  Square water takes into account the directionality of hydrogen bonds. The
model is reviewed and its properties as a solvent for apolar particles are
studied through Monte Carlo simulations. Specific heat measurements are used to
identify phase separation. Data for comparison with the lattice gas on the
square lattice are presented and the relation to non-associating solvents is
discussed. Data for the frequency of hydrogen bonds as a function of
temperature indicate a slower rate of bond breaking for the hydration shell as
compared to bulk water particles.
