[ 听力基础 ] 二

Posted 2023-03-08 we1less

1. What do the speakers mainly discuss?
A. Organic processes by which minerals are formed
B. Geometric arrangements of atoms in different crystals
C. Recent studies of mineral formation in magma
D. What minerals are and how they are formed

3. Why does the professor discuss the minerals diamond and graphite, which are both composed of carbon?
A. To illustrate that the crystalline structure is an important distinguishing feature of a mineral
B. To explain that the two minerals are far apart on Bowen's chart of mineral formation
C. To emphasize that both minerals are inorganic substances
D. To make the point that graphite contains more impurities than diamond does

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Professor: Okay, let's start with it's a naturally occurring solid substance. That means(对比) that it's not a liquid or a gas and it's formed by natural geologic processes, right? So diamond mined from the earth would fit this definition, but(转折) a synthetic diamond, that's been produced in a laboratory, wouldn't. Now, I am glad(态度) Julia said minerals are usually inorganic substances, because, well, organic substances, substances that are formed by living organisms, usually aren't considered to be minerals. There are some notable exceptions, like aragonite. Aragonite is a constituent of the shells of many sea creatures. They actually secrete aragonite. But(转折) aragonite can also be formed inorganically. And both(并列) organic and(并列) inorganic aragonite are considered to be minerals. Okay, what else can we add to our definition? Tom.

        geologic  adj. 地质（学）的，地质（学）上的

        mine  n. 矿井;矿;  v. (在某地)开矿，采矿;

        fit  v. 适合，合身;  adj. 健康的，健壮的;合适的  n. 适合，合身;

        definition  n. (尤指词典里的词或短语的)释义，解释;定义;清晰度

        synthetic  adj. (人工)合成的;人造的;综合(型)的  n. 合成物;

        inorganic  adj. 无生物的;无机的

        aragonite  n. 正交（斜方）晶体，文石；霰石

2. What does the professor point out about the mineral aragonite?
A. It has an unusual crystalline structure.
B. It is similar in its chemical composition to diamond.
C. It is a rare mineral.
D. It can be formed by an organic or an inorganic process.

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Professor: Now, let's go over how the process of mineral formation, that is to say, crystallization, begins. There are a few ways, but let's start with the two that are easiest to conceptualize. The one that's most familiar to our everyday lives... Let's say(举例) that you have a solution, a mixture of sodium ions and chloride ions in a container of water. Remember(强调), ions are simply charged atoms. Of course(让步对比), you all know what mineral has dissolved in water to give you that solution.

Woman: Table salt, sodium chloride.

Professor: Right! And obviously(强调) how could you make salt crystals form from the solution? 

Woman: Oh, right! You could just let the water evaporate and eventually(结果) you'd see salt crystals in the container.

Professor: Exactly! Many of us perform that simple experiment as kids. Now, chemically, what happens is, as the water evaporates, the concentration of sodium and chloride ions increases, until(结果) they come together and form salt crystals. 

Woman: Cool!

        go over  仔细检查;认真讨论;用心思考

        crystallization  n. 结晶（作用，过程）；结晶体；晶化;具体化；形象化

        conceptualize  vt. 构思;使形成观念;将…概念化(为…)

        Let's say  假设

        sodium  n. 钠

        ion  n. 离子

        chloride  n. 氯化物

        perform  v. 表演;执行;履行;演出;做;

4. The professor explains how salt crystals form from a solution. What assumption does he make about the students when he explains the process?

A. That the students would benefit from a laboratory demonstration on how salt crystals form

B. That the students have read conflicting material in the textbook on how salt crystals form

C. That some of the students may not know the chemical composition of salt crystals

D. That some of the students may have knowledge from past experimentation about how salt crystals form

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Professor: All right. Now, another way minerals form. Think about how ice forms from water. When water gets cold enough, it crystallizes to form ice, which a book tells us is a mineral. So here, crystallization takes place as a liquid cools down and becomes a solid. Well, essentially the same thing happens with volcanic magma, the extremely hot liquid that originates beneath Earth's crust. It's basically melted rock. As magma cools and begins to solidify, its chemical constituents begin to crystallize into minerals. However(转折), unlike water, which solidifies at a specific temperature, magma crystallizes across a temperature range of hundreds of degrees. Chemically, magma is a mixture of substances. Now, different substances will crystallize at different temperatures. So as magma cools, you'll get different minerals crystallizing out of it at different times.

Professor: We understand this process thanks to the work that a geologist named Norman Bowen did about a century ago. Bowen performed a lot of lab experiments to determine, at what point, different minerals crystallized, as magma cools. He discovered that the first mineral to crystallize is olivine, at a relatively high temperature, followed by a series of other minerals at successively lower temperatures, until finally, quartz will begin to crystallize at the lowest temperature. The order in which minerals crystallize is called Bowens reaction series. Any crystallization process that Bowen observed in his lab is close to what happens in nature. When we analyze igneous rocks, which are rocks formed by the solidification of magma, we find that their mineral composition corresponds to the composition predicted by Bowens experiments.

        takes place  发生;举行;进行;就位

        cool  adj. 凉的;凉爽的;凉快的;酷的; v.(使)变凉，冷却;冷静下来;

        essentially  adv. 本质上;根本上;基本上

        geologist  n. 地质学家

        igneous  adj. 火成的(尤指火山喷出的)

        correspond  vi. 相一致;符合;类似于;相当于;通信

5. The professor discusses situations in which the process of crystallization can begin. What are two situations that he mentions?
Click on 2 answers.
A. When the concentration of atoms in a solution rapidly decreases
B. When liquid evaporates from certain solutions
C. When the temperature of certain liquids drops below a specific point 
D. When high pressure forces certain atoms to bond together in a random arrangement

6. Why does the professor discuss Bowen's laboratory experiments?
A. To explain the basis of the scientific understanding of how minerals form in cooling magma
B. To point out that Bowen's experiments revealed little about igneous rocks
C. To demonstrate how different rates of evaporation affect mineral formation 
D. To argue that what Bowen observed in the laboratory is different from what happens in nature

        certain  adj. 肯定;确定;确实;确信;无疑;(不提及细节时用)某事，某人，某种;

        drop  v. (意外地)落下，掉下，变弱，降低，减少;

        arrangement  n. 安排;筹备;安排方式;布置;商定;

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