📚 IGCSE CCEA Chemistry: Last-Minute Revision Notes | IGCSE CCEA 化学：考前冲刺笔记
This CCEA IGCSE Chemistry revision guide focuses on the most frequently examined concepts, common pitfalls, and essential equations you need to master before the exam. It is designed for last-minute review, helping you secure key marks on papers that test practical skills, factual recall, and problem-solving.
本CCEA IGCSE化学复习指南聚焦最常考的概念、常见易错点和考前必须掌握的方程式。文章针对考前冲刺设计，帮助你在考查实验技能、知识记忆和问题解决的试卷中稳住核心分数。
1. Atomic Structure and the Periodic Table | 原子结构与元素周期表
Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons arranged in shells. The atomic number (Z) is the number of protons and determines the element. The mass number (A) is the sum of protons and neutrons.
原子由含有质子和中子的原子核及按层排布的电子构成。原子序数（Z）等于质子数，决定了元素种类；质量数（A）等于质子数与中子数之和。
Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. They have identical chemical properties because they have the same electron arrangement, but they differ in physical properties such as mass and density.
同位素是质子数相同、中子数不同的同种原子。由于电子排布相同，它们的化学性质相同，但物理性质（如质量和密度）不同。
Electrons occupy shells: the first shell holds up to 2 electrons, the second and third shells hold up to 8 each. The group number in the periodic table tells you the number of outer‑shell electrons for main‑group elements, which dictates their reactivity.
电子分层排布：第一层最多容纳2个，第二、三层最多各容纳8个。主族元素的族数等于最外层电子数，这决定了元素的反应活性。
The Periodic Table is arranged in order of increasing atomic number. Metals are on the left and centre, non‑metals are on the right. Noble gases (Group 0) have full outer shells and are unreactive.
元素周期表按原子序数递增排列。金属位于左侧和中间，非金属在右侧。稀有气体（0族）具有全满最外层电子，性质不活泼。
2. Chemical Bonding and Structures | 化学键与结构
Ionic bonding occurs between metals and non‑metals. Metals lose electrons to form positive cations, while non‑metals gain electrons to form negative anions. The oppositely charged ions are held together by strong electrostatic forces in a giant ionic lattice.
离子键形成于金属和非金属之间。金属失去电子形成阳离子，非金属获得电子形成阴离子。相反电荷的离子通过强静电引力结合成巨型离子晶格。
Ionic compounds have high melting and boiling points because a lot of energy is needed to overcome the strong ionic bonds. They conduct electricity when molten or dissolved in water, as the ions are free to move.
离子化合物熔、沸点高，因为需要大量能量克服强的离子键。它们在熔融或溶于水时能够导电，因为离子可以自由移动。
Covalent bonding is the sharing of electron pairs between non‑metal atoms. Simple molecular substances (e.g. H₂O, CO₂, CH₄) have low melting points and do not conduct electricity because there are no free ions or electrons.
共价键是非金属原子间通过共用电子对形成的。简单分子物质（如H₂O、CO₂、CH₄）熔、沸点低，且不导电，因为没有自由离子或电子。
Giant covalent structures, such as diamond and silicon dioxide, have very high melting points. Diamond has each carbon atom bonded to four others, forming a rigid, non‑conducting network. Graphite has layers that can slide, making it soft and slippery, and it conducts electricity due to delocalised electrons between layers.
巨型共价结构（如金刚石和二氧化硅）熔点极高。金刚石中每个碳原子与另外四个碳原子成键，构成坚硬不导电的网状结构。石墨具有层状结构，层间可滑动，柔软润滑，且因层间离域电子而导电。
Metallic bonding is the attraction between positive metal ions and a ‘sea’ of delocalised electrons. This gives metals high melting points, malleability, and good electrical conductivity.
