📚 Mastering Edexcel IGCSE Chemistry: Key Concepts from the Student Book | 掌握爱德思国际 GCSE 化学：教材核心概念
The Pearson Edexcel International GCSE (9-1) Chemistry Student Book covers all the essential topics required for the examination, from atomic structure to organic chemistry and practical skills. This revision guide highlights key definitions, equations and common mistakes to help you prepare effectively.
Pearson Edexcel 国际 GCSE（9-1）化学教材涵盖了考试要求的所有核心主题，从原子结构到有机化学和实验技能。本复习指南突出关键定义、方程式和常见错误，帮助你高效备考。
1. States of Matter and Kinetic Theory | 物质状态与分子运动论
Particles in a solid are closely packed in a regular arrangement and only vibrate around fixed positions, which gives solids a definite shape and volume. In a liquid, particles are still close but can move past each other, so liquids take the shape of their container.
固体中的粒子紧密排列成规则结构，只在固定位置附近振动，因此固体有确定的形状和体积。液体中粒子仍然紧密但可以相互滑动，因此液体会随容器形状而变化。
Diffusion is fastest in gases because particles move rapidly and have large spaces between them. The rate of diffusion increases with temperature and decreases with increasing molecular mass.
气体中的扩散最快，因为粒子运动迅速且间距大。扩散速率随温度升高而加快，随分子质量增大而减慢。
Changes of state include melting, boiling, condensing and freezing. These are physical changes because no new substances are formed, and mass is conserved during the process.
状态变化包括熔化、沸腾、冷凝和凝固。这些属于物理变化，因为没有新物质生成，且变化过程中质量守恒。
- Solid: fixed shape, fixed volume, particles vibrate. | 固体：形状固定、体积固定，粒子振动。
- Liquid: no fixed shape, fixed volume, particles slide. | 液体：形状不固定、体积固定，粒子滑动。
- Gas: no fixed shape or volume, particles move freely. | 气体：形状和体积均不固定，粒子自由运动。
2. Atomic Structure and the Periodic Table | 原子结构与元素周期表
Every atom contains protons and neutrons in the nucleus, with electrons arranged in shells around the nucleus. The atomic number (Z) is the number of protons, while the mass number (A) is the total number of protons and neutrons.
每个原子由原子核中的质子和中子以及核外分层排布的电子组成。原子序数（Z）是质子数，质量数（A）是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, so they have the same chemical properties but different physical properties.
同位素是质子数相同而中子数不同的同种元素原子，因此化学性质相同但物理性质不同。
Electronic configuration for the first 20 elements can be written as 2,8,8 etc. Elements in the same group have the same number of outer electrons, which determines their chemical reactivity.
前 20 号元素的电子排布可写为 2、8、8 等。同一族元素具有相同的最外层电子数，这决定了它们的化学活泼性。
The Periodic Table arranges elements in order of increasing atomic number. Group 1 alkali metals are very reactive, Group 7 halogens become less reactive down the group, and Group 0 noble gases are inert due to full outer shells.
元素周期表按原子序数递增排列。第 1 族碱金属非常活泼，第 7 族卤素从上到下活泼性逐渐减弱，第 0 族稀有气体因最外层电子已满而化学性质稳定。
3. Chemical Bonding: Ionic, Covalent and Metallic | 化学键：离子键、共价键与金属键
Ionic bonding occurs when a metal transfers electrons to a non-metal, forming positive and negative ions. These ions are held together by strong electrostatic forces in a giant ionic lattice, which explains high melting points and electrical conductivity when molten or dissolved.
离子键发生在金属向非金属转移电子时，形成阳离子和阴离子。这些离子在巨大的离子晶格中通过强静电引力结合，因此离子化合物熔点高，在熔融或溶解时能导电。
Covalent bonding involves the sharing of electron pairs between non-metal atoms. Simple molecular substances such as H₂O and CO₂ have low melting points due to weak intermolecular forces, while giant covalent structures like diamond and silicon dioxide are very hard and have high melting points.
