How does solidification occur? [closed]








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What does it mean that "When vapor pressure of solid is greater than liquid, there is a net conversion from solid to liquid".
What exactly occurs in the process of solidification of liquids?




You can think of the amount of vapor in equilibrium with a particular condensed phase as being indicative of the relative stability of the condensed phase. A more stable condensed phase results in a lower vapor pressure. 


More formally, stability of a pure substance in a particular phase is usually described in terms of its chemical potential $\mu$ in that phase. A lower (more negative) chemical potential implies a higher stability. Equilibrium between two phases means that the chemical potential in both is the same. In addition, the chemical potential of a vapor (assumed to behave like an ideal gas) can be related to the value at some reference pressure $p^\circ$ using the following equation: $$\mu(g) = \mu^\circ + RT\log \left( \frac{p}{p^\circ} \right)$$ This means that at equilibrium with a condensed phase $$\mu(\text{cond}) = \mu^\circ + RT\log \left( \frac{p}{p^\circ} \right)$$ and that the relative chemical potential of condensed phases i and j can be related via their respective vapor pressures as $$\mu\_i-\mu\_j = RT\log \left( \frac{p\_i}{p\_j} \right)$$ This means that if the vapor pressure of phase $i$ is higher than that of $j$, the chemical potential of phase $i$ is greater than that of $j$ at that temperature and pressure of the system. And only the most stable condensed phase survives.


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