth water? This is your body’s way of getting ready to get to work digesting that delicious food.

Once you take a bite and the enzymes start to do their job of breaking large, more complex molecules into smaller particles. In this experiment, starch got broken down into simple sugars that your body could easily move around and use as fuel.

There are three sets of saliva-secreting glands in your mouth. They include a gland in the back of your throat called the parotoid gland, one in your lower jaw called the submandibular gland, and the sublingual gland which is under your tongue. The three work together to secrete up to 2 liters of saliva each day.

Exercises

1. What is the first step in the digestive process?
2. How does saliva help to digest food?
3. Name one or more of the main salivary glands and where they are located.

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We have done some extensive experiments on taste buds: how they are categorized, what tastes they recognize, and we have even mapped their location on your tongue. But we haven’t yet mentioned this fact: not all people can taste the same flavors!

So today we will check to see if you have a dominant or recessive gene for a distinct genetic characteristic. We’ll do this by testing your reaction to the taste of a chemical called phenylthiocarbamide (or PTC, for short). The interesting thing about PTC is that some people can taste it – and generally have a very adverse reaction. However, some people can’t taste it at all.

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Here’s what you need

• 1 vial of PTC paper
• family members

Download Student Worksheet & Exercises

Here’s what you do

1. Put the PTC paper in your mouth. If you have the dominant gene, it will usually taste pretty bitter. It might also be sour or even a little sweet. If it tastes like a piece of paper, you have a recessive gene.
2. After testing your paper, be sure to note whether you are a taster or non-taster.
3. Now test at least five more people in your family and note their reactions as tasters or non-tasters. Also note their relationship to you.
4. If you have enough PTC paper, make a genetic tree of your responses. Put Mom and Dad at the center and list you and your siblings branching out beneath them. Then list both sets of grandparents above each of your parents. Circle the names of family members who test positive and leave the negative testers uncircled.

What’s going on?

The gene that determines whether or not you can taste PTC is a part of your DNA (deoxyribonucleic acid). It is the genetic blueprint that you were born with and it determines everything about you: from hair color to the size of your feet. But DNA also plays an important role in how your five senses function. Colorblindness is a genetic deficiency in which a person cannot see colors has a difficult time with distinguishing them. It can range in severity. Some people who are colorblind can’t tell the difference between colors like red and green, but some see no colors at all. Everything looks like a black and white movie to them. Just like colorblindness, our taste sensitivity can vary. Maybe this explains why some people like liver and brussel sprouts and others can’t stand them!

So to relate this to our test, the ability to taste PTC comes from a gene. We know that if both of your parents can taste it, there is a high likelihood that you will be able to taste it, too. About 70%, or 7 out of 10, people can taste it. But what does it mean?  In truth, not a lot. It doesn’t mean you have a highly developed palate or a better sense of taste. It just means you are lucky enough to have inherited a gene that allows you to taste a disgusting, bitter chemical on a piece of paper. Congratulations!

Exercises

1. What are the tiny hair-like organelles that send taste messages to your brain called?
2. What are the bumps on your tongue called?
3. What kind of trait does this experiment test?

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The buildup of things like food and bacteria where your gums and teeth meet, and also between your teeth, is called plaque. Where plaque lives is also where the bacteria turns the sugar in your mouth into harmful acids that attack your teeth’s enamel and can lead to gum disease. Regular brushing is a great way to remove plaque and keep your mouth healthy.

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Here’s what you need

• 1 4-pack of red disclosing tablets
• 1 clear plastic cup
• 1 mirror
• 1 red crayon
• water

Download Student Worksheet & Exercises

Here’s what you do

1. Disclosing tablets are designed to identify plaque by turning it red. Remove a pill from the packaging and put it in your mouth. Chew it up thoroughly but don’t swallow it. Be very careful not to get any of the dye on clothing or anything else that might stain. The color is very difficult to remove!
2. Take the cup full of water and rinse out your mouth very well. Spit the water out into the sink. Check your mouth in the mirror. All of that red is plaque! Draw a picture of your mouth and use the red crayon to note where the plaque is attacking your teeth and gums.
3. You should have a total of 4 pills in the package. You can test other members of your family, or if you would prefer, test yourself over a period of a few days after you have had a chance to observe and identify where you should be doing a better job of tooth-brushing.

What’s going on?

When you chew the tablets they start to dissolve and mix with your saliva. This makes a water soluble dye that affixes to the bacteria and other particles in your mouth. The dye is absorbed by the bacteria, so it holds onto it even after your mouth is rinsed. This enables you to identify the unbrushed areas in your mouth.

