Why Does Salt Melt Ice?

More thanِ 20 million tons ofِ salt areِ used everyِ year toِ melt snow andِ ice inِ cold northern regions.
But howِ doesِ salt doِ it?

Thirty-two degrees Fahrenheit (0 degrees Celsius) isِ its freezing point—that is, whenِ water reaches 32 °F, itِ turns intoِ ice.
At thisِ temperature, yourِ icy road generally hasِ a thin layer ofِ water onِ top ofِ the ice, andِ the ice molecules andِ water molecules areِ interacting.
When theِ ionic compound salt isِ added toِ theِ equation, itِ lowers theِ freezing point ofِ the water, whichِ means theِ ice onِ the ground can’t freeze thatِ layer ofِ water atِ 32 °F anymore.

But youِ mayِ beِ askingِ how salt lowers theِ freezing point ofِ water.
In water, salt isِ a solute, andِ it willِ break intoِ its elements.
So, ifِ you’re usingِ table salt, alsoِ known asِ sodium chloride (NaCl), toِ melt ice, theِ salt willِ dissolve intoِ separate sodium ions andِ chloride ions.

Unfortunately, chloride isِ superbad forِ the environment.
It canِ kill aquatic animals, andِ that canِ thereby affect otherِ animal populations inِ their food web.
Chloride alsoِ dehydrates andِ kills plants andِ can alter soil composition, making itِ harder forِ vegetation toِ grow.
While someِ otherِ compounds thatِ canِ melt ice andِ snow don’t include chloride, theyِ areِ much moreِ expensive thanِ sodium chloride orِ calcium chloride.