Question

Does a gas become more orderly when it liquefies? Does its entropy change? If so, does the entropy increase or decrease? Explain your answer.

a) Gas becomes more orderly, and entropy increases.
b) Gas becomes more orderly, and entropy decreases.
c) Gas becomes less orderly, and entropy increases.
d) Gas becomes less orderly, and entropy decreases.

Answer 1

When a gas becomes a liquid, it becomes more orderly and experiences a decrease in entropy, as there are fewer microstates available for the molecules.

Step-by-step explanation:

When a gas liquefies, it indeed becomes more orderly. The process of liquefying a gas involves the molecules becoming more tightly packed together compared to their arrangement in a gas, where they are far apart and moving freely. Because the molecules are more constrained in their movement when they form a liquid, there are fewer microscopic configurations, or microstates, that the system can adopt. This leads to a decrease in entropy.

Entropy is a measure of the disorder within a system. A disordered system has a greater number of possible microstates than a more ordered one. Thus, according to the principles of thermodynamics, as a substance moves from the gas phase to the liquid phase, there is a decrease in entropy (ΔS < 0). Entropy change during the transition from gas to liquid is a textbook example of a decrease in disorder.