Homogeneous And Heterogeneous托福聽力原文翻譯及問題答案

Homogeneous And Heterogeneous托福聽力原文翻譯及問題答案

一、Homogeneous And Heterogeneous 托福聽力原文：

NARRATOR: Listen to part of a lecture in a chemistry class.

MALE PROFESSOR: So, just to sum up, matter is anything that has mass and volume, right? Anything that takes up space—and this includes solids, liquids and gases.And if we combine two portions of matter, we get a mixture.

Now, there are two main kinds of mixtures: homogeneous and heterogeneous. Uh maybe I should put this on the board. Whether a mixture is homogeneous or heterogeneous, well, this relates to the notion of “phase”.

Remember, we defined the word “phase” as being one physical state, whether solid, liquid or gas, that, well, that has distinct boundaries and uniform properties.

So, homogeneous mixtures, what are they?

OK, the prefix homo means “same”, so a homogeneous mixture is the same throughout; it contains only one phase. So if you put alcohol in water, the two liquids combine, they disperse into each other, and you can't perceive any boundary between the two any longer. So the mixture contains only one phase—even though two phases went into it—it now contains one phase and we can't detect any boundary between the water and the alcohol once they're mixed together; the two portions combine to form a single phase.

Now, if homogeneous mixtures are ones that are the same throughout, then what do you suppose heterogeneous mixtures are? Right. Mixtures that are different throughout.

If you mix oil and water together, the mixture contains two liquid phases because the oil will float on top of the water because of oil's lower density. They're not going to mix together like alcohol and water do. You can see the boundary between them, and in fact they’re mechanically separable.

The same is true for soil, which is a mixture of solid materials. So if you look closely at a sample of soil, you're gonna see bits of sand, some black matter, maybe even pieces of vegetation. Since you can see all the different components, detect distinct boundaries, we've got multiple phases; and in fact you can pick out the components, the various portions can be mechanically separated.

Now, with some heterogeneous mixtures you can see the different phases with the naked eye.

But that's not so for all of them… like smoke. Actually, that's a good example, because to the naked eye it looks uniform, like it's a single phase. But if you magnify it, you can see that there are tiny solid and liquid particles suspended in the air. So actually, what you’ve got in smoke are three, three phases—solid, liquid and gas, which you can separate by the process of filtration.

Another example, uh dirty water. Ok?

Dirty water is water that has suspended solid matter in it. That can be filtered too. Pass it through a filter and the dirt and whatever else is in there will stay behind on the filter paper, and the clean water will pass through it. Again, depending on the size of the particles in the water, you might need magnification to see them, but even so, they can be detected, the boundaries are detectable, so multiple phases, ok?

Homogeneous mixtures, on the other hand, well, no amount of magnification could reveal a detectable boundary between the components. The mixing extends all the way to the fundamental particle level. And we use the term “solution” to refer to these single phase, homogeneous mixtures...

When salt’s dissolved in water, no amount of magnification is going to show you separate pieces of salt, there are no detectable boundaries between salt and water—so it's a solution.

Even so, what you can do with solutions is separate the parts by a process called distillation. If you distill salt water, water gets boiled away from the solution, and only the salt remains behind. And in your next lab, actually, we'll be using these processes, distillation and filtration, to show how we can separate the different parts of some mixtures.

Now, there are other ways that we can describe mixtures, and one of these is by properties, uh, variable properties.

A real simple example of this is the taste and color of a cup of coffee. The more coffee that's dissolved in the water, the stronger the taste of the coffee, and the darker the color—the darker the solution. So color and taste, these are two variable properties. And these variable properties, they vary of course, because of the relative amounts of the components and the melting or freezing points of liquids, too. A solution of salt water, for example, will have a different freezing point depending on how much salt is dissolved in the water.

二、Homogeneous And Heterogeneous 托福聽力中文翻譯：

旁白：在化學課上聽一節(jié)課的一部分。

男教授：所以，總而言之，物質是任何有質量和體積的東西，對嗎？任何占據(jù)空間的東西，包括固體、液體和氣體。如果我們把兩部分物質結合在一起，我們就得到了混合物。

現(xiàn)在，主要有兩種混合物：均相和非均相。呃，也許我應該把這個寫在黑板上。無論混合物是均質的還是非均質的，這都與“相”的概念有關。

記住，我們將“相”定義為一種物理狀態(tài)，無論是固態(tài)、液態(tài)還是氣態(tài)，都有明顯的邊界和統(tǒng)一的性質。

那么，均質混合物是什么？

好的，前綴homo的意思是“相同”，所以均質混合物在整個過程中都是相同的；它只包含一個階段。因此，如果你把酒精放在水中，這兩種液體會結合，它們會相互分散，你再也看不到兩者之間的界限了。所以混合物只包含一個相，即使有兩個相進入其中，它現(xiàn)在包含一個相，一旦水和酒精混合在一起，我們就無法檢測到它們之間的任何邊界；這兩部分結合形成單相。

