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#26114
Complete Question Explanation
(See the complete passage discussion here: lsat/viewtopic.php?t=10866)

The correct answer choice is (C)

This question asks about the transition temperature of glass, and requires a solid grasp of the passage as a whole. This is because the transition temperature of glass is discussed in both the first and third paragraphs of the passage. In the first paragraph, the author observes that glass has a transition temperature rather than a freezing point, usually a range of a few hundred degrees Celsius. In the third paragraph, the author mentions that in order for glass to flow, it must be heated to at least 350 degrees Celsius.

Answer choice (A): In the third paragraph, the author states that impurities could lower viscosity and speed the flow of medieval glass, not that such impurities could increase the transition temperature of the glass. This choice fails the Fact Test and should be ruled out of contention.

Answer choice (B): The author does not claim that the transition temperature of glass has only recently been calculated with precision—the recent calculations in the passage refer to the amount of time it would take for glass to sag noticeably.

Answer choice (C): This is the correct answer choice. Given the fact that glass requires a temperature of at least 350 degrees Celsius to flow (line 43), and that glass’ transition temperature is generally a range of a few hundred degrees Celsius (lines 15-16), it is fair to infer that glass’ transition temperature is well above 350 degrees Celsius.

Answer choice (D): This is an Opposite Answer, since the transition temperature of glass is the point above which glass takes on the properties of a liquid.

Answer choice (E): This is an Opposite Answer as well, since the third paragraph provides that glass must be heated to at least 350 degrees Celsius to achieve the ability to flow. The passage provides no support for the notion that some types of glass require a temperature well below 350 degrees Celsius.
 Sophia123
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#47119
Hi,

I am still a little confused on the explanation for C. For some reason it is not really clicking with me how these two facts: 1) range is typically a few hundred degrees celsius and 2) need to be heated to at least 350 degrees, would result in suggesting that the upper extreme is "well above" 350 degrees?

I tried to create a range in my mind of a few hundred degrees, so maybe 350 is the midpoint of the transition temperature, so that 500 is the upper end and 100 is the lower end. How can you know that 150 is enough to be constituted as being "well above"

I noticed both of the facts needed when reading but I wasn't able to add these two facts together to understand this inference.

Thanks in advance for your help!

Best,
Sophia
 Malila Robinson
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#47150
Hi Sophia123,
You are almost there! But 350 is not the midpoint, it is the starting point: "...for glass to have more than a negligible ability to flow, it would have to be heated to at least 350 degrees Celsius". So it cannot go below 350, that means the range would start at 350 degrees Celsius and go up to a few hundred degrees Celsius above that.
Hope that helps,
Malila
 falconbridge
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#77968
Malila Robinson wrote:Hi Sophia123,
You are almost there! But 350 is not the midpoint, it is the starting point: "...for glass to have more than a negligible ability to flow, it would have to be heated to at least 350 degrees Celsius". So it cannot go below 350, that means the range would start at 350 degrees Celsius and go up to a few hundred degrees Celsius above that.
Hope that helps,
Malila
I agree with Sophia and am looking for a further explanation of how we can put the info regarding 350 degrees together with the info regarding a few hundred degrees to infer that the upper extreme is WELL ABOVE 350 degrees.
 Paul Marsh
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#78659
Hey falconbridge! A couple portions from this passage come into play here:

"Glass does not have a precise freezing point; rather, it has what is known as a glass transition temperature, typically a range of a few hundred degrees Celsius. 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."

and

"for glass to have more than a negligible ability to flow, it would have to be heated to at least 350 degrees Celsius."

The first quoted portion above tells us that the transition temperature is a few hundred degrees, and below the bottom end of that range, glass does not flow. The second quoted portion tells us that the bottom end of that range is 350 degrees. Thus, we can deduce that the top end of that range is a few hundred degrees above 350 degrees Celsuis.

Hope that helps!

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