What is the latent heat of vaporization at 500 K?

The latent heat of vaporization is the amount of heat required to convert a liquid into vapor without any change in temperature.

Important Concept:

• Latent heat of vaporization depends on the substance, not just the temperature.
• It is usually expressed in J/kg or cal/g.

At 500 K:

• The exact value of latent heat of vaporization cannot be determined unless the substance is specified.
• Different substances have different intermolecular forces, so their latent heats vary.

Example (Water):

• At its boiling point (373 K), water has a latent heat of vaporization ≈ 2260 kJ/kg.
• As temperature increases (like near 500 K), the latent heat of vaporization decreases.
• This is because molecules already have higher kinetic energy and need less additional heat to escape into vapor.

Key Insight:

• Latent heat decreases with increasing temperature.
• At the critical temperature, latent heat becomes zero, because the liquid and gas phases become indistinguishable.

Exam Tip:

• Always check if the substance is mentioned.
• If not, answer conceptually: latent heat varies by substance and generally decreases with temperature.