De-icers work by lowering the freezing point of water, which causes it to turn back from ice into liquid water. Usually this is due to the addition of a chemical compound such as sodium chloride (often called rock salt) or calcium chloride. Most de-icers that you can buy off the shop shelf aren’t designed to melt every piece of ice they come into contact with – they simply break the bond between the ice and the surface allowing for easier manual removal of the ice.
