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  • Water is the liquid of life.

    水是生命的液體。

  • We drink it,

    我們喝它,

  • we bathe in it,

    我們用它來洗澡,

  • we farm,

    來耕種,

  • cook,

    煮飯,

  • and clean with it.

    也用它來清理。

  • It's the most abundant molecule in our bodies.

    它是我們身體內最主要的分子成分。

  • In fact, every life form we know of

    事實上,我們所知道的所有生命體,

  • would die without it.

    如果沒有它都會死去。

  • But most importantly, without water,

    但最重要的是,如果沒有水分,

  • we wouldn't have

    我們不會有

  • iced tea.

    冰茶。

  • Mmmm, iced tea.

    嗯,冰茶。

  • Why do these ice cubes float?

    為什麼這些冰塊會漂浮?

  • If these were cubes of solid argon

    如果這些是塊狀的固體氬,

  • in a cup of liquid argon,

    在一杯液狀的氬當中,

  • they would sink.

    它們會沈下去。

  • And the same goes for most other substances.

    同樣的狀況也會發生在其他的物質身上。

  • But solid water, a.k.a. ice,

    但是固體的水,也就是冰塊,

  • is somehow less dense than liquid water.

    因為某種原因,密度就是比液體的水小。

  • How's that possible?

    這怎麼有可能呢?

  • You already know that every water molecule

    你已經知道每一個水分子

  • is made up of two hydrogen atoms

    都是由兩個氫原子

  • bonded to one oxygen atom.

    和一個氧原子組成的。

  • Let's look at a few of the molecules

    讓我們來看看在一滴水裡面的

  • in a drop of water,

    一些分子,

  • and let's say the temperature is 25 degrees Celcius.

    讓我們假設在攝氏 25 度的溫度下,

  • The molecules are bending,

    這些分子在彎曲,

  • stretching,

    在伸展,

  • spinning,

    在旋轉,

  • and moving through space.

    也在空間中移動。

  • Now, let's lower the temperature,

    現在,讓我們把溫度降下來,

  • which will reduce the amount of kinetic energy

    這會降低每一個分子

  • each of these molecules has

    所含有的動能,

  • so they'll bend, stretch, spin, and move less.

    所以它們將會減少彎曲、 伸展、旋轉和移動的程度。

  • And that means that on average,

    一般來說這就表示

  • they'll take up less space.

    它們會佔用比較小的空間。

  • Now, you'd think that as the liquid water

    現在,你會想到就像是液態的水

  • starts to freeze,

    開始凝結,

  • the molecules would just pack together

    分子會開始擠在一起,

  • more and more closely,

    越來越靠近,

  • but that's not what happens.

    但是這並不是實際上發生的狀況。

  • Water has a special kind

    水有一種很特別的

  • of interaction between molecules

    原子間交互影響作用,

  • that most other substances don't have,

    是大部份其他物質所沒有的,

  • and it's called a hydrogen bond.

    它叫做氫鍵 (Hydrogen bond)。

  • Now, remember that in a covalent bond

    現在,記得在共價鍵(Covalent bond)裡,

  • two electrons are shared,

    會共用兩個電子,

  • usually unequally,

    通常原子之間對電子

  • between atoms.

    是不均等共用。

  • In a hydrogen bond,

    但在氫鍵的情況下,

  • a hydrogen atom is shared, also unequally,

    原子間會共用一個氫原子,

  • between atoms.

    一樣也是在不均等的狀況下。

  • One hydrogen bond looks like this.

    一個氫鍵長得像這樣,

  • Two look like this.

    兩個長得像這樣。

  • Here's three

    這樣是三個,

  • and four

    再來是四個,

  • and five,

    然後是五個,

  • six,

    六個,

  • seven,

    七個,

  • eight,

    八個,

  • nine,

    九個,

  • ten,

    十個,

  • eleven,

    十一個,

  • twelve,

    十二個,

  • I could go on.

