Why don't oil and water mix? - John Pollard

爲何水油不相溶？- John Pollard

譯者: Wenbo Li 審譯者: Regina Chu

Why does salt dissolve in water but oil doesn't?

為什麼鹽會溶於水，但是油卻沒辦法？

Well, in a word, chemistry,

簡單來說，「化學」，

but that's not very satisfying, is it?

但是這個答案並不能滿足你，是吧？

Well, the reason salt dissolves and oil does not

基本上，鹽會溶化但是油不會，

comes down to the two big reasons

跟世間萬物發生的

why anything happens at all:

兩大理由一樣：

energetics

力能學

and entropy.

和熵（失序现象）。

Energetics deals primarily

力能學主要是説

with the attractive forces between things.

物體之間相互的吸引力。

When we look at oil or salt in water,

當我們看著在水中的鹽或是油，

we focus on the forces between particles

我們要在一個 非常非常非常微小的比例裡

on a very, very, very small scale,

在分子的程度下，

the molecular level.

注意粒子之間互相的作用力。

To give you a sense of this scale,

讓你瞭解這個規模到底有多大，

in one glass of water,

一杯水所含有的

there are more molecules

分子數量遠多於

than known stars in the universe.

星空中我們所知道的星星。

Now, all of these molecules are in constant motion,

現在，這些分子全部都持續的在運動，

moving, vibrating, and rotating.

移動，震動，還有旋轉。

What prevents almost all of those molecules

靠著所有分子之間相互的吸引力，

from just flying out of the glass

才能避免這些分子

are the attractive interactions between molecules.

從杯子裡面飛走。

The strength of the interactions

在水本身

between water, itself, and other substances

以及與其他物質之間相互作用的力量，

is what we mean when we say energetics.

就是我們所稱的力能學。

You can think of the water molecules engaging

你可以想像水分子之間，

in a constant dance,

一起持續的跳舞，

sort of like a square dance

像是在跳方塊舞一樣，

where they constantly and randomly exchange partners.

他們持續並隨機的交換舞伴。

Put simply, the ability for substances

簡單來說，物質與水

to interact with water,

交互作用的能力，

balanced with how they disrupt

與物質如何破壞

how water interacts with itself,

水本身如何交互作用達到平衡

plays an important role in explaining

在解釋為何有些東西會溶於水，

why certain things mix well into water

而有些卻無法溶於水的原理中，

and others don't.

起到了重要的作用。

Entropy basically describes

失序現象基本上概括了

the way things and energy can be arranged

物體跟能量可以依照

based on random motion.

隨機的運動被組合。

For example, think of the air in a room.

拿一間房間裡的空氣做例子。

Imagine all the different possible arrangements

在一個有上兆個粒子的空間裡，

in space for the trillions of particles

想像所有不同的可能組合排列，

that make up the air.

這些組成了空氣。

Some of those arrangments

有些的排列，

might have all the oxygen molecules over here

可能氧分子全放在了這裡，

and all the nitrogen molecules over there,

然後全部的氮分子放在那裡，

separated.

全分開的。

But far more of the possible arrangements

但是更有可能出現的組合是，

have those molecules mixed up with one another.

把這些分子都混合在一起。

So, entropy favors mixing.

所以失序現象熱衷於混合組合。

Energetics deals with attractive forces.

力能學講的是吸引力。

And so, if attractive forces are present,

所以，如果有吸引力的話

the probability of some arrangements

有一些組合方式

can be enhanced,

組成機率就會提高，

the ones where things are attracted to each other.

因爲他們都相互吸引。

So, it is always the balance of these two things

所以説總是由這兩個現象（力能學、失序現象）

that determines what happens.

決定了會發生什麽。

On the molecular level,

在分子的層面上，

water is comprised of water molecules,

水是由水分子組成的，

made up of two hydrogen atoms and an oxygen atom.

由兩個氫原子和一個氧原子組成

As liquid water, these molecules are engaged

水在液體狀態下，分子會

in a constant and random square dance

持續的，隨機的跳“方塊舞”，

that is called the hydrogen bonding network.

