📚 Year 9 WJEC Chemistry: Core Knowledge Checklist | Year 9 WJEC 化学：核心知识点梳理
In Year 9, the WJEC chemistry course builds a strong foundation in the fundamental principles of matter, chemical reactions, and Earth science. This article pulls together the essential knowledge you need to master, from particle theory and atomic structure to reactivity series and rock types. Each section provides a clear and concise review of key concepts, making it perfect for end‑of‑topic revision or preparing for assessments.
九年级 WJEC 化学课程为物质的根本原理、化学反应和地球科学打下坚实的基础。本文梳理了你必须掌握的核心知识，从粒子理论和原子结构，到活动性顺序和岩石类型。每一节都对关键概念进行了清晰简明的梳理，适合单元结束复习或备考使用。
1. States of Matter and Particle Theory | 物质状态与粒子理论
All matter is made up of tiny particles that are constantly moving. The arrangement and motion of these particles determine whether a substance is a solid, liquid, or gas.
所有物质都由不断运动的微小粒子构成。粒子的排列和运动方式决定了物质是固体、液体还是气体。
In solids, particles are tightly packed in a regular pattern and vibrate in fixed positions. This gives solids a fixed shape and volume. In liquids, particles are close together but can slide past each other, so liquids have a fixed volume but take the shape of their container. In gases, particles are far apart and move rapidly in all directions, so gases have no fixed shape or volume and can be compressed easily.
固体中粒子紧密排列成规则结构，只能在固定位置上振动，因此固体有固定的形状和体积。液体中粒子仍靠得很近，但能彼此滑动，所以液体有固定体积却会随容器改变形状。气体中粒子相距很远，朝各个方向快速运动，没有固定的形状和体积，且容易被压缩。
Changes of state—melting, freezing, boiling, condensation, sublimation—can be explained by changes in the energy of particles. When heated, particles gain kinetic energy and move more vigorously, overcoming the forces holding them together. During a change of state, temperature stays constant even though energy is being supplied, because the energy is used to break or weaken bonds between particles rather than to raise temperature.
物质状态的变化——熔化、凝固、沸腾、凝结、升华——都可以用粒子能量的变化来解释。加热时粒子获得动能，运动加剧，克服了把它们约束在一起的力。状态变化过程中，即使持续供热，温度也保持不变，因为输入的能量被用来打破或削弱粒子间的键，而不是提高温度。
Diffusion provides evidence for the particle theory. The spreading of a smell across a room or a coloured dye in water occurs because particles move from an area of high concentration to an area of low concentration. Diffusion is fastest in gases and increases with temperature.
扩散现象为粒子理论提供了证据。气味在房间里弥漫或有色颜料在水中扩散，都是因为粒子从高浓度区域向低浓度区域运动。扩散在气体中最快，并且随温度升高而加快。
2. Atoms, Elements and Compounds | 原子、元素和化合物
An atom is the smallest particle of an element that can take part in a chemical reaction. All substances are made from atoms. An element contains only one type of atom and cannot be broken down into simpler substances by chemical means.
原子是参与化学反应的元素最小粒子。所有物质都由原子构成。元素只含有一种类型的原子，不能通过化学方法分解成更简单的物质。
Dalton's atomic theory proposed that atoms are tiny, indivisible spheres, but later discoveries showed that atoms themselves are composed of subatomic particles. The nucleus contains protons (positively charged) and neutrons (neutral), while electrons (negatively charged) orbit the nucleus in shells. In a neutral atom, the number of protons equals the number of electrons.
道尔顿原子论提出原子是微小的不可分的球体，但后来的发现表明原子本身由亚原子粒子组成。原子核包含质子（带正电）和中子（不带电），而电子（带负电）在核外的电子壳层中运动。在中性原子中，质子数等于电子数。
The atomic number (Z) tells you the number of protons in an atom, which determines the element's identity. The mass number (A) is the total number of protons and neutrons. An element can have isotopes—atoms with the same number of protons but different numbers of neutrons. For example, carbon‑12 has 6 protons and 6 neutrons, while carbon‑14 has 6 protons and 8 neutrons.
