At this point, we are all too familiar with the snow that surrounds us. Those of us who spend time driving also know the snow to be the reason that the roads deteriorate so much each winter. Snow falls and covers the roads. Then, the snow melts on the roads because of the heat of continual driving (addition of kinetic energy) and seeps into small cracks in the pavement. Temperatures then drop and the water that melted from the snow in the cracks of the pavement expands as explained in the Brown chapter. When it freezes, water expands. Ice is of a lower density than water and thus takes up more space as the molecules stop moving. This freezing causes cracks and potholes to form and grow as the water beneath the surface of the pavement expands and contracts as the temperature varies.
I also looked into why salt is used during the winter to prevent the formation of ice. Salt lowers the freezing point of water, 32°F/ 0°C. If salt is added, that temperature drops. This is one of the reasons that we don’t see the ocean or salty rivers freezing as quickly or easily as fresh bodies of water. Road salt is polar and thus can be dissolved by water (since water is polar and likes dissolve likes) and will lower its freezing point. A water solution that is 10% salt will freeze at 20°F or -6°C and 20% saline will freeze at 2°F or -16°C—each additional 10% will result in a 10°C cooler freezing temperature.
It is interesting how these two phenomena can be explained by what we learned in class and read about over the past week. I’d be interested to know more about how different pressures affect these phenomena if at all.
As the original post mentions, our state is no stranger to the snow at this point; however, as more and more snow falls, and our salt supply is quickly decreasing, some states have pursued alternatives to keeping our roads safe. As Time.com reports, scholars in Indiana have been working to develop a Beet sugar substance that will work more effectively, melting the snow faster and at a lower temperature than the salt. This substance has an additional property of being sticky, which may even serve as a better preventative of accidents from snow or black ice. This new development reminds us how we can be conscious of eco-friendly advances, even if it is only as a result of depleting salt reserves.
http://time.com/5761/salt-shortage-triggers-beet-juice-cheese-brine-alternatives/
I thought that your post was very interesting! I was always curious about why salt was added to roads so your post was a great refresher! I’m curious though – are there any other polar, soluble substances that can lower the freezing point of water? Is there anything that can increase water’s boiling point?
Another interesting thing about snow and salt in the wintertime is how much it contaminates and affects the environment. When salt leaches into the ground and then the groundwater, not only is human health at risk, but it can erode soil, damage vegetation, affect animals in the surrounding area, and contaminate even the entire watershed. It would be great to see more research on less harmful chemicals than salt (it is chosen because it is so inexpensive) or better methods for salt use (by reducing the initial amount or better dispersal).