KS3 WJEC Chemistry: Core Concepts Overview | KS3 WJEC 化学：核心知识点梳理

📚 KS3 WJEC Chemistry: Core Concepts Overview | KS3 WJEC 化学：核心知识点梳理

This guide brings together the essential chemistry topics for Key Stage 3 students following the WJEC specification. You will explore the particle model, atoms and elements, chemical reactions, acids and alkalis, the periodic table, separation techniques, and the Earth’s atmosphere. Each section presents key ideas in clear English–Chinese pairs, helping you build a solid foundation for further study.

本文梳理了 KS3 WJEC 化学课程的核心知识点，涵盖粒子模型、原子与元素、化学反应、酸与碱、元素周期表、分离技术以及地球大气等内容。每个重点概念均以英中对照的方式呈现，便于你构建扎实的化学基础。

1. States of Matter and the Particle Model | 物质的状态与粒子模型

All matter is made of tiny particles. In solids, particles are packed tightly in a regular pattern and vibrate in fixed positions, which gives solids a definite shape and volume.

所有物质均由微小粒子构成。固体中的粒子排列紧密、有规律，只能在固定位置振动，因此固体具有固定的形状和体积。

In liquids, particles are still close together but can move past each other. This allows liquids to flow and take the shape of their container while keeping a fixed volume.

液体中的粒子仍然紧密，但能够相互滑动。这使得液体可以流动、随容器改变形状，但体积保持不变。

In gases, particles are far apart and move rapidly in all directions. Gases have no fixed shape or volume and can be compressed easily because there is lots of space between the particles.

气体中的粒子间距很大，朝各个方向快速运动。气体没有固定的形状和体积，而且因为粒子间有大量空间，气体很容易被压缩。

The particle model explains changes of state: melting (solid → liquid), freezing (liquid → solid), boiling/evaporation (liquid → gas), condensation (gas → liquid) and sublimation (solid → gas directly). These changes require energy to overcome forces between particles.

粒子模型能够解释状态变化：熔化（固态→液态）、凝固（液态→固态）、沸腾/蒸发（液态→气态）、冷凝（气态→液态）和升华（固态直接变为气态）。这些变化需要能量来克服粒子间的作用力。

Diffusion is the spreading out of particles from an area of high concentration to low concentration. It happens faster in gases because particles move more quickly.

扩散是粒子从高浓度区域向低浓度区域散开的过程。气体中扩散发生得更快，因为粒子运动速度更快。

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2. Atoms, Elements, and Compounds | 原子、元素与化合物

An atom is the smallest particle of a chemical element that can exist. All substances are made from atoms. An element is a pure substance consisting of only one type of atom, for example oxygen (O), iron (Fe) and carbon (C).

原子是能够存在的化学元素的最小粒子。所有物质都由原子构成。元素是由同一种原子组成的纯净物，例如氧（O）、铁（Fe）和碳（C）。

A compound is a substance formed when two or more different elements are chemically bonded together. The properties of a compound are completely different from the elements it contains. For example, water (H₂O) is a liquid formed from hydrogen and oxygen gases.

化合物是由两种或多种不同元素通过化学键结合而成的物质。化合物的性质与组成它的元素完全不同。例如，水（H₂O）是由氢气和氧气生成的液体。

Chemical symbols are shorthand for elements: each symbol has one or two letters, with the first always a capital letter. Chemical formulae show the types and numbers of atoms in a compound, such as CO₂ (one carbon atom, two oxygen atoms) or NaCl (one sodium, one chlorine).

化学符号是元素的缩略表示，由一个或两个字母组成，首字母始终大写。化学式表示化合物中原子的种类和数量，如 CO₂（一个碳原子，两个氧原子）或 NaCl（一个钠原子，一个氯原子）。

It is important to distinguish between compounds and mixtures. In a compound, atoms are chemically joined and can only be separated by chemical reactions. In a mixture, substances are just physically mixed and can be separated using physical techniques.

区分化合物与混合物至关重要。化合物中的原子通过化学键结合，只能用化学反应分开；混合物中的物质只是物理混合，可通过物理方法分离。

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3. Pure Substances and Mixtures | 纯净物与混合物

A pure substance has a fixed melting point and boiling point. Impurities lower the melting point and raise the boiling point, and cause the substance to melt or boil over a range of temperatures. This difference helps us check purity.

纯净物有固定的熔点和沸点。杂质会降低熔点、升高沸点，并使物质在某一温度范围内熔化或沸腾。这一差异有助于我们检验纯度。

Most materials around us are mixtures. A solution is a mixture of a solute dissolved in a solvent. In a solution, the particles are evenly spread and do not settle out.

