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Balloon Inflating in a Bottle
What is needed?
- An adult to supervise
- One small party balloon
- One small bottle. A 16 ounce pop bottle works well
- A kettle
What to do?
Boil the kettle. Get the adult to put 1 tablespoon of water from the kettle into the empty pop bottle. The bottle will be very hot and full of steam at this point. Get the adult to hold the bottle still on a counter using an oven mitt or other protection for their hands.
After 20 seconds stretch the opening of the party balloon over the mouth of the bottle. Now stand back and let the bottle cool off with the balloon covering the opening.
Notice that as the bottle cools, the balloon gets sucked into the bottle. If you had just the right amount of water left when you put the balloon on the bottle, the balloon will actually 'inflate' into the bottle until it fills the whole inside!
What is happening?
When water boils it becomes steam. As the water boils away, the steam fills the whole inside of the bottle. If you had just taken the bottle and set it on the counter to cool without adding the balloon, the steam would have cooled and condensed back into a very small amount of water. The water is smaller than the steam and takes up less space so more air is needed to fill the gap. This comes through the open bottle neck.
What you did in this experiment was put a rubber balloon in the way of the air trying to get back in the bottle and the balloon is pulled inside instaed. If you were really lucky it would have inflated inside the bottle!
