Expansion of Gas

You will need:

• a balloon
• an empty bottle
• a basin with hot water (be careful!)

Steps:

1. Stretch the balloon's mouth and fit it to the bottle's mouth
   
2. Hold the bottle for a minute or two in the hot water. Be careful!
   You'll see this:
   
3. Now pour a lot of cold water on the bottle then your balloon will be like in the first picture again.

What was we actually do?
We want to prove that gas can expand when it's hotter / warmer and it will be contracts when it's colder / cooler. It's called expansion and contraction.