A process by which water molecules become associated (or react) with other substances without destruction of the water molecule. (1) Water molecules (dipoles) become adsorbed on ions or on solid surfaces exhibiting electrostatic charge. (2) Water molecules become imbibed as a result of conditions which tend to cause osmotic absorption of water into the space between the crystal surfaces (as in montmorillonite clays). (3) Water molecules become bound chemically at fixed points as part of the crystal lattice of hydrated substances. The water becomes water of crystallization and loses the properties of the original water.