Adding sugar or salt to water lengthens the freezing process. One gram molecular weight of sugar to 1 liter of water lowers the freezing point by -1.86 degrees Celsius. One molecular weight of salt to 1 liter of water results in a decrease of -3.72 degrees Celsius.
Molecules in regular water slow down enough to become ice at 0 degrees Celsius. In water and solute mixtures, the solute molecules must be separated from the water molecules before freezing can begin. This process creates additional heat, thereby lowering the freezing point. The addition of any solute to water has the same effect.