📚 IGCSE Edexcel Chemistry: Last-Minute Revision Notes | IGCSE Edexcel 化学：考前冲刺笔记
This set of last-minute revision notes covers the essential concepts, definitions, equations, and common pitfalls for the IGCSE Edexcel Chemistry exam. Use these concise summaries to reinforce your understanding, memorise key facts, and boost your confidence right before the test.
这份考前冲刺笔记涵盖了IGCSE Edexcel化学考试的核心概念、定义、方程式和常见易错点。利用这些简明的总结来巩固理解、记忆关键事实，并在考前增强信心。
1. Atomic Structure & Periodic Table | 原子结构与周期表
Atoms contain a central nucleus made of protons and neutrons, surrounded by electrons arranged in shells. The proton number (atomic number, Z) defines the element, while the mass number (A) is the total of protons and neutrons.
原子包含一个由质子和中子组成的中心原子核，周围是分层排布的电子。质子数（原子序数Z）决定了元素种类，而质量数（A）是质子数与中子数之和。
Relative masses and charges of subatomic particles must be memorised: proton = 1, +1; neutron = 1, 0; electron = 1/1836, –1. Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons; they have identical chemical properties but slightly different physical properties.
必须记住亚原子粒子的相对质量和电荷：质子 = 1, +1；中子 = 1, 0；电子 = 1/1836，–1。同位素是质子数相同但中子数不同的同一元素原子；它们化学性质相同，但物理性质略有不同。
Electronic configuration is written as 2,8,1 for sodium (Na) and 2,8,8 for argon (Ar). The group number tells you the number of outer‑shell electrons for Groups 1-2 and 13-18 (Group 13 has 3, Group 18 has 8 except helium). Period number equals the number of occupied shells.
电子排布写作2,8,1代表钠（Na），2,8,8代表氩（Ar）。族数告诉你1-2族和13-18族元素的最外层电子数（13族有3个，18族有8个，氦除外）。周期数等于占用的电子层数。
The Periodic Table is arranged in order of increasing atomic number. Metals are on the left, non‑metals on the right. 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排列。金属在左边，非金属在右边。同族元素具有相似的化学性质，因为它们的最外层电子数相同。
2. Chemical Bonding & Structure | 化学键与结构
Ionic bonding occurs between metals and non‑metals; metal atoms lose electrons to form positive ions (cations), non‑metal atoms gain electrons to form negative ions (anions). The electrostatic attraction between oppositely charged ions forms a giant ionic lattice.
离子键形成于金属和非金属之间；金属原子失去电子形成阳离子，非金属原子得到电子形成阴离子。带相反电荷离子间的静电引力形成巨型离子晶格。
You must be able to draw dot‑and‑cross diagrams for NaCl, MgO, and CaCl₂. Use dots for one species and crosses for the other, and show only outer‑shell electrons. For covalent bonding, shared pairs of electrons between non‑metal atoms are drawn as overlapping circles.
你必须能够画出NaCl、MgO和CaCl₂的点叉图。用点表示一种原子，叉表示另一种，只画最外层电子。对于共价键，非金属原子间共用电子对用重叠圆圈表示。
Simple molecular substances like H₂O, CO₂, CH₄ have low melting and boiling points because of weak intermolecular forces, not weak covalent bonds. Giant covalent structures such as diamond, graphite, and silicon dioxide have very high melting points because many strong covalent bonds must be broken.
简单分子物质例如H₂O、CO₂、CH₄具有低熔点和沸点，这是因为分子间作用力微弱，而非共价键弱。金刚石、石墨和二氧化硅等巨型共价结构具有非常高的熔点，因为需要破坏大量牢固的共价键。
Graphite is exceptional: each carbon atom bonds to three others in layers, with delocalised electrons between the layers, allowing it to conduct electricity and act as a lubricant. Diamond does not conduct electricity because all four outer electrons are used in bonding.
石墨很特殊：每个碳原子与另外三个碳原子结合成层状，层间有离域电子，因此可以导电并用作润滑剂。金刚石不导电，因为所有四个外层电子都用于成键。
Metallic bonding involves a lattice of positive metal ions surrounded by a ‘sea’ of delocalised electrons. This explains malleability (layers can slide) and electrical conductivity.
金属键涉及正金属离子晶格被离域电子的“海洋”包围。这解释了金属的延展性（原子层可以滑动）和导电性。
3. Formulae, Equations & Moles | 化学式、方程式与摩尔
The mole is the amount of substance that contains 6.02 × 10²³ particles. Molar mass (Mᵣ) is the mass of one mole in grams. The key formula is: n = m / M, where n is moles, m is mass in g.
