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  • There's a concept that's crucial to chemistry and physics.

    在化學和物理學中有個關鍵概念

  • It helps explain why physical processes go one way and not the other:

    有助於解釋是此非彼的物理現象

  • why ice melts,

    冰為什麼會融化?

  • why cream spreads in coffee,

    奶油為什麼會在咖啡裡散開來?

  • why air leaks out of a punctured tire.

    為什麼穿了孔的輪胎會漏氣?

  • It's entropy, and it's notoriously difficult to wrap our heads around.

    這是「熵」的概念,非常難以理解

  • Entropy is often described as a measurement of disorder.

    有個說法常把熵 用來衡量不規則的程度

  • That's a convenient image, but it's unfortunately misleading.

    雖然合宜,卻很容易誤導

  • For example, which is more disordered -

    例如,下列哪種情形比較不規則呢?

  • a cup of crushed ice or a glass of room temperature water?

    一杯碎冰,還是一杯室溫的水?

  • Most people would say the ice,

    大多數人認為冰比較不規則

  • but that actually has lower entropy.

    但實際上冰的熵值比水低

  • So here's another way of thinking about it through probability.

    另一種理解熵的方法是透過機率

  • This may be trickier to understand, but take the time to internalize it

    雖或不易理解,但請耐心內化

  • and you'll have a much better understanding of entropy.

    就會更理解熵

  • Consider two small solids

    想像兩小塊固體

  • which are comprised of six atomic bonds each.

    各自有六根原子鍵

  • In this model, the energy in each solid is stored in the bonds.

    這模型裡的能量存在固體的原子鍵裡

  • Those can be thought of as simple containers,

    可以把原子鍵想成簡單的能量容器

  • which can hold indivisible units of energy known as quanta.

    裡面裝著不可分割的 能量單位「量子」

  • The more energy a solid has, the hotter it is.

    固體的能量越高就越熱

  • It turns out that there are numerous ways that the energy can be distributed

    這兩個固體

  • in the two solids

    有許許多多的能量分佈方式

  • and still have the same total energy in each.

    而各自的總能量不變

  • Each of these options is called a microstate.

    每一種能量分佈方式稱為一「微態」

  • For six quanta of energy in Solid A and two in Solid B,

    假如固體甲有六個量子,而乙有兩個

  • there are 9,702 microstates.

    那麼就共有 9,702 種微態

  • Of course, there are other ways our eight quanta of energy can be arranged.

    當然還有其它分派八個量子的方式

  • For example, all of the energy could be in Solid A and none in B,

    例如,固體甲擁有八個量子 而固體乙一個也沒有

  • or half in A and half in B.

    或者甲乙各分一半

  • If we assume that each microstate is equally likely,

    如果假設每種微態發生的機率相等

  • we can see that some of the energy configurations

    就會看到某些能量分佈狀態

  • have a higher probability of occurring than others.

    發生的機率高過其他狀態

  • That's due to their greater number of microstates.

    原因是它們的微態總數比較多

  • Entropy is a direct measure of each energy configuration's probability.

    熵直接衡量每種能量分佈狀態的機率

  • What we see is that the energy configuration

    呈現出的是

  • in which the energy is most spread out between the solids

    這兩個固體的能量最分散的時候

  • has the highest entropy.

    熵值最高

  • So in a general sense,

    一般而言

  • entropy can be thought of as a measurement of this energy spread.

    可把熵想成是能量散佈的指標

  • Low entropy means the energy is concentrated.

    低熵值代表能量集中

  • High entropy means it's spread out.

    而高熵值代表能量分散

  • To see why entropy is useful for explaining spontaneous processes,

    為要理解怎樣用熵解釋自發過程

  • like hot objects cooling down,

    像是熱的物體冷卻下來

  • we need to look at a dynamic system where the energy moves.

    必須看能量的動態流動

  • In reality, energy doesn't stay put.

    實際上,能量並非靜止不動

  • It continuously moves between neighboring bonds.

    而是持續在相鄰的原子鍵中移動

  • As the energy moves,

    隨著能量移動

  • the energy configuration can change.

    能量的分佈跟著改變

  • Because of the distribution of microstates,

    根據微態的分佈

  • there's a 21% chance that the system will later be in the configuration

    有 21% 的機率

  • in which the energy is maximally spread out,

    後來會進入能量最分散的狀態

  • there's a 13% chance that it will return to its starting point,

    有 13% 的機率回到初始狀態

  • and an 8% chance that A will actually gain energy.

    還有 8% 的機率 固體甲會增加能量

  • Again, we see that because there are more ways to have dispersed energy

    再次重申,因為分散能量

  • and high entropy than concentrated energy,

    高熵值的微態總數 比能量集中的還多

  • the energy tends to spread out.

    因而能量趨向分散

  • That's why if you put a hot object next to a cold one,

    這就是為什麼把熱的物體 和冷的物體擺一起

  • the cold one will warm up and the hot one will cool down.

    冷的會變熱,而熱的會變冷

  • But even in that example,

    但是同一個例子

  • there is an 8% chance that the hot object would get hotter.

    也有 8% 的機率 熱的物體會變得更熱

  • Why doesn't this ever happen in real life?

    為什麼現實生活裡沒發生這種情形?

  • It's all about the size of the system.

    原因在於系統的規模

  • Our hypothetical solids only had six bonds each.

    我們的模型假設 只有六根原子鍵的固體

  • Let's scale the solids up to 6,000 bonds and 8,000 units of energy,

    如果增加到 6,000 根原子鍵 和 8,000 個單位能量

  • and again start the system with three-quarters of the energy in A

    初始狀態仍是甲有四分之三的能量

  • and one-quarter in B.

    而乙有四分之一的能量

  • Now we find that chance of A spontaneously acquiring more energy

    就會發現甲自發獲得更多能量的機率

  • is this tiny number.

    是個這麽微小的數字

  • Familiar, everyday objects have many, many times more particles than this.

    日常熟知物體的粒子數遠比這多得多

  • The chance of a hot object in the real world getting hotter

    所以現實世界裡 熱的物體變得更熱的機率

  • is so absurdly small,

    小得荒謬

  • it just never happens.

    乃至根本不會發生

  • Ice melts,

    冰塊融化

  • cream mixes in,

    奶油和咖啡混合在一起

  • and tires deflate

    輪胎放氣

  • because these states have more dispersed energy than the originals.

    都是因為這些狀態的能量 比原先狀態的更分散

  • There's no mysterious force nudging the system towards higher entropy.

    並不是某種神秘的力量 驅使系統傾向微調至更高的熵值

  • It's just that higher entropy is always statistically more likely.

    而是因為統計上高熵值更可能發生

  • That's why entropy has been called time's arrow.

    這就是為什麼熵又被稱為時間之箭

  • If energy has the opportunity to spread out, it will.

    如果有機會分散能量,就會分散能量

There's a concept that's crucial to chemistry and physics.

在化學和物理學中有個關鍵概念

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B1 中級 中文 美國腔 TED-Ed 能量 固體 機率 狀態 物體

【TED-Ed】什麼是熵?- 傑夫-菲利普斯 (【TED-Ed】What is entropy? - Jeff Phillips)

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    IS LIU 發佈於 2021 年 01 月 14 日
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