What happens when you place a water balloon on the mouth of a bottle with a flame burning inside? Watch and learn as we experiment together. Explore concepts such as atmospheric pressure, and combustion chemistry by manipulating gases and air. By discovering what establishes a scientific experiment, you will achieve comprehension on many levels while you prepare for more advanced topics.
What you need:
What to do:
As the paper burns in the bottle it heats up the air inside. Particles in the air have more energy and therefore move faster and take up a greater volume when you heat it. The molecules can be seen escaping around the water-balloon and making the water-balloon ‘jump’ and jiggle.
After the flame goes out the air in the bottle will cool and particles will go back to their original energy and speed. This means it takes up less space and begins to contract. Also, there are fewer particles in the bottle since some escaped earlier. So the pressure drops inside the bottle. The inside air pressure and outside air pressure want to be equal but the water balloon won’t let any more air into the bottle. The normal air pressure outside the bottle pushes on the balloon and squeezes it into the bottle.
Notice the water balloon acts as a one-way valve! It lets air out, but won’t let air back in again!
Why doesn’t it work sometimes?
Here are the most common mistakes and solutions!
I understand why the balloon is initially pushed outward. I don't understand the sudden sucking action that pulls the balloon inward. Why and how does the direction of the pressure change so fast?
Its all about equal pressures. As long as the pressure inside equals outside, nothing happens. Once the pressure outside is greater (there are fewer particles inside moving slower now) than the inside it is PUSHED in. Works well with a cider jug and a peeled hard boiled egg, too. Kids love it!
Once the fire goes out, the air inside the bottle cools. As it cools, the pressure inside the bottle drops. The air outside the bottle is at normal atmospheric pressure and is no longer balanced by the air in the bottle pushing out, so the balloon is pushed inside the bottle.
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