摩尔是含有6.02 × 10²³个粒子的物质的量。摩尔质量（Mᵣ）是一摩尔物质的质量，单位克。核心公式是：n = m / M，其中n是摩尔数，m是质量（克）。
To calculate reacting masses, work through: write balanced equation, find moles of known substance, use mole ratio to find moles of unknown, then multiply by molar mass. Always check for limiting reactants.
计算反应质量时，步骤为：写出配平的方程式，求出已知物质的摩尔数，利用摩尔比求出未知物质的摩尔数，再乘以摩尔质量。务必检查是否存在限量反应物。
Concentration is measured in mol/dm³ or g/dm³. The relationship: concentration (mol/dm³) = moles / volume (dm³). To convert cm³ to dm³, divide by 1000.
浓度以mol/dm³或g/dm³计量。关系：浓度（mol/dm³）= 摩尔数 / 体积（dm³）。将cm³转换为dm³需除以1000。
Empirical formula is the simplest whole‑number ratio of atoms in a compound. To find it, divide the mass or percentage of each element by its relative atomic mass, then divide by the smallest result to obtain a ratio.
实验式是化合物中各原子最简整数比。求法是，将每种元素的质量或百分比除以其相对原子质量，然后除以最小结果得到比例。
Percentage yield = (actual yield / theoretical yield) × 100. Reasons for less than 100% include incomplete reaction, side reactions, and loss during purification.
产率百分比 = (实际产量 / 理论产量) × 100。低于100%的原因包括反应不完全、副反应以及提纯过程中的损失。
4. Electrolysis | 电解
Electrolysis is the decomposition of an ionic compound by passing a direct electric current through its molten or dissolved state. The electrolyte must contain free ions to conduct electricity.
电解是利用直流电通过熔融态或溶解态的离子化合物使其分解的过程。电解质必须含有自由离子才能导电。
At the cathode (negative electrode), cations are reduced, gaining electrons. At the anode (positive electrode), anions are oxidised, losing electrons. Remember OIL RIG: Oxidation Is Loss, Reduction Is Gain.
在阴极（负极），阳离子被还原，得到电子。在阳极（正极），阴离子被氧化，失去电子。记住OIL RIG：氧化是失电子，还原是得电子。
In aqueous solutions, water may also be discharged. For a concentrated halide solution, the halogen (Cl₂, Br₂, I₂) forms at the anode. In dilute or sulfate/nitrate solutions, oxygen gas is produced at the anode from OH⁻ ions.
在水溶液中，水也可能被放电。对于浓卤化物溶液，卤素单质（Cl₂、Br₂、I₂）在阳极生成。在稀溶液或硫酸盐/硝酸盐溶液中，阳极由OH⁻生成氧气。
At the cathode, hydrogen is produced if the metal is more reactive than hydrogen (e.g., K, Na, Ca, Mg, Al). Otherwise the metal itself is deposited (e.g., Cu, Ag).
在阴极，如果金属比氢活泼（如K、Na、Ca、Mg、Al），则产生氢气；否则金属本身会析出（如Cu、Ag）。
Aluminium is extracted by electrolysis of aluminium oxide dissolved in molten cryolite. This lowers the melting point and reduces energy cost. The anode must be replaced regularly because the oxygen produced reacts with the carbon anode to form CO₂.
铝是通过电解溶解在熔融冰晶石中的氧化铝来提取的。这降低了熔点，减少了能耗。阳极必须定期更换，因为生成的氧气会与碳阳极反应生成CO₂。
5. Energetics | 能量变化
An exothermic reaction releases heat to the surroundings, causing a temperature rise (ΔH negative). Common examples include combustion, neutralisation, and respiration. An endothermic reaction absorbs heat, causing a temperature drop (ΔH positive), such as photosynthesis and thermal decomposition.
放热反应向环境释放热量，使温度升高（ΔH为负）。常见例子有燃烧、中和和呼吸作用。吸热反应吸收热量，使温度降低（ΔH为正），如光合作用和热分解。
Bond breaking is endothermic (requires energy); bond making is exothermic (releases energy). The overall enthalpy change, ΔH = energy needed to break bonds – energy released when new bonds form.
断键是吸热的（需要能量）；成键是放热的（释放能量）。总焓变，ΔH = 断裂化学键所需能量 – 形成新化学键所释放的能量。
In calorimetry, the heat energy change Q = m × c × ΔT, where m is mass of water (g), c is specific heat capacity (4.2 J/g°C for water), and ΔT is temperature change. Calculate ΔH per mole by dividing Q by number of moles of fuel or reactant.
