Thermodynamics of phase transformations

Consider a simple phase change involving the melting of solid ice to liquid water  

The thermodynamic favorability of this phase change is determined by AG for the transformation process, which is itself dependent on the temperature, pressure, and composition (purity) of the phases. As with any other thermodynamic process, AG for a phase transformation can be determined from the G values for the final versus 

When examining the kinetics of a phase transformation, a typical first step is to calculate the thermodynamic driving force for the process. Consider again the water/ice example above. At equilibrium T=T = 0 °C), the thermodynamic driving force for transformation is zero. However, if the temperature is displaced from this equilibrium temperature, the balance will be upset and a thermodynamic driving force for phase transformation will ensue. How can we quantify this driving force  

Recognize that when T = AGjj d = 0. We thus have 

We can then express the thermodynamic driving force for phase change at any arbitrary temperature T in terms of A5(s, and AT (AT = - T)  

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