The freezing point of a liquid is the temperature at which it changes from a liquid to a solid. The freezing point of water is 32 degrees Fahrenheit (0 degrees Celsius), while the freezing point of salt water is lower, at 28 degrees Fahrenheit (-2 degrees Celsius). This is because salt dissolves in water and separates the water molecules, which makes it harder for them to form the crystals that make up ice. In addition, salt water contains ions, which also interfere with the formation of ice crystals.