共价键涉及非金属原子之间共享电子对。像 H₂O 和 CO₂ 这样的简单分子物质因分子间作用力弱而熔点低，而金刚石、二氧化硅等巨型共价结构则非常坚硬、熔点很高。
Metallic bonding consists of positive metal ions surrounded by a ‘sea’ of delocalised electrons. This model explains why metals conduct electricity and heat, and why they are malleable and ductile.
金属键由正金属离子和周围的离域电子 ‘海洋’ 组成。这一模型解释了金属为何能导电导热，以及为何具有延展性和可塑性。
Common ion charges to remember include Na⁺, Mg²⁺, Al³⁺, Cl⁻, O²⁻ and OH⁻. The formula of an ionic compound must balance the total positive and negative charges.
需要记住的常见离子电荷包括 Na⁺、Mg²⁺、Al³⁺、Cl⁻、O²⁻ 和 OH⁻。离子化合物的化学式必须使正负电荷总数平衡。
4. Chemical Formulae, Equations and Calculations | 化学式、方程式与计算
The mole is the unit for amount of substance. One mole of any substance contains 6.02 × 10²³ particles. Molar mass (M) is the mass of one mole in grams, numerically equal to the relative formula mass.
摩尔是物质的量的单位。1 摩尔任何物质含有 6.02 × 10²³ 个粒子。摩尔质量（M）是 1 摩尔物质的质量，以克为单位，数值上等于相对式量。
At room temperature and pressure (RTP), one mole of any gas occupies 24 dm³. This allows calculations of gas volumes from moles and vice versa.
在常温常压（RTP）下，1 摩尔任何气体的体积为 24 dm³。这可用于气体体积和物质的量之间的换算。
Number of moles = mass ÷ molar mass
物质的量 = 质量 ÷ 摩尔质量
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.
经验式是化合物中原子的最简整数比。求经验式时，将各元素的质量或百分含量除以相对原子质量，再除以最小结果。
Concentration is measured in mol/dm³ or g/dm³. The equation concentration = amount of solute ÷ volume of solution is frequently tested in titration calculations.
浓度以 mol/dm³ 或 g/dm³ 表示。公式 浓度 = 溶质的量 ÷ 溶液体积 在滴定计算中经常考查。
Concentration (mol/dm³) = moles ÷ volume (dm³)
浓度（mol/dm³）= 物质的量 ÷ 体积（dm³）
5. Acids, Bases and Salts | 酸、碱与盐
Acids are proton donors and produce H⁺ ions in aqueous solution. Common acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃). Bases neutralise acids and include metal oxides and hydroxides.
酸是质子给予体，在水溶液中产生 H⁺ 离子。常见酸包括盐酸（HCl）、硫酸（H₂SO₄）和硝酸（HNO₃）。碱能中和酸，包括金属氧化物和氢氧化物。
The pH scale ranges from 0 to 14: values below 7 are acidic, 7 is neutral, and above 7 are alkaline. Universal indicator shows a range of colours depending on pH.
pH 标度范围为 0 到 14：小于 7 呈酸性，等于 7 为中性，大于 7 呈碱性。通用指示剂根据 pH 呈现不同颜色。
Salts are formed when acids react with metals, bases or carbonates. The method of preparation depends on the solubility of the salt; insoluble salts are made by precipitation.
酸与金属、碱或碳酸盐反应生成盐。盐的制备方法取决于其溶解性；不溶性盐通过沉淀法制备。
Soluble salts can be prepared by reacting an acid with an excess insoluble base or metal carbonate, followed by filtration and evaporation. Insoluble salts are made by mixing two soluble solutions and filtering the precipitate.
可溶性盐可用酸与过量的不溶性碱或金属碳酸盐反应，然后过滤、蒸发制得。不溶性盐则通过混合两种可溶性溶液并过滤沉淀来制备。
acid + base → salt + water
酸 + 碱 → 盐 + 水
6. Electrolysis and Electrochemistry | 电解与电化学
Electrolysis is the decomposition of an ionic compound using direct current. The positive anode attracts anions, where oxidation occurs; the negative cathode attracts cations, where reduction occurs.
电解是利用直流电分解离子化合物。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 the electrolysis of molten lead(II) bromide, lead metal forms at the cathode and bromine gas at the
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