What is it called when a substance changes from a liquid to a gas?

The phase transition of a substance changing from a liquid to a gas is referred to as the latent heat of vaporization. This process involves the absorption of energy, specifically in the form of heat, which allows the liquid molecules to gain enough energy to overcome intermolecular forces and enter the gas phase.

In context, latent heat of vaporization is essential in refrigeration and air conditioning systems, where the refrigerant absorbs heat during the phase change from liquid to vapor, thereby cooling the surrounding environment. This concept plays a crucial role in the efficiency and functionality of HVAC systems, making it fundamental for anyone studying for a refrigeration license.

The other options relate to different phase changes or processes. The latent heat of condensation refers to the transition from gas to liquid, latent heat of sublimation involves the direct transition from solid to gas, and latent heat of fusion pertains to the change of state from solid to liquid. Each of these processes involves energy transfer, but they correspond to different phase changes.