What does the law of latent heat refer to?

The law of latent heat specifically describes the amount of heat energy required to change a substance from one state of matter to another without changing its temperature. This process involves overcoming the intermolecular forces present in the material. In the context of the correct answer, the absorption of heat during the phase change from liquid to vapor (evaporation or boiling) is a key example of latent heat.

When a liquid is heated and reaches its boiling point, additional heat is absorbed to enable the molecules to move apart from each other and transition into gas form. This added heat does not increase the temperature but instead facilitates the change in phase, making it a classic illustration of latent heat.

Understanding this principle is vital in various applications, including meteorology, cooking, and fire science, as it helps in grasping how energy changes affect states of matter. The other options refer to different types of heat exchanges or processes that do not fit the definition of latent heat.