評論
打印
Salt vs. Ice
食鹽大戰冰塊
Y: Why does salt melt ice?
為什么食鹽能讓冰塊融化？
D: It lowers the melting and freezing point of water.
是因為食鹽將水的熔點和冰點降低了。
Y: Oh,OK.Wait,I don't get it. Doesn't that mean the salt make ice colder?
等一下，我不明白。這就意味著食鹽讓冰的溫度變得更低嗎？
D: Let me explain.Pure water freezes at thirty-two degrees Fahrenheit,right? At that temperature we can say that the rate of freezing is the same as the rate of melting.
我解釋一下。純凈水的冰點是32華氏度，對吧？這個溫度既是冰點也是熔點。
Y: So in other words, at water's freezing point there's a sort of equilibrium between freezing and melting.
也就是說，水的冰點就是結冰和融化的平衡。
D: Right.Throwing salt on ice upsets the balance.
是的。在冰上灑鹽擾亂了這種平衡。
Y: Upsets it how?
怎么打亂的呢？
D: The salt dissolves into the liquid water, which means that some of the water molecules are replaced by salt. Since there are now fewer liquid water molecules to be captured and frozen by the ice, the rate of freezing drops.
鹽溶解在水中，就是說一部分水分子被鹽取代了。既然結冰的液態水分子減少了，冰點自然降低了。
Y: I think I get it.And Since the rate of melting stays the same, there's more melting going on than freezing. And so the ice melts.
我明白了。水的熔點不變，融化的水分子比結冰的多，所以冰塊就融化了。
D:Right.
對。
Y: Interesting.
很有趣。
D: In fact, anything that dissolves in water will do the trick. You could pour sugar on ice and it will melt. But I guess since salt is cheaper it's used more often.
其實，任何溶于水的物質都可以使冰融化。把糖灑在冰上，冰也會融化。但是我想也許由于鹽比較便宜，所以經常被使用。