原子序数（Z）表示原子中的质子数，决定了元素的身份。质量数（A）是质子数和中子数之和。一种元素可以有同位素——质子数相同但中子数不同的原子。例如，碳‑12 有 6 个质子和 6 个中子，而碳‑14 有 6 个质子和 8 个中子。
Compounds form when atoms of two or more different elements chemically combine in fixed ratios. A compound has properties that are entirely different from the elements it contains. For example, sodium is a reactive metal and chlorine is a poisonous gas, but the compound sodium chloride is safe to eat. Compounds are represented by chemical formulas, such as H₂O for water and CO₂ for carbon dioxide.
两种或多种不同元素的原子以固定比例化合时就形成化合物。化合物的性质与组成它的元素完全不同。例如，钠是活泼金属，氯是有毒气体，但化合物氯化钠可以安全食用。化合物用化学式表示，如水 H₂O、二氧化碳 CO₂。
3. The Periodic Table | 元素周期表
The periodic table organizes all known elements in order of increasing atomic number. The rows are called periods and the columns are called groups. Elements in the same group have the same number of electrons in their outermost shell, which gives them similar chemical properties.
周期表按原子序数递增的顺序排列所有已知元素。横行称为周期，纵列称为族。同一族的元素最外层电子数相同，因此有相似的化学性质。
Group 1 elements are the alkali metals. They are soft, highly reactive metals that react vigorously with water to produce hydrogen gas and an alkaline solution. Reactivity increases down the group because the outer electron is further from the nucleus and more easily lost. Lithium, sodium and potassium are typical Group 1 metals.
第 1 族是碱金属。它们质地较软、非常活泼，与水剧烈反应生成氢气和碱性溶液。自上而下活泼性增加，因为外层电子离核更远，更容易失去。锂、钠和钾是典型的第 1 族金属。
Group 7 elements are the halogens. They are non‑metals and exist as diatomic molecules (F₂, Cl₂, Br₂, I₂). Halogens react with metals to form salts, and their reactivity decreases down the group. A more reactive halogen can displace a less reactive halogen from its salt solution, e.g. chlorine displaces bromine from potassium bromide solution.
第 7 族是卤素。它们是非金属，以双原子分子（F₂、Cl₂、Br₂、I₂）存在。卤素与金属反应生成盐，自上而下活泼性减弱。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，例如氯可从溴化钾溶液中置换出溴。
Group 0 (or 8) contains the noble gases. These elements have full outer electron shells, making them extremely unreactive. They are colourless, odourless gases at room temperature and are used in lighting, welding, and as inert atmospheres. Helium, neon and argon are noble gases.
第 0 族（或第 8 族）是稀有气体。这些元素具有满的外层电子壳，因此极不活泼。室温下为无色无味气体，用于照明、焊接和保护气。氦、氖和氩都是稀有气体。
Between Groups 2 and 3 lies the block of transition metals. They are hard, dense, shiny metals with high melting points, and they form coloured compounds. Many are useful as catalysts, such as iron in the Haber process and platinum in catalytic converters.
第 2 族和第 3 族之间是过渡金属区域。它们是硬、致密、有光泽的高熔点金属，能形成有色化合物。许多过渡金属可用作催化剂，例如哈伯制氨法中的铁和催化转化器中的铂。
4. Chemical Formulas and Equations | 化学式与方程式
Chemical formulas use symbols to show the types and numbers of atoms present. Subscript numbers indicate how many of each atom are in a molecule or formula unit. For example, sulfuric acid is H₂SO₄: 2 hydrogen, 1 sulfur, and 4 oxygen atoms.
化学式用符号表示所含原子的种类和数目。下标数字指示每个分子或式单元中各原子的个数。例如硫酸的化学式是 H₂SO₄：2 个氢原子、1 个硫原子和 4 个氧原子。
equation has the same number of each type of atom on both sides, respecting the law of conservation of mass. Balancing is done by placing numbers (coefficients) in front of the formulas.
