評論
打印
Dr. Dolhun had hydrogen peroxide in the plastic bottle
Dolhun博士的塑料瓶中裝有過氧化氫
Then he added a catalyst, some manganese dioxide
然后他加入了一種催化劑，二氧化錳
or Mn02
也就是MnO2
and got plume of water vapor
最后瓶中噴出一縷蒸汽
So let's talk about how catalyst works
我們來談談催化劑是如何工作的
I'm going to draw a potential energy diagram for this reaction
我將為該反應畫一個勢能圖
So here's my potential energy diagram
這是我的勢能圖
So we have potential energy on the y-axis
勢能位于縱軸上
and the reaction coordinate or time on the x-axis
而反應坐標，或者說時間，位于橫軸上
Reactants are starting at this amount of energy
反應物最開始有這么多能量
and the products have this amount
而產物有這么多能量
Here Ea, that's the activation energy
這里Ea表示活化能
It's the amount of energy you need to add to the reactants
需要給反應物提供這么多能量
to make the reaction go
反應才會發生
And ΔH
而ΔH
that's the amount of energy that's released when the reaction happens
是反應發生時所釋放出來能量的量
Now let's see what happens when I add a catalyst
再看看加入催化劑時會怎樣
With a catalyst, my activation energy is a lot lower
使用催化劑時，活化能大幅降低
And even a small reduction in activation energy
哪怕活化能只降低少許
can make the reaction go thousands of times faster than it normally would
反應也能比通常情況下快數千倍
but notice that regardless of whether or not you have a catalyst
但要注意，不管加不加催化劑
the ΔH, the amount of energy released in the reaction, doesn't change
反應中所釋放能量的量ΔH是不會變化的
So the catalyst only speeds up the reaction
催化劑只加速反應速度
It doesn't change the amount of energy released
不會改變所釋放能量的量
Now take a look at this
看看這個
Notice the size of the bottles
注意瓶子的大小
These are very exothermic reactions
這些是放熱很多的反應
The bottle basically shrunk down to a very very tiny size
同對照組的瓶子比起來，
compared to the control bottles
瓶子縮小了很多
So as you can see, the catalyzed reaction releases so much heat
可以看到，催化反應釋放了很多熱量
that it actually melt the bottles and makes them smaller
讓瓶子開始熔化，變小
Also the catalyst itself remains unchanged by the reaction
另外，催化劑本身在反應中不會變化
and designing catalyst is actually a key subfield of chemistry
而設計催化劑也是化學中的一個重要領域
MIT's Richard Schrock
MIT的理查德·施羅克
won the Nobel Prize working in this field
就因在該領域中的研究獲得過諾貝爾獎
And remember how we used H2O2 on our cuts?
還記得將H2O2涂到傷口的情況嗎
Well, we have an enzyme in our bodies called catalase
我們人體內有一種酶叫過氧化氫酶
that does the same thing as the manganese dioxide that Dr. Dolhun used
其作用同Dolhun博士所使用的二氧化錳相同
That's why when you put hydrogen peroxide on a cut
因此將過氧化氫涂到傷口上時
you see fizzing and bubbles
會產生嘶嘶聲和泡泡
The catalase in your blood is breaking down the hydrogen peroxide
這表示血液中的過氧化氫酶正在分解過氧化氫
And according to recent studies
根據最新研究
low levels of catalase may play a role in the greying process of human hair
低過氧化氫酶水平在頭發變白過程中扮演了重要角色
If catalase levels are low
過氧化氫酶水平偏低時
it can't break down all the hydrogen peroxide in the blood
血液中的過氧化氫就不能被完全分解
and that extra H2O2 starts to bleach your hair from the inside out
殘留的H2O2會從內部將頭發漂白
So to wrap up, catalyst don't change the products of the reaction
總結一下，催化劑不會改變反應的產物
or how much heat is released or absorbed
也不會改變反應釋放或吸收的熱量
They only change the time it takes for the reaction to finish
催化劑只會改變反應完成所需的時間
Alright that's it for me today
今天就到這里
I'll see you next time
我們下次再見
