What does the term "latent heat" refer to?

The term "latent heat" refers specifically to the energy released or absorbed during a phase change of a substance without a change in temperature. This concept is crucial in thermodynamics and plays a significant role in various processes, such as melting, freezing, boiling, and condensation. During these phase changes, energy is required to break intermolecular bonds or is released as bonds are formed, even though the temperature of the substance remains constant until the phase change is complete.

For example, when ice melts to water, it absorbs a considerable amount of heat (latent heat of fusion) from the environment, resulting in a temperature that stays at 0°C until all the ice has melted. Similarly, when water boils, it absorbs latent heat of vaporization, allowing it to transition into vapor at 100°C without a change in temperature during the boiling process. This property is pivotal in systems such as air conditioning and refrigeration, where phase changes of refrigerants are utilized to transfer heat efficiently.