Q27

[katie.raitz]

I arrived at answer C during my review of this question through eliminating the other questions.

A - Unsupported - no discussion of differences in the transition temperature of gasses produced in different time periods.
B - Contradicted - lines 15 and 16 says that there is a typical range of a few hundred degrees. There is no precision mentioned, and it appears that the opposite is true.
D - Contradicted - lines 42 and 43 state that the for glass to have the ability to flow, it would have to be heated to at least 350 degrees. We do not know if 350 degrees is within the transition temperature, so we can't rule out that it effects the tendency of some kinds of glass to flow downward.
E - Unsupported - we are not given any specific numbers or indication about the transition temperature below 350 degrees.

However, C has a sticking point for me in that it says the upper limit is well above 350 degrees. That seems too extreme. The only reasoning that I find that would indicate that it is "well" above 350 degrees is that there is a several hundred degree range listed in lines 15 and 16, and then a mention of at least 350 degrees in 42 and 43. At least means that the transition temperature can go above 350 degrees, but well above seems extreme for me.

I remember reading in other explanations that correct RC answers can sometimes seem not perfect enough to be correct, is that the case for answer C? Or am I missing some evidence in the text?

[ohthatpatrick]

Question Type:
Infer Information

Answer expected in lines/paragraph:
10-19 are were we talk about "transition temperature"

Any prephrase?
We know that glass doesn't have a precise point when it goes from liquid to solid. There's apparently a range of about 300 degrees Celsius where it would be hard to call it definitively one or the other. Once you get below that range, it's a solid, although its atomic structure does still resemble that of liquid class quite a bit.

Correct answer:
C

Answer choice analysis:

(A) The only medieval vs. modern comparison we get tells us that medieval is likely to be less viscous, but it doesn't speak to transition temperatures.

(B) No support for the "only recently" part. It's "only recently" that someone has debunked the downward flow myth, but that's not the same as precisely measuring transition temp.

(C) 350 degrees appears in line 39-43, and it says here that at around 350 degrees, glass would start to act a little more like a liquid. If we combine this fact with what we knew from 10-19, that the transition temperature from solid to liquid is a bandwidth of several hundreds of degrees, then it's reasonable to infer that the 350 degree mark of "okay, it's STARTING to look like a liquid" is somewhere in the middle of that bandwidth. In other words if it takes glass a few hundred degrees to get from solid to liquid, and 350 is when it starts to look more like liquid, then the transition temperature range is probably something like 200 - 500 degrees.

(D) This is more or less contradicted. Even solid glass can flow downward somewhat, according to 23-25, so it seems reasonable that as glass goes from liquid to solid, its transition temperature range IS affecting its ability to flow downward … the closer it gets to solid, the less downward flow.

(E) It's never a SPECIFIC temperature, as far as we know.

Takeaway/Pattern: Tough question. This passage really needs us to understand phase shifts from solid to liquid (and synonyms for liquid such as "molten"). And this correct answer hinges on us interpreting the idea "for the rate of flow to be more than neglibible" as "when it starts to be liquid-y, but isn't yet done transitioning".

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