首页
登录
职称英语
"Physical and Chemical Properties and Changes" → Sugar, water
"Physical and Chemical Properties and Changes" → Sugar, water
游客
2024-01-04
32
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 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 [br] The word pertain in the passage is closest in meaning to
选项
A、compare
B、relate
C、explain
D、change
答案
B
解析
In this passage, relate is a synonym for "pertain." Context comes from the word "relate" in the previous sentence.
转载请注明原文地址:https://tihaiku.com/zcyy/3334221.html
相关试题推荐
Whatadvantagedoesthespeakermentionforeachofthefollowingphysicalactiv
Whatadvantagedoesthespeakermentionforeachofthefollowingphysicalactiv
Whatadvantagedoesthespeakermentionforeachofthefollowingphysicalactiv
Whatadvantagedoesthespeakermentionforeachofthefollowingphysicalactiv
Choosethecorrectletter,A,BorC.TrafficChangesinGranford[br]According
Choosethecorrectletter,A,BorC.TrafficChangesinGranford[br]Whyarec
ChooseTWOlettersA-E.WhichTWOchangestotheorganisationofthisyear’sfes
ChooseTWOlettersA-E.WhichTWOchangestotheorganisationofthisyear’sfes
ChooseTWOlettersA-E.WhichTWOchangestotheorganisationofthisyear’sfes
ChooseTWOlettersA-E.WhichTWOchangestotheorganisationofthisyear’sfes
随机试题
某工程,建设单位委托监理单位承担施工阶段的监理任务,总承包单位按照施工合同约定选
A.1,25-二羟胆骨化醇 B.麦角骨化醇 C.维生素D D.7-脱氢胆固
下列事件的发生,按照《标准施工招标文件》中相关合同条件,只获得费用补偿的有(
七情内伤致病多损伤的脏是()A.心、肝、脾 B.心、肺、脾 C.心、肝
银行监管过程中,有必要开展有效的危机管理,并制订有序的处置方案,具体包括()。
下列关于道德和法律的关系,说法不正确的是()。A.功能互补 B.表现形式
简述现代企业人力资源管理各个历史发展阶段的特点。
进行纤维支气管镜检查时,进镜应A.先检查健侧,再检查患侧 B.先检査患侧,再检
银行一定要关注借款人的( )对公司经营的影响。A.管理水平 B.管理架构
坏死性溃疡性龈炎的特点不包括A.腐败性口臭 B.有家族聚集性 C.牙龈坏死
最新回复
(
0
)