Balloon on a Stove
When you heat up a gas, the molecules – the tiny, tiny pieces of stuff that gas is made up of – start to speed up. If they are still in the same amount of space, that means that they start bumping into each other a lot more than before – that is, they are at a higher pressure. The molecules will try to spread out by taking up more space (to get to a lower pressure) so they don’t hit each other as often. So… when you heat up a gas, it takes up more space.
Don’t believe me? Well, let’s try it.
What you need:
- 1 balloon
- 1 saucepan
- 1 glass bottle (1-2 liters)
What you do:
- Pull the balloon over the mouth of the glass bottle.
- Put the bottle upright in a saucepan of cold water.
- Ask an adult to heat up the saucepan on the stove. As the water heats up, the balloon begins to inflate.
As the water in the pan fills up, the air inside the bottle heats up as well. The molecules of air inside the balloon start to move around faster, so they start to spread out, and the air expands. This means there is high pressure inside the bottle, and the only place for the air to go is into the balloon. If you remove the bottle from the stove, the balloon will slowly shrink to its original size because the molecules slow down and the pressure of the gas is lowered.
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