# Pressure in gases

A teacher heats some water in a drinks can until it is boiling and steam comes out of the can. She quickly turns the can over and puts it into some water. Explain in detail why the can collapses.

My solution will be: By boiling the water, the water changes state from liquid to gas, which is water vapor. The water vapor pushes the air that was originally inside the can out into the atmosphere. So there is less air and water in the can, but the water vapor in the can can still balance the atmospheric pressure, as it is hot means more particle collisions and higher pressure. When the can is turned upside down and placed in the water, all the water vapor quickly condense into drops of liquid in the can, this decreases the pressure. And so the much higher atmospheric pressure crush the can.

My questions is: Why can't we just put the can into the cold water? Why do we need to heat the water in it before? Can someone explain the whole process in detail, I don't completely understand the experiment. Thanks!

kuruman