化学方程式用化学式表示反应，反应物在左侧，生成物在右侧，中间用箭头（→）隔开。配平的方程式两边每种原子的个数相等，这符合质量守恒定律。配平时在化学式前放置数字（系数）。
r example, the word equation for the reaction between hydrogen and oxygen to give water is 'hydrogen + oxygen → water'. The balanced symbol equation is:
2H₂ + O₂ → 2H₂O
State symbols can be added: (s) solid, (l) liquid, (g) gas, and (aq) aqueous (dissolved in water). Thus, the complete equation becomes:
2H₂(g) + O₂(g) → 2H₂O(l)
例如，氢气和氧气反应生成水的文字表达式是‘氢气 + 氧气 → 水’。配平的符号方程式为：
2H₂ + O₂ → 2H₂O
可以添加状态符号：(s) 固态, (l) 液态, (g) 气态, (aq) 水溶液。完整的方程式写作：
2H₂(g) + O₂(g) → 2H₂O(l)
Ionic equations show only the ions that actually change. Spectator ions that appear unchanged on both sides are omitted. For example, the reaction between silver nitrate and sodium chloride can be simplified to:
Ag⁺(aq) + Cl⁻(aq) → AgCl(s)
离子方程式只显示实际发生变化的离子。两边未改变的旁观离子被省略。例如，硝酸银与氯化钠的反应可简化为：
Ag⁺(aq) + Cl⁻(aq) → AgCl(s)
5. Acids, Alkalis and pH | 酸、碱与 pH 值
Acids are substances that release hydrogen ions (H⁺) when dissolved in water. Common laboratory acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and nitric acid (HNO₃). Aqueous solutions of acids have a sour taste (but never taste them) and turn blue litmus paper red.
酸是溶于水时释放氢离子（H⁺）的物质。实验室常见的酸有盐酸（HCl）、硫酸（H₂SO₄）和硝酸（HNO₃）。酸的水溶液有酸味（但绝不可品尝），能使蓝色石蕊试纸变红。
Alkalis are soluble bases that release hydroxide ions (OH⁻) in water. Common alkalis include sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca(OH)₂). Alkalis feel soapy and turn red litmus paper blue.
碱是可溶的、能在水中释放氢氧根离子（OH⁻）的物质。常见碱包括氢氧化钠（NaOH）、氢氧化钾（KOH）和氢氧化钙（Ca(OH)₂）。碱有滑腻感，能使红色石蕊试纸变蓝。
The pH scale, ranging from 0 to 14, indicates how acidic or alkaline a solution is. pH 7 is neutral (pure water). Values below 7 are acidic (lower pH means higher H⁺ concentration), and values above 7 are alkaline (higher pH means higher OH⁻ concentration). Universal indicator or pH probes can be used to measure pH.
pH 值范围从 0 到 14，表示溶液的酸碱度。pH 7 为中性（纯水）。低于 7 是酸性（pH 越低，H⁺ 浓度越高），高于 7 是碱性（pH 越高，OH⁻ 浓度越高）。可以用通用指示剂或 pH 计测定 pH。
Concentrated acids and alkalis contain a large amount of acid or alkali dissolved in a small volume of water. Dilute solutions contain a small amount of acid or alkali. The concentration of an acid is not the same as its strength: strong acids fully ionise in water (e.g. HCl), while weak acids only partially ionise (e.g. ethanoic acid).