Have you ever counted your teeth? They started to appear when you were a baby – about 6 months old or so. Kids have 20 deciduous, or baby teeth. These will fall out and the adult teeth grow in to replace them. Adults usually have 32 total teeth.

Exercises

1. Why does this experiment work at detecting plaque?
2.  How can dentists and moms use this to make sure you’re doing a good job brushing?
3.  What is plaque, and why is it bad for you?

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Involuntary responses are ones that you can’t control, but they are usually in place to help with survival. One good example is when you touch something hot. Your hand does not take the time to send a message to your brain and then have the brain tell your hand to pull away. By then, your hand might be seriously hurt! Instead, your body immediately removes your hand in order to protect it from further harm.

Today you will test an involuntary reflex by using the tendon reflex test. A thick, rubbery band called the patellar tendon holds your knee cap in place. Having one leg on top of the other not only stretches the tendon, but it also makes it possible to see a reaction. You can test the reflex by giving your tendon a tap and watching what happens.

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Here’s what you need

1. 1 knee
2. 1 partner

Download Student Worksheet & Exercises

Here’s what you do

1. Sit with your legs crossed at the knee on the edge of your seat. Reach forward and see if you can feel the patellar tendon. It is right below your knee cap.
2. Ask your partner to gently tap the tendon with the outside edge of their hand. This will look like a careful little karate chop. If your partner gets the right spot it will be obvious. You will notice your leg kick out a little in a reflex reaction.
3. Your partner can try other spots on the tendon if reaction isn’t achieved at first. If it hurts, stop right away! It’s possible that you might not have a tendon response reflex. Not everyone does and that is perfectly normal.

What’s going on?

There are three main parts that make up your peripheral nervous system. They are the autonomic nerves, which control reflexes like the one we have studies here. Autonomic nerves also send information to your organs, blood, and other parts of the body. The second part of your peripheral nervous system is made up of the nerves that deal with the five senses. The last part is your motor nerves. They help you to move the muscles in your body and are responsible for voluntary reactions.

The tendon reflex is in place because the knee is such a sensitive and vulnerable part of the body. When the tendon is stretched out and bumped, your body tries to move the leg and knee out of harm’s way so that it won’t get hurt. As you could probably tell, it’s an involuntary response that neutralizes any conscious, voluntary control that your brain has over the leg through the motor nerves.

Exercises

1. What are the main parts of the nervous system?
2. What are the two parts of the peripheral nervous system and what are their functions?
3. Which part of the nervous system controls involuntary reflexes?

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The skeleton is your body’s internal supporting structure. It holds everything together. In addition to providing support, bones act as shock absorbers when you jump, fall, and run. Bones have big responsibilities and so they must be really strong. They also need to be arranged properly for the best support and shock absorption.

In this experiment, we will look at the internal arrangement of the bones holding together your body.

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Here’s what you need

• 1 toilet paper tube
• 50-100 straws
• 1 roll of tape
• 1 book

Download Student Worksheet & Exercises

Here’s what you do

1. First you will explore different bone structures. Start by taking 20 skinny straws and arrange them randomly in your hand so that they are pointing in different directions.
2. Lay your arm and hand on a table so that it is braced. Next, have a friend place a heavy book on this column of straws. What happens then it’s exposed to the weight?
3. Now take 20 more straws and arrange in a circle so that they are all held vertically in your hand.
4. Repeat step 2 with these more organized straws. Do you notice a difference? The uniformly arranged straws should be stronger than those that were randomly arranged.
5. The tubes inside your bones are more like the uniform model of straws. They also have a kind of glue that hold them in place inside the bones. Let’s incorporate this idea into your model by lining the inside of the toilet paper tube with tape.
6. Next, add some straws inside the tube as well. Add a single layer of straws, then another layer on top of it. Finally, fill the middle of the tube with straws, making sure they are tightly packed.
7. Test your model’s strength by placing a book on top of the tube. What happens when the model is exposed to the book’s weight?
8. For an extra study opportunity, visit the butcher in your local grocery store and ask for the end of a beef bone. (This is sometimes packaged as a soup bone). Look at the end of the bone. What do you see? It should look like a hard outer shell of bone protecting a softer, spongy portion. Draw a picture of your observations.

What’s going on?

