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Make a lung model

You will need:

  • A clean 1.25 or 2L PET bottle
  • Two balloons and a straw
  • Scissors
  • Stickytape
  • Rubber band 

    Lung model
    Making the lung model experiment work!



1. Cut the bottom off the plastic bottle and cut the top off one of the balloons.

2. Stretch the balloon tightly over the bottom of the container so it forms a thin skin like the surface of a drum, and secure very firmly with stickytape. 

This balloon represents the diaphragm.

3. Make a hole through the bottle lid and attach a straw. Place the other balloon inside the lid, with the top of the balloon attached to the straw with the rubber band - the balloon should sit inside the bottle. This balloon represents the 'lung'.

4. Carefully pull the balloon at the base of the bottle and watch the 'lung' balloon inflate.

What's Happening?

When you breathe in, your diaphragm - the muscle at the base of your lungs, contracts. This expands your chest cavity, lowering the air pressure of the cavity below the air pressure outside, and inflating the lungs.

You can see this same principle at work in this 'homemade lung'. When you pull on the diaphragm balloon, it lowers the air pressure in the bottle. This pulls in air from outside the bottle, allowing the balloon at the top - the lung - to inflate.
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