我们身边的大多数材料都是混合物。溶液是溶质溶解在溶剂中形成的混合物，粒子均匀分散且不会沉降。

Other types of mixtures include suspensions (insoluble solid particles that settle on standing) and colloids (particles dispersed but not settling). Mixtures can be separated based on differences in physical properties such as boiling point, solubility and particle size.

其他类型的混合物包括悬浊液（不溶性固体颗粒，静置后沉降）和胶体（颗粒分散但不沉降）。混合物可以利用沸点、溶解度、颗粒大小等物理性质的差异进行分离。

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4. The Periodic Table | 元素周期表

The periodic table arranges all known elements in order of increasing atomic number. It is organised into horizontal rows called periods and vertical columns called groups. Elements in the same group have similar chemical properties because they have the same number of outer shell electrons.

元素周期表按原子序数递增的顺序排列所有已知元素。它由水平的周期和垂直的族组成。同一族元素具有相似的化学性质，因为它们最外层电子数相同。

Group 1 elements are the alkali metals (lithium, sodium, potassium). They are soft, have low density and react vigorously with water to produce hydrogen and an alkaline solution. Reactivity increases down the group.

第Ⅰ族元素是碱金属（锂、钠、钾）。它们质地柔软、密度小，能与水剧烈反应，生成氢气和碱性溶液。反应活性自上而下依次增强。

Group 7 elements are the halogens (fluorine, chlorine, bromine, iodine). They are non-metals that exist as diatomic molecules (F₂, Cl₂, Br₂, I₂). Reactivity decreases down the group, and a more reactive halogen can displace a less reactive one from its salt solution.

第Ⅶ族元素是卤素（氟、氯、溴、碘），属于非金属，以双原子分子（F₂, Cl₂, Br₂, I₂）形式存在。反应活性自上而下减弱，较活泼的卤素能将较不活泼的卤素从其盐溶液中置换出来。

Group 0 contains the noble gases (helium, neon, argon). They are all colourless gases that are extremely unreactive because their atoms have a full outer shell. They are used in lighting and as inert atmospheres.

第0族是稀有气体（氦、氖、氩），均为无色气体，化学性质极不活泼，因为原子最外层电子已达到稳定结构。它们用于照明和充当保护气。

Metals are found on the left and centre of the table, while non-metals are on the right. The dividing line often starts between boron and aluminium and zigzags down.

金属位于周期表左侧和中部，非金属在右侧。分界线通常从硼和铝之间开始，呈锯齿状向下。

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5. Chemical Reactions and Equations | 化学反应与方程式

In a chemical reaction, new substances are formed and the change is usually difficult to reverse. Signs of a chemical change include a colour change, temperature change, formation of a gas (bubbles), and formation of a precipitate (solid appearing in a liquid).

在化学反应中，新物质生成，变化通常难以逆转。化学变化的迹象包括颜色变化、温度变化、气体生成（气泡）以及沉淀形成（液体中出现固体）。

Everyday examples of reactions include burning (combustion), rusting of iron, cooking an egg, and the reaction between vinegar and baking soda. Physical changes, such as melting or boiling, do not create new substances and are easier to reverse.

日常生活中的反应包括燃烧、铁生锈、煮鸡蛋以及醋与小苏打的反应。熔化或沸腾等物理变化不会生成新物质，且较容易逆转。

We can represent reactions using word equations:

methane + oxygen → carbon dioxide + water

我们可以用文字表达式表示反应：

甲烷 + 氧气 → 二氧化碳 + 水

Symbol equations use chemical formulae to show the same reaction more precisely, for example

CH₄ + 2O₂ → CO₂ + 2H₂O

Balancing ensures the total number of each type of atom is the same on both sides, reflecting the law of conservation of mass.

符号方程式使用化学式更精确地表示反应，如

CH₄ + 2O₂ → CO₂ + 2H₂O

配平可以确保同种原子的总数在反应前后相等，体现了质量守恒定律。

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6. Acids, Alkalis, and Neutralisation | 酸、碱与中和

Acids have a pH less than 7. Common laboratory acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃). Household acids include vinegar (acetic acid) and lemon juice (citric acid). Acids taste sour and can be corrosive.

酸的pH值小于7。实验室常见酸包括盐酸（HCl）、硫酸（H₂SO₄）和硝酸（HNO₃）。家用酸包括食醋（醋酸）和柠檬汁（柠檬酸）。酸有酸味，可能具有腐蚀性。

Alkalis are soluble bases that have a pH greater than 7. Examples are sodium hydroxide (NaOH) and calcium hydroxide (Ca(OH)₂). Household alkalis include soap and baking soda. Alkalis feel soapy and can also be corrosive.

