When a gas changes into a liquid, it undergoes a process called vaporization. When the state of matter of a substance changes, as it does during vaporization, it undergoes a phase change.
The point at which a substance changes from a gas to a liquid is called the vaporization point. It is the same as the boiling point, which is the temperature at which a liquid changes into a gas during a process called boiling or evaporation. When a gas changes directly into a solid without undergoing vaporization, the process is called deposition. The opposite of deposition is called sublimation, when a solid turns directly into a gas.