在量热法中，热能变化 Q = m × c × ΔT，其中m是水的质量（g），c是比热容（水为4.2 J/g°C），ΔT是温度变化。通过将Q除以燃料或反应物的摩尔数可计算出每摩尔的ΔH。
A simple energy level diagram shows reactants and products. In an exothermic reaction, products are lower in energy than reactants; in an endothermic reaction, products are higher. Activation energy is the minimum energy needed for a reaction to occur.
简单的能级图表示出反应物与生成物。在放热反应中，生成物的能量比反应物低；在吸热反应中，生成物的能量比反应物高。活化能是反应发生所需的最小能量。
6. Rates of Reaction | 反应速率
Rate of reaction is the change in concentration of a reactant or product per unit time. It can be measured by monitoring volume of gas produced, mass loss, colour change, or appearance of a precipitate.
反应速率是单位时间内反应物或生成物浓度的变化。可通过监测气体体积、质量损失、颜色变化或沉淀生成来测量。
Collision theory states that for a reaction to occur, particles must collide with sufficient energy (equal to or greater than the activation energy) and with correct orientation.
碰撞理论指出，要发生反应，粒子必须发生碰撞，且碰撞能量需达到或超过活化能，同时有合适的取向。
Increasing temperature increases the rate because particles move faster, collide more frequently, and a greater proportion of collisions have energy above the activation energy. A 10°C rise often roughly doubles the rate.
升高温度会提高反应速率，因为粒子运动更快，碰撞更频繁，且更大比例的碰撞具有超过活化能的能量。温度每升高10°C，速率通常约翻倍。
Increasing concentration or pressure increases the number of particles per unit volume, so collisions become more frequent. Increasing surface area of a solid reactant exposes more particles to collisions, speeding up the reaction.
增大浓度或压强会增加单位体积的粒子数目，从而碰撞更频繁。增加固体反应物的表面积可让更多粒子暴露参与碰撞，加速反应。
A catalyst provides an alternative reaction pathway with a lower activation energy. It is chemically unchanged at the end of the reaction. Enzymes are biological catalysts that work under specific temperature and pH conditions.
催化剂提供一条活化能更低的其他反应路径。反应结束后催化剂化学组成不变。酶是生物催化剂，在特定温度和pH条件下发挥作用。
7. Acids, Bases & Salts | 酸、碱与盐
An acid is a proton (H⁺) donor. Common strong acids include HCl, H₂SO₄, HNO₃. A base is a proton acceptor, and an alkali is a soluble base that releases OH⁻ ions in water.
酸是质子（H⁺）的给予体。常见的强酸有HCl、H₂SO₄、HNO₃。碱是质子的接受体，而碱是溶于水后可释放OH⁻离子的可溶性碱。
The pH scale ranges from 0 to 14: acidic solutions have pH < 7, neutral pH = 7, alkaline pH > 7. Universal indicator or a pH meter can be used to measure pH.
pH标度范围是0到14：酸性溶液pH < 7，中性pH = 7，碱性pH > 7。可用通用指示剂或pH计来测量pH值。
Neutralisation: H⁺ + OH⁻ → H₂O. Acid + metal oxide/hydroxide → salt + water. Acid + carbonate → salt + water + CO₂. Acid + metal → salt + hydrogen (except with unreactive metals).
中和反应：H⁺ + OH⁻ → H₂O。酸 + 金属氧化物/氢氧化物 → 盐 + 水。酸 + 碳酸盐 → 盐 + 水 + CO₂。酸 + 金属 → 盐 + 氢气（不活泼金属除外）。
Solubility rules are essential: all sodium, potassium, and ammonium salts are soluble; all nitrates are soluble; chlorides are soluble except lead and silver chlorides; sulfates are soluble except barium, lead, and calcium sulfates; carbonates and hydroxides are generally insoluble except those of Group 1 and ammonium.
溶解性规则至关重要：所有钠盐、钾盐和铵盐都可溶；所有硝酸盐都可溶；氯化物除铅和银的外都可溶；硫酸盐除钡、铅和钙的外都可溶；碳酸盐和氢氧化物除第1族和铵盐外一般不溶。
To prepare a pure, dry sample of a soluble salt, you can use titration for Group 1/ammonium salts, or acid + excess insoluble base/metal/carbonate followed by filtration, evaporation, and crystallisation.
