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Why does salt melt ice? |
Weather
If you live in a snowy place, you’ve probably seen people throwing salt on their sidewalks and using it to melt snow! Why does salt have the special powers to make snow melt?!
Salt and water are both made up of tiny units called “molecules.” Molecules have cool scientific ways of sticking together and interacting. Because salt and water are both made up of molecules that get along really well, when they come into contact with one another, they sort of join together!
You probably already know that ice (such as snow) is frozen water. As water becomes colder, its little molecule units (which normally move around a lot) start to slow down; once they get really cold, they move much less and then turn into ice! When salt is added to the equation, it joins together with some of the cold icy water molecules and causes them to get moving again! – Once the salty water molecules are moving again, they require even colder temperatures than just the pure water before they’ll freeze, and so the snow or ice with its added salt melts back into water!!
Freeze it!
Adding salt to water makes it more difficult for the water to freeze. To see for yourself, try out this experiment!
Have an adult help you prepare to cups of water – one consisting of pure water, and the other consisting of the same amount of water but with a few teaspoons of salt stirred in.
Put the two cups in the freezer at the same time. Check back on them periodically and see which one freezes first! Based on what you’ve learned about the relationship between salt and water, what is the reasoning behind your results??
- “Using Salt to Melt Ice.” 22 Jan. 2004. Teachers
- “Why Does Salt Melt Ice?” Winter Weather. Weather Savvy. 11 Jan. 2010
- Senese, Fred. “Why does salt melt ice?” FAQ. 2007. General Chemistry Online! 11 Jan. 2010
- “Water Properties.” 2002. Iowa Project WET: Water Education for Teachers. 03 Aug. 2009
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