現(xiàn)在，如果均勻的混合物是整個過程都相同的，那么你認為不均勻的混合物是什么？正當不同的混合物。

如果你把油和水混合在一起，混合物包含兩個液相，因為油的密度較低，油會浮在水面上。它們不會像酒精和水那樣混合在一起。你可以看到它們之間的邊界，事實上它們在機械上是可分離的。

土壤也是如此，它是固體材料的混合物。所以如果你仔細觀察土壤樣本，你會看到一些沙子，一些黑色物質，甚至可能是一些植被。因為你可以看到所有不同的組件，檢測不同的邊界，我們有多個階段；事實上，你可以挑選出組件，不同的部分可以機械地分開。

現(xiàn)在，對于一些非均質混合物，你可以用肉眼看到不同的相。

但并非所有人都是如此……就像煙一樣。事實上，這是一個很好的例子，因為在肉眼看來它是均勻的，就像是單相。但是如果你放大它，你可以看到空氣中懸浮著微小的固體和液體顆粒。事實上，煙霧中含有三相固體、液體和氣體，可以通過過濾過程將其分離。

另一個例子，呃，臟水。好啊

臟水是含有懸浮固體物質的水。也可以對其進行過濾。通過一個過濾器，灰塵和其他任何東西都會留在濾紙上，干凈的水也會通過。同樣，根據(jù)水中粒子的大小，你可能需要放大才能看到它們，但即使這樣，它們也可以被檢測到，邊界是可檢測的，所以多個相位，好嗎？

另一方面，均質混合物，無論放大多少，都無法顯示組分之間的可檢測邊界?；旌弦恢毖由斓交玖Ｗ铀?。我們用“溶液”一詞來指這些單相均勻混合物。。。

當鹽溶解在水中時，再大的放大倍數(shù)也無法顯示出鹽的各個部分，鹽和水之間沒有可檢測的邊界，所以它是一種溶液。

即便如此，你能用溶液做的就是通過一種叫做蒸餾的過程來分離零件。如果你蒸餾鹽水，水就會從溶液中煮開，只剩下鹽。在你的下一個實驗室，實際上，我們將使用這些過程，蒸餾和過濾，來展示我們如何分離一些混合物的不同部分。

現(xiàn)在，我們還有其他方法可以描述混合物，其中之一是通過性質，呃，可變性質。

一杯咖啡的味道和顏色就是一個很簡單的例子。在水中溶解的咖啡越多，咖啡的味道越濃，顏色越深，溶液越深。所以顏色和味道，這是兩個可變的屬性。當然，由于組分的相對含量以及液體的熔點或冰點，這些可變性質也會有所不同。例如，鹽水溶液的冰點會有所不同，這取決于水中溶解的鹽量。

三、Homogeneous And Heterogeneous 托福聽力問題：

Q1:1.What does the professor mainly discuss?

A. Characteristics of different types of mixtures?

B. Differences between mixtures and solutions

C. Ways of separating components of mixtures

D. Identifying variable properties of solutions

Q2:2.In the lecture, the professor gives examples of homogeneous and heterogeneous mixtures. For each mixture below, indicate which kind it is.

Homogeneous

Heterogeneous

Dirty water

Salt water

Smoke

Soil

Q3:What is one basis for classifying a mixture as homogeneous or heterogeneous?

A. Whether its component parts are the same type of matter

B. Whether its component parts are present in equal proportions

C. Whether it contains one phase or more than one phase

D. Whether it appears, without magnification, to contain a single component

Q4:4.What can be inferred from the lecture about the process of distillation?

A. It cannot be used if a mixture has variable properties.

B. It can be used to separate the components of homogeneous mixtures.

C. It is used to change heterogeneous mixtures Into homogeneous mixtures.

D. It is a more efficient way of separating components of heterogeneous mixtures than filtration.

Q5:5.Why does the professor mention the freezing point of a mixture?

A. To explain why salt dissolves in water

B. To emphasize that mixtures can exist in a frozen state

C. To show how filtration and distillation differ

D. To give an example of a variable property of mixtures

Q6:6.What does the professor imply when he says this: (PROFESSOR) Then what do you suppose heterogeneous mixtures are?

A. He wants to correct a statement he made previously.

B. He is uncertain whether the students understood his explanation.

C. The meaning of a term should be obvious to the students.

D. The students are probably unaware that they have already seen examples of heterogeneous mixtures.

四、Homogeneous And Heterogeneous

A1:正確答案：A

A2:正確答案：BABB

A3:正確答案：C

A4:正確答案：B

A5:正確答案：D

A6:正確答案：C

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