评论
打印
=====精彩回顾===
How Does Salt Melt Ice
为什么盐可以用于地面除冰
Now that winter’s here, the weather fiends out there are waiting for the next big snowstorm.But before the flakes fall, armies of trucks are loaded full of one of the most important road safety tools out there – salt.
现在，冬季即将来临。喜爱冬天的人们正在期待下一场暴风雪的来临。但是在雪花飘落之前，大量卡车会装满最重要的道路安全工具——盐。
Along with keeping our French fries on point,salt, like sodium chloride,has actually saved a lot of lives,and probably even more fenders thanks to its incredible deicing abilities.
除了让我们的炸薯条更美味之外，盐就像氯化钠一样，由于其除冰能力，实际上挽救了许多人的生命，拯救的挡泥板就更多了。
So here’s a truck throwing salt all over a wintery road.
看看，这里有一辆卡车，在冬季整个结冰的道路上撒盐。
Like everything else in the picture,you can bet that that salt is pretty cold.
就像画面上其他任何地方一样，你可以肯定这些盐绝对非常冷。
This begs the question – how be that something that isn’t hot is melting the ice?
那就出现一个问题——这种并不热的东西是如何融化冰的呢？
Turns out, salt isn’t actually about melting.It’s all about freezing.
事实表明，盐的作用并不是融化冰。而是防止结冰。
The freezing point of pure water rests at 32 degrees Fahrenheit, or 0 degrees Celsius.
纯水的冰点是华氏32度，也就是0摄氏度。
When the temperature of water reaches the freezing point, its normally free-flowing molecules get trapped into an organized crystal structures.
当水的温度到达冰点时，正常情况下自由流动的分子被困为一个有组织的晶体结构。
This is how ice is formed. Salt disrupts this process. Upon hitting water,salt breaks up into two ions:one sodium and one chloride.
这就是冰的形成过程。而盐就是扰乱这个过程。遇到水之后，盐会分解为两个离子：一个钠离子和一个氯离子。
These two ions then move around and take up space in between water molecules, pushing them apart and frustrating their potential links to form ice. This disruption is called freezing point depression.So to put it simply, salt lowers the freezing point of water.
然后这两个离子四处游动，在水分子之间占据空间，将它们分开，打破他们链接形成冰的可能性。这种扰乱过程叫做凝固点降低。简单地说，盐可以降低水的冰点。
But there’s a limit.Salt can only act as a stable deicer in temperatures above 16 degrees Fahrenheit (-9 C).
但是也有一个限制。盐只能在华氏16度（零下九摄氏度）以上作为稳定的除冰剂。
And there’s another drawback to salt.
盐还有另外一个缺点。
Considering that over 20 million tons of road salt is used annually in the U.S.,all that salt has to go somewhere in the spring.
考虑到美国道路每年要使用超过2000万吨盐，到了春天的时候，这些盐总要有去处。
Of those two ions split from dissolved salt,the chloride ions can have a potentially negative effect on the environment.
融化的盐释放的两个离子中，氯离子可能对环境产生负面影响。
Chloride can kill small aquatic critters,dehydrate and kill plants,alter the composition of ground soil near roads, and can limit water circulation that keeps lakes healthy.
氯可能会杀死小型水生生物，使植物脱水甚至死亡，改变道路附近的土壤构成，限制保持湖泊健康的水循环。
All that salt is also corrosive to metal,wreaking havoc on infrastructure.And oh yeah, your wheels too.
这些盐还会腐蚀金属，对基础设施造成严重破坏。是的，你的车轮也会受到损坏。
For these reasons, sand is used as an abrasive for an alternative.
由于这些原因，沙子有时作为研磨料也用来替代盐。
Sand is often used because it’s cheap and maybe cuz folks want to avoid the chloride issues.
通常用沙子是因为比较便宜，也可能是为了避免氯产生的问题。
The thing is, salts have a chemical advantage: because you get 2 or more ions when they dissolve,you get way more melting power for the same handful of deicer.
问题是，盐有着化学方面的优势：因为盐融化的时候会分解为两个或更多离子，同样的一把除冰剂，盐的融冰能力更强。
So sand might be cheap, but you have to use way more of the stuff, and that can leave quite the mess.
所以，沙子或许便宜，但是必须使用更多，可能会导致路面乱七八糟。
Now for super cold temperatures,sodium chloride in sand won’t do the job.Some alternatives that melt ice better include Magnesium Chloride, Calcium Chloride,Potassium Chloride, and Potassium acetate.
对于特别寒冷的温度，沙子中的氯化钠不能发挥作用。一些可以更好地融冰的替代品包括氯化镁，氯化钙，氯化钾和乙酸钾。
Potassium acetate is particularly incredible at deicing because it works at temperatures as low as -75 degree Celsius, while the rest of the bunch work around the -20 degree mark.
乙酸钾的除冰能力非常强，因为在低至零下75摄氏度的气温也能发挥作用。而其他几种只能在零下20度的温度下工作。
Although these alternative chemicals are better at deicing at lower temperatures, most of them have that environment damaging Chloride too,not to mention that they cost way more than that table salt.
尽管这些替代化学品可以在更低的温度下除冰，然而，大部分都会产生对环境有害的氯离子，更不要提其成本远远高于食盐。
And if you’re buying 20 million tons a year of the stuff… well,that’s a lot of money!
而如果你每年要购买2000吨，那要多少钱啊！
So people, keep your eyes on the road, and thank salt for the fine driving conditions.
所以，伙计们，多关注一下路况，多亏盐改善了驾驶环境。
Or, on the other hand, you can shake your fist at it, if you didn’t get that snow day you know you DESERVE.
另一方面，你也可以挥拳庆祝，如果寒冬没有迎来大雪。
