The melting point is the temperature at which solid is converted to liquid. This process is endothermic. The energy required to melt one mole of solid to liquid is called the heat of fusion or the enthalpy of fusion, symbolized as BHs Boiling occurs when the vapor pressure of the liquid becomes equal to the pressure of the environment. The normal boiling point of a liquid is the temperature at which the vapor pressure is equal to exactly 1 atm. 1. Indicate the order of increasing vapor pressure for each set of compounds: For example A