UCSB Science Line
 Why is salt put on icy sidewalks? Question Date: 2009-05-27 Answer 1:The freezing point of water goes down when it has added salt to it. This means that the water will freeze at a lower temperature. The normal freezing point of water is 32degrees F. This means that if it is 32 degrees out or lower, the water on the sidewalks will be ice. If you add salt to this, the freezing point lowers, and so even at lower temperatures the water won't freeze. This means that even if it is 32 degrees outside, the salty water will not freeze. Answer 2:Salt lowers the freezing point of water.So when salt is put on icy sidewalks then the water will freeze at say 14degreesF instead of at32degreesF therefore the sidewalks or roads stay wet longer instead of getting covered with ice. Answer 3:Salty water freezes and melts at a lower temperature. For example, water normally freezes at 0 Celsius (32 Fahrenheit). With a lot of salt added, the freezing point might be something like -10 Celsius (14 Fahrenheit) instead. If the temperature outside is -5 Celsius (23 Fahrenheit), the salty ice would be above its freezing point and will melt.Click Here to return to the search form.

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