∆Hfus refers to the heat of fusion, which is the amount of energy required to change a substance from its solid state to its liquid state at its melting point. In other words, it is the heat absorbed or released when a substance undergoes fusion.
The temperature at which a substance changes from its solid state to its liquid state.
The amount of heat required to raise the temperature of an object by 1 degree Celsius.
A measure of the total energy content in a system.