📚 IGCSE CIE Chemistry: Last-Minute Revision Notes | IGCSE CIE 化学：考前冲刺笔记
This set of rapid-revision notes covers the core ideas, key equations and examiner-favourite pitfalls of the IGCSE CIE Chemistry syllabus. Use it to sharpen your recall in the final days before the exam. Each section pairs a concise English explanation with a Chinese version so you can switch between languages effortlessly.
这份考前冲刺笔记浓缩了IGCSE CIE化学的核心概念、核心方程式和阅卷官最爱的陷阱，适合在考前最后几天快速回顾。每个要点都用英文和中文成对呈现，帮助你中英思维自如切换。
1. States of Matter and Diffusion | 物态与扩散
The kinetic particle model explains the three states: solids have particles in fixed positions vibrating, liquids have particles that slide past each other, gases have particles moving rapidly and randomly. Changing state absorbs or releases energy without changing temperature—this hidden energy is called latent heat.
动力学粒子模型解释了三种物态：固态粒子在固定位置振动，液态粒子可相互滑动，气态粒子快速无规则运动。物态变化时吸收或释放能量但温度不变，这份隐藏的能量称为潜热。
Diffusion is the net movement of particles from high to low concentration until evenly spread. It is fastest in gases, slower in liquids, and almost absent in solids. Lighter molecules (lower Mᵣ) diffuse faster; heating increases the kinetic energy of particles, so diffusion speeds up. Ammonia (NH₃) spreads faster than hydrogen chloride (HCl) because it has a lower molecular mass.
扩散是粒子由高浓度向低浓度的净移动，直至分布均匀。气体扩散最快，液体次之，固体几乎不发生扩散。分子越轻(相对分子质量Mᵣ越小)扩散越快；加热使粒子动能增大，扩散加速。氨气(NH₃)比氯化氢(HCl)扩散快，就是因为它分子更轻。
2. Atomic Structure and Periodic Table | 原子结构与元素周期表
An atom contains protons (p⁺), neutrons (n⁰) and electrons (e⁻). Protons and neutrons make up the tiny, dense nucleus; electrons orbit in shells. Proton number (atomic number Z) defines the element, while nucleon number (mass number A) = protons + neutrons. Isotopes have the same Z but different A due to varying neutron count—chemical properties are identical because the electron arrangement is unchanged.
原子含有质子(p⁺)、中子(n⁰)和电子(e⁻)。质子和中子构成微小致密的原子核，电子分层排布。质子数(原子序数Z)决定元素种类，质量数(A)=质子数+中子数。同位素的Z相同但A不同(中子数不同)，因其电子排布不变，化学性质完全相同。
The Periodic Table arranges elements in order of increasing atomic number. Group number tells you the outer-shell electron count, which governs chemical reactivity. Going down Group I, metals become more reactive because the outer electron is further from the nucleus and easier to lose. Going down Group VII, halogen reactivity decreases because it becomes harder to attract an extra electron into a larger outer shell.
元素周期表按原子序数递增排列。族的数字等于最外层电子数，决定化学活泼性。沿着第I族向下，金属越活泼，因为最外层电子离核越远越容易失去。沿着第VII族向下，卤素活泼性减弱，因为原子变大，吸引外来电子填满外层变得困难。
3. Chemical Bonding and Structure | 化学键与结构
Ionic bonding is the electrostatic attraction between oppositely charged ions, formed when metals transfer electrons to non-metals. Compounds like NaCl consist of a giant ionic lattice; they have high melting points, conduct electricity when molten or dissolved, but are brittle. Covalent bonding is the sharing of electron pairs between non-metal atoms. Simple molecules such as H₂O, CO₂, CH₄ have strong covalent bonds within molecules but weak intermolecular forces, giving low boiling points and poor electrical conductivity.
离子键是带相反电荷离子间的静电吸引力，由金属向非金属转移电子形成。NaCl等化合物由巨型离子晶格构成，熔点高，熔融或溶于水时导电，但质脆。共价键是非金属原子间通过共享电子对形成的。H₂O、CO₂、CH₄等简单分子内部共价键强，分子间作用力弱，因此沸点低且不导电。
Giant covalent structures (diamond, graphite, SiO₂) have billions of atoms linked by covalent bonds. Diamond is extremely hard, non-conductive, while graphite has delocalised electrons between layers, so it conducts electricity and acts as a lubricant. Metallic bonding is a giant lattice of positive metal ions in a ‘sea’ of delocalised electrons—this explains malleability, ductility and electrical conductivity.
