– empty 2 liter
– hot & cold water
- Start by putting your deflated balloon on top of the bottle.
- Turn on the hot water and put the 2 liter under the water (you may need help from a parent).
- Watch the balloon inflate.
- Turn on the cold water and put the two liter under the cold water.
- Watch the balloon deflate
What’s happening here? Inside the 2 liter are air molecules. You can’t see them. Air molecules act differently at different temperatures. When you heat up the bottle with the hot water the molecules move faster and spread apart. They become less dense and blow up the balloon as they take up more space. When the bottle is under the cold water, the air cools and contracts. It will take up less space and deflate!