Asked by: Anonymous
Salt melts ice and snow by lowering its freezing point. Salt is best put on the roads before they freeze or before snow arrives. Then, as snow falls, the salt mixes with it, lowering its freezing point. The result is a brine solution, preventing subsequent ice forming. If roads are already frozen solid, salt is far less effective as there’s no liquid water on the surface.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.
