What does "latent heat of vaporization" signify?

Latent heat of vaporization refers to the amount of heat energy required to convert a specified quantity of liquid into vapor without a change in temperature. This process occurs at the substance's boiling point, where the liquid absorbs heat energy to overcome intermolecular forces, enabling the transition from a liquid state to a gaseous state.

In practical terms, when heat is supplied to a liquid, this energy does not increase the temperature of the liquid but rather is used to change its phase. For instance, when water boils, it transitions to steam at 100 °C but absorbs significant heat in the process, which is quantified as the latent heat of vaporization. This concept is crucial in power engineering, as it plays a key role in the efficiency of boilers and other systems involving phase changes.

The other options describe different thermal processes: the heat released during condensation, the heat required for melting solid to liquid, and heat loss when a vapor cools, none of which accurately define latent heat of vaporization. These processes are related to phase changes, but they do not encapsulate the specific definition associated with converting liquid into vapor at constant temperature.