The process of converting liquid into gas is called **evaporation**. This process involves the transition of molecules from liquid to gas phase, typically occurring when the liquid is heated. As the temperature rises, the kinetic energy of the molecules increases, allowing some of them to escape the liquid phase and enter the air as vapor. This can happen at any temperature, not just at the boiling point. Evaporation plays a critical role in various natural processes, such as the water cycle, where water evaporates from the surface of oceans, lakes, and rivers into the atmosphere.