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ASK DR. SCIENCE |
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ASK DR. SCIENCE |
| > Anonymous Student | ||
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I have a problem. There is a layer of hard-packed snow in my yard. I threw rock salt on it to melt it, but I ended up with rock-shaped holes and things are still slick. Help! | |
| > Dr. Light | ||
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Hey, Citan, we've got a winner here! | |
| > Citan Uzuki | ||
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Indeed. Sir, you've just illustrated the dangers of using fact without reason. | |
| > Mega Man | ||
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Isn't that a bit harsh? | |
| > Dr. Light | ||
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Yes. Yes it is. | |
| > Citan Uzuki | ||
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The fact: Salt, when applied to icy roads, causes the ice to melt. | |
| > Dr. Light | ||
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The reason: salt, when added to water, lowers the freezing point. The change in freezing point depends on both the amount of salt added, and the amount of water (or ice) to which you're adding the salt. | |
| > Citan Uzuki | ||
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Salt trucks add enough salt to the road so that the water has a high concentration, and the freezing point is lowered so that it won't refreeze. | |
| > Dr. Light | ||
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When you added the rock salt to the snow in your yard, it melted the water under it, but the concentration of salt was so low that the snow immediately refroze. The resulting ice is much more hazardous than snow. | |
| > Citan Uzuki | ||
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The holes are caused by the salt "burrowing" through the snow, constantly melting the snow underneath it. | |
| > Mega Man | ||
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We didn't really help him, though. What can he do? | |
| > Lucca | ||
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I prefer napalm to rock salt, personally. | |