Practice these TOEFL iBT listening tests to help you score high in the TOEFL Listening Section. Check the correct answers and audio transcripts below. This video is in the series of NEW TOEFL iBT Preparation: https://www.youtube.com/playlist?list=PL2jvSGmpWX1UMjbc8Onae7i-R6Z8VcPbU.
Questions 6 through 11. Listen to a discussion by some students taking a chemistry class.
(woman 1) I hope you’re ready to discuss the chapter on carbon in our chemistry text. We’re going to be having a quiz on this chapter later today.
(man) I think the main point of the chapter is that carbon is unique because of how many compounds it can form. I believe the chapter said there are more than seven million compounds that contain carbon.
(woman 2) Yeah, that’s right. More than seven million carbon compounds are now known, and there’re only 100,000 compounds made from all the other elements. That's because the carbon atom attaches easily with other carbon atoms and with many other kinds of atoms.
(woman 1) I think that we need to become familiar with some of the better-known carbon compounds. The chapter discusses a few of them. Ah, I remember that it discusses graphite and gasoline, and some others.
(man) It discusses graphite and gasoline, as well as soap and diamonds.
(woman 2) You know, graphite and gasoline seem like they’re made from carbon, but it really seems strange that soap and diamonds are also derived from carbon. . . . Let’s look at graphite first. What does the chapter say about graphite?
(woman 1) Graphite is made only of carbon. Look at the diagram of a graphite molecule in the text. It has rings of six carbon atoms each, and two. of the carbon atoms are part of each ring.
(man) Isn't graphite what’s found in pencils?
(woman 1) Yes. Graphite is the primary component of the lead in pencils.
(woman 2) Um, the next carbon compound is gasoline.
(woman 2) Look at the gasoline molecule in the book. The carbon atoms in this molecule are in a chain rather than in rings, as they were in the graphite molecule.
(man) And, unlike the graphite molecule, which was made only of carbon, the gasoline molecule is a compound of carbon and hydrogen.
(woman 1) This gasoline molecule is a molecule of octane because it contains a chain of eight carbon atoms, and octane means eight. The chapter says that different types of gasoline molecules each contain a chain of, uh, between five and ten carbon atoms.
(man) Now on to the soap molecule. I really didn’t know that soap contained carbon.
(woman 2) Yeah, it does seem strange to think that soap contains carbon, but it does.. . . Now, what about the soap molecule?
(woman 1) There doesn't seem to be a picture of a soap molecule in the text. Oh but the text does say that the soap molecule has a long chain of carbon atoms, a much longer chain than the gasoline atom.
(man) The text says that soap atoms can have anywhere between five and seven carbon atoms in a chain.
(woman 2) Um, are you sure it says five to seven? It’s supposed to be a long chain of carbon atoms, and five to seven doesn't seem right.
(man) Oh, here it is. Excuse me. You really do seem to have a good grasp of the material. The book doesn't say five to seven, it says 15 to 17.
(woman 1) Let me get this straight. A soap molecule has 15 to 17 carbon atoms in a chain, not five to seven.
(woman 2) You got it!
(man) Sorry for the confusion. . . .
(woman 2) It’s OK. All right, now that we understand this, that makes three of the types of carbon molecules we have to deal with, so there’s only one more. The last example of a carbon molecule is diamond. Oh, here’s the diagram of a diamond molecule.
(woman 1) This diamond molecule consists only of carbon, and the carbon atoms are arranged in a very complex pattern.
Oh, that’s what helps to make diamond harder than any other natural substance.
(man) OK. I think we've got all the necessary information on carbon and a few of the many compounds that’re formed from it. In graphite, the carbon was in rings, while in octane and soap, it was in long chains. And in diamond, it was in a very complex pattern.
(woman 2) And graphite and diamond molecules are formed solely from carbon, while gasoline and soap are compounds of carbon atoms and other types of atoms.
(woman 1) I think we’re ready for the quiz today. See you at our next study session, the day after tomorrow.
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Correct Answers:
6. A
7. Has rings of 6 carbon atoms each: Graphite
Has a chain of 8 carbon atoms: Octane
Has a chain of 15-17 atoms: Soap
Has a complex pattern of carbon atoms: Diamond
8. B & C
9. C
10. D
11. A
