Thermodynamic Standard State: Most stable form of a substance at 1 atm pressure and at a specified temperature, usually 25 °C; 1 M concentration for all substances in solutionEnthalpy of Fusion (ΔHfusion): The amount of heat necessary to melt a substance without changing its temperatureEnthalpy of Vaporization (ΔHvap): The amount of heat required to vaporize a substance without changing its temperature