Engineering Thermodynamics/Third Law
Appearance
Third Law of Thermodynamics
[edit | edit source]The Third Law of Thermodynamics extends the definition of Entropy:
Entropy is zero only in a perfect crystal at absolute zero ( 0 kelvin [- 273.15 degree Celsius ]).
The Third Law of Thermodynamics can mathematically be expressed as
lim ST→0 = 0 (1)
where
S = entropy (J/K)
T = absolute temperature (K)
At a temperature of absolute zero there is no thermal energy or heat. At a temperature of zero Kelvin the atoms in a pure crystalline substance are aligned perfectly and do not move. There is no entropy of mixing since the substance is pure. By -VBM