The latent heat of fusion, also known as the enthalpy of fusion, is the amount of heat energy required to change a substance from its solid phase to its liquid phase (melting) or vice versa (freezing) without any change in temperature. During this phase transition, the temperature remains constant while the substance absorbs or releases energy to overcome the intermolecular forces holding the solid structure together

. Key points about latent heat of fusion:

• It is a form of latent heat, meaning the heat energy is "hidden" in the phase change and does not raise the temperature of the substance

• The latent heat of fusion corresponds to the enthalpy change when a substance melts at a constant pressure, typically 1 atmosphere

• For example, the latent heat of fusion of water at 0°C is about 334 joules per gram, which is the energy needed to convert ice at 0°C to liquid water at 0°C without changing temperature

• The process involves breaking the intermolecular bonds in the solid to allow molecules to move more freely in the liquid state, which requires energy input

• Conversely, when a liquid freezes, it releases the same amount of energy, called the heat of solidification, which is equal in magnitude but opposite in sign to the latent heat of fusion

In summary, the latent heat of fusion is the energy required for a substance to change between solid and liquid phases at a constant temperature, reflecting the energy needed to overcome the forces maintaining the solid structure