Read the following passage & mark the letter A, B, C, or D on your answer sheet to indicate the correct answer khổng lồ each of the questions.
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 lớn liquids, readily cleaned and reused, durable yet fragile, và often very beautiful. Glass can be decorated in multiple ways & its optical properties are exceptional. In all its myriad forms - as table ware, containers, in architecture và design – glass represents a major achievement in the history of technological developments.Since the Bronze Age about 3,000 B.C., glass has been used for making various kinds ofobjects. It was first made from a mixture of silica, line and an alkali such as soda or potash, và these remained the basic ingredients of glass until the development of lead glass in the seventeenth century. When heated, the mixture becomes soft và malleable và can be formed by various techniques into a vast array of shapes and sizes. The homogeneous mass thus formed by melting then cools lớn create glass, but in contrast lớn most materials formed in this way (metals, for instance), glass lacks the crystalline structure normally associated with solids, & 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 khổng lồ moisture, and why glassware must be slowly reheated & uniformly cooled after manufacture to lớn 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, going through varying stages of malleability until it flows like a thick syrup. Each stage of malleability allows the glass khổng lồ be manipulated into various forms, by different techniques, & if suddenly cooled the object retains the shape achieved at that point. Glass is thus amenable khổng lồ a greater number of heat-forming techniques than most other materials.
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A. to demonstrate how glass evolved