托福tpo52聽力lecture3 Snowflakes and Ozone

托福tpo52聽力lecture3 Snowflakes and Ozone，那么接下來就跟著中國教育在線的小編詳細了解一下吧。

Snowflakes and Ozone托福聽力原文翻譯及問題答案

一、Snowflakes and Ozone托福聽力原文：

NARRATOR:Listen to part of a lecture in a chemistry class.MALE PROFESSOR:OK,so today we're going to talk about the Arctic,ozone depletion,and…snowflakes. And it’s all related!Let’s start with snowflakes.Now,I find snowflakes fascinating.To even begin to understand them,you need to understand physics,chemistry,and mathematics.Even though there's been a lot of research,there's still actually a lot about snowflakes that we don't understand yet—hard to believe,I know…

Anyway,snowflakes have a particular form:there’s a six-sided center,with six branches or arms that radiate out from it.But how do they get that way?Well,you start with water vapor—you need a pretty humid atmosphere—and that water vapor condenses directly into ice,into an ice crystal.At this point it looks kind of like a thin dinner plate that,rather than being circular,is hexagonal,with six flat edges.It's at this point in the process where we begin to see why each snowflake is unique.Imagine this dinner plate is floating around in the wind,right,and when it encounters water vapor,molecules from that vapor attach to each of the six sides.You begin to see the development of six arms or branches radiating out from the center plate.Each time the snowflake encounters water vapor,more molecules attach to it,leading to more and more complex structures—and,of course,each snowflake takes a unique route through the clouds,on its way down…and so the quantity of water vapor it goes through is gonna be unique for each one.

Now,one important characteristic of snowflakes is that they have something called a quasi-liquid layer—the QLL.Our snowflake is an ice crystal,right?Well,we find a quasi-liquid layer on the surface of ice.It's basically a thin layer of water that's not completely frozen—and it exists at temperatures well below freezing,though the thickness varies at different temperatures.Now this quasi-liquid layer,it plays an important role in what we're going to talk about next…—

uh,…yes,Mary?FEMALE STUDENT:How can liquid exist below freezing?Why doesn't it freeze?MALE PROFESSOR:Well…when water becomes ice,the molecules bond together and they get sort of,uh,locked into place.They can't move around as much anymore.So each molecule is surrounded by other molecules,and they're all locked together.But what about the exterior of the ice?There's a layer of water molecules on the surface…they're attached to molecules only on one side,so they're a bit freer…they can move around a bit more.Think of a,think of a…brick wall.Uh,the bricks in the wall,they have other bricks above and below them,and they're all locked against each other.But that top layer,it only has a layer below it.Now…this can only be taken so far…because of course,bricks don't move at all—they’re not liquid.But if the bricks were water molecules,well,this top layer would be the quasi-liquid layer,and it wouldn't be completely frozen.Does that make sense?So finally,we get to the connection between snowflakes and ozone.Ozone is a gas found in the atmosphere of Earth.Now,there's the ozone found in the stratosphere,which is the layer of the atmosphere from 6 to 30 miles above the Earth.This is considered“good”ozone,which occurs naturally and helps block harmful radiation from the Sun.

But there is also ground-level ozone.It's exactly the same gas,but it's found closer to the surface of the Earth.This ground-level ozone results from human activities,and at high concentrations it can be a pollutant.Now,snowflakes'quasi-liquid layer plays an important role in some complex chemical reactions—we're going to be looking at these in detail later today.But basically,these reactions cause certain chemicals to be released,and these chemicals reduce the amount of ground-level ozone.So…the more branches you have in an ice crystal,the more quasi-liquid layer there is.The more quasi-liquid layer,the more reactions…and the more chemicals that reduce ground level ozone.So you can see why this is such an important system to study and understand.

二、Snowflakes and Ozone托福聽力中文翻譯：

旁白：聽一堂化學課的部分講座。梅爾教授：好的，所以今天我們要討論北極、臭氧消耗和……雪花；這一切都是相關的！讓我們從雪花開始。現在，我發(fā)現雪花很迷人。要開始理解它們，你需要理解物理、化學和數學。盡管已經有了很多研究，但實際上仍然有很多關于雪花的東西我們還不了解，但我知道，很難相信…