要制备纯净干燥的可溶性盐样品，可使用酸碱滴定制备第1族或铵盐，或使用酸加过量不溶性碱/金属/碳酸盐，然后过滤、蒸发、结晶。
8. Metals & Reactivity Series | 金属与反应性序列
The reactivity series lists metals in order of their tendency to lose electrons and form positive ions: K > Na > Ca > Mg > Al > (C) > Zn > Fe > (H) > Cu > Ag > Au. Carbon and hydrogen are included for comparison.
金属活动性顺序按金属失去电子形成阳离子的倾向排列：K > Na > Ca > Mg > Al > (C) > Zn > Fe > (H) > Cu > Ag > Au。其中加入了碳和氢作为参照。
More reactive metals displace less reactive metals from their compounds. For example, Zn + CuSO₄ → ZnSO₄ + Cu. A metal will only react with an acid if it is above hydrogen in the reactivity series.
较活泼的金属可从其化合物中置换出较不活泼的金属。例如，Zn + CuSO₄ → ZnSO₄ + Cu。只有位于氢之前的金属才能与酸反应。
Rusting of iron requires both oxygen and water. Rust is hydrated iron(III) oxide. Barriers (paint, oil, grease), galvanising (coating with zinc) and sacrificial protection (attaching more reactive metal like magnesium) prevent rusting.
铁生锈需要氧气和水同时存在。铁锈是水合氧化铁(III)。隔层（油漆、油、油脂）、镀锌（覆锌层）以及牺牲性保护（附上更活泼的金属如镁）均可防锈。
Alloys are mixtures of a metal with other elements, designed to enhance properties. Steel is an alloy of iron with carbon and other metals; it is harder and less likely to rust than pure iron. Brass (copper and zinc) and bronze (copper and tin) are common alloys.
合金是金属与其他元素的混合物，旨在改善性能。钢是铁与碳及其他金属的合金；它比纯铁更硬且不易生锈。黄铜（铜和锌）和青铜（铜和锡）是常见的合金。
9. Organic Chemistry | 有机化学
Organic compounds contain carbon; hydrocarbons contain only carbon and hydrogen. Alkanes are saturated hydrocarbons with the general formula CₙH₂ₙ₊₂. Their names end in -ane: methane CH₄, ethane C₂H₆, propane C₃H₈, butane C₄H₁₀.
有机化合物含碳；碳氢化合物仅含碳和氢。烷烃是饱和烃，通式CₙH₂ₙ₊₂。其名称以-ane结尾：甲烷CH₄，乙烷C₂H₆，丙烷C₃H₈，丁烷C₄H₁₀。
Alkenes are unsaturated hydrocarbons with the general formula CₙH₂ₙ, containing a C=C double bond. Their names end in -ene: ethene C₂H₄, propene C₃H₆. The double bond makes alkenes more reactive than alkanes, and they undergo addition reactions.
烯烃是不饱和烃，通式CₙH₂ₙ，含C=C双键。其名称以-ene结尾：乙烯C₂H₄，丙烯C₃H₆。双键使烯烃比烷烃更活泼，它们可发生加成反应。
Test for unsaturation: add bromine water (orange) to the sample. In the presence of an alkene, bromine water decolourises rapidly. Alkanes do not decolourise bromine water unless in UV light (substitution reaction).
检验不饱和性：向样品中加入溴水（橙色）。若有烯烃存在，溴水迅速褪色。烷烃除非在紫外光下（取代反应），否则不会使溴水褪色。
Cracking breaks long‑chain alkanes into shorter, more useful alkanes and alkenes. It requires heat and a catalyst (catalytic cracking) or steam (steam cracking). Cracking helps match supply with demand for smaller hydrocarbons and produces alkenes for polymers.
裂化将长链烷烃断裂成较短的、更有用的烷烃和烯烃。需要加热和催化剂（催化裂化）或蒸汽（蒸汽裂化）。裂化有助于使小分子烃类的供需匹配，并生产用于制聚合物的烯烃。
Polymers are long chains formed from small monomers. Addition polymerisation joins alkene monomers without losing any atoms. For example, poly(ethene) is made from ethene. The repeating unit should be drawn with the double bond opened up.
聚合物是由小分子单体形成的长链。加聚反应将烯烃单体连接起来，没有原子损失。例如，聚乙烯由乙烯制成。重复单元应画出打开双键的连接方式。
10. Chemical Analysis | 化学分析
Flame tests identify metal cations: Li⁺ gives crimson red; Na⁺ gives yellow; K⁺ gives lilac; Ca²⁺ gives brick red; Cu²⁺ gives blue‑green. Use a clean nichrome wire dipped in concentrated HCl, then powdered sample, and place in the blue flame of a Bunsen burner.
