Putting rock salt on the roads during a snowstorm is an example of

The answer could honestly be as simple as "Putting rock salt on the roads during a snowstorm is an example of a chemical reaction" but due to lack of context I'm not sure, hope this helps anyways!

 Depression in Freezing Point

Explanation:  When salt is kept on the icy roads, it will form a liquid layer over it thereby lowering the freezing point below the ice. Thus when this salty liquid comes into the contact with the other ice present on the road making the other ice get melt.

This keeps on decreasing the olume of the ice on the road.

Thus it is always advised to put rock salts on the roads during a snowstorm.