key term - Third law of thermodynamics

Definition

The third law of thermodynamics states that the entropy of a perfect crystal at absolute zero temperature is exactly zero. This implies that it is impossible to reach absolute zero in a finite number of steps.

5 Must Know Facts For Your Next Test

1. Entropy approaches zero as the temperature approaches absolute zero for a perfect crystal.
2. It is physically impossible to reach absolute zero temperature.
3. The third law helps define the concept of absolute entropy.
4. Residual entropy can exist in non-perfect crystals even at absolute zero due to disorder.
5. The third law implies that as temperature decreases, the entropy change associated with any process also decreases.

Review Questions

Related terms

Entropy:

A measure of disorder or randomness in a system. In thermodynamics, it quantifies how much energy in a system is unavailable for doing work.

Absolute Zero:

$0 \text{ K}$, theoretically the lowest possible temperature where all thermal motion ceases.

Second Law of Thermodynamics:

$\Delta S_{universe} \geq 0$: Entropy of an isolated system always increases over time and processes occur in a direction that increases total entropy.