📚 Essential Chemistry for Cambridge IGCSE | CIE IGCSE 化学核心考点精讲
This revision guide condenses the most important CIE IGCSE Chemistry concepts into clear explanations, equations and practical reminders. It is suitable for both Core and Extended candidates who need to build confidence quickly before assessments.
本复习指南将 CIE IGCSE 化学最重要的概念浓缩为清晰讲解、化学方程式和实验提醒，适合 Core 与 Extended 考生在考前快速建立信心。
1. States of Matter and Kinetic Particle Theory | 物质状态与粒子运动理论
The kinetic particle model explains solids, liquids and gases in terms of particle arrangement, motion and spacing. In a solid, particles vibrate in fixed positions; in a liquid, they slide past each other; in a gas, they move rapidly and are far apart.
粒子运动模型从粒子的排列、运动和间距来解释固体、液体和气体。固体中的粒子在固定位置振动；液体中的粒子能够相互滑动；气体中的粒子快速运动且彼此相距很远。
| Process | Change | Energy |
|---|---|---|
| Melting | solid → liquid | absorbed |
| Boiling / evaporation | liquid → gas | absorbed |
| Condensation | gas → liquid | released |
| Freezing | liquid → solid | released |
| Sublimation | solid → gas | absorbed |
| Deposition | gas → solid | released |
Diffusion is the spreading of particles from high concentration to low concentration. It is fastest in gases, slower in liquids and negligible in solids because particle motion depends on the state and temperature.
扩散是粒子从高浓度区域向低浓度区域扩散的过程。气体中扩散最快，液体中较慢，固体中几乎不发生，因为粒子运动取决于物质状态和温度。
2. Atomic Structure and the Periodic Table | 原子结构与元素周期表
An atom contains protons and neutrons in the nucleus, with electrons arranged in shells. The proton number Z fixes the identity of an element, while the nucleon number A equals protons plus neutrons.
原子核内含有质子和中子，核外电子分层排布。质子数 Z 决定元素种类，而核子数 A 等于质子数加中子数。
| Particle | Relative mass | Relative charge |
|---|---|---|
| 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 different physical properties such as mass.
同位素是同一种元素中质子数相同但中子数不同的原子。它们的化学性质完全相同，但质量等物理性质不同。
Electrons fill shells in the order 2, 8, 8 for the first three shells in IGCSE. The electronic configuration of sodium (Z = 11) is 2,8,1.
在 IGCSE 范围内，电子按 2、8、8 的顺序填充前三个电子层。钠（Z = 11）的电子排布为 2,8,1。
3. Chemical Bonding: Ionic, Covalent and Metallic | 化学键：离子键、共价键与金属键
Ionic bonding involves electron transfer from a metal to a non-metal, producing positive and negative ions. The electrostatic attraction between oppositely charged ions forms a giant ionic lattice.
离子键涉及电子从金属向非金属转移，从而形成正离子和负离子。带相反电荷的离子之间的静电吸引力形成巨型离子晶格。
Covalent bonding involves shared pairs of electrons between non-metal atoms. Simple molecular substances have low melting points, while giant covalent structures such as diamond and graphite have very high melting points.
共价键涉及非金属原子之间共享电子对。简单分子物质的熔点较低，而金刚石和石墨等巨型共价结构具有很高的熔点。
Metallic bonding consists of positive metal ions surrounded by a sea of delocalised electrons, which explains electrical conductivity and malleability.
金属键由正金属离子和周围的离域电子海组成，这解释了金属的导电性和延展性。
4. Formulae, Equations and Stoichiometry | 化学式、方程式与化学计量
The mole is the unit of amount of substance. One mole of any substance contains 6.02 × 10²³ particles, known as the Avogadro constant.
摩尔是物质的量的单位。1 摩尔任何物质都含有 6.02 × 10²³ 个粒子，这个数值称为阿伏伽德罗常数。
n = m / Mᵣ
To calculate reacting masses, write a balanced equation, convert known mass to moles, use the mole ratio, and convert back to mass.
计算反应质量时，先写出配平的化学方程式，将已知质量换算为摩尔，利用摩尔比，再换算回质量。
Mg + 2HCl → MgCl₂ + H₂
5. Electrolysis and Redox | 电解与氧化还原
Electrolysis uses direct current to break down an ionic compound into its elements. Reduction occurs at the cathode and oxidation occurs at the anode.
