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By Mark W. Meszaros, PhD
Vice President, Carolina Biological Supply Company
What unseen force can instantly crush a can as it is being submerged into water? The answer is all around us—air pressure. Use this surprising and entertaining demonstration to introduce the concept of pressure.
Grades K–12, Unifying Concepts and Process
Grades 5–8, Physical Science
Grades 9–12, Physical Science
Use heat-resistant tongs to pick up the hot can. The hot can and steam may cause burns; handle with care. Wear protective safety eyewear.
This activity demonstrates the power of atmospheric pressure and how a pressure change inside a container may cause a dramatic result.
Atmospheric pressure, commonly called air pressure, is 14.7 lb/in2 or 101 kPa at sea level. When any container, such as the aluminum beverage can, is open to the atmosphere, the pressure outside the can equals the pressure inside the can. When the water in the can is heated to boiling, the can fills with hot air and steam. As long as the can is open to the atmosphere, the gas pressure inside the can is the same as atmospheric pressure.
When the can is inverted and placed in the cold water, the steam inside the can condenses into liquid water, which has much less volume than steam. The water immediately seals the opening of the can to the atmosphere creating a closed system, and the pressure inside is greatly reduced. The pressure outside the can remains 14.7 lb/in2, and the pressure difference crushes the can.