What results from heat transfer when a change of state occurs?

When a substance undergoes a change of state, such as melting, boiling, or sublimation, the heat transfer involved in this process is classified as latent heat. Latent heat is the heat energy absorbed or released during a phase transition at a constant temperature, which does not result in a temperature change of the substance itself.

For example, during the melting of ice to water, the heat energy provided to the ice is used to break the bonds between the molecules rather than to increase the temperature. Similarly, during the boiling of water to steam, the energy is required to convert water to vapor without raising its temperature until the entire liquid has transformed.

This unique aspect of latent heat distinguishes it from sensible heat, which does directly change the temperature of a substance without changing its state. Specific heat capacity pertains to the amount of heat required to change the temperature of a unit mass of a substance by one degree Celsius and does not directly apply during a phase change. Thermal expansion relates to changes in the physical volume of materials with temperature fluctuations, which also does not specifically describe the heat transfer during a change of state. Thus, latent heat correctly captures the essence of heat transfer associated with changes in state.