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The science of salt on snowy, icy roads

Posted at 2:49 PM, Dec 24, 2020
and last updated 2020-12-25 08:36:40-05

In this experiment, you will learn why cities use salt on snowy and icy roads during the winter.

What you'll need for this experiment:

  • Ice Cubes
  • Two bowls, plates, or cups
  • Salt (any kind will work, but different types will have slightly different results)

First, put a few ice cubes in each of the bowls. One bowl will be just the plain ice cubes, set that aside. In the other bowl, measure out some salt and sprinkle it on top of the ice cubes. Give it five or 10 minutes and watch what happens.

The bowl with only ice looks pretty much the same, the ice will still be mostly frozen. However, the ice with the salt will be partially melted. It will look like the salt is eating into the ice cubes. Why does this happen? Although it looks like the salt is melting the ice, that's not exactly what is happening.

The salt actually lowers the freezing point of water, which helps to disrupt the formation of the ice crystals. That helps turn the ice back into liquid water! That water then helps to melt more of the ice, and the process compounds. Pure water freezes at 32°, while saltwater freezes at even colder temperatures. The specific temperature depends on how much salt is in the water.

When doing this experiment at home, try using different types of salts, notice which is more or less effective. Is there another substance you think might help to melt the ice?

If you try this experiment at home, let Kristen know through an email or social media.

Next time you see a salt truck on the roads during snowy weather, you'll know why salt is used AND how it works!

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