The accompanying diagram shows how entropy varies with temperature for a substance that is a gas at the highest temperature shown. (c) If this substance is a perfect crystal at T = 0 K, what is the value of S at this temperature?

Key Concepts

Entropy

Entropy is a measure of the disorder or randomness in a system. In thermodynamics, it quantifies the number of microscopic configurations that correspond to a thermodynamic system's macroscopic state. Higher entropy indicates greater disorder, while lower entropy suggests more order. Understanding entropy is crucial for analyzing the behavior of substances at different temperatures.

Third Law of Thermodynamics

The Third Law of Thermodynamics states that as the temperature of a perfect crystal approaches absolute zero (0 K), the entropy of the crystal approaches a constant minimum, which is typically zero. This principle implies that at absolute zero, a perfect crystal has no disorder, and thus its entropy is zero. This law is fundamental in understanding the behavior of materials at low temperatures.

Temperature and Phase Changes

Temperature is a measure of the average kinetic energy of the particles in a substance. As temperature changes, substances can undergo phase changes, affecting their entropy. For gases, the entropy increases significantly with temperature due to increased molecular motion and disorder. Recognizing how temperature influences entropy is essential for interpreting thermodynamic diagrams and understanding the state of a substance.