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?
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.
Are you ready to play with the science of snow (and ice)? Take a look at these K-12 science experiments:
- What Makes Ice Melt Fastest?: If you were in charge of keeping roads clear of ice and snow, would you use salt? What else might work? This quick and easy experiment helps you explore what's best.
- Slip Sliding Away: Experimenting with Friction: Ice is slippery, but what about other materials? Compare slip angles between icy and non-icy surfaces.
- How Does Atmospheric Temperature Affect the Water Content of Snow?: Snow can be light and fluffy or heavy and clumpy—what accounts for the difference? Discover how temperature affects snow conditions.
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!