Jasmine: My name is Jasmine.
Chrissy: And I'm Chrissy.
Jasmine: We're from NIU STEAM and...
Chrissy: This is The Sound of Science on WNIJ.
Jasmine: We've seen snow totals far below average this winter, which means that if you've driven past a road salt storage facility you've noticed the mounds of salt just waiting to be deployed. Maybe you've wondered how it is that road salt even works. Wonder no more!
Chrissy: We remember from high school science class that water freezes at about 32° Farenheit and 0° Celsius. Road salt lowers the freezing point of water, preventing ice from forming or helping melt existing ice. When salt dissolves in water, it creates a saline solution that disrupts the formation of ice crystals. The effectiveness of road salt depends on temperature. Common rock salt (sodium chloride) becomes less effective below 15°F, while other salts can work at lower temperatures.
Jasmine: What happens when it's colder than 15°F? Different formulations of salt can be used to combat below 0 temperatures. Calcium Chloride has a temperature rating of -20°F because as it dissolves in water, heat is generated as a biproduct of a chemical reaction. Magnesium Chloride is effective to about -5°F and is less corrosive than Calcium Chloride.
Chrissy: Maybe you've seen the smaller industrial trucks with tanks on the back spraying lines on the road. These trucks carry a liquid mix of salt and water that is sprayed on roads in a process called "pre-wet salting". There are various benefits to this: increasing efficiency by working quickly and effectively, reducing overall salt use, reducing environmental impact (creating less salt runoff into soil and waterways compared to dry spreading), saves money as less salt is needed (reducing material costs and labor for reapplication), and improved road safety as the liquid prevents ice from bonding to the pavement.
Jasmine: You've been listening to The Sound of Science on WNIJ, where you learn something new every day.
