Bulk water systems bond orientational ordering

Whenever two phases come in contact with one another, an interfacial region forms within which physical and chemical characteristics of each phase are disturbed relative to interior (bulk) regions of each phase. At the air-water interface, for example, the directional orientation of water molecules is more pionounced than in bulk solution, in order to compensate for the lack of hydiogen-bonding partners on the gas-phase side of the interface. As a consequence, the dielectric constant and other solvent characteristics that influence liemical reactions are perturbed to some degree. Solute molecules added to mi water or solvent-water systems may reside predominately in one phase or the other, or may concentrate in the interfacial region. Whether or not solute molecules are surface-active depends on the relative energies of possible dilute solute, solute-solvent, and solvent-solvent interactions (Tanford, 1980). 

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