Describe the absolute entropy and the third law of thermodynamics.

(N/A) The entropy of a system is related to the molecular motion. As the temperature of a system rises,these motions become more vigorous and entropy increases. Conversely,when the temperature is lowered,the entropy decreases.
The third law of thermodynamics states that the entropy of a perfectly ordered pure crystalline substance approaches zero as the temperature approaches absolute zero $(0 \ K)$.
This law applies specifically to pure crystalline solids due to both theoretical arguments and practical evidence.
It is important to note that the entropy of solutions and supercooled liquids is not zero at $0 \ K$.
For a pure substance,the absolute entropy at a given temperature $T$ can be calculated by summing the $\frac{q_{rev}}{T}$ increments from $0 \ K$ to $T$.