Salt makes ice melt by lowering the temperature at which water freezes, so the ice turns into liquid water even when it is below 0°C.

Quick Scoop

When salt (usually sodium chloride) touches ice, it dissolves into the thin film of liquid water that always exists on the ice surface, splitting into sodium and chloride ions. These ions interfere with how water molecules lock into a solid crystal, so it becomes harder for water to stay frozen as ice.

Because of this interference, the freezing point of the water–salt mixture drops below 0°C, a phenomenon known as freezing point depression. The existing ice then starts to melt to reach this new, lower freezing point, creating a salty water solution called brine.

As more ice melts into brine, the liquid spreads, breaking up the ice and making it easier to clear from roads and sidewalks. If it gets extremely cold (well below the new freezing point of the salty water), even salty brine can eventually freeze again, which is why ordinary road salt stops working in very low temperatures.

Information gathered from public forums or data available on the internet and portrayed here.