浓酸和浓碱是大量酸或碱溶于少量水中得到的。稀溶液的酸碱含量较少。酸的浓度和强度是不同的概念：强酸在水中完全电离（如 HCl），弱酸只部分电离（如乙酸）。
6. Neutralisation and Salts | 中和反应与盐
Neutralisation occurs when an acid reacts with a base or alkali to form a salt and water. The H⁺ ions from the acid react with OH⁻ ions from the alkali to produce water:
H⁺(aq) + OH⁻(aq) → H₂O(l)
酸与碱或碱性物质反应生成盐和水的过程称为中和。酸中的 H⁺ 离子与碱中的 OH⁻ 离子结合生成水：
H⁺(aq) + OH⁻(aq) → H₂O(l)
A salt is an ionic compound formed when the hydrogen of an acid is replaced by a metal or ammonium ion. The name of the salt comes from the acid and the metal: hydrochloric acid produces chlorides, sulfuric acid produces sulfates, and nitric acid produces nitrates. For example:
NaOH + HCl → NaCl + H₂O (sodium chloride)
Ca(OH)₂ + H₂SO₄ → CaSO₄ + 2H₂O (calcium sulfate)
盐是酸中的氢被金属或铵根离子取代而形成的离子化合物。盐的名称由酸和金属决定：盐酸生成氯化物，硫酸生成硫酸盐，硝酸生成硝酸盐。例如：
NaOH + HCl → NaCl + H₂O 氯化钠
Ca(OH)₂ + H₂SO₄ → CaSO₄ + 2H₂O 硫酸钙
Salts can be prepared by several methods: neutralisation with an indicator and titration for soluble salts of weak acids or alkalis; reacting metals, metal oxides, or carbonates with acids and then crystallising. Insoluble salts can be made by precipitation—mixing two solutions containing the required ions and filtering off the precipitate.
制备盐的方法有多种：利用指示剂和滴定制备弱酸或弱碱的可溶性盐；用金属、金属氧化物或碳酸盐与酸反应后结晶。不溶性盐可通过沉淀法制备——混合含有目标离子的两种溶液，过滤出沉淀。
Acids also react with carbonates to produce a salt, water, and carbon dioxide gas. This reaction can be used to test for carbonates, as bubbling the gas through limewater turns it milky.
酸与碳酸盐反应生成盐、水和二氧化碳气体。这个反应用可用于检验碳酸盐，因为将气体通入石灰水会使其变浑浊。
7. Reactivity Series of Metals | 金属活动性顺序
The reactivity series arranges metals in order of their tendency to undergo chemical reactions. Based on experimental evidence, a typical reactivity series from most to least reactive is:
Potassium > Sodium > Calcium > Magnesium > Aluminium > Zinc > Iron > Lead > Copper > Silver > Gold
活动性顺序根据金属发生化学反应的倾向进行排列。基于实验证据，典型的从最活泼到最不活泼的顺序为：
钾 > 钠 > 钙 > 镁 > 铝 > 锌 > 铁 > 铅 > 铜 > 银 > 金
Metals react with dilute acids to produce hydrogen gas and a salt. The more reactive the metal, the faster and more vigorous the reaction. Metals above hydrogen in the series react with acids, while those below hydrogen generally do not. For instance, magnesium reacts quickly with hydrochloric acid, whereas copper does not react.
金属与稀酸反应生成氢气和盐。金属越活泼，反应越快、越剧烈。活动性顺序中排在氢前面的金属能与酸反应，排在氢后面的通常不能。例如，镁与盐酸迅速反应，而铜则不反应。
Displacement reactions occur when a more reactive metal displaces a less reactive metal from its compound. If an iron nail is placed in copper sulfate solution, iron displaces copper, turning the solution from blue to green as iron sulfate forms, and a brown coating of copper appears on the nail.
更活泼的金属能把较不活泼的金属从其化合物中置换出来。将铁钉放入硫酸铜溶液中，铁会置换出铜，溶液由蓝色变为绿色的硫酸亚铁，铁钉表面出现红棕色的铜镀层。
Reactivity also determines the method of extraction from ores. Very unreactive metals like gold are found as the native metal. Metals in the middle of the series, such as iron, can be extracted by reduction with carbon. The most reactive metals (potassium, sodium, calcium, magnesium, aluminium) are extracted by electrolysis of molten compounds, because carbon cannot reduce them.
金属的活动性还决定了从矿石中提取金属的方法。很不活泼的金属如金以天然单质形式存在。处于活动性顺序中间的金属（如铁）可用碳还原得到。最活泼的金属（钾、钠、钙、镁、铝）需通过电解熔融化合物提取，因为碳无法将其还原。
8. Extraction and Uses of Metals | 金属的提取与用途
Most metals are found in the Earth's crust as ores—minerals containing the metal combined with other elements, often as oxides or sulfides. The extraction method depends on the metal's position in the reactivity series.
