This mole. Yep, this number has a second name.The mole. 这个摩尔，没错，这个常数有另一个名字,摩尔.

　　Chemists use the term mole to refer to the quantities that are at the magnitude of 602 sextillion. 化学家使用这个术语来表示602乘以10的21次方这个数量。

　　This is known as a molar quantity. 就是大家知道的摩尔常数。

　　Atoms and molecules are so small, that chemists have bundled them into groups called moles. 原子和分子太小了，所以化学家将它们分成一群一群的，每一群就叫做一摩尔。

　　Moles are hard for students to understand because they have a hard time picturing the size of a mole, or of 602 sextillion. 摩尔对于学生是很难了解的，因为他们很难想象一摩尔的数量，或是602乘以10的21次方。

　　It's just too big to wrap our brains around. 它实在大到大脑难以理解。

　　Remember our 18.01 milliliters of water? Well, that's a mole of water. 记得刚刚说的18.01毫升的水吗？那就是1摩尔的水。

　　But how much is that? 但是这有多少？

　　Exactly what does 602 sextillion look like? Maybe this'll help. 602乘以10的21次方看起来像什么？也许这个例子会有帮助。

　　Exchange the water particles for donuts. 用甜甜圈来代替水分子。

　　If you had a mole of donuts, they would cover the entire earth to a depth of eight kilometers, which is about five miles. 假如你有1摩尔的甜甜圈，它们会在整个地球表面堆高8公里，大约是5英里。

　　You really need a lot of coffee for that. 你需要很多咖啡来配。

　　If you had a mole of basketballs, you could create a new planet the size of the earth. 如果你有1摩尔的篮球，你可以制造和地球一样大的星球。

　　If you received a mole of pennies on the day you were born 如果你一出生时有1摩尔的钱，

　　and spent a million dollars a second until the day you died at the age of 100, 你每一秒花一百万直到100岁时死的那一天，

　　you would still have more than 99.99% of your money in the bank. 你还有99.99%以上的钱在银行里。

　　OK. Now we sort of have an idea how large the mole is. 好了，现在我们大概对1摩尔有个概念了。

　　So how do we use it? 那么我们如何用它？

　　You might be surprised to know that chemists use it the same way you use pounds to buy grapes, deli meat, or eggs. 你也许会惊讶化学家使用它的方法，就如同你用磅来买葡萄、熟食肉类或鸡蛋。

　　When you go to the grocery store, you don't go to the deli counter and ask for 43 slices of salami,  当你到杂货店时，你不会走到柜台要43片腊肠，

　　you buy your salami by the pound. 你会买几磅的腊肠。

　　When you buy your eggs, you buy a dozen eggs. 当你买鸡蛋时，你会买一打鸡蛋。

　　When we hear the word dozen, we probably think of the number 12. 当我们听到打这个字，我们会想到数字 12。

　　We also know that a pair is two, a baker's dozen is 13, a gross is 144, and a ream of paper is...anybody? 我们也知道一双就是2，面包师父的一打是13，一箩是144，一令纸......谁知道？

　　A ream is 500. Well, a mole is really the same thing. 一令纸是500张。一摩尔也是一样的。

　　For a chemist, a mole conjures up the number 6.02 times 10 to the 23rd, not a fuzzy little animal. 对化学家而言，1摩尔就是6.02乘以10的23次方，而不是毛绒绒的动物。

　　The only difference is that the other quantities are more famili ar to us. 唯一的差别是我们比较熟悉其他的计数单位。

　　So there you have it. The story of the mole, Avogadro, basketballs, and how to buy salami at the grocery store. 现在你知道了摩尔的故事、阿伏加德罗、篮球、还有去杂货店怎么买腊肠了。