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Make a lung model

Instructions

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

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.

Place the other balloon inside the bottle, with the top of the balloon attached to the bottle with the rubber band - the balloon should sit inside the bottle. This balloon represents the 'lung'.

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

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You will need:

A clean 1.25 or 2L PET bottle
Two balloons
Scissors
Stickytape
Rubber band 

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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