Crushed Can

This experiment is a classic demonstration of air pressure that also shows how drastically matter changes as it moves from one state to another.

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You will need:

  • several aluminum soft drink cans
  • kitchen tongs or an oven mitt to pick up hot cans
  • a bowl of cold water
  • a hot plate or a hot skillet on the stove

You will need several cans, because you will want to do this one several times. Place about half an inch of water into the bottom of a soft drink can. Place the skillet or pan on the burner of the stove and turn the heat on low. Because of the shape of the cans, you may want to add some water to the pan, to help transfer heat. You can also try laying the can on its side to speed things up. Wait for the water in the can to start boiling. You will see steam coming out the top of the can. Use the tongs or the oven mitt to QUICKLY pick up the can and turn it upside down as you plunge it into the bowl of cold water. Instantly, the can will be crushed.

When the water begins to boil, it forms water vapor. This water vapor takes up a lot more space than it did when it was water. A few drops of liquid water can form enough water vapor to fill the can, pushing out all of the air. When you put the can into the cold water, the water vapor condensed back into water. This leaves very little air pressure inside the can. The surrounding air tries to rush in to equalize the pressure, but the opening of the can is under water. The water does not move into the can as quickly as the air would, and the pressure of the surrounding air crushes the can.

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