Which substance, calcium chloride or sodium chloride, melts ice faster and why?

Without trying the experiment, I would expect sodium chloride to melt ice more quickly than calcium chloride simply because sodium chloride is more soluble in water. Anything that dissolves easily in water can melt ice, even sugar! A water-soluble material interferes with the crystalline structure of ice and, assisted by the tendency of everything to maximize randomness, converts the orderly arrangement of solid ice and soluble solid to the less orderly mixture of soluble material dissolved in liquid water. Both calcium chloride and sodium chloride are water soluble and thus melt ice, but sodium chloride is substantially more soluble than calcium chloride and ought to work faster. However, molecule for molecule, calcium chloride will melt more ice than sodium chloride. That's because a single calcium chloride molecule decomposes into three separate ions in solution (one calcium ion and two chlorine ions). In contrast, a sodium chloride molecule only forms two separate ions in ... more