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Unit 19: Biology Part 2 Page 103 of 137

What’s happening: The air you breathed out displaced, or moved the water,
allowing you to see how much air you exhaled.

Experiment: The Pressure’s On

Materials:

 Milk carton
 Tape

 Water

You are able to breathe because of differences in the pressure in your body
as compared to the pressure outside your body. But what happens when

the pressure changes? Conduct this experiment to see.

1. Punch three pencil-sized holes in a ½ liter carton of milk.

2. Tape over the holes with one long piece of tape, so they are
completely covered
3. Add water to the milk carton, so it is completely full
4. Quickly rip the tape off the carton and make observations.

What’s happening: You should have noticed that the lowest hole had the
most water flowing out of it. This is where pressure was the greatest.
Similarly, air pressure at low elevations (such as sea level) is greater than at
high elevations (such as when you are flying in an airplane.) Some people
have a harder time breathing at high elevations, and if you get high enough
artificial pressure must be added.

Experiment: The Job of a Kidney

Materials:

 Sand
 Water
 Yellow food coloring
 Cheesecloth
 Large bowl

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