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
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 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
Which of the sentences below best expresses the information in the highlighted statement in the passage? The other choices change the meaning or leave out important information.
选项
A、Properties that are classified as intensive identify the type of substance and the extent of it present in the surrounding matter.
B、The quantity of a substance influences its extensive properties, but the characteristics of the substance define the intensive properties.
C、Where the intensive and extensive properties are found in substances is important in identifying their characteristics.
D、Both intensive and extensive properties tend to have quantitative rather than qualitative characteristics present.
答案
B
解析
The quantity of a substance paraphrases "the amount present" in reference to extensive properties and the characteristics of the substance paraphrases "characterize a particular kind of matter" in reference to intensive properties.
转载请注明原文地址:https://kaotiyun.com/show/tQyO777K
0
托福(TOEFL)
相关试题推荐
DothefollowingstatementsagreewiththeinformationgiveninReadingPassage2?Inboxes22-26onyouranswersheetwriteTRU
LivingDunesWhenyouthinkofasanddune,youprobablypictureabarrenpileoflifelesssand.Butsanddunesareactuallydyn
Matchinginformationandfeature.OutofAfrica:solarenergyfromSaharaVivienneWaltreportsonhowtheSaharaDesertcouldo
HistoryofRefrigerationRefrigerationisaprocessofremovingheat,whichmeanscoolinganareaorasubstancebelowthee
TheStudyofChimpanzeeCultureA.Afterstudyingthesimilaritiesbetweenchimpanzeesandhumansforyears,researchershav
Whataretheadvantagesanddisadvantagesofsendingthingsbyair?WhenwillthecustomerarriveinCanada?
【21】Whichgraphshowstherelativepopularityofdifferentcinemas?
HowdidthetravellerhearaboutNewYork?Thetravellerlikedthedifferentkindsof______.
Thievesoftentargetstudents’homesbecausestudents______.Theinsurancecompanyhasa24______.
WriteNOMORETHANTWOWORDSforeachanswer.BeWellOnlineProgramme=interactivewebsitewithresourcestohelpreach
随机试题
简述当代中国民族问题仍然存在的因素和民族问题的主要内容。
粪便中可能含有一定的病理性结晶,以下关于病理性结晶的叙述,错误的是
不属于霍乱弧菌生物学特性的是
甲从书画市场上购得乙的摄影作品《鸟巢》,与其他摄影作品一起用于营利性展览。丙偷偷将《鸟巢》翻拍后以自己的名义刊登在某杂志上,丁经丙同意将刊登在该杂志上的《鸟巢》又制作成挂历销售。对此,下列哪一选项是正确的?(2008年试卷三第21题)
在施工流水作业中,指某个专业队在一个施工段上的施工作业时间是( )。
有8个相互独立的投资方案A、B、C、…、H,投资期限的寿命期为1年,投资额及1年后的净收益见下表。当筹集资金的条件如下时。最优的选择是什么?根据以上资料,回答下列问题:资金筹集的数量没有限制,但资本的利率为r=10%,上述方案中不可行的是(
在中国传统职业道德言论中,符合现代职业素质要求的是()
一、注意事项 1.申论考试,与传统作文考试不同,是对分析驾驭材料的能力与对表达能力并重的考试。 2.作答参考时限:阅读资料40分钟,作答110分钟。 3.仔细阅读给定的资料,按照后面提出的“申论要求”依次作答。二、给定资料(1)
A,B都是n阶矩阵,并且B和E+AB都可逆,证明:B(E+AB)-1B-1=E-B(E+AB)-1A.
Whatisthemainideaofthethirdparagraph?Whatisnovelaboutthisnewapproach?
最新回复
(
0
)