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
44
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, a carcinogen
选项
A、explodes under pressure
B、conducts electricity
C、causes cancer
D、tarnishes in air
答案
C
解析
... to act as a poison or carcinogen (cancer-causing agent)." An explanation of a word or phrase often appears immediately after it in parentheses. Choices A, B, and D are not correct because they are intensive chemical properties that are mentioned before the reference to a carcinogen.
转载请注明原文地址:https://kaotiyun.com/show/kQyO777K
0
托福(TOEFL)
相关试题推荐
DothefollowingstatementsagreewiththeinformationgiveninReadingPassage3?Inboxes36-40onyouranswersheet,writeTR
BIRDMIGRATIONABirdshavemanyuniquedesignfeaturesthatenablethemtoperformsuchamazingfeatsofendurance.Theyareeq
AncientPeopleinSaharaOnOct.13,2000,PaulSereno,aprofessorfromtheUniversityofChicago,guidedateamofpalaeon
ThePearlA.Thepearlhasalwayshadaspecialstatusintherichandpowerfulallthroughthehistory.Forinstance,women
AccordingtoMrSingh,onwhichthingdomanypeoplemakesuperficialobservations?Whatisbecomingmorewidelyavailabletop
SECTION3Questions21-30Questions21-24CompletethenotesonthepurposesofalessonplanusingNOMORETHANTHREEWORDSf
【21】Shesaysthatnon-nativespeakerstudentsneedtoanticipateand______inordertogetinvolvedinseminardiscussions.
Theprofessorsaysthatsuperhighways______.【27】
WhatisthepurposeofJaneandRick’smeetingwiththetutor?
WriteNOMORETHANTWOWORDSforeachanswer.BeWellOnlineProgramme=interactivewebsitewithresourcestohelpreach
随机试题
痉挛性脑瘫临床表现不包括
蛛网膜下腔出血最常见的病因是
下列合同中,既可以是有偿合同也可以是无偿合同的有哪些?
股权投资基金管理人申请基金管理人登记需要提交的材料或资料包括()。I.法律意见书Ⅱ.年度财务报表Ⅲ.高管基本信息Ⅳ.公司章程Ⅴ.合伙人名单
城市最低收入家庭申请廉租住房须提供的申请材料包括()。
督察人员在现场督察中在什么情况下可以将警察带离现场?
下列关于法律与道德关系的表述中,错误的是()。
从历史的角度看,生态问题只有通过不断重建天人之间的统一才能解决,仅仅赞美自然的原初形态,一味讴歌、缅怀天人之间的原始统一,只能得到某种抽象、空泛的满足,而无法真正解决生态的问题。生态的危机因人而起,也只有通过人自己的合理活动来克服。单纯地由于人的作用导致生
Ofallthecomponentsofagoodnight’ssleep,dreamsseemtobeleastwithinourcontrol.Indreams,awindowopensintoaworl
Isitpossibletobebothfatandfit--notjustfitenoughtoexercise,butfitenoughtoliveaslongassomeonealotlighter?
最新回复
(
0
)