Crunch a Can with Air, Water and Science! (continued)
Topics: Middle School, Science
Boiling the water in the can decreases the air pressure inside, creating a partial vacuum. The water vapor produced by boiling the water pushes air out of the can, creating a lower pressure system inside of the can. Immersing the can in the cold water causes the can to implode because the pressure exerted by the water and air outside the can is greater then the pressure inside the can.
Condensation also occurs when the water vapor inside the can (a gas) quickly cools when the can is immersed in the cold water. The water vapor rapidly condenses and turns the water vapor into liquid water again. The molecules of the liquid water droplets take up less space inside the can than the molecules of the gaseous water vapor, once again causing the can to be crushed by the greater external pressure exerted by the water in the bowl and air pressure around the can.
Hopefully your child observed that more water came out of the can than was originally placed inside. The extra water was forced into the can as a result of the greater air pressure outside of the can.
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Lori Stewart is a freelancer specializing in the development of science education materials. As a high school science teacher, Lori had several students place first and second in NASA's Student Involvement Program national competition.
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Comments from readers
Rather than putting the can in a pan I set it directly on the burner so all the heat went to the can rather than the entire surface of the pan.
The kids loved it!