I use the crushing of an aluminum can to demonstrate to the students that while the air is hot in the can it will push on the inside of the can with equal pressure as the outside pressure because hot air expands and has more energy than cooler air.  When I place the hot can of water and air in a cold bath upside down the can will be crushed from the outside in because the air inside the can is cooled and the cooled air condenses which creates lower pressure inside the can than outside, thus crushing the can.

Demostrations