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
2025-02-05
24
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 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/3944013.html
相关试题推荐
"PhysicalandChemicalPropertiesandChanges"Sugar,water,andaluminumare
"PhysicalandChemicalPropertiesandChanges"Sugar,water,andaluminumare
"PhysicalandChemicalPropertiesandChanges"Sugar,water,andaluminumare
"PhysicalandChemicalPropertiesandChanges"Sugar,water,andaluminumare
"PhysicalandChemicalPropertiesandChanges"Sugar,water,andaluminumare
"PhysicalandChemicalPropertiesandChanges"Sugar,water,andaluminumare
"PhysicalandChemicalPropertiesandChanges"Sugar,water,andaluminumare
______crudehydrocarbonsintosuchproductsasgasolineandpetrochemicalsisat
AHumanbloodhasBachemicalcompositionsimilartoCaseawaterfromwhichourD
Whenfarmers______theircropswithchemicals,excessphosphoruscanwashintori
随机试题
EatingDisorders:FactsAboutEatingDisordersandtheSearchforSoluti
ToSaveTrees,FightingOneAlienInsectwithOthersRusty
“学习结束后,学生能够识别肺炎病人存在的主要护理问题”。属于()A.认知
我国设防的建筑抗震措施一般应用于地震烈度为多少度的地区?()A.5~10度
对于定量数据,反映其集中趋势的数字特征有( )A.平均数 B.中位数 C.
患儿男,胎龄32周,出生体重1000g,窒息史,生后1月,有机械通气及吸氧史,进
旅游者不慎将机票遗失,要求补票,( )是在补票过程中不正确的做法。A.旅游者机
《关于企业申请境外上市有关问题的通知》中的“四五六条款”,其中“五”是表示(
拟对某湿陷性黄土地基采用灰土挤密桩加固,采用等边三角形布桩,桩距1.0m,桩长6
农产品质量安全的主要目标有( )。A.确保农业增收,农民增收和农业可持续发展
最新回复
(
0
)