We then learned that the water vapor can condense to form liquid water (this is what happens on the side of your McDonald’s pop).
Today we talked about the fact that air has pressure. The video below shows what happens when air pressure is not equal on the outside and inside of a can.
Steve Spangler’s Science Website puts it like this: Here’s the real scoop on the science of the imploding can: Before heating, the can was filled with water and air. By boiling the water, it changed states from a liquid to a gas. This gas is called water vapor. The water vapor pushed the air that was originally inside the can out into the atmosphere. When the can was turned upside down and placed in the water, the water vapor condensed and turned back into the water. Water molecules in the liquid state are many, many times closer together than molecules in the gas state. All of the water vapor that filled up the inside of the can turned into only a drop or two of liquid, which took up much less space. This small amount of water cannot exert much pressure on the inside walls of the can, so the pressure of the air pushing from the outside of the can is great enough to crush it. The sudden collapsing of an object toward its center is called an implosion. Hey, air pressure is powerful!