Which scenario demonstrates entropy increase due to an increase in the number of molecules?

Which scenario demonstrates entropy increase due to an increase in the number of molecules?

• A. Condensation of a gas into a liquid
• B. Increase in the number of gas molecules from 1 to 2
• C. Deposition of a gas to a solid
• D. Freezing of a liquid

Answer: (B)

Entropy is a measure of how many ways energy and particles can be arranged—the number of accessible microstates. When you add more molecules to a system at the same temperature and volume, there are more particles that can occupy different positions and carry energy, so the number of possible configurations (microstates) increases. That larger number of microstates means higher entropy, since S is proportional to the natural log of the number of microstates. In contrast, processes that condense a gas to a liquid, deposit a gas to a solid, or freeze a liquid move the system toward more order, reducing the number of possible arrangements and thereby decreasing entropy. So increasing the number of molecules from one to two increases entropy due to the greater number of accessible microstates.

Entropy is a measure of how many ways energy and particles can be arranged—the number of accessible microstates. When you add more molecules to a system at the same temperature and volume, there are more particles that can occupy different positions and carry energy, so the number of possible configurations (microstates) increases. That larger number of microstates means higher entropy, since S is proportional to the natural log of the number of microstates.

In contrast, processes that condense a gas to a liquid, deposit a gas to a solid, or freeze a liquid move the system toward more order, reducing the number of possible arrangements and thereby decreasing entropy. So increasing the number of molecules from one to two increases entropy due to the greater number of accessible microstates.