大多数金属以矿石形式存在于地壳中——矿石是含有金属与其他元素（常为氧或硫）结合而成的矿物质。提取方法取决于金属在活动性顺序中的位置。
Blast furnace extraction of iron involves reducing iron ore (mainly Fe₂O₃) with carbon (coke) at high temperatures. Limestone is added to remove impurities as slag. The key reactions are:
C + O₂ → CO₂
CO₂ + C → 2CO
Fe₂O₃ + 3CO → 2Fe + 3CO₂
高炉炼铁是在高温下用碳（焦炭）还原铁矿石（主要为 Fe₂O₃）。加入石灰石以形成炉渣除去杂质。关键反应为：
C + O₂ → CO₂
CO₂ + C → 2CO
Fe₂O₃ + 3CO → 2Fe + 3CO₂
Electrolysis is used for extracting aluminium from its ore, bauxite (Al₂O₃). Aluminium oxide is dissolved in molten cryolite to lower the melting point, and a direct electric current decomposes the compound. At the cathode, aluminium ions are reduced to aluminium metal; at the anode, oxide ions are oxidised to oxygen gas. The overall equation:
2Al₂O₃(l) → 4Al(l) + 3O₂(g)
电解法用于从铝土矿（Al₂O₃）中提取铝。将氧化铝溶解在熔融冰晶石中降低熔点，通直流电使化合物分解。阴极上铝离子还原为铝单质；阳极上氧离子氧化为氧气。总反应式：
2Al₂O₃(l) → 4Al(l) + 3O₂(g)
Metals are chosen for specific uses based on their properties. Aluminium is used for aeroplane bodies because it has low density and resists corrosion. Copper is used for electrical wiring due to its excellent electrical conductivity and ductility. Stainless steel (an alloy of iron with chromium and nickel) is used for cutlery and surgical instruments because it is hard and corrosion‑resistant. Gold and silver are used in jewellery because they are unreactive and attractive.
根据性能选择金属用于特定用途。铝密度低、耐腐蚀，用于飞机机体；铜导电性优异且延展性好，用于电线；不锈钢（铁与铬、镍的合金）坚硬耐腐蚀，用于餐具和手术器械；金和银不活泼且美观，用于珠宝。
The transition metals often have multiple uses. For instance, nickel is used in coinage and rechargeable batteries, while iron is the main component of steel, used in construction.
过渡金属通常有多种用途。例如镍用于造币和充电电池，而铁是钢的主要成分，用于建筑。
9. Earth's Atmosphere and Resources | 地球大气与资源
The Earth's atmosphere has changed dramatically over geological time. Early atmosphere was formed by volcanic activity and contained mainly carbon dioxide, water vapour, and small amounts of ammonia and methane. Almost no oxygen was present.
地球大气在地质时间尺度上发生了巨大变化。早期大气由火山活动形成，主要含二氧化碳、水蒸气以及少量氨和甲烷，几乎没有氧气。
The evolution of photosynthetic organisms—cyanobacteria and later plants—gradually increased oxygen levels through the process:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
This removed carbon dioxide from the atmosphere, locking it away in fossil fuels and carbonate rocks. Today's atmosphere is approximately 78% nitrogen, 21% oxygen, and 0.04% carbon dioxide, with traces of noble gases and varying amounts of water vapour.
光合生物（蓝藻以及后来的植物）的演化通过下述反应逐渐提升了氧气水平：
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
这个过程从大气中移走了二氧化碳，将其以化石燃料和碳酸盐岩石的形式固定下来。如今的大气成分约为 78% 氮气、21% 氧气和 0.04% 二氧化碳，并含有微量稀有气体和含量变化的水蒸气。
Human activities, especially the burning of fossil fuels and deforestation, have increased carbon dioxide levels, contributing to the enhanced greenhouse effect and climate change. The greenhouse gases, including CO₂, methane, and water vapour, trap infrared radiation and warm the Earth's surface.
