Q24

[betsy.abraham]

I was stuck between B and D. I can see how D is right because lines 41- 43, but is B wrong because "a few millennia" isn't supported (it should rather say something along the lines of "beyond the age of the universe (lines 29-30))? Thank you!

[ManhattanPrepLSAT1]

Exactly right betsy.abraham!

Someone might argue that rather than fixing (B) by changing "a few milennia" to "beyond the age of the universe," one might substitute "trillions of years" (line 34), but either way, the figure is way off. Nice work!

Answer choice (D) is supported in lines 39-43.

Incorrect Answers
(A) contradicts the passage which says it will NOT behave as a liquid. (lines 18-19)
(B) is unsupported. "Trillions of years" or the "age of the universe" would have been better than "a few millennia."
(C) contradicts the passage. Above the glass transition point, glass will behave as a liquid. (lines 39-43)
(E) twists the statement made in lines 7-10 about a fixed crystal structure.

#officialexplanation

[seychelles1718]

So is A actually referring to the "persistent belief" shared by many people?

[ohthatpatrick]

Yes, (A) does sound more like the persistent (wrong) belief people have.

But also, as the previous poster said, lines 18-19 are telling us that

"Glass will behave as a solid (physical properties) even though it has certain properties of liquids (amorphous atomic structure)"

[andrewgong01]

Yes, (A) does sound more like the persistent (wrong) belief people have.

But also, as the previous poster said, lines 18-19 are telling us that

"Glass will behave as a solid (physical properties) even though it has certain properties of liquids (amorphous atomic structure)"

I am still a bit unclear with the translation of lines 18-19 as I chose "A" because it felt like a paraphrase of Lines 18-19.. I am not seeing where it says that the glass behaves as a solid because the passage says it "takes on the properties of a solid", which is similar to choice A that says "certain properties of solids".

I am also not seeing where the previous poster also said that the quoted lines indicate glass does not behave as a liquid because the text says "glass retains an amorphous atomic structure", which would seem to suggest it behaves like liquid since it has an amorphous structure or at least does not in turn imply it does not behave like a liquid.

Perhaps the stronger reason to get rid of "A" is that "D" is directly stated (but sneaky in that it is placed away from where the passage first talks about atomic structure).

Is the scientific intuition covered in P1 factually "wrong" or are they factually correct but misunderstood by people. In particular, from Line 9 onwards, the author says that the wrong idea emerged from "a misunderstanding of the fact that atoms in...not fixed crystal structure" but it was unclear to me if the fixed crystal structure idea is factually wrong or if the fact is correct but it leads to a confusion/misunderstanding. This may be my other confusion on why "A" should be eliminated in that Lines 18-19 are just factually wrong and the author clearly has a stance that the old belief is wrong

[ohthatpatrick]

I don't think "behave as a solid though it has properties of a liquid" is adequately supported; I just think it's more supported than the converse.

We're talking about glass below its freezing point, so common sense suggests we classify it as a solid. I think the passage is just making the interesting "side note" that even though it's now technically a solid, it still has the amorphous atomic structure of a liquid.

We can't go from "has amorphous atomic structure" to "behaves like a liquid".

Line 23-25 indicates that "SOLID materials including glass can flow slightly."

The passage is clarifying a misconception:
"Medieval windows are thicker at the bottom because glass flows downward like a very viscous liquid."

Reality:
"SOLID glass still retains an amorphous atomic structure, so the force of gravity DOES cause glass to flow slightly, but that miniscule atomic flow is not why medieval windows are thicker. To get to THAT thickness, at this super slow rate of atomic drift, it would take trillions of years."

[syp]

Can one of the instructors please further elaborate why C is wrong? I referred only to the first paragraph for this question because the question referred to atomic structure of glass, which was elaborated on in the first paragraph. I didn't think to look at the third paragraph because it didn't verbatim mention atomic structure of glass. It referred to the chemical composition instead. Are these two concepts being equated in the passage? Thanks.

[ohthatpatrick]

Yuck. This is one of my least favorite questions.

Yes, it is fair game for this question to be testing lines 41-43, since it says "for [categorically] glass to noticeably flow, it must be heated to at least 350 degrees".

What troubles me about (C) and (D) is the sloppy use of "its glass transition temperature" as though it is some definable value.

Glass transition temperature is defined in line 14-16 as "a range of a few hundred degrees Celsius."

So what does it mean to REACH your glass transition temperature? You hit the lowest number in that range, or that highest number?

And when (C) says "even when it reaches its glass transition temperature", is it referring to reaching it from below by heating a solid until its liquid, or reaching it from above by cooling a liquid into a solid?

The key part of (C) to focus on is the "even when". That is essentially saying that "glass ALWAYS behaves as a solid".

The line you were using, line 17-19, is specifically about how glass behaves BELOW the glass transition temperature.

We know from line 11-12 that both liquid glass and solid glass exist, so it can't be that glass always behaves as a solid.

Hope this helps.

[MysongO386]

Since D only claims that glass flows "under its own weight", I think it is actually better supported by the beginning of paragraph 3, which tell you that even solid glass flows, just extremely slowly. If even solid glass flows, it's unlikely that glass at transition temperate does not flow. I don't think the passage makes it clear whether glass is solid or liquid at the transition temperate range, or whehter 350 celcius is witin that range.