首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
"Physical and Chemical Properties and Changes" Sugar, water, and aluminum are different substances. Each substance has specif
"Physical and Chemical Properties and Changes" Sugar, water, and aluminum are different substances. Each substance has specif
admin
2018-07-24
41
问题
"Physical and Chemical Properties and Changes"
Sugar, water, and aluminum are different substances. Each substance has specific properties that do not depend on the quantity of the substance. Properties that can be used to identify or characterize a substance—and distinguish that substance from other substances—are called characteristic properties. They are subdivided into two categories: physical properties and chemical properties.
The characteristic physical properties of a substance are those that identify the substance without causing a change in the composition of the substance. They do not depend on the quantity of the substance. A Color, odor, density, melting point, boiling point, hardness, metallic luster or shininess,
ductility
,
malleability
, and
viscosity
are all characteristic physical properties. For example, aluminum is a metal that is both ductile and malleable. B Another example of a physical property is water. Whether a small pan of water is raised to its boiling point or a very large kettle of water is raised to its boiling point, the temperature at which the water boils is the same value, 100 degrees C or 212 degrees F. C Similarly, the freezing point of water is 0 degree C or 32 degrees F. These values are independent of quantity. D
Characteristic properties that relate to changes in the composition of a substance or to how it reacts with other substances are called chemical properties. The following questions pertain to the chemical properties of a substance.
1. Does it burn in air?
2. Does it decompose (break up into smaller substances) when heated?
3. What happens when it is placed in an acid?
4. What other chemicals will it react with, and what substances are obtained from the reaction?
Characteristic physical and chemical properties—also called intensive properties—are used to identify a substance. In addition to the characteristic physical properties already mentioned, some intensive physical properties include the tendency to dissolve in water, electrical conductivity, and density, which is the ratio of mass to volume.
Additional intensive chemical properties include the tendency of a substance to react with another substance, to tarnish, to corrode, to explode, or to act as a poison or carcinogen (cancer-causing agent).
Extensive properties of substances are those that depend on the quantity of the sample, including measurements of mass, volume, and length. Whereas intensive properties help identify or characterize a particular kind of matter, extensive properties relate to the amount present.
If a lump of candle wax is cut or broken into smaller pieces, or if it is melted (a change of state), the sample remaining is still candle wax. When cooled, the molten wax returns to a solid. In these examples, only a physical change has taken place; that is, the composition of the substance was not affected.
When a candle is burned, there are both physical and chemical changes. After the candle is lighted, the solid wax near the burning wick melts. This is a physical change; the composition of the wax does not change as it goes from solid to liquid. Some of the wax is drawn into the burning wick where a chemical change occurs. Here, wax in the candle flame reacts chemically with oxygen in the air to form carbon dioxide gas and water vapor. In any chemical change, one or more substances are used up while one or more new substances are formed. The new substances produced have their own unique physical and chemical properties.
The apparent disappearance of something, like the candle wax, however, is not necessarily a sign that we are observing a chemical change. For example, when water evaporates from a glass and disappears, it has changed from a liquid to a gas (called water vapor), but in both forms it is water. This is a phase change (liquid to gas), which is a physical change. When attempting to determine whether a change is physical or chemical, one should ask the critical question: Has the fundamental composition of the substance changed? In a chemical change (a reaction), it has, but in a physical change, it has not.
Glossary
ductility: can be drawn into wire malleability: can be shaped viscosity: thick, resistant to flow
Look at the four squares [■] that show where the following sentence could be inserted in the passage.
It can be made into wire or thin, flexible sheets.
Where could the sentence best be added?
Click on a square [ ■ ] to insert the sentence in the passage.
选项
A、
B、
C、
D、
答案
B
解析
Pronoun reference is a transitional device that connects the insert sentence with the previous sentence. The pronoun "If in the insert sentence refers to "aluminum" in the previous sentence. The description of aluminum as "ductile" and "malleable" in the previous sentence means that this metal can be made into wire or shaped into flexible sheets as stated in the insert sentence.
转载请注明原文地址:https://kaotiyun.com/show/F3fO777K
0
托福(TOEFL)
相关试题推荐
Labeltheplanbelow.Writethecorrectletter,A-l,nexttoquestions16-20Whereinthemuseumarethefollowingplaces?Gal
Completethenotesbelow.WriteNOMORETHANTWOWORDSforeachanswer.HowtokillbadinsectsChemicalmethodsThesesolutions
Completethenotesbelow.WriteNOMORETHANTHREEWORDSforeachanswer.GIVINGASPEECHReasonsfornervousnessLecturers
Completethenotesbelow.WriteNOMORETHANTHREEWORDSforeachanswer.GIVINGASPEECHReasonsfornervousnessLecturers
Completethesentencesbelow.WriteNOMORETHANTWOWORDSforeachanswer.Duringtheflight,______facilitieshelpedhimdist
Completethenotesbelow.WriteONEWORDONLYforeachanswer.DevelopmentStudiesDevelopmentStudiesattemptstounderstand-
Labelthemapbelow.WritethecorrectletterA-I,nexttoQuestions11-15.Takethepaththroughthe______
Choosethecorrectletter,A,BorC.Alisathinksthatfamoussuccessfulpeople
Whatdoesthepassagemainlydiscuss?WhichofthefollowingismentionedassupportingthePleistoceneoverkillhypothesis?
Amergerisachievedwhenacompanypurchasedtheproperty(ofother)firms,(thus)absorbingthem(into)onecorporatestructur
随机试题
按照标准内容的性质,标准可分为()
女性,48岁。反复双手近端指间关节、双膝关节痛伴晨僵2年,肘部伸侧可触及皮下结节,质硬、无触痛。最有助于确定诊断的辅助检查是
不属于白斑的发病特点的是
《安全生产法》是建筑安全生产法律体系框架的最高层级,“加强劳动保护,改善劳动条件”是有关安全生产方面最高法律效力的规定。()
某商业楼为五层框架结构,设一层地下室,基础拟采用承台下桩基,柱A截面尺寸800mm×800mm,预制方桩边长350mm,桩长27m,承台厚度800mm,有效高度h0取750mm,板厚600mm,承台及柱的混凝土强度等级均为C30(ft=1.43N/mm2)
关于工程项目管理组织结构的确定表述不正确的是()。
2019年8月,某房地产公司采取基价并实行超基价分成方式委托销售开发产品,假设截至当年12月31日,房地产公司、中介公司与购买方三方共签销售合同的成交额为5000万元,其中房地产公司获得基价、超基价分成额分别为4200万元和500万元。房地产公司企业所
法国作家罗曼·罗兰的《名人传》包括了《贝多芬传》《米开朗基罗传》《托尔斯泰传》三部传记。其中,()饱受耳聋折磨。
甲将一台笔记本电脑送给乙,并约定乙不得转让给第三人,否则甲有权收回。其后甲向乙交付了该电脑。下列说法正确的是()。
巨大的投资热情和市场需求背后,短视频的发展短板令人担忧:内容创作新意__________,同质化严重;平台盈利模式__________,只顾短期盈利,长期规划不足;监管机制__________,版权保护缺位,低俗内容和创意抄袭大行其道。依次填入画
最新回复
(
0
)