When common salt (sodium chloride) is mixed with ice, its melting point decreases. This is a phenomenon known as freezing point depression.

Here's why:

* Salt dissolves in water: When salt is added to ice, it dissolves in the thin layer of water that forms on the surface of the ice.

* Disruption of water molecules: The dissolved salt ions (sodium and chloride) interfere with the ability of water molecules to form a regular, crystalline structure (ice). This disruption makes it harder for the water molecules to freeze.

* Lower freezing point: As a result, the freezing point of the water is lowered, meaning that the ice will melt at a lower temperature than pure water.

In simpler terms, salt makes the ice melt faster because it lowers the temperature at which ice can exist. This is why salt is used to melt ice on roads and sidewalks in winter.