Latent Heat of Vaporization

 The latent heat of vaporization, denoted by

${𝐿}_{𝑣}$, is the amount of heat energy required to change a unit mass of a substance from a liquid phase to a gas phase (or vice versa) at constant temperature and pressure. It represents the energy needed to overcome the intermolecular forces holding the liquid together and to convert it into a gas without changing its temperature.

The latent heat of vaporization is typically expressed in units such as joules per gram (J/g) or kilojoules per kilogram (kJ/kg). It varies for different substances and depends on factors such as the substance's molecular structure, intermolecular forces, and pressure.

Mathematically, the latent heat of vaporization can be calculated using the formula:

${𝐿}_{𝑣}=\frac{𝑄}{𝑚}$

where:

• ${𝐿}_{𝑣}$ is the latent heat of vaporization,
• $𝑄$ is the amount of heat energy absorbed or released during the phase change,
• $𝑚$ is the mass of the substance undergoing the phase change.

For example, the latent heat of vaporization of water at its normal boiling point (100°C or 373.15 K) is approximately 2260 J/g or 2260 kJ/kg. This means that it takes 2260 joules of energy to vaporize one gram of liquid water at 100°C into steam, or 2260 kJ to vaporize one kilogram of liquid water at 100°C into steam, without changing the temperature.

Understanding the latent heat of vaporization is essential in various applications, including heating and cooling systems, distillation, steam engines, and power generation.