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# Bill Nye Demonstration: Atmospheric Pressure

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Author: Bill Nye
##### Objective:

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.

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Tutorial

## The Experiment

What you need:

• A balloon (ordinary party balloon)
• A wide-mouth bottle (pasta sauce bottles or big juice bottles are great for this, use a glass jar if you can’t find a bottle)
• A pair of tongs
• Matches
• Small piece of paper or tissue

What to do:

1. Fill the balloon with water. (Put the balloon onto a tap and fill it until it is slightly bigger than the mouth of the jar or bottle.)
2. Light a half-tissue while holding the tissue with tongs.
3. Stuff the tissue into the bottle and quickly put the water-balloon on top.
4. The balloon should be pushed into the bottle.
5. To get the balloon out, tip the bottle and pull on the knot until it ‘pops’ out!

## What's Happening?

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!

• Don’t use too much paper. It will go out (extinguish itself), before you can get it in through the mouth of the bottle.
• Blow into the bottle between tries. You need new oxygen each time. Once a flame has burnt the oxygen inside the bottle, you won’t get another flame to survive. This is essential. But try not to breath any smoke in, because it’s not healthy. Instead of blowing, use a hair dryer if you can.
• Maybe your water balloon is just too big? (Or the mouth of your bottle is just too small.)
• The Egg-in-the-bottle version is the same except you use a hard-boiled egg (peeled) instead of a water balloon. Beware: it’s messier and hard to do more than once!!!

## Air Pressure Handout

Full Screen

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