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
49
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] Look at the four squares [■] that show where the following sentence could be inserted in the passage.
It can be made into wire or thin, flexible sheets.
Where could the sentence best be added?
Click on a square [ ■ ] to insert the sentence in the passage.
选项
A、
B、
C、
D、
答案
B
解析
Pronoun reference is a transitional device that connects the insert sentence with the previous sentence. The pronoun "If in the insert sentence refers to "aluminum" in the previous sentence. The description of aluminum as "ductile" and "malleable" in the previous sentence means that this metal can be made into wire or shaped into flexible sheets as stated in the insert sentence.
转载请注明原文地址:https://tihaiku.com/zcyy/3329463.html
相关试题推荐
CancerandChemicalsLastyear,CaliforniagovernorGeor
CancerandChemicalsLastyear,CaliforniagovernorGeor
CancerandChemicalsLastyear,CaliforniagovernorGeor
CancerandChemicalsLastyear,CaliforniagovernorGeor
CancerandChemicalsLastyear,CaliforniagovernorGeor
CancerandChemicalsLastyear,CaliforniagovernorGeor
Whatchangeswouldmakeyourhometownmoreappealingtopeopleofyourage?
"SymbioticRelationships"Symbiosisisaclose,long-lastingphysicalrelatio
"SymbioticRelationships"Symbiosisisaclose,long-lastingphysicalrelatio
"SymbioticRelationships"Symbiosisisaclose,long-lastingphysicalrelatio
随机试题
DRAMAINANCIENTGREECE1LongbeforetheancientGreekscou
Whatisthesourceofthisextremeself-confidencefoundinalmostalloptim
如图所示,长管并联管段1、2,两管段直径相等d1=d2,沿程阻力系数相等,长度l
充氮保护是抑制爆炸的有效措施。下列利用氮气的措施中,不属于抑制爆炸措施的是(
运用各种统计指标和统计分析方法,对经过整理的综合资料进行分析研究,揭示事物的本质
瘢痕灸多用于治疗A.肺痨瘰疬 B.虚寒病证 C.风寒痹痛 D.阳痿早泄
需要,较低唤醒水平的运动项目是( )A、短跑 B、举重 C、射箭 D、拳
Thechangeinthatvillagewasmiraculou
在分析市场利率和利率期货价格时,需要关注宏观经济数据及其变化,主要包括()。A
项目申请报告的编制要重点论述( )等方面。A.产品技术方案 B.规划布局 C
最新回复
(
0
)