這個被叫做『氫鍵作用』。

Entropy favors keeping

失序現象這個『DJ』熱衷於

the square dance going at all times.

持續地開這場方塊舞舞會。

There are always more ways

因爲水分子類似

that all the water molecules can arrange

方塊舞舞會的分子組合方式

in a square dance,

會要比

as compared to if the water molecules

排舞組合方式

did a line dance.

組合可能性要多。

So, the square dance constantly goes on.

所以，水分子們一直持續 開這個方塊舞舞會。

So, what happens when you put salt in the water?

那麽，如果你把鹽放入水裏會怎麽樣？

Well, on the molecular level,

在分子的層面上來説，

salt is actually made up of two different ions,

鹽是由兩個不同的離子——

chlorine and sodium,

氯和鈉,

that are organized like a brick wall.

組成的一個類似墻磚似的組成。

They show up to the dance

他們也成群結隊的

as a big group in formation

參加了舞會

and sit on the side at first,

剛開始祇是坐在一旁，

shy and a bit reluctant to break apart

不好意思，也不願意與小伙伴們分開

into individual ions to join the dance.

以獨立自主的『離子』身份去參加舞會。

But secretly, those shy dancers

但是慢慢的，那些不好意思的鹽們，

just want someone to ask them to join.

祇想有人可以邀請他們一起去跳舞。

So, when a water randomly bumps into one of them

所以，當一個水分子 隨意的觸碰到了他們，

and pulls them into the dance away from their group,

然後把他們從小伙伴身邊拉開， 拉去跳舞的時候，

they go.

他們就跟著水走了。

And once they go into the dance,

祇要他們跟著去一起跳舞，

they don't come back out.

他們就再也不會回去。

And in fact, the addition of the salt ions

實際上，這些新來的鹽離子們，

adds more possible dance positions

爲方塊舞增加了

in the square dance,

更多的空間

so it is favored for them to stay dancing with water.

所以鹽離子們來跳方塊舞是受到歡迎的。

Now, let's take oil.

現在，咱們再來説説油。

With oil, the molecules are sort of interested

對油來説他們的分子是想

in dancing with water,

和水一起跳舞的，

so entropy favors them joining the dance.

所以分子想要分散著去參加舞會。

The problem is that oil molecules

但問題是油分子

are wearing gigantic ballgowns,

穿著大禮服

and they're way bigger than water molecules.

而且身材還比水分子大好多。

So, when an oil molecule gets pulled in,

所以當油分子參加舞會的時候，

their size is really disruptive to the dance

他們的體積破壞了整個舞會

and the random exchange of partners

以及水分子們參加的

that the waters engage in,

整臺舞會非常重要的

a very important part of the dance.

『隨機換舞伴』活動，

In addition, they are not great dancers.

再加上，油分子們跳的也不好

The water molecules try to engage

水分子們試圖讓

the oil molecules in the dance,

油分子們參加舞會

but they just keep bumping into their dresses

但是他們總是會被 油分子的禮服裙撞倒，

and taking up all the room on the dance floor.

然後霸占整個舞會。

There are way more ways the waters can dance

如果油分子們離開舞會

when the oil gets off the floor,

水分子們能跳的更好，

so the waters squeeze out the oil,

所以水分子們就把油分子們趕出了舞會

pushing it back to the bench with the others.

將油分子和他的伙伴們趕到臺下

Pretty soon, when a large number of oils

過了一會，一大堆油分子

have been squeezed over to the side,

就被趕了下去

they band together to commiserate

他們搭伴在一起抗議

about how unfair the waters are being

水分子們是多麽的不公平

and stick together as a group.

水分子們是多麽的不公平

So, it is this combination

就是這種分子之間

of the interactions between molecules

互相作用的組合

and the configurations available to them

以及他們在移動時

when they're moving randomly

自己的構造

that dictates whether they mix.

決定了他們相溶或不相溶。

In other words, water and oil don't mix

換句話來講，水和油之間的不相溶

because they just don't make great dance partners.

就是他們不是互相的好舞伴！