In your experiment, it should have been readily apparent that the more organized and uniform straws were much stronger than the randomly arranged ones. Your own bones have a similar pattern in their soft, spongy part called cancellous bone. This portion of bone has a honeycombed structure which makes the bones very strong, but relatively light.  The tiny tubes that make up the honeycomb are called the Haversian system and the actual tissue of the structures is made up of collagen. This allows them to maintain flexibility, but they are still composed of minerals – notably calcium and phosphorus which give them their hardness and strength.

Exercises

1. Name some of the parts that make up our skeletal system.
2. What is the smooth, hard, protective layer on the outside of bones called?
3. What is the inside spongy, porous, honeycombed bone called?
4. What is the network of tubes inside bones called?

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In this experiment, we will continue to explore Ruffini’s endings in your skin. We also look at your body’s ability to detect temperature and regulate its own temperature. You will study how the body cools and warms itself.

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Here’s what you need

1. 1 bottle of rubbing alcohol
2. 1 cotton ball
3. 1 liquid crystal thermometer strip
4. 1 cotton glove

Download Student Worksheet & Exercises

Here’s what you do

1. Position the thermometer strip on the back of your hand. Give it a moment to register the temperature of your body. Record this temperature as a base reading for your data.
2. Put some rubbing alcohol on a cotton ball. Now use the cotton ball to wipe the alcohol on the surface where you took the reading, right on the back of your hand. Quickly put the thermometer strip right back on the spot where you have put the alcohol and take another reading. Note the temperature in your records.
3. Now put the glove on your hand and run around in the yard, do some jumping jacks, or find another way to be physically active for 3 minutes. When you have worked up a sweat, come back to the experiment area. With your hand still in the glove, put the liquid crystal thermometer on the back of your hand where you took the first reading. Record this temperature information in your data records.
4. Finally, take off the glove and observe your hand. Can you tell that your sweat glands have been working? If so, have they been very active or just a little active?

What’s going on?

Your body likes to keep your temperature in equilibrium, which is a state of balance. It works hard to regulate your temperature and avoid any sudden changes that could be harmful. Constant and predictable is your body’s goal and it uses your skin to help.

When you are cold, blood flow to the skin is reduced in order to help stem the loss of heat. Your hair also stands on end in an error to trap air next to the body and help insulate it…although this doesn’t work very well for most of us! This is a more effective tool against heat loss with much furrier mammals.

In order to cool you down, skin can use some of your three million sweat glands. Sweat absorbs and displaces extra heat and can also close openings to cells on the surface to avoid excess gains in heat.

Your data in the lab should have simulated the effects of body temperature in three different conditions: equilibrium, excess cold, and excess heat.

Exercises

1. What is equilibrium?
2. How does equilibrium relate to body temperature?
3. How does our body help to cool us down?

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Your fingers have receptors which perform various jobs. In addition to touch, they can detect pressure, texture, and other physical stimuli.  One specialized type of receptors is called Ruffini’s receptors. They are good at identifying changes in pressure and temperature. In this experiment, we will test their ability to distinguish between hot and cold temperatures. We are actually going to try and trick your Ruffini endings. Do you think it will work?

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Here’s what you need

• 3 glasses
• 1 Celsius/Fahrenheit thermometer
• hands
• 1 clock with second hand
• hot water
• cold water
• ice cubes (optional)
• room-temperature water

Download Student Worksheet & Exercises

Here’s what you do

1. Place the three glasses in front of you on a table. They should be in a row: left, middle and right.
2. Put hot water from the faucet into the first glass on your right. Pour very cold water from the tap into the far left glass. You can even add a couple of ice cubes if you have them available. Finally, fill the glass that is in the middle with room temperature water.
3. Now use your right hand to hold on to the glass on the right with hot water. Really spread out your fingers and wrap them around the glass. Do the same thing with your left hand and the glass filled with cold water. Be sure to check the clock and leave your hands on the glasses for exactly one minute.
4. After one minute, take your hands and put them both on the middle glass. (You may need to stack one on top of the other if your glasses are narrow). Note the temperature you feel with each hand: hot, cold, or medium. You can use the thermometer to record the actual water temperature.
5. Now repeat steps 1-4. This time, switch the hot and cold glasses so that you are holding the hot water with your left hand and the cold water with your right hand. Compare these results with your initial results. Do both hands respond in a similar way or is one more sensitive that the other?
6. Some questions to think about:

Does the temperature of the middle glass feel warmer, cooler, or the same when you touch it with your hand that was holding the warm glass?
What does your hand that was touching the cold glass feel when it touches the middle glass?
What do you feel when both hands are on the middle glass?
Why do you think your hands are not the best instruments for determining temperature?

