The correct answer is option 3, latent heat of vaporization. This concept refers to the amount of heat energy required to change a substance from its liquid state to its gaseous state at a constant temperature, without any increase in temperature.

Let`s dissect the other options to understand why they are not the correct answers.

Option 1, specific heat capacity, refers to the amount of heat energy required to raise the temperature of a substance by a certain amount. It does not specifically relate to the process of changing a liquid to a gaseous state without any change in temperature.

Option 2, mechanical equivalent of heat, is a concept that states that a certain amount of mechanical work is equal to a certain amount of heat energy. It is not directly related to the process of changing a liquid to a gaseous state.

Option 4, quenching, refers to the process of rapidly cooling a heated object in a liquid medium to achieve certain desired properties, such as hardening metals. It does not relate to the process of changing a liquid to a gaseous state without any change in temperature.

In summary, latent heat of vaporization is the correct concept that describes the amount of heat energy required to change a liquid to a g