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Incredible Can Crush

In this demonstration, students see firsthand how matter changes states and the incredible impact of atmospheric pressure on objects.

Air is made up of matter and takes up space and has mass. If the amount of air inside an object changes, the atmospheric pressure outside of the object may have a greater impact on the object itself.

Lowering the pressure inside a pop can by heating it up creates a situation in which the pressure of the atmosphere can crush the pop can. This happens because the small amount of water that is placed inside the pop can becomes water vapour when it is heated up and displaces the air inside the can. Then, when the pop can is quickly cooled, the water vapour returns to a liquid state and since the air pressure outside of the can is greater than that on the outside, the pop can is quickly crushed. 

Objectives

  • Describe the properties of a solid, a liquid, and a gas.

  • Describe the transitions between different states of matter.

Materials

  • Per Class or Demo:
    empty pop can
    tongs
    container
    cold water
    hot plate

Key Questions

  • What happens to water inside the pop can when it is heated up?
  • What happens to the air inside the pop can when the water becomes steam?
  • Why does the pop can get crushed when it is quickly cooled?

What To Do

Preparation:

  1. Rinse out an empty pop can for the demonstration.
  2. Set aside a container filled with ice-cold water.
  3. Add approximately 10mL (1 tablespoon) of water to the empty pop can.
  4. Discuss what you are going to do with your students and ask them to record predictions for each stage of the experiment

Demonstration:

  1. Use the hot plate to heat up the water inside the pop can.
  2. As the water heats up and comes to a boil, it will become visible as steam. The steam will fill up the interior of the can and displace the air inside the pop can. Any remaining air will heat up as well.
  3. Use the tongs to remove the can from the heat and quickly turn it over, mouth first, into the container of cold water. The pop can should become crushed because the very little remaining air quickly cools and the steam becomes liquid. Since the atmospheric pressure is greater than the pressure of the leftover air inside the can, the pop can is crushed.
  4. Turn off the hot plate and discuss what happened as a group.

Teacher tip: Practice this demonstration before trying it in front of the class.