碱是可溶性的碱，pH值大于7。例如氢氧化钠（NaOH）和氢氧化钙（Ca(OH)₂）。家用碱包括肥皂和小苏打。碱有滑腻感，也可能具有腐蚀性。

The pH scale runs from 0 (strongly acidic) to 14 (strongly alkaline), with 7 being neutral, like pure water. Indicators such as litmus, universal indicator, and red cabbage juice change colour according to pH.

pH值范围为0（强酸性）至14（强碱性），7为中性，如纯水。指示剂如石蕊、通用指示剂和红卷心菜汁会根据pH值改变颜色。

Neutralisation is a reaction between an acid and an alkali:

acid + alkali → salt + water

For example:

HCl + NaOH → NaCl + H₂O

This reaction has many uses, such as treating acidic soil with lime, relieving indigestion with antacid tablets, and treating bee stings.

中和反应是酸与碱之间的反应：

酸 + 碱 → 盐 + 水

例如：

HCl + NaOH → NaCl + H₂O

该反应有多种用途，例如用石灰处理酸性土壤、用抗酸药片缓解消化不良以及处理蜂蛰。

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7. Metals and Non-metals | 金属与非金属

Metals are typically shiny, good conductors of heat and electricity, malleable (can be hammered into shape) and ductile (can be drawn into wires). Most have high melting points and are solid at room temperature, except mercury.

金属通常有光泽，是热和电的良导体，具有延展性（可锤打成形）和可塑性（可拉成丝）。除汞外，大多数金属熔点较高，在室温下为固态。

Non-metals have contrasting properties: they are often dull, poor conductors, brittle when solid, and have lower melting and boiling points. Many are gases at room temperature, such as oxygen and nitrogen.

非金属性质相反：通常无光泽，导热和导电性差，固态时易碎，熔点和沸点较低。许多非金属在室温下为气体，如氧气和氮气。

The reactivity series lists metals in order of their reactivity: potassium, sodium, calcium, magnesium, aluminium, zinc, iron, copper, silver, gold. More reactive metals react more vigorously with oxygen, water and acids.

金属活动性顺序按活泼程度排列：钾、钠、钙、镁、铝、锌、铁、铜、银、金。越活泼的金属与氧气、水和酸的反应越剧烈。

When metals react with oxygen they form metal oxides – this is an oxidation reaction. For example:

2Mg + O₂ → 2MgO

Many metals corrode over time, and iron rusts in the presence of oxygen and water.

金属与氧气反应生成金属氧化物——这是氧化反应。例如：

2Mg + O₂ → 2MgO

许多金属会随时间腐蚀，铁在氧气和水共同作用下会生锈。

A more reactive metal can displace a less reactive metal from its compound. For instance, zinc displaces copper from copper sulfate solution:

Zn + CuSO₄ → ZnSO₄ + Cu

This is called a displacement reaction and helps us extract metals from ores.

较活泼的金属可以将较不活泼的金属从其化合物中置换出来。例如，锌能从硫酸铜溶液中置换出铜：

Zn + CuSO₄ → ZnSO₄ + Cu

这种反应称为置换反应，有助于从矿石中提取金属。

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8. Separation Techniques | 分离技术

Filtration is used to separate an insoluble solid from a liquid. The mixture is poured through filter paper in a funnel; the solid residue stays on the paper while the filtrate passes through.

过滤用于分离不溶性固体与液体。混合物倒入漏斗中的滤纸，固体残渣留在滤纸上，滤液则通过滤纸流下。

Evaporation and crystallisation are used to obtain a soluble solid from a solution. Evaporation simply heats the solution so the solvent boils off, leaving the solid behind. Crystallisation involves gentle heating to evaporate some solvent, then allowing the solution to cool so crystals form slowly.

蒸发和结晶用于从溶液中获得可溶性固体。蒸发通过加热溶液使溶剂沸腾离去，留下固体；结晶则是微微加热以蒸去部分溶剂，然后让溶液冷却，使晶体缓慢析出。

Simple distillation separates a liquid from a solution by boiling the liquid and then condensing the vapour back into a pure liquid. This is useful for obtaining pure water from salt water.

简单蒸馏通过煮沸溶液中的液体，然后将蒸气冷凝变回纯液体，从而将液体与溶液分离。这种方法常用于从盐水中制取纯水。

Chromatography separates mixtures of soluble substances dissolved in the same solvent. A spot of the mixture is placed on chromatography paper, and the paper is dipped in a solvent. Different substances travel different distances because they have different solubilities and attractions to the paper.

