What does the term "latent heat" refer to?

Latent heat refers specifically to the heat that is absorbed or released by a substance during a phase change, such as from solid to liquid (melting) or from liquid to gas (vaporization), without a change in temperature. This concept is crucial in thermodynamics and power engineering because it impacts how systems behave when substances undergo phase changes.

During these changes, energy is being transferred but does not result in temperature variation; instead, it is utilized to alter the molecular structure of the substance involved. For instance, when ice melts to water, the temperature remains at 0 degrees Celsius until all the ice has transitioned to liquid. Understanding this allows engineers to design and operate systems efficiently, particularly in processes involving heat exchangers and boilers, where phase changes are common.

The other choices may relate to heat transfer and energy but do not capture the unique aspect of latent heat, which specifically pertains to phase changes without temperature changes.