Na+Cl- : Winter is coming, use it on the road! (and here is why)

Consulting is  unique but prominent avenue for physical therapists. Often we are called into sites to evaluate working conditions and develop solutions to optimize workplaces to maximize safety & productivity by reducing strain , fatigue, and potential for injury. In fact integrating into the world of ergonomics is a pretty natural fit for physical therapists.

My classmates and I are working on an ergonomics consulting project for our health and wellness course. We are tasked to restructure the process that a train station uses to distribute salt on it’s platform and grounds in the wintery months.

During discussions I heard a lot about “salt melting ice” …then I had a flash back to high school chemistry and got way too excited. Interested in a mini chemistry lesson ? Well, read on my friends…My classmates had no choice and know to patiently indulge my silly tangents. (I love you guys!)

mortons

 Technically, salt doesn’t melt ice, it lowers the freezing point of water. We all know that ice forms when the temp of the water is 0° Celsius  (32°F). When you add salt, that temperature drops, so a 10% salt solution freezes at -6° C (20° F) …add more salt to the solution: a 20% salt solution freezes at -16° C (2° F).

So, sprinkling some salt on an icy road dissolves into the liquid water in the ice and lowers the freezing point slowly spreading out as more ice becomes water. If you live in a cooler climate you’ve probably seen this happen, the ice immediately around the grain of salt melts, and then spreads out from that point. (RESISTANCE IS FUTILE hard water!)

Well, turns out not completely futile. If the temp of the roadway is TOO cold [normally lower than  -9° C (15° F)] salt really won’t have an effect because there is no liquid water to start the dissolving process.

At this point, I recommend …ummm, staying inside with hot coco in your jammies and reading by the fire and most certainly not driving….or sand over the ice to provide traction.

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