Why Do We Put Salt on Icy Roads?

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Winter is officially here, and for those of you at more northern latitudes, you know what that means: snow and ice. And while walking in a winter wonderland is certainly wonderful, slipping and sliding can mean some nasty injuries.

Highway department to the rescue! Before the snow even has a chance to fall, government trucks drive up and down the streets dumping salt all over the place.

The biggest reason for pouring salt on icy roads is that salt lowers the freezing point of water. Water normally freezes at 32 degrees Fahrenheit, but when you add salt, that threshold drops to 20 degrees (or even 2 degrees) Fahrenheit.

And no, there really is no difference between the salt on the road and the stuff on your kitchen table. The only difference is the size. The salt on the roads has crystallized in larger pieces, while normal table salt has been crushed into tiny grains.

If you ever want to conduct your very own science experiment, pour ice salt onto freezing water. You can watch as the water surrounding each grain of salt melts. From there, the melting quickly spreads.

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January 3, 2014 - 9:30am
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