Door 7: Reverse balloon inflation

NB! Experiments must always follow the safety rules that apply to laboratory experiments. Remember gloves and safety goggles.

You need:

• Some large glass bottles
• Balloons

Recipe:

1. Heat a bottle (or a large flask) with warm water. If you use a kettle, wear gloves to hold the bottle
2. Drain the water
3. Take the balloon and stretch it gently over the tip of the bottle
4. Cool the bottle by keeping it under cold tap water
5. At first it will just hang over the bottle, then the balloon will be sucked into the bottle

What happens is that the hot bottle heats the air inside the bottle, and when the air inside the bottle cools, the air pressure inside the bottle drops. Then the balloon will be sucked inwards into the bottle, with the balloon opening completely open.