托福tpo52听力lecture3 Snowflakes and Ozone

托福tpo52听力lecture3 Snowflakes and Ozone，那么接下来就跟着中国教育在线的小编详细了解一下吧。

Snowflakes and Ozone托福听力原文翻译及问题答案

一、Snowflakes and Ozone托福听力原文：

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托福听力中文翻译：

旁白：听一堂化学课的部分讲座。梅尔教授：好的，所以今天我们要讨论北极、臭氧消耗和……雪花；这一切都是相关的！让我们从雪花开始。现在，我发现雪花很迷人。要开始理解它们，你需要理解物理、化学和数学。尽管已经有了很多研究，但实际上仍然有很多关于雪花的东西我们还不了解，但我知道，很难相信…

无论如何，雪花有一种特殊的形状：有一个六边形的中心，有六个分支或臂从它向外辐射。但它们是如何做到这一点的呢？好吧，从水蒸气开始，你需要一个相当潮湿的大气，水蒸气直接凝结成冰，变成冰晶。在这一点上，它看起来有点像一个薄的餐盘，不是圆形的，而是六角形的，有六个平边。在这个过程中，我们开始了解为什么每一片雪花都是独一无二的。想象一下这个餐盘在风中飘浮，对吧，当它遇到水蒸气时，来自水蒸气的分子会附着在六个面上。你开始看到从中心板向外辐射的六个臂或分支的发展。每一次雪花遇到水蒸气，就会有更多的分子附着在雪花上，导致越来越复杂的结构，当然，每一片雪花都有一条独特的路线穿过云层，向下……因此，它穿过的水蒸气量对每一片来说都是独一无二的。

现在，雪花的一个重要特征是它们有一种叫做准液体层的东西——QLL。我们的雪花是冰晶，对吧？我们在冰的表面发现了一个准液体层。它基本上是一层薄薄的水，没有完全冻结，存在于远低于冰点的温度下，尽管厚度在不同的温度下有所不同。现在这个准液体层，在我们接下来要讨论的内容中扮演着重要的角色-

呃……是的，玛丽？女学生：液体在冰点以下如何存在？为什么它不结冰？男教授：嗯……当水变成冰时，分子会结合在一起，然后它们会，呃，锁定在某个位置。他们再也不能到处走动了。所以每个分子都被其他分子包围，它们都被锁在一起。但是冰的表面呢？表面有一层水分子……它们只附着在分子的一侧，所以它们有点自由……它们可以更多地移动。想想，想想…砖墙。呃，墙上的砖块，上面和下面都有其他砖块，它们都相互锁着。但最上面的一层，下面只有一层。现在……这只能走这么远……因为当然，砖根本不会移动，它们不是液体。但如果这些砖块是水分子，那么顶层将是准液体层，并且不会完全冻结。这有意义吗？最后，我们来看看雪花和臭氧之间的联系。臭氧是一种存在于地球大气层中的气体。现在，在平流层中发现了臭氧，平流层是地球上方6至30英里处的大气层。这被认为是“好的”臭氧，它是自然产生的，有助于阻挡来自太阳的有害辐射。

但也有地面臭氧。它是完全相同的气体，但发现它离地球表面更近。这种地面臭氧源于人类活动，在高浓度下，它可能是一种污染物。现在，雪花的准液体层在一些复杂的化学反应中扮演着重要角色——我们将在今天晚些时候详细讨论这些。但基本上，这些反应会导致某些化学物质释放，这些化学物质会减少地面臭氧的数量。所以……冰晶中的分支越多，准液体层就越多。准液体层越多，反应就越多……减少地面臭氧的化学物质也越多。所以你可以明白为什么这是一个需要学习和理解的重要系统。

三、Snowflakes and Ozone托福听力问题：

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托福听力答案：

A1:正确答案：AD

A2:正确答案：D

A3:正确答案：D

A4:正确答案：A

A5:正确答案：C

A6:正确答案：B