compounds contain regions that are polar (or charged) and regions that are nonpolar (Table 4-2). When amphipathic compounds are mixed with water, the two regions of the solute molecule experience conflicting tendencies; the polar or charged, hydrophilic region interacts favorably with the solvent and tends to dissolve, but the nonpolar, hydrophobic region has the opposite tendency, to avoid contact with the water (Fig. 4-7a). The nonpolar regions of the molecules cluster together to present the smallest hydrophobic area to the solvent, and the polar regions are arranged to maximize their interaction with the aqueous solvent (Fig. 4-7b). These stable structures of amphipathic compounds in water, called micelles, may contain hundreds or thousands of molecules. The forces that hold the nonpolar regions of the molecules together are called hydrophobic interactions. The strength of these interactions is not due to any intrinsic attraction between nonpolar molecules. Rather, it results from the system's achieving greatest thermodynamic stability by minimizing the entropy decrease that results from the ordering of water molecules around hydrophobic portions of the solute molecule.