1. Draw the analogous curves for water.
2. You might be concerned that if we double σ while doubling S, V, and n, we must keep the geometry of the system as a "slab" of fixed thickness. This means that there will be surface interaction energies with the walls that are also proportional to σ. How do we separate these energies from y σ? Can you think of procedures to do this? Consider two sorts:
(i) Make measurements of containers filled with pure vapor, pure liquid, and a mixture of the two.
(ii) Employ a container with periodic boundary conditions. The latter might be difficult in practice but could be feasible in the world one can simulate with computers