In thefieldof chemistry, the understanding of the word “air” has undergoneradicalchange. Airfor John Mayow, a seventeenth-century chemist, wasessentiallyareceptacleforairborneparticles, andthroughthem manifested avarietyof chemical properties. But although Mayow and a few other chemists diddetectspecificchemical properties in what we call gases (including ourcarbondioxide), most chemists left them unaccounted for until the beginning of the eighteenthcentury. As chemists becameawarethat theatmosphereitself (and not just particleswithinit) had a role to play incombustion,respiration, and other reactions, they did notattributethis to the chemical properties ofairbut rather to substances thataircouldabsorbandreleaseaccording to circumstances. Thus,airprovided aphysicalenvironment in which some reactions took place.

In the early 1700s, theairwas widely seen as just such an environment, and “air” and “theair” were one and the same thing. Chemists were not in thehabitof regarding airs or gases as having different chemical properties. There wassimplyair. Oneobviousreasonfor this waspractical. Chemists could examine solids and liquids, exposing them to avarietyof tests and seeing how they contributed toassortedreactions. Chemists had, however, nocomparableway of examiningair; and they came to view chemistry as thesumtotal of the reactions of solids and liquids, excluding gases. Chemists stressed chemical qualities overphysicalproperties like weight and let physicistsdealwithair. Chemists generally did not examineair, and they did not try to weigh it. That does not mean that chemists did not weigh substances. They did a lot of weighing, and pharmacists and metallurgists did more. But weighing gases was outside theirbrief. In theEncyclopediaof Diderot and d'Alembert, published between 1751 and 1775, readers were told that “the incoercibility of gases will remove them from our researches for a long time to come.”

By the time of theEncyclopedia, however, this had begun to change. One of the first and key sources of change was the invention by the Reverend Stephen Hales of a newinstrument, the pneumatic trough. Thisinstrumentis important for what it made possible in the handling ofair. Thehistoryof its invention and early use illustrates thedifferencethere may be between the motives for inventing adeviceand the ways in which thatdeviceis used.

Hales was a botanist and chemist as well as a physiologist. He wrote a book in 1727 investigatingmechanicalsubjects like thepressureofsapin plants. But Hales went further, addressing chemical as well asphysiologicalquestions. He urged chemists toconsiderairchemically. He described aninstrumentfor washing theairproduced in thecourseof a chemicalreaction. Hewantedto get rid of impurities in theairby letting it passthroughwater. Airpassed from areactionvesselthroughwater in a trough (ortube) and then into asecondvesselthat waspartlyfilled with water and that couldcaptureair.

In devising thisapparatus, Hales had coincidentally furnished aninstrumentfor catching and holdingair, which could then be subjected to various tests. Used in this way, theapparatusbecame known as the pneumatic trough. Half acenturyafter its invention, it became astapleof the chemicallaboratory. It also became one of the key instruments in thereformof chemistry that we know as the chemicalrevolutionbecause it wasessentialto incorporating a whole newstateof matter, thegaseousstate, into chemistry, alongside the already studiedsolidandliquidstates. Once that step had been taken, it was possible tospeculateand then todemonstratethat thegaseousstate, like thesolidandliquidstates, couldcontainavarietyof chemical substances. This was anenormousstep, and it did not happenovernight. Hales had shown thataircould be contained, washed, and purified, and tested chemically as well as physically. This, however, did notleadhim to think that there was more than one kind ofair. Airfor him remainedair, not one of a number of airs. Other chemists would take thatessentialstep.

Questions:
question_stem: According to paragraph 1, John Mayow believed which of the following about air?
choices: tag: A
text: Air was not involved in chemical reactions such as combustion and respiration.

tag: B
text: The absorption and release of substances in the air depended on the gases in the atmosphere.

tag: C
text: Carbon dioxide was the most important component of air and allowed chemical reactions to take place.

tag: D
text: The air had no chemical properties but contained particles that did.
answer_key: D
explanation: 题干提问 John Mayow 对空气的看法。定位到本段第二、三两句：essentially a receptacle for airborne particles, and through them manifested a variety of chemical properties；although Mayow and a few other chemists did detect specific chemical properties in what we call gases，简而言之为：John Mayow 觉得 air 是一个装载颗粒的容器，但 air 本身不具有化学性质。所以答案 D 符合。A 与定位句中的 through them manifested a variety of chemical properties 相反；B 选项中的 absorption and release 不是 John Mayow 提出的；C 未提到 Carbon dioxide was the most important component。

question_stem: What is the main point of paragraph 2?
choices: tag: A
text: Diderot and d'Alembert were the first to recognize that gases were a third state of matter.

tag: B
text: Advances in pharmacy and metallurgy led to a better understanding of gases.

tag: C
text: Early chemists had no tools for investigating the chemical properties of gases.

