What is the quantity of heat a liquid must absorb for 1 gram to be converted from liquid to gaseous state?

The quantity of heat that a liquid must absorb to convert 1 gram of the liquid into its gaseous state is known as the heat of vaporization. This term specifically refers to the amount of energy needed to overcome the intermolecular forces that hold the molecules together in the liquid phase, allowing them to transition into the vapor phase. The heat of vaporization is a crucial concept in thermodynamics and is particularly important in processes like boiling and evaporation.

In contrast, heat of fusion refers to the energy required to convert a solid into a liquid, which is not applicable in this scenario. Specific heat pertains to the amount of heat required to change the temperature of a substance by a certain amount, and thermal energy is a more general term that describes the total energy possessed by the molecules in a substance, encompassing kinetic and potential energy. Thus, the correct choice specifically reflects the energy required for phase transition from liquid to gas.