How Salt Melts Ice

Why does throwing salt on ice make it melt… even when it’s below freezing?

And why does it stop working when it gets REALLY cold? Ice melts when

water molecules can break free faster than they lock back into the ice crystal.

Salt doesn’t “ heat up” the ice. It changes the rules by lowering water’s freezing point.

Here’s the trick: salt dissolves into ions—sodium and chloride—and those ions get in the way

of ice forming. But salt needs a little liquid water to start dissolving.

Even on ice, there’s often a microscopic film of water on the surface.

As it dissolves, it makes brine—salty water—and brine freezes at a lower temperature than pure