* Salt is routinely used to make icy roads and sidewalks safe in the winter. As soon as the salt comes in contact with the ice, the surface of the ice starts to melt. This only works, however, if the temperature outside is at or near freezing. If it is too cold outside, the ice itself becomes very dry and salt is not as effective in melting it. Salt Reduces Freezing Temperature of Water
* Salt works by lowering the freezing temperature of water. Salt water needs to reach a colder temperature than pure water to freeze. This is why salted ice on roads that are near the freezing temperature of pure water (32 degrees Fahrenheit) will melt and not refreeze immediately. The ice forms very salty water that will not freeze unless temperatures drop significantly.
* Salt separates into ions when it comes to into contact with ice. The ions disrupt the hydrogen cells in the ice, causing the freezing point of the ice molecules to drop, which in turn causes it to melt. Effects
* The more the ice molecules melt, the less there is for freezing ice molecules to cling onto. Even if temperatures are below zero, there will be more ice melting than freezing. As the salt doesn't melt, only a small amount is required to melt a large quantity of ice. Therefore, using a larger quantity of salt will not make ice melt faster. Freezing
* The freezing point of water is 0 degrees Centigrade (32 degrees Fahrenheit). More accurately, 0 degrees is the point at which water is melting at the same rate it is freezing, creating a balance. At 0 degrees, water molecules are moving very slowly, and a solid begins to form out of the water, which is ice. How Does Salt Affect the Ice?
* When the water has reached an equilibrium at 0 degrees, the ice, undisturbed, will remain ice. If any foreign substance is added to the ice like salt, the water molecules can't attach to form ice as quickly, and so the freezing point (or ice formation rate) is lowered, while...