 What’s going on?

Your hands are designed to adapt to temperature. Touching the warm glass relaxes the muscles of your hands, increases circulation, and enhances flexibility. When your hand touches the cold glass the cells on your skin’s surface begin to contract to minimize loss of heat and your hand becomes less flexible. Then, when you grab the middle can your hands get a bit confused. Relatively speaking, the middle glass feels warmer to the hand that was holding the cold glass and it feels cooler to the hand that was holding the warm one. The hands are still feeling the temperature, but your brain gets confused.

Did you know that our skin does not have receptors to indicated burning hot? This sensation is actually created by three different receptors which fire at the same time: pain, cold, and warm. This explain why to some people, very hot things actually feel cold. If you could prepare a group of alternating hot and cold metal bars, touching them with your fingers would be an odd experience. Your brain will think they are too hot to touch and will tell you to pull away your hand!

Exercises

1. Does the temperature of the middle glass feel warmer, cooler, or the same when you touch it with your hand that was holding the warm glass?
2. What does your hand that was touching the cold glass feel when it touches the middle glass?
3. What do you feel when both hands are on the middle glass?
4. Why do you think your hands are not the best instruments for determining temperature?
5. Which nerve endings help to detect changes in temperature?

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Skin has another function that it vital to your survival: temperature regulation. Being exposed to high temperatures causes your skin’s pores to open up and release sweat onto your body. This helps cool us off by the resulting process of evaporation.

Your pores will close in extremely cold temperatures. Also, the body stops blood flowing to the skin in order to conserve heat for the important vital organs and their processes.

In this lab, we study the moisture that your skin produces – even when you are not aware of it!

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Here’s what you need

• 1 gallon baggie
• 1 string, 12 inches long
• 1 assistant
• 1 clock

Download Student Worksheet & Exercises

Here’s what you do

1. Record a description of how moist your hand is prior to putting it in the baggie. This is at 0 minutes.
2. Put your hand in the baggie and ask your assistant to tie it closed around your wrist. No air should be able to get in or out of the baggie. Record the time for tracking purposes.
3. Check your hand every 10 minutes for a half hour. With each observation note the amount of moisture that has accumulated. Record your observations at 10 minutes, 20 minutes, and 30 minutes.
4. What do you think will happen if you go outside and run around with your hand inside the bag? Try it and see if it accelerates the process.

What’s going on?

Sweat glands are always producing moisture on our skin. Most of the time, we don’t really notice this process. By enclosing your hand in plastic, this moisture can’t evaporate as it normally would. The bag collects and condenses it.

It is interesting to note that your body can produce up to a gallon of water in extremely hot temperatures – 110 degrees Fahrenheit and higher. This is one of the reasons it’s so important to stay hydrated in extreme heat!

Exercises

1. How is sweat released from the body through the skin?
2. How does sweat help to cool the body?
3. What did you observe at the 30 minute mark in your experiment?
4. What is evaporation and how is it different from condensation?

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This lab has two parts. First, you will learn a bit about how specific chemicals react in a specific manner. And next, you will learn a bit of biology: the structure of bird bones and the minerals that compose them.

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Here’s what you need

• 4 fresh chicken wing bones, meat removed
• 1-16 oz. bottle of distilled white vinegar
• 2-12 oz. plastic cups
• 1 fresh egg
• 1 spoon

Here’s what you do

1. Make sure all the meat and cartilage is gone. Check near the joints for soft, white-gray matter and clean it off. Now break a bone in half. What does the inside look like? Note the color and hardness for your data. Be sure to wash your hands well after studying the bones.
2. Pour some vinegar in a cup and gently place the bones in the solution. Add more to cover the bones, if needed. Put the cup in a spot where it won’t be disturbed for a few days. It will take a while for the vinegar to fully react with the bones.
3. Take a look at the egg and note its color and hardness in your experiment data. Now carefully place the fresh egg in the second cup and pour vinegar over it. Be sure to completely cover the egg. You will need to cover the egg or keep an eye on it. The vinegar will evaporate and will need to be replenished. This portion of the experiment will take around 24 hours.
4. Use the spoon to remove the egg after 24 hours has passed. Set it down and gently push on it. What happened to the part that used to be shell? Check your notes from the previous day and note any changes that have occurred in the color and hardness of the egg after it has been in the vinegar.
5. After a few more days, take the chicken bones out of the vinegar. Bend them and see what happens. Do they break as easily as they did the first day? Look at your data and compare the color and hardness of the bones now to how they looked on the first day. Record the changes you observe.

