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 spe
"Physical and Chemical Properties and Changes" → Sugar, water, and aluminum are different substances. Each substance has spe
admin
2012-01-14
43
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 substance.A Color, odor, density, melting point, boiling point, hardness, metallic luster or shininess, ductility, malleability, and viscosity are all characteristic physical properties. For exam pie, 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 tem- perature 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 degrees 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 sub stance 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
According to the passage, the classification of characteristic properties as "physical" or "chemical" is determined by
选项
A、whether there has been a change in the structure of the substance
B、what happens when the quantity of the substance is increased
C、their classification as either extensive or intensive samples
D、the disappearance of a substance from one form to another
答案
A
解析
"Has the fundamental composition of the substance changed? In a chemical change...it has, but in a physical change, it has not." Choice B is not correct because the quantity refers to extensive properties, not to the difference between physical or chemical properties. Choice C is not correct because both physical and chemical properties are intensive properties. Choice D is not correct because the apparent disappearance of a substance is not necessarily a sign that we are observing a chemical change.
转载请注明原文地址:https://kaotiyun.com/show/DQyO777K
0
托福(TOEFL)
相关试题推荐
Completetheflowchartbelow.ChooseNOMORETHANTHREEWORDSfromthepassageforeachanswer.Writeyouranswersinboxes7-1
Accordingtothewriter,whatproblemsarefacedwhenregulatingvideogames?
ClassifythefollowingcharacteristicsasrelatingtoASocialScienceBMedicalScienceCBothSocialScienceandMedicalScien
TheConceptofChildhoodinWesternCountriesThehistoryofchildhoodhasbeenaheatedtopicinsocialhistorysincetheh
TheConceptofChildhoodinWesternCountriesThehistoryofchildhoodhasbeenaheatedtopicinsocialhistorysincetheh
AtthestartofhertalkRebeccapointsoutthatnewgraduatescanfindithardto______.Whenshehaddevelopedaportfolioo
AccordingtoMrSingh,onwhichthingdomanypeoplemakesuperficialobservations?HowmanychildrendoesMrSinghhave?
CircleTHREElettersA~E.WhichTHREEofthefollowingusesofdamwaterarementioned?(A)providingwaterforlivestock(B)wate
Whichgroupgavethefollowingadvice?TickColumnAifitwasmainlywomen.TickColumnBifitwasmainlymen.TickColumnCi
A、Thenumberofimpulsestransmittedtothegrasshopper’slegs.B、Theageofthegrasshopper.C、Thenumberofsensoryorgansthe
随机试题
根据下列统计资料回答问题。耐磨材料可分为金属耐磨材料、陶瓷耐磨材料和树脂耐磨材料,2014—2020年各类耐磨材料的消费量如下表所示:将①金属耐磨材料、②陶瓷耐磨材料和③树脂耐磨材料按2014—2020年消费量年均增速(以2014年为基础)从高到
连接查询是关系数据库最重要的查询,包括________、自然连接、非等值连接、自身连接、外连接和复合条件连接查询。
简述垄断并没有消除竞争的原因。
某女,30岁,人工流产3次,4年前自然分娩1次,平时男用工具避孕,近2年白带量多,色黄,质黏稠,近日有性交出血,妇科检查宫颈中度糜烂。治疗首选()
恒定流指河流( )恒定时的形态。
下列不属于同宫系统调的特点的是()
概述皮亚杰认知发展阶段理论的主要内容。
西周法制的基本特点是在“明德慎罚"的前提下,将下面的哪一项原则制度化、法律化?
在合同关系中,当事人因防止损失扩大而支出的合理费用应当()。
「高齢者数」の増加は、年金、医療、介護等により、国家全体での社会保障費負担を増加させる。方、「少子高齢化」は、高齢者が社会に占める割合、すなわち「高齢者率」の上昇を意味するが、高齢者の絶対数が必ずしも増加しているとは限らない。すなわち、「少子高齢化」は、国
最新回复
(
0
)