(Note: I am posting this in the classical physics section because it has a connection with Thermodynamics, also this is NOT a homework question, I am just trying to get a handle on what is going on) I was looking through some old questions I had written down and decided I would ask to see if anyone can make sense of this: If you take an ion, for example Na+, and place it in a water bath with surface effects, the ion prefers to sit in the deeper portion of the water bath. Why? Now my guess is that if you take an ion in a water bath, water molecules gather around the ion and create a solvation shell, which minimizes the free energy associated with the ion in the bath. If the ion is nearer to the surface, the amount of solvation sites taken by water decreases due to a competition between pulling water molecules away from the surface (where they are already at an equilibrium) and creating a solvation shell to minimize the free energy associated with the ion floating around in the solution. But I have a sneaking suspicion that my thinking isn't quite right.