Homeschool Science: Why Does Salt Melt Ice?

WDSMI

It’s that time of year when we see plenty of ice and snow around the country. Many will have taken notice of the practice of putting salt on ice and snow to help to melt it. This little experiment will help to explain that. Here’s how it works:

  • What you’ll need: A few simple things from around your house. A piece of string, a glass of water, some ice cubes, and some table salt.
  • What to do:
  1. Place the ice cubes in the glass of water. They should float to the top of the glass. Have your child dip the string into the cup and attempt to catch one of the ice cubes with it. Note: It shouldn’t work.
  2. Now have your child drape the string across the tops of a couple of the ice cubes. Sprinkle a little of the salt on top of the ice and wait for a minute or two.
  3. Have your child pull out their string and see what they’ve caught this time!
  • What they’ll learn: The first time your child puts the string in the glass, they do not catch any ice cubes because there is nothing for the string to adhere to. Adding salt to the glass slightly raises the temperature of the ice, making it melt a little. However, it is still cold enough in the glass that the water refreezes around the string. This time when your child lifts the string up, the ice comes with it because it has reformed around the string.

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