金属键是金属阳离子与“离域电子海”之间的吸引力。这使得金属具有高熔点、延展性和良好的导电性。
3. Stoichiometry and Mole Calculations | 化学计量学与摩尔计算
The mole is the unit for amount of substance. One mole of any substance contains 6.02 × 10²³ particles (Avogadro constant). You must be confident using the key equation:
摩尔是物质的量的单位。1摩尔任何物质含有6.02×10²³个微粒（阿伏伽德罗常数）。你必须熟练运用关键公式：
number of moles (n) = mass (m) / molar mass (M)
物质的量(n) = 质量(m) / 摩尔质量(M)
For gases at room temperature and pressure (r.t.p.), one mole occupies 24 dm³. The volume of a gas can be found using:
在常温常压（r.t.p.）下，1摩尔气体体积为24 dm³。气体体积可通过下式计算：
volume of gas (dm³) = number of moles × 24
气体体积(dm³) = 物质的量 × 24
Concentration of a solution is measured in mol/dm³. Use:
溶液浓度单位为mol/dm³。公式：
concentration (mol/dm³) = number of moles / volume (dm³)
浓度(mol/dm³) = 物质的量 / 体积(dm³)
Balancing equations and calculating reacting masses are central to stoichiometry. Always check that the number of atoms of each element is the same on both sides. Use mole ratios from balanced equations to work out the mass of product or reactant.
配平化学方程式和计算反应质量是化学计量学的核心。务必检查两边每种元素的原子数相同。利用配平方程式中的摩尔比，计算产物或反应物的质量。
4. Acids, Bases and Salts | 酸、碱和盐
Acids are substances that produce hydrogen ions (H⁺) in aqueous solution. Strong acids (e.g. HCl, H₂SO₄, HNO₃) fully ionise, while weak acids (e.g. ethanoic acid) partially ionise.
酸是在水溶液中产生氢离子（H⁺）的物质。强酸（如HCl、H₂SO₄、HNO₃）完全电离，弱酸（如乙酸）部分电离。
Bases are substances that neutralise acids. Alkalis are soluble bases that produce hydroxide ions (OH⁻) in water. Neutralisation can be represented as:
碱是能中和酸的物质。可溶的碱称为碱，它在水中产生氢氧根离子（OH⁻）。中和反应表示为：
H⁺(aq) + OH⁻(aq) → H₂O(l)
The pH scale measures the acidity or alkalinity of a solution; pH less than 7 is acidic, pH 7 is neutral, and pH greater than 7 is alkaline. Universal indicator or pH probes can be used to determine pH.
pH标度衡量溶液的酸碱度：pH<7为酸性，pH=7为中性，pH>7为碱性。可用通用指示剂或pH计测定。
Making salts: a soluble salt can be prepared by reacting an acid with a metal, a metal oxide, a metal hydroxide, or a metal carbonate. For example:
盐的制备：可溶性盐可通过酸与金属、金属氧化物、金属氢氧化物或金属碳酸盐反应制得。例如：
2HCl(aq) + MgO(s) → MgCl₂(aq) + H₂O(l)
Titration is used to determine the concentration of an acid or alkali by neutralisation. Burettes, pipettes, and suitable indicators (e.g. phenolphthalein, methyl orange) are used for accurate volume measurements.
滴定法通过中和反应测定酸或碱的浓度。使用滴定管、移液管和合适的指示剂（如酚酞、甲基橙）进行精确体积测量。
5. Electrolysis | 电解
Electrolysis is the decomposition of an ionic compound, when molten or in solution, by passing an electric current through it. The positive anode attracts anions, where oxidation occurs; the negative cathode attracts cations, where reduction occurs.
电解是电流通过熔融态或溶液中的离子化合物使其分解的过程。正极（阳极）吸引阴离子，发生氧化反应；负极（阴极）吸引阳离子，发生还原反应。
In electrolysis of molten lead(II) bromide (PbBr₂): at the cathode, lead metal is formed (Pb²⁺ + 2e⁻ → Pb); at the anode, bromine gas is produced (2Br⁻ → Br₂ + 2e⁻).
电解熔融溴化铅（PbBr₂）时：阴极产生金属铅（Pb²⁺ + 2e⁻ → Pb）；阳极产生溴气（2Br⁻ → Br₂ + 2e⁻）。
In aqueous solutions, water can also be oxidised or reduced. For example, electrolysis of dilute sodium chloride solution yields hydrogen at the cathode and oxygen at the anode, because H⁺ is more easily reduced than Na⁺, and OH⁻ is more easily oxidised than Cl⁻ under these conditions.