    我可以繼續下去。

  • In a single drop of water,

    在一滴水裡面,

  • hydrogen bonds form extended networks

    氫鍵形成延伸的網絡,

  • between hundreds, thousands, millions,

    由數百個,數千個,數百萬個,

  • billions, trillions of molecules,

    數十億個,數兆個分子所組成,

  • and these bonds are constantly breaking and reforming.

    而且這些連結鍵持續的斷裂與重組。

  • Now, back to our water as it cools down.

    現在,回到我們冷卻的水。

  • Above 4 degrees Celcius,

    當溫度在攝氏4度以上時,

  • the kinetic energy of the water molecules

    水分子的動能

  • keeps their interactions with each other short.

    會使它們之間的交互作用時間短暫。

  • Hydrogen bonds form and break

    氫鍵會連結然後斷裂,

  • like high school relationships,

    就像是高中時的感情關係,

  • that is to say, quickly.

    像是大家說的,都很短暫。

  • But below 4 degrees,

    但是當溫度降到 4 度以下,

  • the kinetic energy of the water molecules

    水分子的動能

  • starts to fall below the energy

    開始降到低於

  • of the hydrogen bonds.

    氫鍵的動能。

  • So, hydrogen bonds form much more frequently

    這樣一來,氫鍵建立的頻率

  • than they break

    會高於它們斷裂的頻率,

  • and beautiful structures start to emerge

    這個時候從一團混亂之中,

  • from the chaos.

    一個美麗的架構開始出現。

  • This is what solid water, ice,

    這就是固態的水 - 冰,

  • looks like on the molecular level.

    從分子組合的角度來看,

  • Notice that the ordered, hexagonal structure

    注意那些有秩序的六角形,

  • is less dense than the disordered structure

    比起液態水的無秩序結構

  • of liquid water.

    來得鬆散。

  • And you know that if an object is less dense

    你知道如果一個物體的密度低於

  • than the fluid it's in,

    液體的密度,

  • it will float.

    它會浮起來。

  • So, ice floats on water,

    所以冰塊會浮在水裡。

  • so what?

    那又如何?

  • Well, let's consider a world without floating ice.

    那讓我們來想想 一個沒有漂浮冰塊的世界。

  • The coldest part of the ocean

    這樣一來,海洋最寒冷的部分

  • would be the pitch-black ocean floor,

    就會在漆黑海底,

  • once frozen, always frozen.

    一旦結凍,永遠凍結。

  • Forget lobster rolls

    別再想龍蝦捲,

  • since crustaceans would lose their habitats,

    因為甲殼類動物會失去牠們的棲息地,

  • or sushi since kelp forests wouldn't grow.

    也不用想吃壽司,因為海草也長不出來。

  • What would Canadian kids do in winter

    當沒有了結冰池塘曲棍球和冰釣,

  • without pond hockey or ice fishing?

    加拿大小孩冬天能夠做什麼?

  • And forget James Cameron's Oscar

    我們也可以忘記 詹姆士卡麥隆贏得的奧斯卡獎,

  • because the Titanic totally would have made it.

    因為鐵達尼一定可以安然到達目的地。

  • Say goodbye to the white polar ice caps

    我們也要跟極地的白色冰帽說再見,

  • reflecting sunlight

    它們反射陽光,

  • that would otherwise bake the planet.

    不然地球就會被烤熟。

  • In fact, forget the oceans as we know them,

    實際上,我們可以忘掉我們知道的這些海洋,

  • which at over 70% of the Earth's surface area,

    它們覆蓋地球超過百分之七十的表面,

  • regulate the atmosphere of the whole planet.

    調節整個地球的氣候。

  • But worst of all,

    但最糟的是,

  • there would be no iced tea.

    我們就不會有冰茶了。

  • Mmmmm, iced tea.

    嗯,冰茶。

Water is the liquid of life.

水是生命的液體。

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B1 中級 中文 美國腔 TED-Ed 分子 冰塊 動能 斷裂 溫度

TED-Ed】為什麼冰會浮在水面上?- 喬治-扎伊丹和查爾斯-莫頓 (【TED-Ed】Why does ice float in water? - George Zaidan and Charles Morton)

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    Halu Hsieh 發佈於 2021 年 01 月 14 日
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