What is defined as the latent heat of fusion?

The latent heat of fusion is defined as the amount of heat energy that is released when a substance changes from a liquid to a solid at its freezing point. In the context of water, when water freezes and turns into ice, it releases a specific amount of energy. This process does not change the temperature of the water or the ice but rather involves the transition of the phase from liquid to solid.

When we refer to the latent heat of fusion specifically, we are talking about the energy that is associated with this phase change. Therefore, the correct choice accurately depicts this concept by highlighting the heat energy that is released during the freezing process. Understanding this helps clarify the energy dynamics involved in phase changes, which are important in various meteorological and environmental processes.

The other options pertain to different concepts, such as the heat needed for boiling (latent heat of vaporization) or the energy required for freezing, which is not the same as the latent heat of fusion.