Question

Define the latent heat of vaporization.

Answer 1

- Hint: Heat signifies energy, so it can be energy related to a substance which is needed to change one state to another state. So heat of vaporization will be mainly related to the phase change from the liquid phase to the vapour phase.

Complete step-by-step solution -

First, we need to understand what latent heat is: it is the energy absorbed or released when a thermodynamic system undergoes a phase change and the temperature of the system remains constant during this process.
So the latent heat of vaporization is the energy required to transform a substance in the fluid phase into the gaseous phase at a constant temperature. We can also define the latent heat of vaporization as the heat absorbed or emitted by 1 gram of a substance at a constant temperature. It is a function of pressure when the transformation takes place. Another way of defining is that it is the work done to overcome the attractive forces between the molecules.
Example: When water is heated up to its boiling point, there is an increase in the temperature of the water until it reaches the boiling point. When it reaches the boiling point and we keep on heating the water, we can see that there is no change in the water temperature. So where does all this heat go? The heat which is not observed is used to change the phase of water. The latent heat is used to convert water from a liquid phase to the vapour phase.

Additional Information:
The idea of Latent heat was introduced by Joseph during the 1750s.

Note: Latent heat of Fusion: It is the heat released or absorbed or released when a substance in a solid-state is transformed into a fluid state.
The units used for enthalpy of vaporization are Joules per mole (J/mol) or Kilojoules per mole (KJ/mol).
Although kilojoules per kilogram (kJ/kg) or joules per gram (J/g) (specific heat of vaporization), and older units like kilocalories per mole (kcal/mol) and calories per gram (cal/g) are sometimes still used, among others.