# What is DeltaG for a solid melting at its normal melting point?

Nov 12, 2016

$\Delta G$ is $0$ for a process at constant $T$ and $P$.

Since we are looking at the normal melting point of water ice, it means that we are at a constant ${T}_{\text{nmp}}$ and ${P}_{\text{norm" = "1 atm}}$.

From the Maxwell Relation:

$\mathrm{dG} = - S \mathrm{dT} + V \mathrm{dP}$

But at constant $T$ and $P$, $\mathrm{dT} = 0$ and $\mathrm{dP} = 0$. Therefore:

$\textcolor{b l u e}{\Delta {G}_{\text{melt}}} = - S \left(0\right) + V \left(0\right) = \textcolor{b l u e}{0}$