在水溶液中，水也可能被氧化或还原。例如，电解稀氯化钠溶液时，阴极产生氢气，阳极产生氧气，因为在此条件下H⁺比Na⁺更容易还原，OH⁻比Cl⁻更容易氧化。
Aluminium is extracted by electrolysis of aluminium oxide dissolved in molten cryolite. The process requires a large amount of energy and uses carbon anodes, which are oxidised to CO₂ during the reaction.
铝是通过电解溶解在熔融冰晶石中的氧化铝来提取的。该过程需要大量能量，并使用碳阳极，反应中碳被氧化为CO₂。
6. Rates of Reaction | 反应速率
The rate of a reaction can be measured by the speed at which a reactant is used up or a product is formed. Common methods include measuring the volume of gas produced over time, change in mass, or formation of a precipitate.
反应速率可通过反应物消耗或产物生成的速度来衡量。常用方法包括测量气体产生体积随时间的变化、质量变化或沉淀的生成。
Factors affecting rate: concentration (or pressure for gases), temperature, surface area of solids, and the presence of a catalyst. Increasing concentration, temperature, or surface area increases the frequency and/or energy of successful collisions, as described by collision theory.
影响反应速率的因素：浓度（或气体压强）、温度、固体表面积以及催化剂的存在。根据碰撞理论，增加浓度、温度或表面积都会增加有效碰撞的频率和/或能量。
Catalysts provide an alternative reaction pathway with lower activation energy, increasing the rate without being used up. Enzymes are biological catalysts.
催化剂提供活化能较低的反应途径，加快反应速率而自身不被消耗。酶是生物催化剂。
A typical rate experiment: the reaction between marble chips (CaCO₃) and hydrochloric acid, measuring the volume of CO₂ released. Plotting volume against time gives a curve; the slope decreases as the reaction proceeds. Rate can be calculated from the slope of the tangent at a specific time.
典型的速率实验：大理石碎片（CaCO₃）与盐酸反应，测量释放的CO₂体积。以体积对时间作图得到一条曲线，随着反应进行斜率减小。可通过特定时刻的切线斜率计算瞬时速率。
7. Reversible Reactions and Equilibria | 可逆反应与平衡
Some reactions are reversible; the products can react to re‑form the reactants. A dynamic equilibrium is reached in a closed system when the forward and reverse rates are equal and the concentrations of reactants and products remain constant.
一些反应是可逆的，产物能重新反应生成反应物。在密闭系统中，当正逆反应速率相等，反应物和产物的浓度保持恒定时，即达到动态平衡。
The position of equilibrium can be altered by changing temperature or pressure (for gases). Le Chatelier’s principle states that if a system at equilibrium is subjected to a change, the system will shift to oppose the change.
改变温度或压强（对气体）可以改变平衡位置。勒夏特列原理指出，如果平衡系统受到改变，系统将朝着减弱这种改变的方向移动。
Increasing temperature favours the endothermic reaction. For example, in the Haber process (N₂ + 3H₂ ⇌ 2NH₃, exothermic forward), raising the temperature shifts equilibrium to the left, reducing yield of ammonia. Lower temperature gives higher yield but too slow a rate, so a compromise temperature (about 450 °C) is used, together with an iron catalyst.
升高温度有利于吸热反应。例如，哈伯法制氨（N₂ + 3H₂ ⇌ 2NH₃，正反应放热），升高温度平衡左移，降低氨的产率。低温产率高但速率太慢，故采用折中温度（约450°C）并配合铁催化剂。
Increasing pressure favours the side with fewer gas molecules. For the Haber process, high pressure (about 200 atm) is used to shift equilibrium right, increasing yield. Pressure must be balanced with safety and cost.
增大压强有利于气体分子数较少的一侧。哈伯法中采用高压（约200 atm）使平衡右移，提高产率，但需平衡安全与成本。
8. Redox Reactions and the Reactivity Series | 氧化还原反应与活动性顺序
Oxidation is the loss of electrons; reduction is the gain of electrons. A redox reaction is one in which both oxidation and reduction occur simultaneously. The reactivity series lists metals in order of their tendency to lose electrons and form positive ions.