巨型共价结构(金刚石、石墨、二氧化硅)拥有无数共价键连成的网络。金刚石极硬、不导电；石墨层间有离域电子，因此能导电，还可用作润滑剂。金属键是金属阳离子沉浸在离域电子“海洋”中的巨型结构，由此解释金属的延展性和导电性。
4. Stoichiometry and Moles | 化学计量与摩尔
Relative atomic mass (Aᵣ) is the weighted average mass of an atom on the scale where ¹²C = 12. One mole of any substance contains 6.02 × 10²³ particles (Avogadro constant). Number of moles n = mass (g) ÷ molar mass M (g mol⁻¹). For gases at room temperature and pressure (rtp), molar volume ≈ 24 dm³ mol⁻¹, so volume = n × 24 dm³.
相对原子质量(Aᵣ)是以¹²C=12为基准的原子平均质量。1摩尔任何物质含有6.02 × 10²³个粒子(阿伏伽德罗常数)。摩尔数 n = 质量(g) ÷ 摩尔质量 M (g mol⁻¹)。对常温常压气体，摩尔体积约为 24 dm³ mol⁻¹，故气体体积 = n × 24 dm³。
Empirical formula shows the simplest whole-number ratio of atoms; use percentage composition or masses, divide by Aᵣ, then divide by the smallest value. Molecular formula is a multiple (n) of the empirical formula: n = relative molecular mass ÷ empirical formula mass. Limiting reactant determines how much product forms; percentage yield = (actual yield ÷ theoretical yield) × 100%.
经验式表示原子最简整数比：由百分组成或质量除以各自的Aᵣ，再除以最小的商值。分子式是经验式的整数倍(n)：n = 相对分子质量 ÷ 经验式质量。限制反应物决定产物的量；产率 = (实际产量 ÷ 理论产量) × 100%。
5. Energetics and Reaction Rates | 能量变化与反应速率
Exothermic reactions transfer energy to the surroundings (temperature rises), e.g. combustion, neutralisation. Endothermic reactions absorb energy (temperature falls), e.g. photosynthesis, thermal decomposition. Bond breaking is endothermic, bond making is exothermic. The overall enthalpy change ∆H is the balance between energy absorbed to break bonds and energy released when new bonds form.
放热反应向环境释放能量(温度升高)，如燃烧、中和反应。吸热反应吸收能量(温度下降)，如光合作用、热分解。断裂化学键吸热，形成化学键放热。总焓变∆H是断键吸收能量与成键释放能量的代数和。
For a reaction to occur, particles must collide with sufficient energy (activation energy Eₐ) and correct orientation. Increasing temperature, concentration or surface area boosts the frequency of successful collisions. Catalysts provide an alternative reaction pathway with lower Eₐ, increasing the rate without being used up. Biological catalysts are called enzymes.
反应发生要求粒子碰撞且能量达到活化能(Eₐ)并取向合适。升高温度、增加浓度或增大固体表面积都能提高有效碰撞频率。催化剂提供较低Eₐ的替代路径，加快反应而自身不消耗。生物催化剂称为酶。
6. Acids, Bases and Salts | 酸、碱与盐
Acids release H⁺ ions in water; common laboratory acids are HCl, H₂SO₄, HNO₃. Bases neutralise acids to form salt and water; alkalis are soluble bases that release OH⁻ ions. pH scale 0–14 measures acidity: pH < 7 is acidic, pH = 7 neutral, pH > 7 alkaline. Universal indicator and litmus are typical indicators.
酸在水中释放H⁺；实验室常见酸有HCl、H₂SO₄、HNO₃。碱能中和酸生成盐和水；可溶性碱( alkali )释放OH⁻离子。pH 0–14衡量酸碱度：pH<7酸性，pH=7中性，pH>7碱性。常用指示剂有通用指示剂和石蕊。
Salts can be prepared by neutralisation, by reacting a metal with an acid, or by precipitation. Titration is used to make soluble salts of Group I and ammonium; excess solid method is used for most other soluble salts. Strong acids fully ionise in water, while weak acids (e.g. ethanoic acid) only partially ionise, giving a higher pH for the same concentration.
