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How Low Can You Go? Melting Road Ice

Dropping the freezing point of water can help keep roads free of ice, making them safer for driving. What are the best tools for the job?

Salted street in the snow

In the eastern United States, this winter's Arctic temperatures and non-stop snowstorms have kept snowplow drivers on their toes. Snow and ice reduce friction between car tires and the road, making it slippery and more dangerous to drive, so snowplow drivers' hard work is essential. Even if people are advised to stay off the roads, emergencies like heart attacks and house fires don't pay any attention to the weather report, so emergency vehicles must be able to use the roads at all times.

Snowplows push snow off of the roads, but sometimes that is just one part of their job. They may also spray sand, salt, and chemical deicers onto the road. Sand can provide car tires with increased traction on slippery ice, while salt and chemical deicers can melt existing ice and snow or pretreat roads in advance of a storm. By spraying something onto the road that will lower the freezing temperature of water, slippery ice is less likely to form.

Finding a Better Ice-Buster

While salt is often used to help keep community roads and highways clear of ice, it isn't necessarily the best (or only) tool for the job. For example, the further the temperature is below freezing, the less effective salt becomes, until it loses its ability to melt ice at all. Dry rock salt can also be blown off of the road by wind and fast-moving vehicles, in which case it doesn't get a chance to do its job. These reasons, plus cost-effectiveness and environmental concerns, are some of the reasons why municipalities may spray roads with liquid chemical deicers, such as magnesium chloride. In our house, this process is known as "pinstriping" because of the white lines it leaves on the roads as it dries. These liquid deicers can't be blown away and also are effective at lower temperatures.

More creatively, some localities are using food processing by-products to pretreat their roads. In Wisconsin, a big cheese-making state, some municipalities fill those big snowplow spray tanks with cheese brine! It's a win-win, because the cheese producers would otherwise have to pay to have cheese brine hauled away as waste, and now this "waste product" is being put to good use. Several other states, such as Ohio, North Dakota, and Pennsylvania, have experimented with liquid by-products that come from processing sugar beets.

Snow Day!

Are you ready to play with the science of snow (and ice)? Take a look at these K-12 science experiments:

Wind chill factor...fog...is weather one of your favorite topics? Take a look at Science Buddies' Weather and Atmosphere Project Ideas for more hands-on fun!


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