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Unit 19: Biology Part 2 Page 101 of 137

V-shape of the second straw into the triangle hole of the bent straw.
6. Cement the two straws together, and allow plenty of time to dry.
7. Cut a hole in the bottom of a clear plastic cup, the size of the bottom of a
straw.

8. Push the open end of the straw into the bottom of the cup, going through
the hole. Cement the straw into the hole.
9. Cut the neck off of a large balloon.

10. Carefully stretch the cut balloon over the top opening of the cup. Do not
crack the cup. Secure the edges with a large rubber band.

11. Squeeze the bottom balloon gently and observe what happens to the
small balloons.

What’s happening: The large balloon represents the diaphragm. When you
squeeze it, air is forced out, slightly inflating the small balloons. This is a
model of an exhale. How could you model an inhale?

Experiment: What’s in an Exhale?

When you breathe out, you breathe out many things. Carbon dioxide, the
waste product of respiration, is the most important. “See” the carbon
dioxide in this activity.

Materials:

 1 teaspoon Bromthymol Blue
 1 cup
 Straw

1. Place about a teaspoon of Bromthymol Blue (BTB) in a cup

2. Place the straw in the solution and exhale (blow) into the straw.

3. Observe what happens to the blue liquid.

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