Balloon Inside a Bottle

Warning: please do not attempt this experiment without adult supervision. With proper supervision it is safe, but if you don't feel comfortable with it, try another experiment!

What is Needed


* One small party balloon

* One small bottle. A 16 ounce pop bottle works well.

What to Do

Put approximately 1 tablespoon of water into the empty pop bottle. Then put the bottle into a microwave oven and turn the oven on high. Boil the water in the bottle until the water is almost gone. The bottle will be very hot and full of steam at this point. Using and oven mitt or other protection for your hands, carefully remove the bottle from the microwave oven and set it on a counter. Immediately take off the oven mitt and 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 you boiled the small amount of water inside the bottle, the water became steam. As the water boiled away, the steam filled the whole inside of the bottle. If you had just taken the bottle and set it on the counter to cool at this point (doing nothing else) the steam would have cooled and condensed back into a very small amount of water and air would have pushed into the open neck of the bottle to fill the space left by the condensing steam. What you did in this experiment then was to put a rubber balloon in the way of the air as it was pushing into the bottle to fill the space left by the condensing steam.

Other Things to Try


If you like this kind of experiment, check out a slightly more 'explosive' version of this in the Imploding Pop Can Experiment.