What defines "latent heat"?

Latent heat is a term used to describe the amount of heat absorbed or released by a substance during a phase change without a change in temperature. This means that during processes such as melting, freezing, vaporization, or condensation, the heat energy is either absorbed or released while the temperature of the substance remains constant.

For instance, when ice melts into water, it absorbs heat (latent heat of fusion) from its surroundings, but the temperature of the ice-water mixture does not increase until all the ice has melted. Similarly, when water vapor condenses into liquid water, it releases latent heat without an increase in temperature.

This characteristic is critical in various applications, particularly in refrigeration and climate control, where phase changes are harnessed to effectively transfer thermal energy without a direct increase in temperature of the refrigerant, thus maintaining desired cooling effects.

Other options describe different heat-related concepts. For example, temperature change during heating or cooling refers to sensible heat, while total heat content encompasses both latent and sensible heat, and heat lost to the environment during refrigeration relates to energy efficiency and system performance rather than the definition of latent heat itself.