2 liter plastic soda bottle, sharp scissors, masking tape, rubber bands, garbage bags, balloon

Procedure:

1. Carefully cut off the bottom of the soda bottle

2. Take your balloon and put it inside the bottle. Carefully stretch the balloon over the mouth of the bottle. This will be the lung itself.

3. Using the plastic bag cut out a square piece of plastic from the trash bag. Make the square 12 by 12 ( 30 by 30 cm) inches.

4. Take the plastic sheet and fold it in half twice

5. Take the folded sheet and, beginning at the folded corner, twist a one inch (2.5 cm) section and secure it with tape. You can use this like a handle.

6. Lay the sheet down and unfold it. Keep the handle on the underside.

7. Set the open part of the bottle down on the sheet. This part becomes the diaphragm.

8. Predict what you think you will happen when you move the plastic sheet out and in.

9. Hold on to your bottle and move the plastic sheet out and in. Record your results.

10. Hold the bottle so the mouth is near your cheek and move the surface of the plastic in and out. What do you feel?

11. Extra mucus that forms in the lungs during a cold and with some respiratory diseases has an effect on the function of the lungs. To explore this, add one spoonful of water to the balloon. Push and pull on the plastic and observe what happens. How has the addition of water affected the ability of the lungs to function properly? How does the extra "mucus" affect the amount of air that can be inhaled?

You can view a working model here.  This is the real thing in action.

Follow-Up:

1. What does each part of the model correspond to in the human respiratory system?

2. What are the limitations of this model?

3. In moving the sheet down, what process is simulated? Explain the changes in pressure.

4. In moving the sheet up, what process is simulated? Explain the changes in pressure.

5. How accurate was your prediction?

6. Explain this graph.