What does the third law of thermodynamics indicate about the entropy of a perfect crystalline substance at absolute zero?

The third law of thermodynamics states that as the temperature of a perfect crystalline substance approaches absolute zero (0 Kelvin), the entropy of that substance approaches a minimum value, which is zero. Entropy is a measure of the disorder or randomness of a system, and at absolute zero, a perfect crystal would be in a state of complete order with no thermal motion of its particles. In this idealized state, there would be only one way to arrange the particles in the crystal, resulting in zero entropy.

This conclusion is significant because it establishes a baseline for measuring the entropy of substances at temperatures above absolute zero, allowing scientists to better understand how entropy behaves in various states of matter. The implications of the third law help us comprehend phenomena such as the behavior of materials at low temperatures, including superconductivity and other phase transitions.