Lungs are an essential organ for mammals that are part of our breathing system. Create this model to help you understand how the lungs and diaphragm work. The bottle will act like the chest, the balloon at the bottom like the diaphragm and the balloon in the centre will be like a lung. 

You will need 

A plastic bottle 

A straw

An elastic band 

Scissors 

Two balloons

Play dough 

Method 

Ask an adult to help you to cut the bottle in half.  Throw away the bottom half and keep the top half. 

Tie a know in one end of one balloon and cut off the opposite end. 

Stretch the cut end around the bottom of your plastic bottle.

Place a straw in the neck of the other balloon and secure tight with the elastic band - be careful not to crush the straw! 

Test if you can blow through the straw to inflate the balloon. 

Put the straw and the balloon into the neck of the bottle and secure them with play dough to make a seal. 

Hold up your bottle and pull the knot. 

The balloon inside should inflate, and, as you let go of the know, the middle balloon should deflate. 

When the knotted balloon is pulled, it creates more space inside the bottle. Air comes down the straw and fills the balloon - just like breathing in! 

When you let go of the knot, the space no longer exists which causes the balloon to deflate - just like exhaling!