Question

The quantity of heat involved when a substance changes its physical state (phase) as it melts, vaporizes, dissolves in water, or changes directly from a solid to a gas.

A. Enthalpies of Solution (ΔHsol),
B. Vaporization (ΔHvap),
C. Fusion (ΔHfus),
D. Sublimation (ΔHsub)

Answer 1

The quantity of heat involved when a substance changes its physical state during melting is called the enthalpy of fusion (ΔHfus), during vaporization it's called the enthalpy of vaporization (ΔHvap), for dissolving in water it's the enthalpy of solution (ΔHsol), and for changing directly from solid to gas it's the enthalpy of sublimation (ΔHsub).

Step-by-step explanation:

The quantity of heat involved when a substance changes its physical state is related to different enthalpies depending on the phase change occurring. For melting, the process is known as fusion and the corresponding heat is the enthalpy of fusion (ΔHfus), which is the amount of heat required to change one mole of a substance from the solid state to the liquid state.

When a substance vaporizes, the energy change is referred to as the enthalpy of vaporization (ΔHvap), the heat needed to change one mole of a liquid to a gas at its boiling point. The dissolution process, which is when a solute dissolves in a solvent, involves the enthalpy of solution (ΔHsol). Lastly, when a substance changes directly from a solid to a gas, the heat involved in this phase change is the enthalpy of sublimation (ΔHsub).