Why do they grit the roads with rock salt in winter? What does the salt do to the water to reduce ice on the roads? Is this somehow related to how salt affects the boiling point of water? Keywords to search for: colligative properties, boiling, freezing, ions, solutions, solvent, Raoult’s law
Meanwhile, I’ll let Plasticine models from Ithaca and cheesy music explain:
Incidentally, if it is too cold, no amount of salt will prevent the roads freezing, but if climate predictions are to be believed then that will not be a problem for much longer. (Unless the computer models are all wrong and we are heading for another ice age…now where did I put that hot-water bottle?)