bp's science: why we put salt on the roads when it snows (v.1)

Salt-encrusted cars indicate winter, no doubt about it. Just watch The Office, which is filmed in Los Angeles, CA. When they want you to think it's a cold Scranton, PA winter, they cover the cars in the parking lot with white salty-looking stuff. So, why do they put salt on the roads during the winter?

Answer: Because salt decreases the melting point of ice. Or in other words, salt causes ice to freeze at lower temperatures than it would normally. Water usually freezes at 0 degrees Celsius, but when salt is added, the melting point of the ice mixture is -18 degrees Celsius. This means that it can continue to snow but it won't be icy on the roads.

So what happens when it's more that -18 degrees Celsius outside? Adding salt to the roads won't work. That's when we add gravel and dirt to the roads to help with traction, but you've just got to deal with the snow and ice. I've heard tales of those who live up north. They drive on snow and ice all winter. That's cold!

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