Examkin

Question

Difficulty: MediumLatent Heat and Changes of State

During the vaporization of a pure liquid at its boiling point under constant atmospheric pressure, the absorbed thermal energy increases the average kinetic energy of the molecules while maintaining a constant temperature.

Answer: Answer

Answer

False. Temperature is directly proportional to the average kinetic energy of molecules. Because temperature remains constant during phase changes, the average kinetic energy remains unchanged, while the latent heat increases molecular potential energy.
The correct answer is False because temperature measures average kinetic energy directly. Since temperature remains constant during boiling, molecular kinetic energy cannot increase; instead, heat input goes entirely into increasing molecular potential energy.

Step-by-Step Solution

1
Relate temperature to molecular kinetic energy.
By the kinetic theory of matter, absolute temperature TT is directly proportional to the average translational kinetic energy 12mvˉ2\frac{1}{2}m\bar{v}^2 of the molecules.
Temperature is a microscopic measure of molecular motion.
2
Examine the state of temperature during vaporization at the boiling point.
During boiling, temperature remains constant until the phase change from liquid to gas is completely finished.
Latent heat absorption occurs at constant temperature.
3
Deduce which molecular energy component changes during latent heat absorption.
Since temperature does not change, average kinetic energy stays constant. The absorbed latent heat increases intermolecular potential energy by breaking intermolecular bonds and performing work during expansion against atmospheric pressure.
Thermal energy supplied during a phase transition goes into potential energy rather than kinetic energy.

Key Concept

Microscopic interpretation of latent heat and temperature during a phase change
Rate this question

Topics

Latent Heat and Changes of State

More questions from this topic