Why Salt?

Yesterday brought the area a considerable amount of accumulating ice as freezing rain/rain immediately froze on impact with the super chilled ground. However, many of the main roads never became iced over, even during the peak of the system. We can attribute this to the copious amounts of salt that were put down prior to the deep freeze. We all know that salt helps to melt ice, but have you ever wondered why it is so effective sometimes, and other times it just doesn’t seem to get the job done? Wonder no more! It has to do with salt’s freezing point. Salt lowers the freezing point of water/ice. Water freezes at 32°F… unless there is salt mixed in with the water. In a 10% salt solution of water, the freezing point drops from 32° to 20°, and a 20% salt solution of water drops the freezing point all the way down to 2°. This means that when you sprinkle salt on sidewalks or roadways it can melt the ice it is applied to. This is a very effective process when temps are above 20°. When they are lower, they reach the new freezing point that the salt gives to the ice therefore canceling it out. -Greg

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Posted under ice, science, winter weather

This post was written by qni_it on January 28, 2013

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