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全國(guó)英語(yǔ)六級(jí)考試聽(tīng)力摸底練習(xí)
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part 1
Salt vs. Ice
食鹽大戰(zhàn)冰塊
Y: Why does salt melt ice?
為什么食鹽能讓冰塊融化?
D: It lowers the melting and freezing point of water.
是因?yàn)槭雏}將水的熔點(diǎn)和冰點(diǎn)降低了。
Y: Oh,OK.Wait,I don't get it. Doesn't that mean the salt make ice colder?
等一下，我不明白。這就意味著食鹽讓冰的溫度變得更低嗎?
D: Let me explain.Pure water freezes at thirty-two degrees Fahrenheit,right? At that temperature we can say that the rate of freezing is the same as the rate of melting.
我解釋一下。純凈水的.冰點(diǎn)是32華氏度，對(duì)吧?這個(gè)溫度既是冰點(diǎn)也是熔點(diǎn)。
Y: So in other words, at water's freezing point there's a sort of equilibrium between freezing and melting.
也就是說(shuō)，水的冰點(diǎn)就是結(jié)冰和融化的平衡。
D: Right.Throwing salt on ice upsets the balance.
是的。在冰上灑鹽擾亂了這種平衡。
Y: Upsets it how?
怎么打亂的呢?
D: The salt dissolves into the liquid water, which means that some of the water molecules are replaced by salt. Since there are now fewer liquid water molecules to be captured and frozen by the ice, the rate of freezing drops.
鹽溶解在水中，就是說(shuō)一部分水分子被鹽取代了。既然結(jié)冰的液態(tài)水分子減少了，冰點(diǎn)自然降低了。
Y: I think I get it.And Since the rate of melting stays the same, there's more melting going on than freezing. And so the ice melts.
我明白了。水的熔點(diǎn)不變，融化的水分子比結(jié)冰的多，所以冰塊就融化了。
D: Right.
對(duì)。
Y: Interesting.
很有趣。
D: In fact, anything that dissolves in water will do the trick. You could pour sugar on ice and it willmelt. But I guess since salt is cheaper it's used more often.
其實(shí)，任何溶于水的物質(zhì)都可以使冰融化。把糖灑在冰上，冰也會(huì)融化。但是我想也許由于鹽比較便宜，所以經(jīng)常被使用。
part 2
The Biggest Magnet
最大的磁體
A: What's the biggest magnet ever?
究竟什么是最大的磁體?
B: Well, that's a great question. Well, for starters you'd have to mention whoppers like the hybrid magnet at the National High Magnetic Field Lab in Tallahassee, Florida.This magnet weighs thirty-four tons and stands twenty-two feet tall.Giant magnets in hospitals, physics labs, and other facilities help in cutting edge research. However, even a magnet the size of a building can't compete with a magnet the size of a planet.
嗯，問(wèn)得好。對(duì)于初學(xué)者來(lái)說(shuō)，不得不提一下那些龐然大物，比如佛羅里達(dá)塔拉哈西的國(guó)家高磁場(chǎng)實(shí)驗(yàn)室的混合磁體。這塊磁鐵重34噸，立起來(lái)有22英尺高。醫(yī)院，物理實(shí)驗(yàn)室和其他設(shè)備里的巨型磁體對(duì)尖端研究有幫助。然而，即使是一塊建筑物大小的磁體也不能和一塊行星大小的磁體相匹敵。
A: A magnet the size of a planet?
一塊行星大小的磁體?
B: The Earth itself is a magnet! Researchers think it's the effect of convection currents in our planet's molten interior that causes the entire Earth to behave as one gigantic magnet, with a North and South Pole.Whenever you look at a compass, what you're doing is reading the magnetic field of the planet on which you are standing.
地球本身就是一塊磁體。研究者們認(rèn)為，是地球內(nèi)部熔巖里對(duì)流流的作用使得整個(gè)地球像個(gè)擁有南北磁極的巨型磁體一樣運(yùn)轉(zhuǎn)。每當(dāng)你看著指南針的時(shí)候，你所做的.就是讀取你所在行星的磁場(chǎng)。
A: So that must be the biggest magnet than anywhere.
所以那就是最大的磁體咯。
B: Yet, even a magnet the size of a planet can't compete with a magnet the size of a star.
但是，即使是行星大小的磁體也不能和恒星大小的磁體相匹敵。
A: A star?
恒星?
B: what about the sun? The sun is a magnet. In this case, the magnetic field is probably generated by swirling plasma. Magnetic storms on the sun are powerful enough to have an effect on satellites and communication systems all the way here on Earth.
比如說(shuō)太陽(yáng)?太陽(yáng)是一塊磁體。假若這樣，磁場(chǎng)可能是由旋動(dòng)的等離子產(chǎn)生的。太陽(yáng)上的磁暴威力足夠強(qiáng)大，可以對(duì)人造衛(wèi)星和地球上通信系統(tǒng)的各個(gè)方面產(chǎn)生影響。
A: So is that?
那就是最大的了?
B: Not even close. There are things in space that put all of these magnets to shame.
還差得遠(yuǎn)呢。宇宙中還有更多讓這些磁體相形見(jiàn)絀的事物呢。
A: Super magnet in space? What are they?
宇宙中的超強(qiáng)磁體?是些什么呢?
B: Next time.
下次再說(shuō)吧。
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