tag: D
text: By performing various tests on solids and liquids, chemists were able to better understand gases.
answer_key: C
explanation: 组织结构题。题干问第二段落的主旨。本题需要大致浏览整个段落，凝练出主旨，重点关注段落首尾部分。本段第二句提出了段落主要观点：化学家不认为空气或气体具有不同的化学性质，并在后续提出了该看法的理由：Chemists had, however, no comparable way of examining air; and they came to view chemistry as the sum total of the reactions of solids and liquids, excluding gases。所以本段的描述的主旨符合选项 C：早期化学家没有方法来研究气体的化学性质。选项 A 信息本段中为提及；B 中提到的 Advances in pharmacy and metallurgy 文章未提及，文章也没提到 better understanding of gases。D 中的 chemists were able to better understand gases 表述意思与原文相反，原文意思化学家无法检测了解气体。

question_stem: The word “comparable” in the passage is closest in meaning to
choices: tag: A
text: effective

tag: B
text: equivalent

tag: C
text: reliable

tag: D
text: easy
answer_key: B
explanation: Comparable 意思为“类似的，可比较的”，符合的即为 equivalent：等同的；A 有效的；C 可靠的；D 简单的。

question_stem: The author includes the quotation from the “Encyclopedia of Diderot and d'Alembert” in order to
choices: tag: A
text: support the argument that pharmacists and metallurgists were better at studying gases than chemists were

tag: B
text: emphasize that chemists did not consider gases to be a subject for their study

tag: C
text: suggest that physicists were no more concerned with gases than chemists were

tag: D
text: argue that Diderot and d'Alembert deliberately limited the amount of research done on gases
answer_key: B
explanation: 定位题干信息到最后一句话，大意为：百科全书指出空气不可压缩性使得它很长一段时间内都未被研究。结合前文内容，就近前两句指出化学家也会称重，但是他们不称重气体，也就是不会被研究。故而最后一句话中 the incoercibility of gases will remove them from our researches 进一步指出了气体为什么不会被研究。故而符合的是答案 B，强调了化学家不研究气体这一点。A 中的比较无法体现；C 选项的物理学家和化学家的比较不能从百科全书这个引用中得出；D 选项 deliberately limited the amount of research 文章未提及。

question_stem: According to paragraph 4, Hales made an important contribution to chemistry by proposing that chemists do which of the following?
choices: tag: A
text: Consider mechanical subjects as well as chemical ones

tag: B
text: Use cleaner air in their experiments

tag: C
text: Provide detailed descriptions of the devices they used

tag: D
text: Think about air in chemical terms
answer_key: D
explanation: 题干问 Hales 对化学做的重大贡献是他提出化学家应该做什么。通过关键词 Hales、proposing that chemists do 等信息定位到本段第四句：He urged chemists to consider air chemically.故而答案选 D。A 中的 Consider mechanical subjects 未提到；B 中的 Use cleaner air 未提及；C 选项并非他要求化学家做的事，答非所问。

question_stem: The word “staple” in the passage is closest in meaning to
choices: tag: A
text: regular feature

tag: B
text: effective tool

tag: C
text: new device

tag: D
text: distinct advantage
answer_key: A
explanation: Staple 在文中为名词词性，释义为：主要的产品、常用的物品；故而答案符合的只有 A，regular feature 可解释为常规要素；B 解释为有效的工具，有效不符合原词释义；C 解释为新设备，新不符合原词释义；D 解释为独特的优势，不符合替换。

question_stem: Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
choices: tag: A
text: Because of Hales' apparatus, the study of the gaseous state of matter played just as important a role in the chemical revolution as the study of the solid and liquid states did.

tag: B
text: It was essential for chemists to devise new instruments such as Hales‘ apparatus in order to study different states of matter alongside one another.

tag: C
text: Hales‘ apparatus helped revolutionize the field of chemistry by making it possible for chemists to study a third state of matter the gaseous state.

tag: D
text: Hales‘ apparatus was a key development in the chemical revolution because it allowed scientists to transform gaseous matter into different states of matter.
answer_key: C
explanation: 本句中包含因果逻辑的考察，原句核心意思为：Hales' apparatus 是化学改革的重要工具，因为它将气体这种新物质状态也包含进了 chemistry；A 选项首先因果逻辑不符合原句，其次 the study of the gaseous state of matter played just as important a role…提到的重要性比较原句未提及；B 选项核心意思为：化学家需要发明新的工具去研究物质的不同状态，核心意思不符合原句，也未体现原句的因果逻辑；D 选项中的原因部分“transform gaseous matter into different states of matter”描述不符合原句。

question_stem: According to paragraph 5, Hales did not understand that air can
choices: tag: A
text: take various chemical forms

tag: B
text: be washed and purified

tag: C
text: be tested chemically as well as physically

tag: D
text: be contained for experimentation purposes
answer_key: A
explanation: 题干问 Hales 不明白空气的什么。根据关键词 did not understand 定位到本段倒数第2、3两句 This, however, did not lead him to think that there was more than one kind of air. Air for him remained air, not one of a number of airs.大致意思为 Hales 不认为有多种气体，他认为只有一种气体。故而答案选 A。B、C 选项与原文描述相反，根据倒数第4句“Hales had shown that air could be contained, washed, and purified，and tested chemically as well as physically“；D 文章为提及。