评论
打印
Hi, I'm Jessic
嗨 我是Jessica
And today, I'm going to be talking about a chemical demonstration
今天我要讲的化学演示
I like to call "Money to Burn"
叫作"烧钱"
and chemist Dr. Bassam Shakhashir
化学家Bassam Shakhashiri博士
here he is
这就是他
is actually going to be showing us the dem
将为我们进行这个演示
He's the president of the American Chemical Societ
他是美国化学学会主席
and is performing this demo right here at MIT
他在我们MIT进行了这个演示
Let's see if he has some money to bur
看看他是怎么烧钱的
What I'm going to do now i
下面我将
I'm going to reach in here, I'm going to take a dollar bil
从钱包里拿出一张美钞
and I'm going to put it into flame just like that
像这样把它放到火焰里
Was that too fast?
这是否太快了
What we always do in science is repeat the experiment
在科学里 我们总喜欢重复实验
So I think although it looks like a dollar bill
它虽然看起来像美钞
it's not a real dollar bill
但不是真正的美钞
I bring it close to the flame
我让它靠近火焰
It disappears into thin air. It looks like magic, right?
它瞬间消失掉了 这很像魔术 不是吗
I love magi
我很爱魔术
Magic is engaging
魔术很迷人
but not informativ
但说明不了问题
How is that dollar bill burning up so quickly?
那张美钞是如何快速燃烧掉的
Well, it's actually not a dollar bil
实际上 它不是一张美钞
It's called flash pape
而是一张闪光纸
And it's paper that has been treated with chemical
这种纸用化学药剂处理过
to make it burn quickly and leave no ashes
让它能够快速燃烧 而且不留灰烬
Now flash paper has been nitrate
闪光纸被硝化过
Practically what that means is tha
实际也就是
you soak the paper in a mixture of concentrated nitric and sulfuric acid
将纸张浸入到浓的硝酸硫酸混合物中
The cellulose in the paper then reacts with the aci
纸张中的纤维素会同酸反应
to produce nitrated cellulose and wate
生成硝化纤维素和水
The reaction is this
反应是这样的
So our nitric acid her
这是硝酸
mixes with the cellulose
同纤维素反应
Now this is actually just one unit in the big polymer that is cellulos
这其实只是纤维素大聚合物中的一个单元
It's got lots of little units of C6H10O5
纤维素包括很多单元
So in this equation, I'm only writing one unit
而这个方程中 我只写了一个单元
And that's creating nitrated cellulose and wate
这会生成硝化纤维素和水
Now the nitro group, the NO2, is the reactive grou
硝基NO2是活性基团
and it can be very reactive depending on the molecule that it's in
在有些分子中时 它的活性会非常高
You've no doubt heard of nitroglycerin
你们肯定听说过硝酸甘油
which looks like thi
它是这样的
It's an explosive liquid
它是一种爆炸性液体
Or TNT
还有TNT
which actually stands for trinitrotoluene
全称是三硝基甲苯
It looks like thi
它是这样的
So all of these molecules have nitro group in them
所有这些分子中都有硝基
And it's the nitro or NO2 groups that make these molecules explosiv
正是硝基NO2让这些分子具有爆炸性
Now let's watch what happens when Dr. Shakhashiri tries this again
下面再来看Shakhashiri博士的第二次尝试
but this time with a real dollar bil
不过这次 他将用到真正的美钞
I'd like someone in the audience to
我想问某位观众
let me borrow from them a real one dollar bill
借一张真正的一美元钞票
Is there someone in the audience who would let me
在座各位谁愿意
who would trust me with a real one dollar bill?
借一张一美元钞票给我吗
Or a five-dollar bill
五美元钞票也行
Steve, how about a twenty-dollar bill, ha? Steve
有二十美元钞票吗
You've got a twenty-dollar bill?
有二十美元钞票吗
Okay, here's one-dollar bill
好的 一美元钞票
It's a real one dolla
货真价实
but you don't know what I'm going to do with it, don't you?
你不知道我会拿它做什么
