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.