Icy Roads and Salt

On a day like today, when the roads are a combination of snow, sleet, and ice, you might get the curious question from so many kids: “Why are the putting salt on the road?”


The answer is: Freezing Point Depression. A common example is the lowering of the freezing point of water (a solvent) when salt is added (solute). The combination of salt and water freezes at a lower temperature than 32 degrees Fahrenheit resulting in a slushy road-way and not a frozen one. A great way to experience this phenomenon with your kids at home is making ice cream in a bag. You’ll use rock salt and ice to get a solution that is below the freezing point of your favorite ice cream ingredients (mine include the whole milk, cream, sugar, and vanilla). Put the ice cream mixture into a sealable sandwich bag, put that in another sealable freezer bag, add ice and salt, close and mix for 20 or so minutes.

The following sites have some great instructions that are easy to follow:

http://crafts.kaboose.com/ice-cream-in-a-bag.html

http://familyfun.go.com/recipes/homemade-ice-cream-in-a-bag-684806/

http://www.ehow.com/how_4879437_ice-cream-bag-minutes.html

~Dean Whitfield
Math and Science Department Chair