Figure Out What Happened
When we heated up our cans, we boiled the water inside them. When the water boiled, it turned into steam. When it turned into steam, it took up more space in the cans and pushed out most of the air. When it pushed out most of the air, it caused the air pressure inside the cans to be less than the pressure outside them.
Then when you placed the can upside-down in the ice bath, the steam rapidly turned back into water. Since water takes up less space than steam, and no air could enter into the can because the opening was submerged in water, the air outside the can exerted pressure on the can making it collapse! It may have even pulled some water up with it into the can!
The reason the same doesn’t occur with the other can is because air was allowed to enter in through the top of the can and equalize the air pressure.
It’s important to note we were placing extreme measures on our experiment. You don’t get the same crazy effect on your water bottle when driving down a mountain, because it’s much more gradual. But it does explain why you feel tightness in your chest when the air is colder.
Next time you're recycling aluminum cans, forget the can crusher, and use this experiment instead! Did we just make chores fun?