The hydrogen bonds among its molecules have a strong effect on how water absorbs and transmits heat. At low temperatures, water exists as solid ice, its molecules immobilized in organized crystals. As it warms up, it first melts to become liquid water; and then the liquid water is vaporized to form steam. Each phase is affected by hydrogen bonding.
Hard Water: Dissolved Minerals
Water is so good at dissolving other substances that apart from distilled water, it’s seldom found in anything like pure form. Tap water is quite variable in composition, depending on its ultimate source (well, lake, river) and its municipal treatment (chlorination, fluoridation, and so on). Two common minerals in tap water are carbonate (CO3) and sulfate (SO4) salts of calcium and magnesium. Calcium and magnesium ions are troublesome because they react with soaps to form insoluble scums, and because they leave crusty precipitates on showerheads and teapots. Such so-called hard water can also affect the color and texture of vegetables, and the consistency of
bread dough. Hard water can be softened either city-wide or in the home, usually by one of two methods: precipitating the calcium and magnesium by adding lime, or using an ion-exchange mechanism to replace the calcium and magnesium with sodium. Distilled water, which is produced by boiling ordinary water and collecting the condensed steam, is fairly free of impurities.