Newly made glass is very strong, but it begins to lose strength the in

Newly made glass is very strong, but it begins to lose strength the instant it is made. Simply blowing on its surface can significantly reduce its strength. And while glass has the capacity to bear heavy loads—a necessary requirement in structural applications—it cannot easily withstand bending forces. Protective coatings are one way to give glass greater strength, although this can affect transparency, one of the main reasons for using glass. Also, altering the composition of the glass can make it harder for cracks to form, but this alteration can mean loss of other desirable properties, or make the glass more expensive to manufacture.

The manufacturing process can be modified to keep the surface of the glass clear and free of cracks. Strong, clear glass for laptop displays is made by maximizing the surface area in contact only with air as the glass cools. But with glass used for structural purposes, tempering processes are typically used. In heat tempering the surface of the glass is cooled more rapidly than the interior, a process that allows the interior of the glass to become more dense. In chemical tempering the sodium ions at the surface are replaced with potassium ions, which are larger, and this achieves much the same compression as does the heat tempering process.

Tempering makes cracks less likely to form, but breakages can still occur. When tempered glass breaks, it breaks into many smaller pieces than does ordinary glass. In structural applications this is actually preferred, since smaller pieces are generally less likely to cause injury. Use of laminated glass in a structure helps to maintain the structure’s integrity in the event that the glass breaks. Glass is laminated by sandwiching thin polymer layers between layers of glass. This adds strength and keeps large broken pieces from shattering. One problem with this, however, is that it makes fabricating glass for structural purposes very difficult, since each piece must be cut, polished, and drilled for the connecting fittings before it is tempered. In fabrication, precise measurements and extremely small margins of error are needed to avoid potentially destructive stresses in the assembled structure.

1. Which of the following terms, if substituted for the term “integrity” in the highlighted sentence, would LEAST alter the meaning of the sentence?

 A )  Completeness
 B )  Conformity
 C )  High quality
 D )  Soundness
 E )  Complexity


2. The highlighted sentences indicate an advantage associated with the use of tempered glass in structural applications. This advantage is most analogous to the advantage indicated by which of the following?

 A )  The use of glass fiber in telephone cable has the advantage that it allows a much greater volume of information to be transmitted simultaneously and without electromagnetic interference, as compared with copper cable.
 B )  Diesel engines on passenger aircraft have the advantage that, in the event of a crash, diesel is, as compared with other aviation fuels, relatively unlikely to catch fire or explode.
 C )  An advantage of using high-index plastic instead of glass in lenses for people who need to wear glasses is that plastic lenses are very light and durable.
 D )  An advantage of using natural methods of pest control in farming is that, as compared with methods based on chemical pesticides, it poses a much smaller risk to farmers than even normal use of chemical pesticides.
 E )  Ozone is a highly reactive form of oxygen, toxic to animals and humans, but its reactivity is an advantage in enabling it to remove certain odors, such as smoke, from buildings.


3. The primary purpose of the passage is to

 A )  advocate the use of a particular manufacturing process to enhance the benefits of a product
 B )  explain the manner in which various properties of a material enhance its use for a certain purpose
 C )  propose technological solutions to problems that typically arise with the use of a material for a certain purpose
 D )  describe various processes typically used to render a material suitable for a certain purpose and outline some of their limitations
 E )  provide reasons for thinking that a particular use proposed for a material is not appropriate in view of limitations inherent in the material


4. The passage suggests that glass used in “structural applications” (see highlighted phrase)

 A )  is normally used to support other pieces of glass
 B )  usually contains predrilled holes to facilitate connection and support
 C )  very rarely breaks in large pieces if it breaks
 D )  usually needs maximum transparency
 E )  is often so constructed as to mitigate the risks arising from breakage