Why does adding salt to water lower its freezing point?
The balance between freezing and melting processes can easily be upset. If the ice/water mixture is cooled, the molecules move slower. The slower-moving molecules are more easily captured by the ice, and freezing occurs at a greater rate than melting. You can see a demonstration of this by clicking on the temperature in the animation and setting it to a lower value (say, -10). Conversely, heating the mixture makes the molecules move faster on average, and melting is favored. Reset the animation and then enter a higher value for the temperature (say 10) and watch what happens. Adding salt to the system will also disrupt the equilibrium. Consider replacing some of the water molecules with molecules of some other substance. The foreign molecules dissolve in the water, but do not pack easily into the array of molecules in the solid. Try hitting the “Add Solute” button in the animation above. Notice that there are fewer water molecules on the liquid side because the some of the water has be