焰色反应鉴定金属阳离子：Li⁺呈深红色；Na⁺呈黄色；K⁺呈淡紫色；Ca²⁺呈砖红色；Cu²⁺呈蓝绿色。用洁净的镍铬丝蘸取浓盐酸，再蘸取粉末样品，置于本生灯蓝色火焰中。
Sodium hydroxide precipitates help identify metal ions in solution: Cu²⁺ gives a blue precipitate; Fe²⁺ a green precipitate; Fe³⁺ a brown precipitate; Al³⁺ and Zn²⁺ both give white precipitates, but the precipitate of Al³⁺ does not dissolve in excess NaOH, while Zn²⁺ does dissolve (amphoteric).
氢氧化钠沉淀有助于鉴定溶液中的金属离子：Cu²⁺生成蓝色沉淀；Fe²⁺生成绿色沉淀；Fe³⁺生成棕色沉淀；Al³⁺和Zn²⁺都生成白色沉淀，但Al³⁺的沉淀不溶于过量NaOH，而Zn²⁺的沉淀会溶解（两性）。
Tests for anions: Carbonates (CO₃²⁻) fizz with dilute acid, releasing CO₂ which turns limewater milky. Sulfates (SO₄²⁻) give a white precipitate with acidified barium chloride. Halides (Cl⁻, Br⁻, I⁻) give precipitates with acidified silver nitrate: white for chloride, cream for bromide, yellow for iodide; solubility in ammonia confirms the halide.
阴离子检验：碳酸根（CO₃²⁻）遇稀酸冒泡，释放出使石灰水变浑浊的CO₂。硫酸根（SO₄²⁻）与酸化的氯化钡产生白色沉淀。卤离子（Cl⁻、Br⁻、I⁻）与酸化的硝酸银产生沉淀：氯化银白色，溴化银奶油色，碘化银黄色；沉淀在氨水中的溶解性可确认卤离子种类。
Gas tests: Hydrogen pops with a lighted splint; oxygen relights a glowing splint; carbon dioxide turns limewater milky; chlorine bleaches damp litmus paper; ammonia turns red litmus blue and gives a white smoke with HCl vapour.
气体检验：氢气遇点燃的木条发出爆鸣声；氧气可使带火星的木条复燃；二氧化碳使石灰水变浑浊；氯气漂白湿润的石蕊试纸；氨气使红色石蕊试纸变蓝，并与HCl蒸气产生白烟。
11. Common Exam Pitfalls | 常见考试陷阱
Never confuse intermolecular forces with covalent bonds when explaining melting points of simple molecules. State that it is weak intermolecular forces that are overcome, not the strong covalent bonds within the molecule.
在解释简单分子物质的熔点时，千万不要混淆分子间作用力与共价键。要说克服的是微弱的分子间作用力，而非分子内牢固的共价键。
When writing ionic equations, ensure charges and atoms balance. For spectator ions, cancel them out. Always use state symbols: (s), (l), (g), (aq).
书写离子方程式时，要确保电荷和原子守恒。旁观离子要去掉。始终使用状态符号：(s)、(l)、(g)、(aq)。
In electrolysis, if the question does not specify molten or aqueous, deduce it from context. In aqueous solutions, consider the reactivity series and the ions present. Anode material matters: a reactive anode (like copper) can dissolve instead of evolving oxygen.
在电解题目中，若未明确说明是熔融态还是水溶液，需根据上下文推断。在水溶液中，要考虑金属活动性顺序和存在的离子。阳极材料很重要：活泼阳极（如铜）可能会溶解，而不是产生氧气。
Bond energy calculations must sum the energies for breaking all reactant bonds and subtract the sum for forming product bonds. A common mistake is to forget to multiply by the number of each bond type in the balanced equation.
键能计算必须将断裂所有反应物化学键的能量求和，再减去形成所有生成物化学键的能量之和。常见错误是忘记乘以配平方程式中每种键的数目。
When preparing salts, if the required salt is not soluble, use precipitation. Mix two soluble salts containing the required ions, filter, wash with distilled water, and dry between filter papers.
制备盐时，若所需盐不可溶，则使用沉淀法。混合两种含有目标离子的可溶性盐，过滤，用蒸馏水洗涤，并在滤纸间干燥。
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