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Third Law of Thermodynamics


The third law of thermodynamics is essentially a statement about the ability to create an absolute temperature scale, for which absolute zero is the point at which the internal energy of a solid is precisely 0.

Various sources show the following three potential formulations of the third law of thermodynamics:

  1. It is impossible to reduce any system to absolute zero in a finite series of operations.
  2. The entropy of a perfect crystal of an element in its most stable form tends to zero as the temperature approaches absolute zero.
  3. As temperature approaches absolute zero, the entropy of a system approaches a constant

What the Third Law Means

The third law means a few things, and again all of these formulations result in the same outcome depending upon how much you take into account:

Formulation 3 contains the least restraints, merely stating that entropy goes to a constant. In fact, this constant is zero entropy (as stated in formulation 2). However, due to quantum constraints on any physical system, it will collapse into its lowest quantum state but never be able to perfectly reduce to 0 entropy, therefore it is impossible to reduce a physical system to absolute zero in a finite number of steps (which yields us formulation 1).

Laws of Thermodynamics
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