#25 - Concept Reference, Must Be True

[Administrator]

Complete Question Explanation
(See the complete passage discussion here: lsat/viewtopic.php?t=10866)

The correct answer choice is (B)

In the opening paragraph, the author refers to the persistent misconception that glass flows slowly like a very viscous liquid, which he attributes to the fact that glass lacks a fixed crystalline atomic structure (lines 6-10).

Answer choice (A): This is an Opposite Answer, as the atomic structure of glass is amorphous rather than crystalline.

Answer choice (B): This is the correct answer choice. As prephrased above, the author attributes the common misconception about glass to a misunderstanding of its amorphous atomic structure.

Answer choice (C): The passage does outline the differences in glass making between medieval and modern times, but the author makes no assertion that this fact is commonly misunderstood.

Answer choice (D): In the third paragraph, the author mentions that impurities may have affected the viscosity of medieval glass, but there is no mention of an erroneous assumption equating the transition temperatures of the two kinds of glass.

Answer choice (E): In the first paragraph, the author mentions that solid and liquid glass are thermodynamically dissimilar, so this is not an erroneous assumption.

[jmramon]

Hi,

I understand why B is correct, however I’m having trouble eliminating A despite the explanation above. Doesn’t lines 7-10 state “the confusion probably arose partly from a misunderstanding of the fact that the atoms in glass are not arranged in a fixed crystal structure” (the atomic structure of solid glass isn’t crystalline when people thought it was before) and lines 16-19 state that “cooled below the lower end of this range, molton glass retains an amorphous atomic structure” (meaning the atomic structure is amorphous)? I realize A incorrectly says that “the atomic structure of solid glass is crystalline rather than amorphous,” which is the opposite of what’s said in the lines listed above, but isn’t this question looking for an erroneous assumption? Please help, this passage was extremely confusing to me. Thanks!

[courtneybayon]

Hi,

I understand why B is correct, however I’m having trouble eliminating A despite the explanation above. Doesn’t lines 7-10 state “the confusion probably arose partly from a misunderstanding of the fact that the atoms in glass are not arranged in a fixed crystal structure” (the atomic structure of solid glass isn’t crystalline when people thought it was before) and lines 16-19 state that “cooled below the lower end of this range, molton glass retains an amorphous atomic structure” (meaning the atomic structure is amorphous)? I realize A incorrectly says that “the atomic structure of solid glass is crystalline rather than amorphous,” which is the opposite of what’s said in the lines listed above, but isn’t this question looking for an erroneous assumption? Please help, this passage was extremely confusing to me. Thanks!

Same. Can someone please explain why answer A is an opposite answer? I think I understand the aspect of it being opposite because it is opposite of the fact in that the atomic structure of solid glass isn't crystalline but amorphous, which is opposite of answer A. However, the question asks of the erroneous assumption which answer A illustrates the myth that glass flows. Can someone elaborate why answer A is wrong and why answer B is the correct answer?

[James Finch]

Hi Courtney and JM,

This is a difficult question because the passage does not explicitly contrast crystalline and amorphous atomic structures. This makes it more difficult to find the erroneous premise that the question is asking for, although it does give us the conclusion that flows from that premise as a hint.

Going back to the passage, specifically lines 7-10, we are told:

"...the confusion probably arose partly from a misunderstanding of the fact that the atoms in glass are not arranged in a fixed crystal structure."

This, coupled with the next sentence, is stating that both solid and liquid glass have amorphous atomic structures, and that glass researchers knew this. We can then further infer that they used this understanding to mistakenly theorize that glass continually flowed downwards, even in a solid state, as they wouldn't have believed that glass flowed as solid if they believed it had a "fixed crystal" atomic structure.

Looking at the answer choices, and combing them with the question prompt, (A) and (B) are saying opposite things. (A) is stating that researchers mistakenly believed window glass flowed downward because they believed that the atomic structure of solid glass was crystalline, meaning a structure that was largely immobile. This is the opposite of what is stated in lines 7-19, and it doesn't make sense for them to believe both in a crystalline atomic structure and window glass flowing downwards.

Answer choice (B) says that the researchers understood that solid glass has an amorphous atomic structure and assumed from that knowledge that it behaved like a liquid even in solid form. This comports exactly with what is said in lines 7-19.

Hope this clears things up!

[jmramon]

Thank you for your response, James. However, I’m still not getting why B is correct. Are we not looking for an “erroneous assumption”? If A is a wrong assumption and B is a correct assumption in accord with the stimulus, how is the correct answer (B) not erroneous? This seems to go against what the question is asking for. I’d think B would be right if the question asked for a correct assumption, but isn’t the question asking for the opposite?

[James Finch]

Hi JM,

There is nothing in the passage about anyone believing what is mentioned in (A); in fact, lines 8-10 indicate that people have long known (A) to be untrue, and that glass has an amorphous atomic structure.

Lines 16-25 explain what was commonly, and mistakenly believed:

"Cooled below the lower end of this range, molten glass retains an amorphous atomic structure, but it takes on the physical properties of a solid.

However, a new study debunks the persistent belief that stained glass windows in medieval cathedrals are noticeably thicker at the bottom because the glass
flows downward. Under the force of gravity, certain solid materials including glass can, in fact, flow slightly."

The paragraph goes on to explain that this process would take billions of years to be noticeable to humans, from which we can infer that glass does not act like a liquid, even a very viscous one (like melted cheese or lava) but instead more like an actual solid with a crystalline atomic structure. This is the mistaken assumption that had been made, and so (B) is the correct answer.

[jmramon]

I appreciate you taking great time to explain this one to me, James. After rereading the passage again, I think I understand your point that, “This comports exactly with what is said in lines 7-19”. Thank you! I think that by tackling these harder ones in-depth now I will be much better prepared for this Saturday’s test