Question

In terms of chemical potential, less associated water corresponds to higher chemical potential, and more associated water to a lower chemical potential than the reference state. Explain using free energy considerations.

Answer 1

As the pressure increases, the phase with the smallest molar volume is going to be favored (because that will have the lowest increase in Gibbs energy).  Generally speaking, a solid has a lower molar volume than a liquid (water being a weird exception to this rule) and liquid has a lower molar volume than gas.  Thus as you increase pressure, you generally go from gas to liquid to solid, as you would expect.

Water, unlike almost all other pure substances, expands when it freezes.  Arguably, this is one of the properties of water that allows for the persistence of many different lifeforms on earth because it means that ice floats.  Thus lakes do not freeze solid in the winter time because the ice actually forms an insulating layer.

dG_m = -S_mdT

the phase with the greatest molar entropy will decrease the most when the temperature increases.  Gas obviously has the greatest entropy per mole and indeed at high temperature, it has the most negative Gibbs energy (it is the most stable phase at high temperature).  However, this equation says that as you drop the temperature, gas destabilizes faster than liquid or solid, so at some point the liquid (which has an intermediate molar entropy) will dominate and as the temperature is decreased farther, the solid (with the lowest molar entropy) will dominate.