Variation of G with T for Solid, Liquid and Gaseous Phase

1 Variation of Gibbs Energy Function, G with Temperature, T for the Solid, Liquid and Gaseous Phases of a Pure Substance, at Constant Pressure (dP = 0) 

From the above rationale (and without having made any prior or additional assumptions) we see that our analysis leads - via thermodynamic argument - to a prediction that pure materials existing in their normal phases exhibit melting and boiling phenomena, as is observed experimentally. 

Asa caveat to the considerations involving the solid phase it should be mentioned that some solids undergo mesomorphic changes before melting (although these have been assumed not to occur in the solids so far discussed). 

Liquid and Gaseous Phases of a Pure Substance, at Constant Pressure (dP =0) 

Since Ss S, the solid G versus Tcurve is flatter than the (3 versus T curve resulting in an intersection at Tm Since Sg or Ss the gas curve dips down the most and intersects with the liquid curve at Tb 

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Variation of G with T for Solid, Liquid and Gaseous Phase... 

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