2. Things You Need Plastic bottle Modeling clay/Blu tack 2 balloons
Scissors
Straw
Sticky tape
Elastic band

3. Steps 1-5
1-Get a plastic bottle 2-Cut the plastic bottle about ¾ way down the bottle. 3-Take a balloon then inflate it then deflate it. 4-Now tie the balloon up and cut of the top. 5-Put the top of the balloon on the big whole and secure it in place with tape.

4. Steps 6-8
6-Get the straw and the other balloon then put the straw in the balloon after that put the rubber band over the mouth of the balloon then twist the rubber band over it to make a air tight seal. 7-Insert the balloon and straw through the neck of the bottle. 8-Once you've done that take your blu tack or modeling clay and make a air tight seal with it at the top of the bottle and your done.

5. Conclusion The model lung should look like that
In conclusion when you pull down on the balloon it acts like your diaphragm it creates more room so it opens up like the balloon it creates more space for air to fill up the air comes down the wind pipe and into your lungs so then your lungs expand
The model lung should look like that