氧化是失去电子；还原是得到电子。氧化还原反应中氧化和还原同时发生。金属活动性顺序按金属失去电子形成阳离子的倾向排列。
A more reactive metal can displace a less reactive metal from its compound. For example, zinc displaces copper from copper(II) sulfate solution: Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s). Zinc is oxidised, Cu²⁺ ions are reduced.
较活泼的金属能从化合物中置换出较不活泼的金属。例如，锌从硫酸铜溶液中置换出铜：Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)。锌被氧化，Cu²⁺被还原。
Rusting of iron requires both oxygen and water. Rust prevention methods include painting, oiling, galvanising (coating with zinc), and sacrificial protection, where a more reactive metal (e.g. zinc or magnesium) is attached and corrodes instead of iron.
铁生锈需要氧气和水同时存在。防锈方法包括涂漆、涂油、镀锌以及牺牲保护法（连接更活泼的金属如锌或镁，使其代替铁腐蚀）。
Oxidising agents (e.g. oxygen, chlorine) accept electrons; reducing agents (e.g. carbon, hydrogen) donate electrons. In the blast furnace, carbon monoxide reduces iron(III) oxide to iron: Fe₂O₃ + 3CO → 2Fe + 3CO₂.
氧化剂（如氧气、氯气）接受电子；还原剂（如碳、氢气）提供电子。在高炉中，一氧化碳将氧化铁还原为铁：Fe₂O₃ + 3CO → 2Fe + 3CO₂。
9. Organic Chemistry – Alkanes, Alkenes and Alcohols | 有机化学 – 烷烃、烯烃和醇
Hydrocarbons are compounds containing only hydrogen and carbon. Alkanes (general formula CₙH₂ₙ₊₂) are saturated hydrocarbons with single C–C bonds. They are fairly unreactive but burn well in oxygen to form CO₂ and H₂O.
烃是仅含氢和碳的化合物。烷烃（通式CₙH₂ₙ₊₂）是具有单键的饱和烃。它们反应性较弱，但能在氧气中充分燃烧生成CO₂和H₂O。
Alkenes (general formula CₙH₂ₙ) contain a carbon‑carbon double bond and are unsaturated. They undergo addition reactions, such as with bromine water (orange to colourless) and hydrogen (hydrogenation). Ethene (C₂H₄) is the simplest alkene.
烯烃（通式CₙH₂ₙ）含有碳碳双键，属于不饱和烃。它们能发生加成反应，如与溴水反应（橙色变为无色）和加氢反应。乙烯（C₂H₄）是最简单的烯烃。
Alcohols contain the functional group –OH. Methanol (CH₃OH) and ethanol (C₂H₅OH) are the first two members. Ethanol can be made by fermentation of sugars using yeast at 30–40 °C, or by hydration of ethene with steam and a phosphoric acid catalyst.
醇含有官能团–OH。甲醇（CH₃OH）和乙醇（C₂H₅OH）是前两个成员。乙醇可通过酵母在30–40°C发酵糖类制得，或通过乙烯与水蒸气在磷酸催化下加成制取。
Carboxylic acids have the –COOH group. Ethanoic acid is the acid found in vinegar. It reacts with alcohols to form esters in a reversible reaction, using concentrated sulfuric acid as a catalyst.
羧酸含有–COOH基团。乙酸是醋中的酸，它与醇在浓硫酸催化下发生可逆酯化反应，生成酯。
Crude oil is a mixture of hydrocarbons separated by fractional distillation. Fractions differ in boiling point, viscosity, and flammability. Longer‑chain hydrocarbons have higher boiling points and are used as fuels, bitumen, etc.
原油是烃的混合物，通过分馏分离。各馏分的沸点、黏度和易燃性不同。碳链越长的烃沸点越高，用作燃料、沥青等。
10. Chemical Analysis and Experimental Techniques | 化学分析与实验技术
Identifying common gases: hydrogen burns with a squeaky pop; oxygen relights a glowing splint; carbon dioxide turns limewater milky; chlorine bleaches damp litmus paper; ammonia turns damp red litmus blue.
