The Third Law states, “The entropy of a perfect crystal is zero when the temperature of the crystal is equal to absolute zero (0 K).” According to Purdue University, “The crystal must be perfect, or else there will be some inherent disorder.

Four general rules of thermodynamic modelling reveal four laws of Nature: (1) when the system is well separated from its environment, its energy must be defined for all states and must emerge as an additive, exchangeable, and conserved property; (2a) when the system is uncorrelated from any other system, its entropy …

Terms in this set (3)

• first law. conservation of energy – energy is neither created nor destroyed.
• second law. the entropy of the universe increases with any spontaneous process and remains unchanged for an equilibrium process.
• third law. the entropy of a pure crystalline solid at 0 K is 0.

Hint: The third law of thermodynamics states that the entropy of a perfectly ordered crystalline substance is zero at absolute zero of the temperature. This law is also known as the Law of Conservation of Energy, and states that energy cannot be created or destroyed in an isolated system.

Zero entropy means perfect knowledge of a state ; no motion, no temperature, no uncertainty. Occurs at absolute zero.

Spontaneity is dependent on temperature—some processes are spontaneous at some temperatures, and some are not. For a temperature above 100 °C, the boiling of water is spontaneous. For a temperature below 100 °C, the condensation of water is spontaneous.

So yes, ΔG is 0 at the boiling point (and also at the freezing point).

As delta G is a factor of change in temperature, delta G = 0 at the boiling point.

At higher temperatures, the melting process occurs spontaneously, so we can deduce that ΔH is positive and ΔS is also positive. We already know that melting is endothermic and increases entropy, so it seems the free energy equation works. We can see that the melting of an ice cube is spontaneous for high temperatures.