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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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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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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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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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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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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Everything living produces some sort of odor. Flowers use them to entice bees to pollinate them. We know that the tastes of foods are enhanced by the way that they smell. As humans, each of us even has own unique odor.

In this lab, we look at the diffusion of scents. They start in one place, but often end up spread around the room and can be detected by many people.

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Here’s what you need

• • 1 onion
  • 1 lemon
  • 1 bottle of ground cinnamon
  • 1 clove of fresh garlic
  • 1 garlic press
  • 1 pile of fresh coffee grounds
  • 1 kitchen knife
  • 1 cutting board
  • 1 variable-speed fan
  • 1 clock with a second hand

Download Student Worksheet & Exercises

Here’s what you do

1. Start in a room big enough so that you can prepare the foods at one end and your friends or family members can be at the other end, but positioned so they can’t see what you’re doing.
2. You will need a simple map of the room showing the locations of your partners, the source of the odor, and the fan (which will help with the scent diffusion). Create a new map for each smell.
3. Turn on the fan and begin with the onion. Ask an adult to help you with cutting the onion into several small pieces. Be sure to hold the chopped pieces up in front of the fan. Ask your partners to raise their hands when they smell the onion. If they don’t smell it, they can leave their hands down. Note on the onion map where its smell is detected. Indicate with a line the farthest area where the onion is smelled. This is its leading edge.
4. Check in with your partners once per minute for five minutes. Ask them to raise their hands and repeat the process of noting the areas where the smell is detected. Each time you check, draw a line to indicate the farthest area the smell reaches. This will give you an idea of how fast and how far the smell diffused.
5.  Repeat steps 3 and 4 with each item: cut and smash the lemon and press the garlic. Which odors travel the farthest? Which ones travel the fastest?

What’s going on?

Many factors affect how quickly odors diffuse. First, the air is constantly moving. As the air molecules in the room are colliding with each other (and with the odor molecules) they help to move the smells farther through the room. Second, the fan makes a huge difference. It accelerates the natural process of air and odor molecules and moves them much farther and faster than they would go otherwise. Finally, the air temperate plays an important role. If the temperature is higher, the air and odor molecules will move faster.

As humans, we can boast about 10,000,000 smell cells in our noses. This seems pretty impressive…unless you compare us to canines. Dogs have over 200,000,000 smelling cells in their nasal cavities!

Exercises

1. Which odors travel the farthest?
2.  Which ones travel the fastest?
3. Why do we use the fan?
4. Does air temperature matter?

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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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