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  • Sitting around a campfire, you can feel its heat,

    圍坐著營火,你可以感受到熱度、

  • smell the woody smoke, and hear it crackle.

    木頭的煙燻味以及劈啪作響的聲音。

  • If you get too close,

    如果你靠得太近,

  • it burns your eyes and stings your nostrils.

    會灼傷眼睛而且刺激鼻子。

  • You could stare at the bright flames forever

    你可以一直盯著明亮的火焰,

  • as they twist and flicker in endless incarnations.

    因為它們處於無盡的扭動和閃耀狀態

  • But what exactly are you looking at?

    但你真正看到的是什麼?

  • The flames are obviously not solid,

    火焰很明顯地不是固體,

  • nor are they liquid.

    也不是液體。

  • Mingling with the air, they're more like a gas,

    和空氣混合,火焰更像是氣體,

  • but more visible--and more fleeting.

    但是火焰更可見也更迅速。

  • And on a scientific level, fire differs from gas

    從科學層面上來看,火焰不同於氣體,

  • because gases can exist in the same state indefinitely

    因為氣體可以無限期地處於同一種狀態,

  • while fires always burn out eventually.

    但是火焰終會燃燒殆盡。

  • One misconception is that fire is a plasma,

    有種誤解認為火是等離子體,

  • the fourth state of matter in which atoms

    物質的第四種狀態,

  • are stripped of their electrons.

    也就是原子失去電子的狀態。

  • Like fire and unlike the other kinds of matter,

    和火一樣而與其他物質不同的是,

  • plasmas don't exist in a stable state on earth.

    等離子體不以固定的狀態存在。

  • They only form when gas is exposed to an electric field or superheated

    當氣體暴露於電場之中,

  • to temperatures of thousands or tens of thousands of degrees.

    或者溫度高達數千萬度時,它們才會形成。

  • By contrast, fuels like wood and paper burn

    相較之下,木頭和紙張燃燒的溫度

  • at a few hundred degreesfar below the

    只有幾百度,遠低於

  • threshold of what's usually considered a plasma.

    等離子體的溫度門檻。

  • So if fire isn't a solid, liquid, gas,

    那麼,如果火焰不是固體、液體、氣體

  • or a plasma, what does that leave?

    或等離子體,那還能是什麼?

  • It turns out fire isn't actually matter at all.

    其實,火焰根本不是物質。

  • Instead, it's our sensory experience of a

    它是對於燃燒化學反應的

  • chemical reaction called combustion.

    一種感官體驗。

  • In a way, fire is like the leaves changing color in fall,

    某種程度上,火焰就像秋天變色的樹葉、

  • the smell of fruit as it ripens,

    水果成熟時的味道

  • or a firefly's blinking light.

    或是螢火蟲的閃光。

  • All of these are sensory clues that a

    這些都是發生化學反應時的

  • chemical reaction is taking place.

    感官線索。

  • What differs about fire is that it engages a lot of

    火焰較不同的地方在於,它同時

  • our senses at the same time, creating the kind of vivid

    牽涉到很多感覺,進而形成一種

  • experience we expect to come from a physical thing.

    從實體事物中才能獲得的生動體驗。

  • Combustion creates that sensory experience

    燃燒反應利用燃料、熱度和氧氣

  • using fuel, heat, and oxygen.

    來創造出感官體驗。

  • In a campfire, when the logs are heated to their ignition temperature,

    營火中,當木頭被加熱到燃燒溫度時,

  • the walls of their cells decompose,

    它們的細胞壁會分解,

  • releasing sugars and other molecules into the air.

    釋放糖及其他分子到空氣中。

  • These molecules then react with airborne oxygen

    這些分子和空氣中的氧氣發生作用,

  • to create carbon dioxide and water.

    產生二氧化碳和水。

  • At the same time, any trapped water in the logs

    同時,木頭中的水份會

  • vaporizes, expands, ruptures the wood around it,

    蒸發、膨脹並使木頭裂開,

  • and escapes with a satisfying crackle.

    發出劈啪的聲響。

  • As the fire heats up, the carbon dioxide and water vapor

    當火焰溫度升高,燃燒反應產生的二氧化碳

  • created by combustion expand.

    及水蒸氣會膨脹。

  • Now that they're less dense, they rise in a thinning column.

    密度降低後,它們會呈薄柱狀上升。

  • Gravity causes this expansion and rising, which gives

    重力使得火焰膨脹及上升,

  • flames their characteristic taper.

    進而使其呈現特有的錐型。

  • Without gravity, molecules don't separate

    沒有重力的話,分子不會因為

  • by density and the flames have a totally different shape.

    密度而分離,火焰的形狀也會完全不同。

  • We can see all of this because combustion

    我們可以看到這一切是因為

  • also generates light.

    燃燒反應也會產生光。

  • Molecules emit light when heated,

    分子受熱時會發光,

  • and the color of the light depends

    而光的顏色取決於

  • on the temperature of the molecules.

    分子的溫度。

  • The hottest flames are white or blue.

    溫度最高的火焰是白色或藍色。

  • The type of molecules in a fire can

    火焰中的分子類型

  • also influence flame color.

    也會影響火焰的顏色。

  • For instance, any unreacted carbon atoms from the logs

    例如,木頭上未反應的碳原子會

  • form little clumps of soot that rise

    形成小團的煤灰飄到

  • into the flames and emit the yellow-orange

    火焰中,發出我們會聯想到營火的,

  • light we associate with a campfire.

    橘黃色的光。

  • Substances like copper, calcium chloride,

    像銅、氯化鈣和氯化鉀這些物質,

  • and potassium chloride can add their

    能夠在混和物中

  • own characteristic hues to the mix.

    加入自己獨有的色調。

  • Besides colorful flames,

    除了五顏六色的火焰,

  • fire also continues to generate heat as it burns.

    火焰在燃燒時也會持續產生熱能。

  • This heat sustains the flames by keeping

    熱能靠著保持燃料的溫度

  • the fuel at or above ignition temperature.

    等於或高於燃點,來維持火焰。

  • Eventually, though, even the hottest fires

    但最終,即使是溫度最高的火焰,

  • run out of fuel or oxygen.

    也會耗盡燃料或氧氣。

  • Then, those twisting flames give a final hiss

    然後,這些扭曲的火焰發出最後的嘶嘶聲,

  • and disappear with a wisp of smoke

    隨著一縷煙消失,

  • as if they were never there at all.

    彷彿從未存在過。

Sitting around a campfire, you can feel its heat,

圍坐著營火,你可以感受到熱度、

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B2 中高級 中文 美國腔 TED-Ed 火焰 溫度 燃燒 木頭 離子體

【TED-Ed】火是固體嗎?還是液體或氣體?(Is fire a solid, a liquid, or a gas? - Elizabeth Cox)

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    Samuel 發佈於 2018 年 11 月 08 日
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