PPT Slide
The Second Law of Thermodynamics ñ All spontaneous processes occur in the direction that increases the total entropy of the universe (system plus surroundings).
_Suniv = _Ssys + _Ssurr
- Entropy is not conserved: _Suniv is increasing
- For a reversible process: _Suniv = 0.
- For a spontaneous process (i.e. irreversible): _Suniv > 0.
- Note: the second law states that the entropy of the universe must increase in a spontaneous process. It is possible for the entropy of a system to decrease as long as the entropy of the surroundings increases.
- For an isolated system, _Ssys = 0 for a reversible process and _Ssys > 0 for a spontaneous process.