Thermodynamics/Applications of the third law

At the limit of absolute, which is a temperature that cannot be physically reached, the equilibrium of a system tends towards an constant, that is independent of the other intensive properties. The constant that is approached is taken to be zero (third law).

Therefore, this constant reference of 0 at 0 degrees Kelvin, gives meaning to the specific values of entropy, and not "up to an additive constant" as seen with the change in entropy given by in the formula described in the second law.

This principle is irreducibly linked to the quantum indistinguishability of identical particles.

No body can reach a temperature below absolute zero[1]. This statement can be compared to saying, "a bottle cannot be less than empty." If that statement were not true, that would imply a body can have a negative mass or negative volume.

References

  1. ↑ However, since temperature is the intensive variable associated with entropy S, in statistical thermodynamics, in particular cases, we can have negative temperatures but in this case it has nothing to do with the thermal notion of hot and cold; the temperature T is then only the intensive parameter associated with S such that T = (δU / δS)V,N .
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