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It is easy to underestimate the central role of chemistry in modern society, but chemical products are essential if the world's population is to be clothed, housed, and fed. The world's reserves of fossil fuels (e. g. oil, natural gas, and coal) will eventually be exhausted, some as soon as the 21st century, and new chemical processes and materials will provide a crucial alternative energy source. The conversion of solar energy to more concentrated, useful forms, for example, will rely heavily on discoveries in chemistry. Long-term, environmentally acceptable solutions to pollution problems are not attainable without chemical knowledge. There is much truth in the aphorism that "chemical problems require chemical solutions". Chemical inquiry will lead to a better understanding of the behaviour of both natural and synthetic materials and to the discovery of new substances that will help future generations better supply their needs and deal with their problems.
Progress in chemistry can no longer be measured only in terms of economics and utility. The discovery and manufacture of new chemical goods must continue to be economically feasible but must be environmentally acceptable as well. The impact or new substances on the environment can now be assessed before large-scale production begins, and environmental compatibility has become a valued property of new materials. For example, compounds consisting of carbon fully bonded to chlorine and fluorine, called chlorofluorocarbons (or Freons), were believed to be ideal for their intended use when they were first discovered. They are nontoxic, nonflammable gases and volatile liquids that are very stable. These properties led to their widespread use as solvents, refrigerants, and propellants in aerosol containers. Time has shown, however, that these compounds decompose in the upper regions of the atmosphere and that the decomposition products act to destroy stratospheric ozone. Limits have now been placed on the use of chlorofluorocarbons, but it is impossible to recover the amounts already dispersed into the atmosphere.
The chlorofluorocarbon problem illustrates how difficult it is to anticipate the overall impact that new materials can have on the environment. Chemists are working to develop methods of assessment, and prevailing chemical theory provides the working tools. Once a substance has been identified as hazardous to the existing ecological balance, it is the responsibility of chemists to locate that substance and neutralize it, limiting the damage it can do or removing if from the environment entirely. The last years of the 20th century will see many new, exciting discoveries in the processes and products of chemistry, Inevitably, the harmful effects of some substances will outweigh their benefits, and their use will have to be limited. Yet, the positive impact of chemistry on society as a whole seems beyond doubt.
The underlined word "tainted" in the first paragraph most probably means ______.
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The fruitless search for the cause of the increase in illiteracy is a tragic example of the saying "They can't see the wood for the trees". When teachers use picture books, they are simply continuing a long-establisbed tradition that is accepted without question. And for the past two decades, illustrations in reading primers have become increasingly detailed and obtrusive, while language has become impoverished -- sometimes to the point of extinction.
Amazingly, there is virtually no empirical evidence to support the use of illustrations in teaching reading. On the contrary, a great deal of empirical evidence shows that pictures interfere in a damaging way with all aspects of learning to read. Despite this, from North America to the Antipodes, the first books that many school children receive are totally without text.
A teacher's main concern is to help young beginning readers to develop not only the ability to recognize words, but the skills necessary to understand what these words mean. Even if a child is able to read aloud fluently, he or: she may not be able to understand much of it: this is called "barking at text". The teacher's task of improving comprehension is made harder by influences outside the classroom. But the adverse effects of such things as television, video games, or limited language experiences at home, can be offset by experiencing "rich" language at school.
Instead, it is not unusual for a book of 30 or more pages to have only one sentence full of repetitive phrases. The artwork is often marvellous, but the pictures make the language redundant, and the children have no need to imagine anything when they read such books. Looking at a picture actively prevents children younger than nine from creating a mental image, and can make it difficult for older children. In order to learn how to comprehend, they need to practise making their own meaning in response to text. They need to have their innate powers of imagination trained.
As they grow older, many children turn aside from books without pictures, and it is a situation made more serious as our culture becomes more visual. It is hard to wean children off picture books when pictures have played a major part throughout their formative reading experiences, and when there is competition for their attention from so many other sources of entertainment. The least intelligent are most vulnerable, but tests show that even intelligent children are being affected. The response of educators has been to extend use of pictures in books and to simplify the language, even at senior levels. The Universities of Oxford and Cambridge recently held joint conferences to discuss the noticeably rapid decline in literacy among their undergraduates.
Pictures are also used to help motivate children to read because they are beautiful and eye-catching. But motivation to read should be provided by listening to stories well read, where children imagine in response to the story. Then, as they start to read, they have this experience to help them understand the language. If we present pictures to save children the trouble of developing these creative skills, then I think we are making a great mistake.
Academic journals ranging from educational research, psychology, language learning, psycholinguistics, and so on cite experime
Educators are now recommending that reasoning skills ______ in the class room since recent
Bermard Bailyn has recently reinterpreted the early history of the United States by applying new social research findings on the experiences of European migrants. In his reinterpretation, migration becomes the organizing principle for rewriting the history of preindustrial North America. His approach rests on four separate propositions.
The first of these asserts that residents of early modern England moved regularly about their countryside; migrating to the New World was simply a "natural spillover". Although at first the colonise held little positive attraction for the English -- they would rather have stayed home -- by the eighteenth century people increasingly migrated to America because they regarded it as the land of opportunity. Secondly, Bailyn holds that, contrary to the notion that used to flourish in America history textbooks, there was never a typical New World community. For example, the economic and demographic character of early New England towns varied considerably.
Bailyn's third preposition suggests two general patterns prevailing among the many thousands migrants: one group came as indentured servants, another came to acquire land. Surprisingly, Bailyn suggests that those who recruited indentured servants were the driving forces of transatlantic migration. These colonial entrepreneurs helped determine the social character of people who came to preindustrial North America. At tint, thousands of unskilled laborers were recruited; by the 1730's, however, American employers demanded skilled artisans.
Finally, Bailyn argues that the colonies were a half-civilized hinterland of the European culture system. He is undoubtedly correct to insist that the colonies were part of an Anglo-American empire. But to divide the empire into English core and colonial periphery, as Bailyn does, devalues the achievements of colonial culture, as Bailyn claims, that high culture in the colonies never matched that in England. But what of seventeenth-century New England, where the settlers created effective laws, built a distinguished university, and published books？ Bailyn might respond that New England was exceptional. However, the ideas and institutions developed by New England Puritans had powerful effects on North American culture.
Although Bailyn goes on to apply his approach to some thousands of indentured servants who migrated just prior to the revolution, he fails to link their experience with the political development of the United States. Evidence presented in his work suggests how we might make such a connection. These indentured servants were treated as slaves for the period during which they had sold their time to American employers. It is not surprising that as soon as they served their time they passed up good wages in the cities and headed west to ensure their personal independence by acquiring land. Thus, it is in the west that a peculiarly American political culture began, among colonists who were suspicious of authority and intensely antiaristocratic.
The author of the passage states that Bailyn failed to ______.
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