常见气体的鉴别：氢气点燃有尖锐爆鸣声；氧气使带火星木条复燃；二氧化碳使石灰水变浑浊；氯气使湿润石蕊试纸褪色；氨气使湿润红色石蕊试纸变蓝。
Cation tests:
- Flame tests: Li⁺ – red, Na⁺ – yellow, K⁺ – lilac, Ca²⁺ – brick red, Cu²⁺ – blue‑green.
- Adding sodium hydroxide: Cu²⁺ forms a blue precipitate; Fe²⁺ forms a green precipitate turning brown on standing; Fe³⁺ forms a red‑brown precipitate; Al³⁺ and Zn²⁺ form white precipitates that dissolve in excess NaOH.
阳离子检验：
- 焰色反应：Li⁺–红色，Na⁺–黄色，K⁺–紫色，Ca²⁺–砖红色，Cu²⁺–蓝绿色。
- 加入氢氧化钠溶液：Cu²⁺形成蓝色沉淀；Fe²⁺形成绿色沉淀，久置变棕；Fe³⁺形成红褐色沉淀；Al³⁺和Zn²⁺形成白色沉淀，溶于过量NaOH。
Anion tests:
- Carbonate (CO₃²⁻): add dilute acid; effervescence of CO₂ which turns limewater milky.
- Sulfate (SO₄²⁻): add barium chloride and dilute HCl; a white precipitate of BaSO₄ forms.
- Halide ions: add nitric acid and silver nitrate; Cl⁻ gives white ppt, Br⁻ cream ppt, I⁻ yellow ppt.
阴离子检验：
- 碳酸根（CO₃²⁻）：加入稀酸，产生使石灰水变浑浊的气泡。
- 硫酸根（SO₄²⁻）：加入氯化钡和稀盐酸，生成BaSO₄白色沉淀。
- 卤离子：加入硝酸和硝酸银，Cl⁻生成白色沉淀，Br⁻生成奶油色沉淀，I⁻生成黄色沉淀。
Separation techniques: filtration separates insoluble solids from liquids; evaporation/crystallisation obtains soluble salt from solution; simple distillation separates a solvent from a solution; fractional distillation separates liquids with different boiling points; paper chromatography separates mixtures of soluble substances, with Rf values used for identification.
分离技术：过滤分离不溶性固体与液体；蒸发/结晶从溶液中获得可溶盐；简单蒸馏分离溶剂和溶液；分馏分离不同沸点的液体；纸色谱分离可溶性混合物，利用Rf值进行鉴定。
11. Environmental and Industrial Chemistry | 环境与工业化学
Air is a mixture of gases: about 78% nitrogen, 21% oxygen, and small amounts of argon, carbon dioxide, and water vapour. The main source of air pollution is burning fossil fuels, which releases CO₂, SO₂, NOₓ, and particulates.
空气是气体的混合物：约78%氮气、21%氧气以及少量氩气、二氧化碳和水蒸气。空气污染主要源于化石燃料燃烧，释放CO₂、SO₂、氮氧化物和颗粒物。
Acid rain is formed when sulfur dioxide and nitrogen oxides dissolve in water vapour, forming sulfuric and nitric acids. It harms aquatic life, damages buildings, and leaches nutrients from soil. Catalytic converters in cars reduce NOₓ emissions.
酸雨由二氧化硫和氮氧化物溶解于水蒸气形成硫酸和硝酸，危害水生生物、腐蚀建筑并淋洗土壤养分。汽车催化转化器可降低氮氧化物排放。
The greenhouse effect: gases such as CO₂, methane, and water vapour absorb infrared radiation, trapping heat and warming the Earth. Enhanced greenhouse effect from human activity is linked to climate change and rising sea levels.
温室效应：CO₂、甲烷和水蒸气等气体吸收红外辐射，捕获热量使地球变暖。人类活动造成的增强温室效应与气候变化和海平面上升相关。
Industrial processes: the Haber process makes ammonia, used for fertilisers. The Contact process produces sulfuric acid: sulfur → SO₂ → SO₃ → H₂SO₄, using vanadium(V) oxide catalyst. The conditions of temperature and pressure are optimised for yield and rate.
工业过程：哈伯法合成氨，用于化肥生产。接触法制硫酸：硫→SO₂→SO₃→H₂SO₄，使用五氧化二钒催化剂。通过优化温度与压强兼顾产率与速率。
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