制备盐可用中和反应、金属与酸反应或沉淀法。滴定法适用于制备第I族盐和铵盐；过量固体法适合大多数其他可溶盐。强酸在水中完全电离，弱酸(如乙酸)仅部分电离，相同浓度下弱酸的pH更高。
7. Electrolysis | 电解
Electrolysis is the decomposition of a compound using direct electric current. In a molten ionic compound, the positive cation moves to the cathode (reduction) and the negative anion moves to the anode (oxidation). For example, molten lead(II) bromide gives lead at the cathode and bromine gas at the anode: Pb²⁺ + 2e⁻ → Pb (reduction); 2Br⁻ → Br₂ + 2e⁻ (oxidation).
电解是利用直流电分解化合物。在熔融离子化合物中，阳离子移向阴极发生还原，阴离子移向阳极发生氧化。如熔融溴化铅：阴极得铅 Pb²⁺ + 2e⁻ → Pb；阳极得溴气 2Br⁻ → Br₂ + 2e⁻。
In aqueous solutions, water can also be discharged. At the cathode, H⁺ (from water) is reduced to hydrogen gas if the metal is more reactive than hydrogen; otherwise the metal itself plates out. At the anode, a halide ion (Cl⁻, Br⁻, I⁻) is preferentially oxidised; if no halide is present, OH⁻ gives oxygen gas. Electroplating and aluminium extraction (Hall–Héroult process) are key industrial applications.
在水溶液中，水自身也可放电。阴极：若金属比氢活泼，H⁺(来自水)被还原为氢气，否则金属析出。阳极：卤素离子(Cl⁻, Br⁻, I⁻)优先氧化；若无卤离子，则OH⁻放电生成氧气。电镀和铝的电解提取(霍尔–埃鲁法)是重要的工业应用。
8. Reactivity Series and Metal Extraction | 金属活动顺序与冶炼
The reactivity series ranks metals from most to least reactive: K > Na > Ca > Mg > Al > (C) > Zn > Fe > (H) > Cu > Ag > Au. A more reactive metal displaces a less reactive metal from its oxide or salt solution. Rusting of iron requires both oxygen and water; barrier protection, galvanising and sacrificial protection are common prevention methods.
金属活动顺序为：K > Na > Ca > Mg > Al > (C) > Zn > Fe > (H) > Cu > Ag > Au。活泼金属能将较不活泼金属从其氧化物或盐溶液中置换出来。铁生锈需要氧气和水同时存在；常用的防锈方法有隔离层保护、镀锌和牺牲阳极保护。
Extraction method depends on position in the series. Metals above carbon are extracted by electrolysis of their molten oxides (e.g. Al from Al₂O₃ dissolved in cryolite). Metals below carbon can be reduced by heating with carbon or carbon monoxide (e.g. Fe from Fe₂O₃ in a blast furnace). Very unreactive metals like gold occur native.
冶炼方法取决于金属的活动顺序。碳以上的金属采用电解熔融氧化物的方法(如铝从溶解在冰晶石中的Al₂O₃电解制得)。碳以下的金属用碳或一氧化碳热还原(如高炉中用Fe₂O₃炼铁)。极不活泼的金以单质形式存在于自然界。
9. Air and Water | 空气与水
Clean dry air is about 78% nitrogen, 21% oxygen, and small amounts of argon (0.9%), carbon dioxide (0.04%) and water vapour. Common air pollutants include carbon monoxide (toxic, binds to haemoglobin), sulfur dioxide and nitrogen oxides (acid rain), and particulates (respiratory problems). Catalytic converters in cars remove CO and NO, converting them into CO₂ and N₂.
洁净干燥的空气约含78%氮气、21%氧气，以及少量氩气(0.9%)、二氧化碳(0.04%)和水蒸气。常见空气污染物有一氧化碳(有毒，与血红蛋白结合)、二氧化硫和氮氧化物(酸雨)、颗粒物(引发呼吸系统疾病)。汽车催化转化器可将CO和NO转化为CO₂和N₂。
Water treatment involves filtration, sedimentation, chlorination and sometimes fluoridation. Hard water contains dissolved Ca²⁺ or Mg²⁺ ions that form scum with soap; temporary hardness (caused by hydrogencarbonates) can be removed by boiling, while permanent hardness (caused by sulfates) requires washing soda or ion exchange. Water tests include anhydrous copper(II) sulfate (turns blue) and cobalt chloride paper (pink to blue) for water vapour.