What’s going on?

Calcium is the mineral in both bones and eggshells that makes them hard.  Putting the bones and egg in vinegar caused the calcium to begin to react. Vinegar leached calcium from both the bones and the shell, which caused their hardened structure to become weak.

Did you know that your bones and teeth contain 99% of the calcium in your body? About ¾ of your bones are compact, but the remaining ¼ of them is spongy. But do you think your bones or your teeth are harder? The second hardest material in your entire body is the compact, hard bone. Your teeth enamel is actually the hardest material.

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This experiment has two parts. For the first half, you will mix two chemicals that will produce heat and gas. The temperature receptors in your skin will be able to detect the heat. Your ears will detect the gas at it vibrates and escapes its container.

In the second portion you will demonstrate a characteristic in a chemical reaction. For this experiment, it will be an endothermic reaction, which is the absorption of heat energy. This type of reaction is easy to notice because it makes things cold to touch.  The chemical you will be using, ammonium nitrate, is actually used in emergency cold packs.

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Here’s what you need

• 1 measuring cup
• 1 bottle of calcium chloride
• 1 bottle of ammonium nitrate
• 2 resealable baggies
• water

Download Student Worksheet & Exercises

Here’s what you do

1. Put about ½ cup of warm water in one of the baggies.
2. Add about a third of an ounce of calcium chloride to the water. Close the baggie and start to roll around the pellets with your fingers. As they start to dissolve, the chemical also starts to increase the temperature of the water.
3. Now dispose of these ingredients down the drain. Flush with lots of running water.
4. Open the ammonium nitrate and fill its cap with pellets. Put these in the second baggie.
5. Start to pinch the ammonium nitrate through the plastic bag and check for a temperature change. Does anything happen in the absence of water?
6. Now put a small amount of water (about room temperature) into the bag. Fill it about ¼ of the way full.
7. Hold the bottom of the bag with both hands and begin to rock it back and forth a bit. This should start to dissolve the pellets. With your hands on the water, you should start to note a temperature decrease. If this doesn’t work, roll the pellets around as you did with the calcium chloride.
8. When you are finished, you can pour the contents out on to brown spot of grass (because ammonium nitrate is a main ingredient in many fertilizers). Or if you would prefer, just empty the contents down the drain.

What’s going on?

Calcium chloride splits into calcium ions and chloride ions when it is mixed with water. As this occurs, energy is released in the form of heat. This is the same heat energy you felt when holding the baggie and rubbing the pellets.

Adding ammonium nitrate to water causes both its ammonium and nitrate ions to dissolve, which results in heat absorption as iconic bonds are broken. This is an endothermic reaction.

The point of both of these experiments is that the Ruffini’s endings in your skin are what allow the heat and/or cold data to be collected and sent to your brain for translation.

Your skin has many other parts in addition to its receptors. Some examples include hair, blood vessels, and sweat glands. Blood vessels and sweat glands respond to heat and cold, helping to control your body’s temperature. You are probably familiar with how sweat glands help to cool you down (evaporation), but how about blood vessels?  As an example,  if you run around outside on a hot day, your cheeks get red  because the blood vessels on your skin’s surface have dilated, which brings more blood to the surface and allows the body to cool its insides a bit.

Exercises

1. Which chemical when mixed with water was an endothermic (absorbed heat and felt cold) reaction?
2. Which chemical resulted in an exothermic reaction (gave off heat)? Why does this happen?
3. What are ways that the human body can detect temperature?

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In addition to looking pretty neat with all those loops and whirls, your fingertips are great at multitasking. The skin on them has a ton of receptors that help us to gather a lot of information about our environment such as texture, movement, pressure, and temperature.

This experiment will test your ability to determine textures by using touch receptors. You will use shoeboxes with holes cut into them to make texture boxes. Each box will have a textured surface that you can feel, but not see. Through the receptors in your fingers, you will determine whether the surface is rough, waxy, soft, or smooth.

