首页
登录
职称英语
"Physical and Chemical Properties and Changes" Sugar, water, and aluminum are
"Physical and Chemical Properties and Changes" Sugar, water, and aluminum are
游客
2024-01-03
45
管理
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 [br] The word which in the passage refers to
选项
A、properties
B、tendency
C、density
D、ratio
答案
C
解析
"... some intensive physical properties include the tendency to dissolve in water, electrical conductivity, and density, which [density] is the ratio of mass to volume." The pronoun "which" does not refer to Choices A, B, or D.
转载请注明原文地址:https://tihaiku.com/zcyy/3329454.html
相关试题推荐
Whatadvantagedoesthespeakermentionforeachofthefollowingphysicalactiv
Whatadvantagedoesthespeakermentionforeachofthefollowingphysicalactiv
Whatadvantagedoesthespeakermentionforeachofthefollowingphysicalactiv
Choosethecorrectletter,A,BorC.TrafficChangesinGranford[br]Whyarec
ChooseTWOlettersA-E.WhichTWOchangestotheorganisationofthisyear’sfes
ChooseTWOlettersA-E.WhichTWOchangestotheorganisationofthisyear’sfes
ChooseTWOlettersA-E.WhichTWOchangestotheorganisationofthisyear’sfes
ChooseTWOlettersA-E.WhichTWOchangestotheorganisationofthisyear’sfes
ChooseTWOlettersA-E.WhichTWOchangestotheorganisationofthisyear’sfes
ChooseTWOlettersA-E.WhichTWOchangestotheorganisationofthisyear’sfes
随机试题
Thispracticebookisintendedforforeignengineersorstudentsofengineeri
Ifyouweretobeginanewjobtomorrow,youwouldbringwithyousomebasic
WhichofthefollowingstatementsisTRUE?[br][originaltext]TheUNeased
Ittakesenergytomakeacar,andittakesenergytorunit.Energyisexpensiv
分专业脱产培训的特点包括()。A.具有定期轮训的特性 B.强调标准化规范化培
某地新建一栋65m的财贸金融楼,其消火栓充实水柱应为()。A.≮10m B
《中华人民共和国公务员法》自()起施行。A.2005年4月20日 B.200
丙公司拥有一台专有设备,该设备账面原价450万元,己计提折旧330万元,丁公司
某矿业工程施工进度计划网络图如图3所示: 施工中发生了以下事件: 事件1
(2021年真题)路基出现横向裂缝的原因有()。A.路基填料直接采用了液
最新回复
(
0
)