Egg in a bottle
This is another classic demonstration. You will need; a glass bottle, some paper, matches or a lighter and either a hardboiled egg with the shell taken off or a water balloon. It doesn’t matter which one you use as long as it is slightly bigger than the opening of the bottle.
Start by setting the piece of paper on fire. Then put the burning paper in the bottle and quickly put the egg or balloon on top. You may see it flutter/dance a bit this is due to the fire heating the air so it expands and some of it is push out of the bottle.
The fire will then go out (because there is no oxygen left). The air left in the bottle then starts to cool and condenses. This means that the air presser inside the bottle is less than outside it. Due to this air outside the bottle pushes on the egg or balloon and forces it in.
