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Suck a water balloon into a bottle

If you are not an adult, find one to help you. Matches are strictly not for kids.

NB: The pdf sample pages from the book Serious Science Party Tricks are an even better explanation of how to do this. They make a great print out.

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
  • A tissue

What to do:

  • 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.)
  • Light a half-tissue while holding the tissue with tongs.
  • Stuff the tissue into the bottle and quickly put the water-balloon on top.
  • The balloon should be pushed into the bottle.
  • To get the balloon out, tip the bottle and pull on the knot until it ‘pops’ out!
The water balloon will squeeze into the bottle

Why does it work?

As the tissue burns in the bottle it heats up the air inside. Air always gets bigger when you heat it. So the hot air takes up more room than before. You may see it 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 shrink back to its old size. But the water balloon won’t let any more air into the bottle. So the pressure drops inside 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?

Some people are having trouble with this one. Here are the most common mistakes and solutions!

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