Homogeneous And Heterogeneous托福听力原文翻译及问题答案
2024-04-03 18:32:52 来源：中国教育在线
Homogeneous And Heterogeneous托福听力原文翻译及问题答案
一、Homogeneous And Heterogeneous 托福听力原文：
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 托福听力中文翻译：
旁白：在化学课上听一节课的一部分。
男教授：所以，总而言之，物质是任何有质量和体积的东西，对吗？任何占据空间的东西，包括固体、液体和气体。如果我们把两部分物质结合在一起，我们就得到了混合物。
现在，主要有两种混合物：均相和非均相。呃，也许我应该把这个写在黑板上。无论混合物是均质的还是非均质的，这都与“相”的概念有关。
记住，我们将“相”定义为一种物理状态，无论是固态、液态还是气态，都有明显的边界和统一的性质。
那么，均质混合物是什么？
好的，前缀homo的意思是“相同”，所以均质混合物在整个过程中都是相同的；它只包含一个阶段。因此，如果你把酒精放在水中，这两种液体会结合，它们会相互分散，你再也看不到两者之间的界限了。所以混合物只包含一个相，即使有两个相进入其中，它现在包含一个相，一旦水和酒精混合在一起，我们就无法检测到它们之间的任何边界；这两部分结合形成单相。
现在，如果均匀的混合物是整个过程都相同的，那么你认为不均匀的混合物是什么？正当不同的混合物。
如果你把油和水混合在一起，混合物包含两个液相，因为油的密度较低，油会浮在水面上。它们不会像酒精和水那样混合在一起。你可以看到它们之间的边界，事实上它们在机械上是可分离的。
土壤也是如此，它是固体材料的混合物。所以如果你仔细观察土壤样本，你会看到一些沙子，一些黑色物质，甚至可能是一些植被。因为你可以看到所有不同的组件，检测不同的边界，我们有多个阶段；事实上，你可以挑选出组件，不同的部分可以机械地分开。
现在，对于一些非均质混合物，你可以用肉眼看到不同的相。
但并非所有人都是如此……就像烟一样。事实上，这是一个很好的例子，因为在肉眼看来它是均匀的，就像是单相。但是如果你放大它，你可以看到空气中悬浮着微小的固体和液体颗粒。事实上，烟雾中含有三相固体、液体和气体，可以通过过滤过程将其分离。
另一个例子，呃，脏水。好啊
脏水是含有悬浮固体物质的水。也可以对其进行过滤。通过一个过滤器，灰尘和其他任何东西都会留在滤纸上，干净的水也会通过。同样，根据水中粒子的大小，你可能需要放大才能看到它们，但即使这样，它们也可以被检测到，边界是可检测的，所以多个相位，好吗？
另一方面，均质混合物，无论放大多少，都无法显示组分之间的可检测边界。混合一直延伸到基本粒子水平。我们用“溶液”一词来指这些单相均匀混合物。。。
当盐溶解在水中时，再大的放大倍数也无法显示出盐的各个部分，盐和水之间没有可检测的边界，所以它是一种溶液。
即便如此，你能用溶液做的就是通过一种叫做蒸馏的过程来分离零件。如果你蒸馏盐水，水就会从溶液中煮开，只剩下盐。在你的下一个实验室，实际上，我们将使用这些过程，蒸馏和过滤，来展示我们如何分离一些混合物的不同部分。
现在，我们还有其他方法可以描述混合物，其中之一是通过性质，呃，可变性质。
一杯咖啡的味道和颜色就是一个很简单的例子。在水中溶解的咖啡越多，咖啡的味道越浓，颜色越深，溶液越深。所以颜色和味道，这是两个可变的属性。当然，由于组分的相对含量以及液体的熔点或冰点，这些可变性质也会有所不同。例如，盐水溶液的冰点会有所不同，这取决于水中溶解的盐量。
三、Homogeneous And Heterogeneous 托福听力问题：
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:正确答案：A
A2:正确答案：BABB
A3:正确答案：C
A4:正确答案：B
A5:正确答案：D
A6:正确答案：C
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