Winter Weather Special: The science behind ice melts and the differences between them
As the winter season approaches, the likelihood of waking up to ice on your driveway or on the roads is on the rise. Ice melts are the most common solution to this problem, but it is good to know how different ice melts work and what might be best for you. The two most popular types of ice melt, calcium chloride and sodium chloride, will most likely be what you reach for on the shelves when choosing.
All ice melts work by simply lowering the freezing point of water, so that the freezing of the water occurs at lower temperatures. Due to the molecular structure of water, it takes on the structure of hexagons once it freezes. The ice melts work by disrupting that molecular structure, leading to the breaking of the ice itself. Rock salt, or sodium chloride, which is one of the more common types of ice melt, is effective to as low as 15 degrees Fahrenheit.
Another ice melt, calcium chloride, becomes more important later in the winter season once the weather is too cold for sodium chloride to be effective. It can prevent or melt ice from forming down to -25 degrees Fahrenheit, and is essential when dealing with bitterly cold temperatures. This mix contains what is known as an exothermic reaction, which causes the temperature near the ice melt to increase.
Scientifically, an exothermic reaction is a chemical reaction that releases energy, in this case, in the form of heat, to its surroundings. The chemical reaction that the calcium chloride pellets have with water, ice formation, or moisture leads to heat being released by the pellets. As the surrounding area is impacted by this reaction, it leads to better resistance against ice formation on the ground.
When comparing calcium chloride and sodium chloride, the main difference is that calcium chloride has an exothermic reaction. Although sodium chloride still disrupts the molecular structure of ice, it does not have the same release of heat or energy that calcium chloride has. This means that when it comes to colder temperatures, calcium chloride becomes more effective at preventing ice from forming.
This can be seen in a simple experiment with two cups of water and the two different types of ice melt. After adding one ice melt to one cup of water and the other ice melt to the second cup, a large temperature difference is noticed. The cup with the sodium chloride will not change much due to the lack of an exothermic reaction. The cup with the calcium chloride, however, will very quickly climb in temperature as the release of energy takes place.
Those ice melts are the most common methods for an average homeowner, but the Missouri Department of Transportation has some other unique ways of keeping ice off the road. MoDOT states that a more basic salt brine works well until reaching 25 degrees Fahrenheit. In the 5-degree to 25-degree range, beet juice is added to the mixture. This is because the sugar in the juice helps the salt brine work at lower temperatures and also lessens the corrosive properties of the salt that is typically used. Once temperatures drop into the -10 to 5 degree Fahrenheit range, calcium chloride is added to the mixture.
Although beet juice may not be readily available to the average homeowner like MoDOT, a good rule of thumb at home is to use sodium chloride ice melt until temperatures drop below 15 degrees Fahrenheit. Once deeper, colder icy conditions occur, calcium chloride will become the better option to get through the winter season.
