Thermodynamics/The Third law of thermodynamics

The third law of thermodynamics is associated with the descent to its ground quantum state of a system whose temperature approaches a limit that the concept of absolute zero (0 Kelvin).

Also known as the Nernst principle, the third law of thermodynamics can be stated as:

   Definition:
   The Third Law of thermodynamics

   At absolute zero, a pure body in a perfect crystalline state has zero entropy.

${\displaystyle {\displaystyle {at}\quad T=0\ K,\quad \forall p,\quad S=0\quad for\ a\ crystal}}$

The third law is not necessary in the application of classical thermodynamics.