电解利用直流电将离子化合物分解为组成它的元素。阴极发生还原反应，阳极发生氧化反应。
Cathode: Pb²⁺ + 2e⁻ → Pb
Anode: 2Br⁻ → Br₂ + 2e⁻
Redox reactions can be remembered by OIL RIG: Oxidation Is Loss of electrons, Reduction Is Gain of electrons.
氧化还原反应可以用 OIL RIG 来记忆：氧化是失去电子，还原是得到电子。
6. Energetics and Rates of Reaction | 能量变化与反应速率
Exothermic reactions release heat to the surroundings, while endothermic reactions absorb heat. Bond breaking is endothermic and bond making is exothermic.
放热反应向环境释放热量，而吸热反应从环境吸收热量。断键需要吸收能量，成键会释放能量。
ΔH = ΣE(bonds broken) − ΣE(bonds formed)
Reaction rate depends on concentration, temperature, surface area and catalysts. Increasing temperature increases the frequency and energy of collisions, so more collisions exceed the activation energy.
反应速率取决于浓度、温度、表面积和催化剂。升高温度会增加碰撞频率和碰撞能量，因此有更多碰撞超过活化能。
7. Acids, Bases and Salts | 酸、碱与盐
Acids release H⁺ ions in water; bases accept H⁺ ions. Alkalis are soluble bases that release OH⁻ ions.
酸在水中释放 H⁺ 离子；碱接受 H⁺ 离子。可溶性碱称为碱溶液，它们释放 OH⁻ 离子。
| Reaction | Products |
|---|---|
| acid + metal | salt + hydrogen |
| acid + base | salt + water |
| acid + carbonate | salt + water + carbon dioxide |
Salt preparation depends on solubility: soluble salts can be made by titration, while insoluble salts are made by precipitation.
盐的制备取决于溶解度：可溶性盐通常用滴定法制备，不溶性盐则用沉淀法制备。
8. The Periodic Table: Trends and Groups | 周期表规律与各族元素
Group I alkali metals become more reactive down the group because the outer electron is further from the nucleus and more easily lost. Group VII halogens become less reactive down the group because the outer shell is further from the nucleus and attracts electrons less strongly.
第 I 族碱金属从上到下活泼性逐渐增强，因为最外层电子离核越来越远，越容易失去。第 VII 族卤素从上到下活泼性逐渐减弱，因为最外层电子离核越来越远，对电子的吸引能力越弱。
Noble gases in Group VIII have full outer shells, so they are unreactive. Transition metals form coloured compounds and often act as catalysts.
第 VIII 族稀有气体最外层电子已满，因此化学性质不活泼。过渡金属通常能形成有色化合物，并常用作催化剂。
9. Metals and Extraction | 金属与冶炼
The reactivity series lists metals from most reactive to least reactive: K, Na, Ca, Mg, Al, Zn, Fe, Pb, H, Cu, Ag, Au. A more reactive metal can displace a less reactive metal from its compound.
金属活动性顺序从强到弱为：K、Na、Ca、Mg、Al、Zn、Fe、Pb、H、Cu、Ag、Au。较活泼的金属能把较不活泼的金属从其化合物中置换出来。
C(s) + O₂(g) → CO₂(g)
CO₂(g) + C(s) → 2CO(g)
Fe₂O₃(s) + 3CO(g) → 2Fe(l) + 3CO₂(g)
Aluminium is extracted by electrolysis of molten aluminium oxide: 2Al₂O₃ → 4Al + 3O₂.
铝通过电解熔融氧化铝的方法冶炼：2Al₂O₃ → 4Al + 3O₂。
10. Organic Chemistry | 有机化学
Alkanes have the general formula CₙH₂ₙ₊₂ and alkenes have the general formula CₙH₂ₙ. Alkenes turn bromine water colourless, while alkanes do not.
烷烃的通式是 CₙH₂ₙ₊₂，烯烃的通式是 CₙH₂ₙ。烯烃能使溴水褪色，而烷烃不能。
Alcohols contain the –OH functional group and carboxylic acids contain the –COOH functional group. Fermentation of glucose produces ethanol and carbon dioxide.
醇含有 –OH 官能团，羧酸含有 –COOH 官能团。葡萄糖发酵生成乙醇和二氧化碳。
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
11. Chemical Analysis and Practical Skills | 化学分析与实验技能
Gas tests are essential: oxygen relights a glowing splint, hydrogen gives a squeaky pop, carbon dioxide turns limewater milky, and chlorine bleaches damp litmus paper.
气体检验是必考内容：氧气能使带火星的木条复燃，氢气产生爆鸣声，二氧化碳使石灰水变浑浊，氯气能使湿润的蓝色石蕊试纸褪色。
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