1. Entropy changes in irreversible Processes
To obtain the change in entropy in an irreversible process we have to calculate DS along a reversible path between the initial state and the final state.
Freezing of water below its freezing point
Irrev
H2O( l , -10 °C)
H2O( s , -10 °C)
H2O( l , 0°C)
H2O( s , 0 °C)

2. Absolute entropy of a substance
Third law of thermodynamics:
The entropy of each pure element or substance in a perfectly crystalline form is zero at absolute zero.

3. Spontaneous process

5. Helmholtz free energy

6. Gibb’s Free Energy

7. Combining the First and Second law

9. The Thermodynamic SquareP U G T V A

10. S H P U G T V A

11. The variation of Gibb’s energy with temperature.

12. Variation of the Gibb’s energy with pressure

13. Conditions for equilibrium between Phases 

15. Various Equilibrium conditions
Capacity
Factor
Intensity
Equilibrium
Condition S T
At const. U,V V P
At const. V,T ni i
At const. P,T

16.  

17. Phase changes of pure component

18. Temperature dependence of phase stability

19. Response of melting temperature to the applied pressure