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Posted by on Jul 27, 2015 in Tell Me Why |

Why Does Salt Melt Ice?

Why Does Salt Melt Ice?

Salt enables ice to melt because it lowers the temperature at which water freezes. How does this melt ice? When you sprinkle salt on an icy sidewalk or roadway, the salt dissolves in the small amount of water present on the surface of the ice.

This makes salt water. The salty water melts the ice. The salt does not really prevent water from freezing into ice. The freezing point of salt water is much lower than the freezing point of ordinary water. If the outside temperature is below the temperature at which salt water freezes, the ice will not melt even if salt is added.

Salt melts Ice due to freezing point depression, the phenomenon that occurs when the freezing point of a liquid (a solvent) is lowered by adding another compound to it, such that the solution has a lower freezing point than the pure solvent.

Having salted roads and sidewalks in winter makes getting around safer. But the widespread use of salt during the winter has many negative effects, some immediate and others indirect and long-term.

The most visible impact is on plants along the roadside where the salt causes dehydration that harms leaves, stems, root systems and seeds. But salt also leads to colonization of salt tolerant species (some invasive) — and therefore reduces species diversity.

Animals are also affected. Birds often mistake road salt crystals for seeds. Consuming salt even in small amounts can be toxic for birds. Mammals such as deer are attracted to roads to lick the salt, which leads to more vehicle-related wildlife kills.

High concentrations of salt can also be found in snow-melt, which many animals drink. And let’s not forget that all this salt in the melted ice runs eventually into water bodies from which we get our drinking water. The bottom line is that salt is not good for our Wild City — so use it sparingly.

Content for this question contributed by Blaise Yaksick, resident of Clairton, Allegheny County, Pennsylvania, USA