What is latent heat?

Latent heat refers to the heat energy that is absorbed or released by a substance during a phase change, such as melting, freezing, vaporization, or condensation, without causing a change in temperature. This means that when a substance transitions from one state to another—like ice melting into water or water evaporating into steam—the temperature remains constant while energy is being added or removed.

Understanding this concept is critical in refrigeration and air conditioning because these systems often rely on the phase changes of refrigerants to absorb and release heat effectively. For example, during the evaporation process, a refrigerant absorbs latent heat from the environment, which allows the internal temperature of a space to decrease without a rise in temperature until the phase change is complete.

The other choices don't accurately define latent heat. The first choice refers to sensible heat, which does involve temperature change. The third choice addresses evaporative cooling, which is a specific application of latent heat but does not encompass its broader definition. The fourth choice also pertains to sensible heat, as it involves raising the temperature of a solid rather than a state change. Thus, the correct answer clearly highlights the unique characteristic of latent heat in phase transitions.