问题 选择题

右图所示装置可用于测定空气中氧气的含量,实验前在集气瓶内加入少量水,并做上记号。下列说法中不正确的是(   )

A.该实验证明空气中氧气的含量约占1/5

B.实验时红磷一定要过量

C.实验前一定要检验装置的气密性

D.红磷燃烧产生大量的白雾,火焰熄灭后立刻打开弹簧夹

答案

答案:D

题目分析:根据测定空气中氧气含量的实验的注意事项和现象分析。

A、根据空气中氧气所占体积可知,该实验的正确结论是氧气约占空气体积的1/5 ,正确;

B、该实验中红磷要足量,才能保证把氧气全部耗尽,使实验结论更精确,正确;

C、由于本实验的原理是,利用红磷燃烧消耗集气瓶中的氧气后,使瓶内压强小于外界大气压,当打开弹簧夹时,在瓶内外压强差的作用下,水就会被压入瓶中,使液面大约上升至原来瓶内气体体积的1/5;故若装置漏气,则当氧气耗尽时,空气会及时进入补充,则无法实现压强的改变,故实验前一定要检验装置的气密性,正确;

D、红磷燃烧会产生大量的白烟,燃烧结束后不能立刻打开弹簧夹,因为此时装置内剩余的气体仍在膨胀,压强偏大,故测量的结果会小于1/5,错误。故选D

点评:熟记测定空气中氧气含量的实验的注意事项是解题的关键,为保证实验的成功,装置的气密性要好;药品的量要足,能把氧气全部耗尽;要等到装置冷却到室温再打开弹簧夹读数等。

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问答题

A Frenchman, the psychologist Alfred Binet, published the first standardized test of human intelligence in 1905. (46)But it was an American, Lewis Terman, a psychology professor at Stanford, who thought to divide a_test taker’s "mental age," as revealed by that score, by his or her biological age to derive a number that he called "IQ". It would be hard to think of a pop-scientific coinage that has had a greater impact on the way people think about themselves and others.

(47)No country: embraced the IQ more thoroughly than the U.S., where millions of people have their IQ measured annually, many with a direct descendant of Binet’s original test, although not necessarily for the purpose Bin et intended. He developed his test as a way of identifying public school students who needed extra help in learning, and that is still one of its leading uses.

But the broader and more controversial use of IQ testing has its roots in a theory of intelligence—part science, part sociology—that developed in the late 19th century, before Binet’s work and entirely separate from it. (48)Championed first by Charles Darwin’s cousin Francis Galton, it held that intelligence was the most valuable human attribute, and that if people who had a lot of it could be identified and put in leadership positions, all of society would benefit.

Terman believed IQ tests should be used to conduct a great sorting out of the population, so that young people would be assigned on the basis of their scores to particular levels in the school system, which would lead to corresponding socioeconomic destinations in adult life. The beginning of the IQ-testing movement overlapped with the eugenics movement—hugely popular in America and Europe among the "better sort".

In 1958 a British sociologist named Michael Young coined the word "meritocracy" to denote a society that organizes itself according to IQ-test scores. Terman and many other early advocates of IQ testing had in mind the creation of an American meritocracy, though the word didn’t exist then. (49)They believed IQ tests could be the means to create, for the first time ever, a society in which advantage would go to the people who deserved it rather than to those who had been born into it.

In order to believe this, though, you have to believe that merit and a score on an IQ test are the same thing. (50)Long before IQ was invented, America prided itself on beinga country without a class system, in which people of talent and industry would rise and be rewarded. The advent of intelligence tests did not dramatically affect the degree of social mobility in the U.S.—at least not enough for any change to show up in the social-science data.

(48)Championed first by Charles Darwin’s cousin Francis Galton, it held that intelligence was the most valuable human attribute, and that if people who had a lot of it could be identified and put in leadership positions, all of society would benefit.