Soal Latihan dan Jawaban Reading Comprehension 53
Glass is a remarkable substance made from the simplest raw materials. It can be
colored or colorless, monochrome or polychrome, transparent, translucent, or opaque.
It is lightweight impermeable to liquids, readily cleaned and reused, durable yet
fragile, and often very beautiful Glass can be decorated in multiple ways and its
(5) optical properties are exceptional. In all its myriad forms – as table ware, containers,
in architecture and design – glass represents a major achievement in the history of
Since the Bronze Age about 3,000 B.C., glass lias been used for making various
kinds of objects. It was first made from a mixture of silica, line and an alkali such as
(10) soda or potash, and these remained the basic ingredients of glass until the development
of lead glass in the seventeenth century. When heated, the mixture becomes soft and
malleable and can be formed by various techniques into a vast array of shapes and
sizes. The homogeneous mass thus formed by melting then cools to create glass, but in
contrast to most materials formed in this way (metals, for instance), glass lacks the
(15) crystalline structure normally associated with solids, and instead retains the random
molecular structure of a liquid. In effect, as molten glass cools, it progressively stiffens
until rigid, but does so without setting up a network of interlocking crystals customarily
associated with that process. This is why glass shatters so easily when
dealt a blow. Why glass deteriorates over time, especially when exposed to moisture,
(20) and why glassware must be slowly reheated and uniformly cooled after manufacture to
release internal stresses induced by uneven cooling.
Another unusual feature of glass is the manner in which its viscosity changes as it
turns from a cold substance into a hot, ductile liquid. Unlike metals that flow or
“freeze” at specific temperatures glass progressively softens as the temperature rises,
(25) going through varying stages of malleability until it flows like a thick syrup. Each stage
of malleability allows the glass to be manipulated into various forms, by different
techniques, and if suddenly cooled the object retains the shape achieved at that point.
Glass is thus amenable to a greater number of heat-forming techniques than most other
Reading Comprehension 53
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To demonstrate how glass evolved
To explain the purpose of each component of glass
To show the versatility of glass
To explain glassmaking technology
They are liquid
They were the same for centuries.
They are transparent
They are very heavy.
It has a random molecular structure.
It has an unusually low melting temperature.
It has an interlocking crystal network.
It has varying physical properties.
the glass must be reheated and evenly cooled.
The glass must be kept moist until cooled.
The glass must be shaped to its desired form immediately
the glass must be cooled quickly.
It gradually becomes softer as its temperature rises.
It has better optical properties.
It retains heat while its viscosity changes.
It resists breaking when heated