人类活动，尤其是燃烧化石燃料和砍伐森林，增加了二氧化碳水平，加剧了温室效应和气候变化。包括 CO₂、甲烷和水蒸气在内的温室气体会捕获红外辐射，使地球表面变暖。
The Earth provides many natural resources. Finite resources, such as metal ores and crude oil, will one day run out. Renewable resources, like timber and fresh water, can be replenished. Sustainable development aims to meet our needs without compromising the ability of future generations to meet theirs, for example by recycling metals and reducing waste.
地球提供了许多自然资源。有限资源如金属矿石和原油终将耗尽。可再生资源如木材和淡水可以补充。可持续发展的目标是在不损害后代满足其需求的能力的前提下满足我们的需求，例如通过回收金属和减少废弃物来实现。
Potable water is obtained from fresh water sources through filtration and sterilisation, or from sea water by desalination (distillation or reverse osmosis), which requires large amounts of energy.
饮用水通过过滤和消毒从淡水源获得，或通过脱盐（蒸馏或反渗透）从海水获得，但脱盐需要大量能源。
10. Rock Cycle and Types of Rocks | 岩石循环与岩石类型
Rocks are classified into three main groups based on how they are formed: igneous, sedimentary, and metamorphic. The rock cycle describes the continuous processes by which rocks are transformed from one type to another over geological time.
根据形成方式，岩石可分为三大类：火成岩、沉积岩和变质岩。岩石循环描述了在地质时间内岩石由一种类型不断转化为另一种类型的连续过程。
Igneous rocks form when molten magma or lava cools and solidifies. Intrusive igneous rocks, like granite, cool slowly beneath the Earth's surface and have large crystals. Extrusive igneous rocks, like basalt, cool rapidly on the surface and have small or no visible crystals.
火成岩由岩浆或熔岩冷却凝固形成。侵入火成岩如花岗岩在地表下缓慢冷却，晶体较大。喷出火成岩如玄武岩在地表快速冷却，晶体很小或肉眼不可见。
Sedimentary rocks are formed from fragments of other rocks, dead plant and animal matter, or from minerals precipitating from solution. Layers of sediment build up and get compacted and cemented over millions of years. Limestone (mainly calcium carbonate), sandstone, and shale are common examples. Fossils are often found in sedimentary rocks.
沉积岩由其他岩石的碎屑、动植物遗骸或从溶液中沉淀出的矿物形成。沉积物层层堆积，经数百万年的压实和胶结而成岩。石灰岩（主要成分碳酸钙）、砂岩和页岩是常见的沉积岩。沉积岩中常发现化石。
Metamorphic rocks are formed when existing rocks are changed by heat and pressure deep inside the Earth. The minerals recrystallize without melting, producing harder, more compact rocks. Marble is formed from limestone; slate is formed from shale. Metamorphism can create new textures and banded appearance.
变质岩由原有岩石在地球深处受到热和压力的作用而形成。矿物在不熔化的情况下重结晶，产生更硬、更致密的岩石。大理岩由石灰岩变质而成；板岩由页岩变质而成。变质作用可产生新的结构和条带状外观。
The rock cycle is driven by tectonic processes. Weathering and erosion break down rocks into sediments; burial and compaction turn sediments into sedimentary rock; heat and pressure cause metamorphism; melting produces magma that cools to form igneous rock. Uplift and exposure complete the cycle.
岩石循环由构造运动驱动。风化和侵蚀将岩石分解为沉积物；埋藏和压实使沉积物变成沉积岩；热和压力引起变质作用；熔融产生岩浆，冷却后形成火成岩。隆起和暴露完成整个循环。
Limestone has many uses including building stone, making cement and concrete, and in the blast furnace. However, quarrying limestone can lead to environmental issues such as landscape scarring, dust, and noise.
石灰岩有许多用途，包括建筑石材、制造水泥和混凝土以及用于高炉炼铁。然而，开采石灰岩可能导致景观破坏、粉尘和噪音等环境问题。
Published by TutorHao | Chemistry Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图