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Got 5/7 correct in 12:40 minutes, including 5 minutes to read and 7:40 minutes to answer the questions.
1234567------------------------------------------------------------------------------------------P1In paragraph one the author describes materials that are of interest to researchers: Glassy metals. Then the author proceeds by giving us the difference between metallic and non metallic alloys. The main difference is the formation of the crystalline structure under different temperatures conditions. This part if full of details concerning the reasons.
Purpose: to describe how glassy metals origin from metal and non metallic alloys.
P2In this paragraph the author presents attempts to model the structure of glassy metals. Hard spheres are used for the purpose. Then the author describes the difference between real alloys and the spheres: the dimensions of the atoms.
Purpose: to describe attempts to model the structure of glassy metals.
P3Here the author explains why glassy metals are promising in terms of their applications. Then she claims that an obstacle regarding the crystalline structure is there but it is likely to be overcome.
Purpose: To highlight the advantages in terms of application of glassy metals.
Main pointTo describe the structure of glassy metals and to highlight the advantages in terms of application.
------------------------------------------------------------------------------------------1. The author is primarily concerned with discussing
Pre-thinking
Main point question
To describe the structure of glassy metals and to highlight the advantages in terms of application.
(A) crystalline solids and their behavior at different temperatures
Partial scope(B) molten materials and the kinetics of the formation of their crystalline structure
Partial scope(C) glassy metals and their structural characteristics
(D) metallic alloys and problems in determining their density
out of scope(E) amorphous materials and their practical utilization
out of scope ------------------------------------------------------------------------------------------2. The author implies that the rate at which the molten materials discussed in the passage are cooled is a determinant of the
Pre-thinking
Assumption question
From P1: The difference between the two is in the kinetics or rate of formation of the crystalline structure, which is controlled by factors such as the nature of the chemical bonding and the ease with which atoms move relative to each other. Thus, in metals, the kinetics favors rapid formation of a crystalline structure, whereas in nonmetallic glasses the rate of formation is so slow that almost any cooling rate is sufficient to result in an amorphous structure.
We can easily see how the "rate" influences the form that the materials are going to take.
(A) chemical composition of the resulting solids
the chemical composition is not affected(B) strength of the chemical bonds that are formed
strength as well is not discussed(C) kinetics of the materials’ crystalline structure
the kinetics is also the rate. So saying that the kinetics affects the kinetics is quite nonsense (D) structure the materials assume
In line with pre-thinking(E) stability of the materials’ crystalline structure
the stability of the crystalline structure is not related to the rate of formation. ------------------------------------------------------------------------------------------3. The author’s speculation about the appropriateness of models using spheres of two sizes for binary alloys would be strongly supported if models using spheres of two sizes yielded
Pre-thinking
Inference question
From P2: One difference between real alloys and the hard spheres used in Bernal models is that the components of an alloy have different sizes, so that models based on two sizes of spheres are more appropriate for a binary alloy, for example. The smaller metalloid atoms of the alloy might fit into holes in the dense, random-packed structure of the larger metal atoms.
What we should pay attention to here is the last sentence. It seems that if the atoms of the alloy fit, the result would be good.
(A) values for density identical to values yielded
by one-sphere models using the smaller spheres only
We don't have any connection between the one shaper model and the 2 spheres model (B) values for density agreeing nearly perfectly with experimentally determined values
Arrived here by POE and don't find reasons to eliminate this option(C) values for density agreeing nearly perfectly with values yielded by models using spheres of three sizes
Same reasoning as in choice A(D) significantly different values for density depending on the size ratio between the two kinds of spheres used
We don't have sufficient information to infer this statement(E) the same values for density as the values for appropriately chosen models that use only medium-sized spheres
Again the connection between medium sized spheres and the two spheres used in this case is missing ------------------------------------------------------------------------------------------4. The author’s attitude toward the prospects for the economic utilization of glassy metals is one of
Pre-thinking
Author's attitude question
Very optimistic: One of the most promising......One residual obstacle to practical applications that is likely to be overcome is
(A) disinterest
(B) impatience
(C) optimism
(D) apprehension
(E) skepticism
------------------------------------------------------------------------------------------5. According to the passage, which of the following determines the crystalline structure of a metallic alloy?
Pre-thinking
Detail question
From P1: When a molten metal or metallic alloy is cooled to a solid, a crystalline structure is formed that depends on the particular alloy composition.
(A) At what rate the molten alloy is cooled
(B) How rapid the rate of formation of the crystalline phase is
(C) How the different-sized atoms fit into a dense, random-packed structure
(D) What the alloy consists of and in what ratios
(E) At what temperature the molten alloy becomes solid
------------------------------------------------------------------------------------------6. Which of the following best describes the relationship between the structure of liquid metals and the structure of glassy metals, as it is presented in the passage?
Pre-thinking
Detail question
The question itself is easy but it is important to consider the order used in the question stem.
Question stem: Which of the following best describes the relationship between the structure of liquid metals(1) and the structure of glassy metals(2), as it is presented in the passage?
From P2: The structure of glassy metals is thought to be similar to that of liquid metals.
(A) The latter is
an illustrative example of the former
(B) The latter is a large-scale version of the former.
(C) The former is a structural elaboration of the latter.
(D) The former provides an instructive contrast to the latter.
(E) The former is a fair approximation of the latter.
------------------------------------------------------------------------------------------7. It can be inferred from the passage that, theoretically, molten nonmetallic glasses assume a crystalline structure rather than an amorphous structure only if they are cooled
Pre-thinking
Inference question
From P1: Thus, in metals, the kinetics favors rapid formation of a crystalline structure, whereas in nonmetallic glasses the rate of formation is so slow that almost any cooling rate is sufficient to result in an amorphous structure.
(A) very evenly, regardless of the rate
(B) rapidly, followed by gentle heating
(C) extremely slowly
(D) to room temperature
Out of context. At room temperature non metallic glasses are not cooled(E) to extremely low temperatures
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