Why Does Adding Salt to Water Lower the Freezing Point?
Water ordinarily freezes at 0 degrees Celsius or 32 degrees Fahrenheit. In a system at this temperature, the rate of freezing is the same as the rate of melting. This is known in chemistry as a dynamic equilibrium. Any change in the temperature will change the rates of freezing and melting, and the entire system will freeze or thaw. Adding salt changes these rates but without changing the temperature. The salt causes the rate of freezing to occur slower than the rate of the rate of thawing, causing the ice to melt and requiring a lower temperature to reattain equilibrium.