色谱法用于分离溶解在同一溶剂中的多种可溶性物质。将混合物点在色谱纸上，把纸浸入溶剂中。不同物质因溶解度及与纸的吸力不同，移动距离也不同。

Decanting and using a separating funnel can separate immiscible liquids, such as oil from water. Each technique relies on a particular physical property, allowing chemists to obtain pure materials from mixtures.

倾析和使用分液漏斗可以分离不相溶的液体，如油和水。每种技术都依赖特定的物理性质，使化学家能从混合物中获得纯净物质。

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9. Earth and Atmosphere | 地球与大气

The Earth has a layered structure: a thin solid crust, a semi-solid mantle, a liquid outer core, and a solid inner core. The crust is made up of tectonic plates that move slowly, causing earthquakes and volcanoes.

地球具有层状结构：薄而坚固的地壳、半固态的地幔、液态的外核和固态的内核。地壳由缓慢移动的构造板块组成，板块运动会引发地震与火山喷发。

Rocks are classified into three main types. Igneous rocks form from cooled magma or lava (e.g., granite, basalt). Sedimentary rocks form from compressed layers of sediment (e.g., limestone, sandstone) and often contain fossils. Metamorphic rocks form when existing rocks are changed by heat and pressure (e.g., marble from limestone).

岩石分为三大类。火成岩由冷却的岩浆或熔岩形成（如花岗岩、玄武岩）；沉积岩由沉积物层层挤压形成（如石灰岩、砂岩），常含化石；变质岩是在热与压力作用下原有岩石发生变化而形成（如由石灰岩变质而成的大理岩）。

The early atmosphere was mostly carbon dioxide and water vapour, with little oxygen. Over billions of years, photosynthesis by plants and algae increased oxygen levels to about 21%, while carbon dioxide decreased. Today’s atmosphere contains approximately 78% nitrogen, 21% oxygen, and small amounts of other gases.

早期大气主要由二氧化碳和水蒸气组成，氧气极少。经过数十亿年，植物与藻类的光合作用将氧气含量提升至约21%，同时二氧化碳减少。如今的大气约含78%氮气、21%氧气及少量其他气体。

The carbon cycle describes how carbon moves between the atmosphere, oceans, living organisms, and rocks. Photosynthesis removes CO₂, while respiration, combustion and decay return it. The greenhouse effect keeps Earth warm, but human activities such as burning fossil fuels are increasing CO₂ levels, enhancing the effect and contributing to global warming.

碳循环描述碳在大气、海洋、生物和岩石之间的流动。光合作用吸收二氧化碳，呼吸作用、燃烧和腐烂又将二氧化碳释放回大气。温室效应使地球保持温暖，但人类燃烧化石燃料等活动正在升高二氧化碳浓度，加剧温室效应，导致全球变暖。

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10. Energy Changes in Reactions | 反应中的能量变化

Chemical reactions either release energy to the surroundings or absorb energy from the surroundings. An exothermic reaction gives out heat, causing the temperature of the surroundings to rise. Everyday exothermic reactions include combustion (burning fuels), respiration in cells, and neutralisation.

化学反应要么向周围环境释放能量，要么从周围环境吸收能量。放热反应释放热量，使环境温度升高。日常的放热反应包括燃烧（燃料燃烧）、细胞呼吸及中和反应。

An endothermic reaction takes in heat energy, causing a temperature drop in the surroundings. Examples are thermal decomposition (e.g., heating calcium carbonate to make lime) and photosynthesis in plants. Some endothermic reactions are used in cold packs for sports injuries.

吸热反应吸收热量，导致环境温度降低。例子包括热分解（如加热碳酸钙制取石灰）和植物的光合作用。某些吸热反应被用于制作运动损伤冷敷包。

Reaction profiles can be drawn to show the energy change during a reaction. They indicate the energy of reactants and products, and the activation energy – the minimum energy needed to start the reaction. In an exothermic profile, the products have less energy than the reactants; in an endothermic profile, the products have higher energy.

可以画出反应能量图来表示反应中的能量变化。图中标出反应物和生成物的能量，以及活化能——启动反应所需的最小能量。在放热图中，生成物的能量低于反应物；在吸热图中，生成物的能量高于反应物。

Catalysts provide an alternative reaction pathway with a lower activation energy, allowing the reaction to proceed faster without being used up. Understanding energy changes helps chemists control industrial processes and design efficient fuels.

催化剂提供了活化能更低的替代反应路径，使反应加快而自身不被消耗。理解能量变化有助于化学家控制工业过程并设计高效燃料。

Published by TutorHao | Chemistry Revision Series | aleveler.com

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