What does the Third Law of Thermodynamics state about entropy?

The Third Law of Thermodynamics indeed states that as the temperature of a perfect crystalline substance approaches absolute zero, its entropy approaches zero. This is based on the idea that at absolute zero (0 Kelvin), a perfectly ordered crystalline structure would have only one microstate available for its molecules, leading to no disorder or randomness; hence, the entropy, which is a measure of disorder, is zero.

In this scenario, the assumption is that the crystal is in a perfect state with no defects or impurities. In reality, most substances will not reach absolute zero, but the principle holds in theory and helps to define the concept of entropy in terms of absolute thermodynamic conditions.

Understanding this law is key for grasping concepts involving phase transitions and the behavior of materials at very low temperatures in chemistries, such as superconductors or the behavior of quantum systems at cryogenic temperatures. The other options do not accurately represent the principles set forth by the Third Law of Thermodynamics.