水处理包括过滤、沉降、氯化消毒，有时加氟。硬水含有溶解的Ca²⁺或Mg²⁺，与肥皂生成浮渣。暂时硬水由碳酸氢盐引起，煮沸可去除；永久硬水由硫酸盐引起，需用洗涤碱或离子交换法软化。检验水的试剂有无水硫酸铜(变蓝)和氯化钴试纸(遇水由粉变蓝)。
10. Organic Chemistry Basics | 有机化学基础
Organic compounds are based on carbon chains. Alkanes (CₙH₂ₙ₊₂) are saturated hydrocarbons; methane CH₄, ethane C₂H₆ are examples. They are generally unreactive, but combust completely in plentiful oxygen to give CO₂ and H₂O, or incompletely to give CO (carbon monoxide). Alkenes (CₙH₂ₙ) contain a C=C double bond, so they decolourise bromine water, acting as a test for unsaturation.
有机化合物以碳链为基础。烷烃(CₙH₂ₙ₊₂)为饱和烃，如甲烷CH₄、乙烷C₂H₆。烷烃通常不活泼，但在充足氧气中完全燃烧生成CO₂和H₂O，不完全燃烧生成CO。烯烃(CₙH₂ₙ)含C=C双键，可使溴水褪色，是检验不饱和键的方法。
Crude oil is separated by fractional distillation according to boiling points. Cracking breaks long-chain alkanes into smaller, more useful alkanes and alkenes using heat and a catalyst. Addition polymerisation joins many small alkene monomers (e.g. ethene) to form a long saturated polymer (poly(ethene)), a reaction that opens the double bond.
石油通过分馏按沸点差异分离。裂化是将长链烷烃在加热和催化剂作用下断裂为更短链的烷烃和烯烃。加成聚合是将众多烯烃单体(如乙烯)的双键打开，连接成长链饱和聚合物(聚乙烯)。
11. Experimental Techniques and Analysis | 实验技能与分析
Measurement apparatus must be chosen for precision: burette (±0.05 cm³), pipette (±0.02 cm³), measuring cylinder (±0.5 cm³). Heating devices include spirit burner, Bunsen burner, water bath and electric heater. Separation methods: filtration for insoluble solid + liquid, crystallisation for soluble solid, simple distillation for a liquid from a solution, fractional distillation for miscible liquids with close boiling points, and paper chromatography for coloured mixtures.
选择量具要注意精度：滴定管(±0.05 cm³)、移液管(±0.02 cm³)、量筒(±0.5 cm³)。加热器具包括酒精灯、本生灯、水浴、电热板。分离方法：不溶性固体与液体用过滤，可溶固体用结晶，从溶液中蒸出液体用简单蒸馏，沸点相近互溶液体用分馏，有色混合物用纸上层析。
Chromatography separates substances based on their different solubilities and adsorption to the paper. The Rf value is distance moved by spot ÷ distance moved by solvent front; it is characteristic for a given substance under fixed conditions. Purity can be assessed by melting point and boiling point—pure substances melt/sharply, while impurities lower melting point and widen the range, and raise boiling point.
层析根据不同物质在固定相和流动相中的溶解与吸附差异进行分离。比移值Rf = 斑点移动距离 ÷ 溶剂前沿移动距离，在固定条件下是物质的特征值。纯度可用熔点和沸点判断——纯物质熔融/沸腾敏锐，杂质使熔点降低、熔程变宽，并使沸点升高。
12. Quick Tips for Exam Success | 考前抢分要点
Always write state symbols (s), (l), (g), (aq) in equations when asked. Use full sentences for ‘describe’ questions; be numerical and precise for ‘calculate’ questions. When comparing, use comparative words (higher, lower, faster). In electrolysis, remember that the cathode attracts cations (reduction). Keep an eye on the unit—convert cm³ to dm³ (÷1000) when using the molar volume. Double-check whether a question asks for an ionic equation (show only reacting ions) or a full equation.
书写方程式时务必标清状态符号(s)、(l)、(g)、(aq)。’描述’题用完整句子；’计算’题给出数值并带单位。比较题使用比较级词汇(更高、更低、更快)。电解题记住阴离子移向阳极氧化，阳离子移向阴极还原。留意单位——使用摩尔体积时cm³需除以1000转为dm³。注意题目要求的是离子方程式(仅展示反应离子)还是完整方程式。
For organic chemistry, draw displayed formulae clearly, showing every atom and bond. In energetics, label exothermic ∆H as negative, endothermic as positive on energy profiles. Finally, manage your time: spend no more than 1.5 minutes per mark in theory papers, and leave time to check your answers—common slips can cost you a grade.
有机化学中，绘制显示式时要标出所有原子和化学键。能量图中，放热反应标识 ∆H 为负值，吸热为正值。最后，合理分配时间：理论卷约每分1.5分钟，留出检查时间，避免低级失误拉低等级。
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