A Moment of Science

The Invisible Hand

Want to try a neat experiment that shows air pressure at work? "The Invisible Hand" on this Moment of Science.

Want to try a neat experiment that shows air pressure at work? Follow these steps.

You’ll need a stove, an empty aluminum soda can, kitchen tongs, and a saucepan.

First, put about a tablespoon of water in the soda can, and a little cold water in the saucepan.

Next, heat the water in the soda can on the stove until it boils.

Once there’s steam coming out of the can, pick up the can with the kitchen tongs and put it face down in the cold water in the pan.

The can will start to collapse!

When the water in the can boiled, the water vapor pushed all the air out of the can. And when you flipped the can and put it in the pan, the cold water cooled the vapor, making it condense. This left the can empty inside, allowing the pressure of the air outside the can to crush it.

Normal air pressure is about 15 pounds per square inch. Since the can was about three inches high and two inches wide, the air pressure on it was 15 pounds per six inches, or ninety pounds of air pressure used to crush the can.

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