What is the term for the heat absorbed or emitted during a phase change at constant temperature and pressure?

The term that describes the heat absorbed or emitted during a phase change while maintaining constant temperature and pressure is known as latent heat. This process occurs without a change in temperature, which distinguishes it from other heat transfer processes. When a substance changes from one phase to another, such as from solid to liquid (melting) or from liquid to gas (vaporization), it absorbs or releases a specific amount of energy, referred to as latent heat. This energy is crucial for the rearrangement of molecular structures during phase changes, but it does not result in a temperature increase.

For instance, during the melting of ice, heat is absorbed to break the intermolecular bonds, allowing the solid ice to transition into water, while the temperature remains constant until the phase change is complete. Understanding latent heat is essential in several applications, such as understanding weather phenomena and designing efficient heating and cooling systems.