  A comprehensive, semi-quantitative model for the thermodynamics of
hydrophobic solvation is presented. The model is based on a very simple premise
suggested by the scaled particle theory and treats both solute and solvent
molecules as hard spheres. A connection between the peculiarly large
heat-capacity change for hydrophobic solvation and the large temperature
dependence of the thermal expansivity of water is found. Analysis reveals a
possible physical origin for the converging behavior of solvation entropies for
a series of homologous hydrophobic compounds. The model suggests that the low
solubility and the large heat-capacity change of hydrophobic solvation stem
from two distinct aspects of water molecules: the static geometry of the
molecule and the dynamic hydrogen bonding network, respectively.
