英語聽力文摘 無霜冷凍

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MP3下載

https://online2.tingclass.net/lesson/shi0529/0007/7643/254.mp3

https://image.tingclass.net/statics/js/2012

昇華是指一種物質從固態(tài)不經(jīng)過液態(tài)直接轉化為氣態(tài)的過程，是物質在溫度和氣壓低于三相點的時候發(fā)生的一種物態(tài)變化。與昇華相反的過程稱做凝華，指物質從氣態(tài)直接變成固態(tài)。這樣的例子有結霜。昇華是吸熱的反應，所需的熵是汽化熱和熔化熱之和。

Frost-free freeze physics--it's more than a tongue-twister(繞口令).

“Sublimation” is when ice turns into a gas without passing through the usual intermediary liquid state. If you leave your ice cubes in back of the freezer for a month or so, you might notice they start to shrink. That’s because they are sublimating: the ice is turning to water vapor even though it never melted.

But I tried this experiment myself and my ice cubes never shrunk! All I got was a cold head! Then, physicist John Carini explained to me that it only works if you have a frost-free freezer.

Why is that?It’s in the nature of sublimation. When we say that ice can turn into water vapor, what we mean is that (1)fast-moving water molecules can actually (2)fling themselves off the surface of the ice cube and into the surrounding air. That’s what evaporation means. The more molecules that can free themselves of the ice this way, the more the ice has turned into vapor.

But wait!In order to do that, the air around the ice cube can’t (3)be saturated with water already. If it is, there’s no room for more molecules and evaporation can’t take place. Frost-free freezers keep the air from becoming saturated so that it won’t freeze on the walls. But that also means ice-cubes can sublimate nonstop!

Notes:

(1)fast-moving adj.移動迅速的

Candy as a fast-moving consumer goods, products price is not high, still attracts the public consumption.

糖果作為快速消費品，公司產(chǎn)品單價也不高，仍然吸引著大眾消費。

(2)fling off發(fā)出;甩掉;挫敗

It's good to fling off heavy clothing now that spring is here.

春天來了，脫掉厚厚的棉衣是適時的。

(3)be saturated with 被…所飽和;充滿著

Permit this entire period of time to be saturated with BLUE LIGHT.

這段期間，讓藍色之光充滿你的整個存在。