What triggers a chemical reaction? - Kareem Jarrah

譯者: CHEN KaiWei 審譯者: Max Chern

You know how sometimes you go to bake a cake

你是否有這樣的經歷： 你要去烤蛋糕

but your bananas have all gone rotten,

但發現你的香蕉全腐爛了

your utensils have rusted,

你的餐具已經生鏽

you trip and pour all of your baking soda into the vinegar jug,

你被絆倒，將全部的 小蘇打攪拌倒入醋壺

and then your oven explodes?

然後你的烤箱爆炸

My friend, you and your chemical reactions have fallen victim to enthalpy and entropy

我的朋友，你和你的化學反應 已成了焓與熵的犧牲品

and, boy, are they forces to be reckoned with.

而且各位，這兩個 都是不可忽視的力量

Now, your reactants are all products.

現在，你的反應物都變成生成物

So, what are these "E" words, and what's their big idea?

所以這些E字頭單字到底是什麼？ 他們又有何意義？

Let's start with enthalpy,

讓我們從焓開始

an increase or decrease of energy during a chemical reaction.

它是化學反應過程中 能量的上升或下降

Every molecule has a certain amount of chemical potential energy

每一個分子都有一定量的化學位能

stored within the bonds between its atoms.

儲存在原子間的鍵上

Chemicals with more energy are less stable,

含能量越多的化學物質 就會越不穩定

and thus, more likely to react.

因此，比較容易產生反應

Let's visualize the energy flow in a reaction,

讓我們想像一下反應中的能量流動

the combustion of hydrogen and oxygen, by playing a round of crazy golf.

氫和氧的燃燒反應 就好像打了一場瘋狂的高爾夫

Our goal is to get a ball, the reactant, up a small rise

我們的目的就是把一個球 （即反應物）送上一個小坡

and down the other much steeper slope.

然後從另一個 更陡的斜坡下滑

Where the hill goes up, we need to add energy to the ball,

當球要上坡,我們需要在球增加能量

and where it goes down, the ball releases energy into its surroundings.

而當球要下滑時，球會釋放能量至四周

The hole represents the product, or result of the reaction.

球洞代表生成物 或是反應的結果

When the reaction period ends, the ball is inside the hole,

當反應過程結束 球就會進洞

and we have our product: water.

我們就會得到生成物：水

This, like when our oven exploded, is an exothermic reaction,

就像是我們的烤箱爆炸 這是一種放熱反應

meaning that the chemical's final energy is less than its starting energy,

意味著化學物最後的能量 比最初的能量還低

and the difference has been added to the surrounding environment

而他們之間的能量差 已釋放到周圍環境

as light and heat.

變成光及熱

We can also play out the opposite type of reaction,

我們也可以執行 另一種相反的反應

an endothermic reaction,

吸熱反應

where the final energy is greater than the starting energy.

它最後的能量會 比當初的能量還高

That's what we were trying to achieve by baking our cake.

那就是我們試圖 經由烤蛋糕達成的反應

The added heat from the oven would change the chemical structure

烤箱的熱能將會改變

of the proteins in the eggs and various compounds in the butter.

雞蛋內蛋白質和奶油中 各種成份的化學結構

So that's enthalpy.

這是焓

As you might suspect,

我們或許會疑惑

exothermic reactions are more likely to happen than endothermic ones

放熱反應為什麼 比吸熱較容易發生

because they require less energy to occur.

這是因為放熱反應 需要外加的能量比較少

But there's another independent factor that can make reactions happen:

另外還有一個獨立因子 也是可以讓化學反應發生的

entropy.

熵

Entropy measures a chemical's randomness.

熵是測量化學物的亂度

Here's an enormous pyramid of golf balls.

這裡有一個用高爾夫球 堆疊而成的巨大金字塔

Its ordered structure means it has low entropy.

它有條理的結構 意味著它有著較低的熵

However, when it collapses, we have chaos everywhere,

然而當它倒塌時到處混亂一片

balls bouncing high and wide.

球彈跳的高且廣

So much so that some even go over the hill.

多到有些球直接翻過了山坡

This shift to instability, or higher entropy,

這轉移成不穩定狀態 或是較高的熵

can allow reactions to happen.

能讓反應發生

As with the golf balls, in actual chemicals

如同高爾夫球在實際化學物

this transition from structure to disorder gets some reactants past the hump

這種從有次序到無次序的轉變 會使反應物越過山丘

and lets them start a reaction.

使它們產生反應

You can see both enthalpy and entropy at play

你可以看到焓和熵一起演出，

when you go to light a campfire to cook dinner.

在你點燃營火準備煮晚餐時。

Your match adds enough energy

你的火柴提供了足夠的能量

to activate the exothermic reaction of combustion,

啟動燃燒的放熱反應

converting the high-energy combustible material in the wood

進而轉化木頭中的 高能量可燃物質

to lower energy carbon dioxide and water.

成能量低的二氧化碳和水

Entropy also increases and helps the reaction along

熵也增加和幫助 整個反應持續進行

because the neat, organized log of wood

這是因為排列整齊 有條理的木頭

is now converted into randomly moving water vapor and carbon dioxide.

現在轉化為自由移動的 水蒸氣和二氧化碳

The energy shed by this exothermic reaction

這些放熱反應放出的能量

powers the endothermic reaction of cooking your dinner.

正好提供煮晚餐的吸熱反應熱能

Bon appétit!

現在你可以享用了!