I can't seem to resolve how salt melts ice on a cold day.
Imagine starting with an equilibrated small bowl of ice in the kitchen freezer at -18C and a separate tablespoon of sodium chloride (also at -18C). The salt is then placed on the ice without ever leaving the freezer.
If you asked me for my naive prediction of what would happen, I would have said nothing. You have two solids well below their freezing points and there should be no liquid water that would be needed to solvate the Na+ Cl- ions.
Doing this experiment, I find a puddle of brine the next day. This shows there must've been some liquid water present to start solvating the ions, I believe this liquid water comes from the quasi-liquid phase at the surface of the ice (present at temperatures like -18C).
But some source seem to disagree, there is no mention of premelted ice surface here:
This explanation also demands that some energy to initiate melting:
This earlier SA article says that the quasi liquid layer does indeed dissolve the salt:
Is the freezer experiment sufficient to show that there is a quasi liquid layer on ice at -18C? It is hard to reconcile with some of the above articles.