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Here’s what you need

• 4 shoeboxes with lids
• 1 soup can
• 1 pencil
• 1 pair of scissors
• 1 sheet of sandpaper
• 1 sheet of wax paper
• 1 sheet of flannel fabric
• 1 sheet of plastic
• 1 glue gun
• 1 pair of gloves
• partners

Download Student Worksheet & Exercises

Here’s what you do

1. Using the soup can as a guide, draw a circle at the end of a shoebox.  Then use the scissors to cut out the circle.
2. Cut a piece of sandpaper to fit the bottom of the shoebox (a ruler might also be handy to get an exact measurement). Glue the sandpaper to the inside bottom of the shoebox. Put the lid on the box and label it as Box 1.
3. Repeat the first two steps for each of the boxes, putting the wax paper, flannel, and plastic in boxes 2-4. Be sure to label each.
4. Now ask a partner to reach into each box, feel the texture, and describe it as rough, waxy, soft, or smooth. Record their answer. Use undecided if they aren’t sure.
5. Once your friend has identified a texture and you have recorded their response, open the box so that you can both see what material they have evaluated. Be sure to note in your data whether your friend was correct with a Y or N. Repeat steps 4 and 5 for each of the boxes.
6. Have your friend leave the room or look away so that you can rearrange the box lids. Then give them the gloves to wear and repeat the test using gloved hands. Record the data and compare the effectiveness of gloved hands. Does this have an impact on the touch receptors?

What’s going on?

The fabric of the gloves interferes with the ability of our touch receptors to function fully. Our fingertips are feeling the fabric of the gloves on their receptors and this makes it difficult to perceive what they are touching through the gloves.

We have 5 different types of receptors. They are types of nerve endings in our skin and are connected to our brains.

• The ones that respond to deep pressure are called Pacini’s endings and they are embedded deep in our skin.
• Merkel’s endings detect moderate pressure.
• Meissner’s ending respond to vibrations and light pressure.
• Ruffini’s ending, which detect changes in temperature, can also respond to pressure.
• Our pain receptors are called free endings.

Exercises

1. Name, in order, the three main layers of skin.
2. Which layer of skin contains the mechanoreceptors? Name two more items in this layer.
3. Name the five types of nerve endings and their specialization.

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Did you know that the patterns on the tips of your fingers are unique? It’s true! Just like no two snowflakes are alike, no two people have the same set of fingerprints. In this experiment, you will be using a chemical reaction to generate your own set of blood-red prints.

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Here’s what you need

• 1 oz. bottle of baking soda or sodium carbonate (washing soda)
• water
• 1 sheet of goldenrod paper
• 1 paper towel
• 1 magnifying lens

Download Student Worksheet & Exercises

Here’s what you do

1. Pour a couple teaspoons of the baking soda (sodium carbonate) into a cup of water. Swish your right index finger in the damp baking soda and then roll that finger on the goldenrod paper. This should leave a bright red fingerprint on the paper. Label it right index.
2. Continue the procedure for each finger on both hands to make a full set of prints. Be sure to label each fingerprint as you make it to identify which print goes to each finger. Don’t forget to make prints of your thumbs!
3. Compare your prints to the basic patterns in the guide. Check for features such as whorls or loops and label them appropriately on your prints. Use abbreviations such as A for accidental, PW for plain whorl, and DL for double loop.
4. After you have identified the dominant pattern on each of your fingertips, prepare a simple chart for each hand to record the data by finger.
5. When you are finished studying your own prints, ask a volunteer to let you make prints of their fingers.

What’s going on?

Goldenrod paper is made using phenolphthalein, a chemical that turns red when exposed to materials with relatively high pH. Baking soda (or sodium bicarbonate) is a base which has a pH of about 8.5. Rolling your baking soda covered fingers on the goldenrod paper creates a chemical reaction which produces a red fingerprint.

Exercises

1. What are the three main types of patterns on fingerprints? Describe each.
2. How do fingerprints have the potential to help solve crime?
3. Why does baking soda (or washing soda) show up red on the paper?
4. What kind of pH do bases have?
5. What kind of reaction do we see when the red fingerprints show up on the paper?

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Your body moves when muscles pull on the bones through ligaments and tendons. Ligaments attach the bones to other bones, and the tendons attach the bones to the muscles.

If you place your relaxed arm on a table, palm-side up, you can get the fingers to move by pushing on the tendons below your wrist. We’re going to make a real working model of your hand, complete with the tendons that move the fingers! Are you ready?

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Here’s what you need:

• five flexible straws
• scrap of cardboard (at least as big as your hand)
• five rubber bands
• 5 feet of string or thin rope (and a lighter with adult help if you’re using nylon rope)
• hot glue with glue sticks
• scissors
• razor

Download Student Worksheet & Exercises

Exercises

1. What types of muscles are connected to our bones?
2. Which type of connective tissue connects our muscles to our bones?
3. What do extensor tendons in our wrist do?
4. What do flexor tendons do?

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