Here's how it works:
* Heat provides energy to the molecules. The molecules in a liquid are constantly moving. When you add heat, you give them more energy.
* Molecules move faster and break free. With enough energy, the molecules start moving so fast that they overcome the forces holding them together as a liquid. They escape into the air as gas.
* The liquid changes state. The process of changing from a liquid to a gas is called evaporation. If you add heat quickly enough, it will cause the liquid to boil.
Think about water:
* Liquid water: You can see and hold water.
* Adding heat: When you heat water on a stove, it gets hotter and hotter.
* Boiling water: At a certain temperature (100°C or 212°F), the water boils and turns into steam. Steam is just water in a gaseous state.