無論如何，雪花有一種特殊的形狀：有一個六邊形的中心，有六個分支或臂從它向外輻射。但它們是如何做到這一點的呢？好吧，從水蒸氣開始，你需要一個相當潮濕的大氣，水蒸氣直接凝結成冰，變成冰晶。在這一點上，它看起來有點像一個薄的餐盤，不是圓形的，而是六角形的，有六個平邊。在這個過程中，我們開始了解為什么每一片雪花都是獨一無二的。想象一下這個餐盤在風中飄浮，對吧，當它遇到水蒸氣時，來自水蒸氣的分子會附著在六個面上。你開始看到從中心板向外輻射的六個臂或分支的發(fā)展。每一次雪花遇到水蒸氣，就會有更多的分子附著在雪花上，導致越來越復雜的結構，當然，每一片雪花都有一條獨特的路線穿過云層，向下……因此，它穿過的水蒸氣量對每一片來說都是獨一無二的。

現在，雪花的一個重要特征是它們有一種叫做準液體層的東西——QLL。我們的雪花是冰晶，對吧？我們在冰的表面發(fā)現了一個準液體層。它基本上是一層薄薄的水，沒有完全凍結，存在于遠低于冰點的溫度下，盡管厚度在不同的溫度下有所不同?，F在這個準液體層，在我們接下來要討論的內容中扮演著重要的角色-

呃……是的，瑪麗？女學生：液體在冰點以下如何存在？為什么它不結冰？男教授：嗯……當水變成冰時，分子會結合在一起，然后它們會，呃，鎖定在某個位置。他們再也不能到處走動了。所以每個分子都被其他分子包圍，它們都被鎖在一起。但是冰的表面呢？表面有一層水分子……它們只附著在分子的一側，所以它們有點自由……它們可以更多地移動。想想，想想…磚墻。呃，墻上的磚塊，上面和下面都有其他磚塊，它們都相互鎖著。但最上面的一層，下面只有一層?，F在……這只能走這么遠……因為當然，磚根本不會移動，它們不是液體。但如果這些磚塊是水分子，那么頂層將是準液體層，并且不會完全凍結。這有意義嗎？最后，我們來看看雪花和臭氧之間的聯系。臭氧是一種存在于地球大氣層中的氣體?，F在，在平流層中發(fā)現了臭氧，平流層是地球上方6至30英里處的大氣層。這被認為是“好的”臭氧，它是自然產生的，有助于阻擋來自太陽的有害輻射。

但也有地面臭氧。它是完全相同的氣體，但發(fā)現它離地球表面更近。這種地面臭氧源于人類活動，在高濃度下，它可能是一種污染物。現在，雪花的準液體層在一些復雜的化學反應中扮演著重要角色——我們將在今天晚些時候詳細討論這些。但基本上，這些反應會導致某些化學物質釋放，這些化學物質會減少地面臭氧的數量。所以……冰晶中的分支越多，準液體層就越多。準液體層越多，反應就越多……減少地面臭氧的化學物質也越多。所以你可以明白為什么這是一個需要學習和理解的重要系統(tǒng)。

三、Snowflakes and Ozone托福聽力問題：

Q1:1.What aspects of snowflakes does the professor mainly discuss?[Click on 2 answers]

A.How they develop into complex structures

B.How they are affected by the presence of ozone

C.The challenges researchers face in studying them

D.The function of their quasi-liquid layer

Q2:2.What does the professor say about the role of water vapor in snowflake formation?

A.Too much water vapor prevents the initial"dinner plate"from forming.

B.Water vapor's role in snowflake formation is not completely understood.

C.Water vapor molecules in snowflakes attract ice particles from the air.

D.Water vapor is necessary for snowflakes to be able to form branches.

Q3:3.What factor helps explain why no two snowflakes are alike?

A.They all freeze at different rates.

B.They all form in slightly different air temperatures.

C.They all begin with a different number of water molecules.

D.They all follow different paths through clouds.

Q4:4.How do molecules in the quasi-liquid layer differ from those in other parts of the snowflake?

A.They are not held in place as tightly as other molecules.

B.They react with ozone to keep the layer from completely freezing.

C.They prevent ice crystals from forming additional branches.

D.They are thinner than other molecules.

Q5:5.What does the professor imply about ice crystals with a large number of branches?

A.They help block harmful radiation from the Sun.

B.They form as a result of complex reactions with ozone.

C.They contribute to a reduction in ground-level ozone.

D.They have a thinner quasi-liquid layer than ice crystals with fewer branches.

6.What can be inferred about the professor when he says this:

A.He doubts that the students have understood his explanation.

B.He does not think that bricks are an ideal illustration of his point.

C.He is not sure that the information he has just given is accurate.

D.He thinks that the similarities between liquid and bricks are surprising.

四、Snowflakes and Ozone托福聽力答案：

A1:正確答案：AD

A2:正確答案：D

A3:正確答案：D

A4:正確答案：A

A5:正確答案：C

A6:正確答案：B

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