Why Choose Calcium Chloride to Melt Ice?

Most non-toxic alkali and alkali-metal salts are composed of two ions--a positively-charged metal ion and a negatively-charged halide ion. For example, a molecule of table salt (NaCl) dissolves into one sodium ion and one chloride ion. Calcium chloride, however, consists of one calcium ion and two chloride ions. When calcium chloride dissolves, three ions are created--50 percent more than table salt. More particles in solution means a greater effect on water's colligative properties. As such, calcium chloride will keep water from freezing into dangerous ice across a greater range of temperatures.

In addition to preventing water from freezing at low temperatures, calcium chloride helps melt ice. When combined with water, dry calcium chloride exothermically dissolves. This means that each salt molecule releases broken ionic bond energy into surrounding ice molecules in the form of thermal energy. This "heat" energy increases the surrounding temperature enough to melt ice, which creates more water for dry salt to exothermically dissolve in.