Students in Mrs. Leininger's 8th Grade Science class crushed cans using heat, and hot and cold water. This is how they did it, according to Mrs. L.:
"We placed about an inch of water in an empty aluminum can and heated the can until the water boiled, and we could see water vapor coming out of the top of the can.
We then used tongs to take the can off the heat source, invert the can, and submerge about two inches of the can into a tub of ice cold water, causing the can to crush in on itself.
I let them think about the why over the weekend and we discussed what happened on Monday. The explanation involved water molecule movement in the form of gas and where pressure would be inside and outside of the can."