📚 KS3 CIE Chemistry: Quick-Reference Formula & Theorem Handbook | KS3 CIE 化学：公式定理速查手册
This handbook covers the most essential chemical formulas, laws, and key principles for KS3 CIE Chemistry. Each section presents a core concept first in English and then in Chinese, helping you build a solid bilingual foundation for revision and exams.
本手册梳理了 KS3 CIE 化学阶段必须掌握的核心公式、定律与原理。每一小节先英文再中文对照讲解，帮助你在复习与考试中打下扎实的双语基础。
1. Law of Conservation of Mass | 质量守恒定律
The total mass of reactants always equals the total mass of products in a chemical reaction. Matter is neither created nor destroyed.
在化学反应中，反应物的总质量永远等于生成物的总质量。物质既不会凭空产生，也不会凭空消失。
Total mass of reactants = Total mass of products
反应物总质量 = 生成物总质量
This law is why all chemical equations must be balanced, with the same number of each type of atom on both sides.
这一定律要求所有化学方程式必须配平，方程式两边各类原子的数目必须相等。
2. Atomic Structure | 原子结构
Atoms are the smallest particles of an element. They consist of a nucleus containing protons and neutrons, surrounded by electrons in shells.
原子是元素最小的粒子。原子由包含质子和中子的原子核以及核外分层排布的电子构成。
| Particle 粒子 | Charge 电荷 | Relative mass 相对质量 |
|---|---|---|
| Proton 质子 | +1 | 1 |
| Neutron 中子 | 0 | 1 |
| Electron 电子 | –1 | 1/1836 ≈ 0 |
Atomic number = number of protons. Mass number = number of protons + number of neutrons.
原子序数 = 质子数。质量数 = 质子数 + 中子数。
3. Electron Configuration & the Periodic Table | 电子排布与周期表
Electrons fill shells in the order 2, 8, 8,... for the first three periods. The group number tells you the number of electrons in the outer shell (for Groups 1–2 and 13–18). The period number tells you the number of occupied shells.
电子按 2, 8, 8……的顺序填充壳层（前三周期）。主族序数（第1、2 族和 13–18 族）等于最外层电子数。周期序数等于电子层数。
- Group 1 elements have 1 outer electron (e.g., Na: 2,8,1).
- 第1族元素有 1 个最外层电子（如 Na：2,8,1）。
- Group 17 elements have 7 outer electrons (e.g., Cl: 2,8,7).
- 第17族元素有 7 个最外层电子（如 Cl：2,8,7）。
Noble gases (Group 18) have full outer shells, making them chemically stable.
稀有气体（第18族）具有满壳层结构，化学性质稳定。
4. Ions and Ionic Bonding | 离子与离子键
Metals lose electrons to form positive ions (cations). Non-metals gain electrons to form negative ions (anions). The charge on a simple ion equals the number of electrons lost or gained.
金属原子失去电子形成阳离子（正离子）。非金属原子得到电子形成阴离子（负离子）。简单离子的电荷数等于失去或得到的电子数。
,1) loses 1 electron → Na⁺ (2,8). Chlorine atom Cl (2,8,7) gains 1 electron → Cl⁻ (2,8,8).
示例：钠原子 Na (2,8,1) 失去 1 个电子 → Na⁺ (2,8)。氯原子 Cl (2,8,7) 得到 1 个电子 → Cl⁻ (2,8,8)。
Ionic compounds form when cations and anions are held together by strong electrostatic forces, forming a giant ionic lattice.
离子化合物由阳离子和阴离子通过强静电作用结合，形成巨型离子晶格。
5. Naming Compounds & Chemical Formulae | 化合物命名与化学式
The formula of a compound shows the symbols of the elements present and the ratio of their atoms. The name often comes from the elements involved, with the metal first.
化学式表示化合物所含元素的符号及其原子个数比。命名时通常金属元素在前，非金属元素在后。
- Sodium chloride: NaCl (Na⁺ and Cl⁻ in 1:1 ratio) | 氯化钠：NaCl（Na⁺ 与 Cl⁻ 比例 1:1）
- Magnesium oxide: MgO (Mg²⁺ and O²⁻) | 氧化镁：MgO
- Water: H₂O (two H, one O) | 水：H₂O
- Carbon dioxide: CO₂ | 二氧化碳：CO₂
For compounds containing polyatomic ions, brackets may be needed: calcium hydroxide is Ca(OH)₂, meaning one Ca²⁺ and two OH⁻ groups.
含原子团的化合物可能需要括号：氢氧化钙为 Ca(OH)₂，表示一个 Ca²⁺ 和两个 OH⁻。
6. Balancing Chemical Equations | 配平化学方程式
A balanced equation has the same number of atoms of each element on both sides. You balance by placing coefficients (whole numbers) in front of the formulae.
配平后的方程式两边每种元素的原子总数相等。配平时，只在化学式前添加适当的数字系数。
Unbalanced: H₂ + O₂ → H₂O
Balanced: 2H₂ + O₂ → 2H₂O (4H and 2O on each side)
未配平：H₂ + O₂ → H₂O
配平后：2H₂ + O₂ → 2H₂O（两边均为 4 个 H 和 2 个 O）
The state symbols (s), (l), (g), (aq) can be added: 2H₂(g) + O₂(g) → 2H₂O(l).
可以添加状态符号：(s) 固、(l) 液、(g) 气、(aq) 水溶液。例：2H₂(g) + O₂(g) → 2H₂O(l)。
7. Relative Atomic Mass & Formula Mass | 相对原子质量与相对分子质量
Relative atomic mass (Aᵣ) is the average mass of an atom of an element compared to 1/12 of the mass of a carbon-12 atom. It has no unit. For KS3, you can use the mass number as an approximation.
相对原子质量（Aᵣ）是该元素一个原子的平均质量与一个碳‑12 原子质量的 1/12 之比，无单位。KS3 阶段可近似取用质量数。
atoms in the formula. E.g., Mᵣ of H₂O = 2×1 + 16 = 18. Mᵣ of CaCO₃ = 40 + 12 + 3×16 = 100.
相对分子质量（Mᵣ）等于化学式中各原子的 Aᵣ 之和。例如 H₂O 的 Mᵣ = 2×1 + 16 = 18；CaCO₃ 的 Mᵣ = 40 + 12 + 3×16 = 100。
This concept is useful when working with conservation of mass and simple stoichiometry.
这一概念在应用质量守恒定律及简单化学计量时非常有用。
8. Acids, Alkalis & the pH Scale | 酸、碱与 pH 标度
Acids produce hydrogen ions (H⁺) in water. Alkalis produce hydroxide ions (OH⁻) in water. The pH scale (0–14) measures how acidic or alkaline a solution is.
酸溶于水产生氢离子（H⁺）。碱溶于水产生氢氧根离子（OH⁻）。pH 标度（0–14）用于衡量溶液的酸碱度。
- pH < 7: acidic (more H⁺) | 酸性（H⁺ 多）
- pH = 7: neutral (pure water) | 中性（纯水）
- pH > 7: alkaline (more OH⁻) | 碱性（OH⁻ 多）
Universal indicator or pH probe can be used to measure pH. Strong acids (e.g., hydrochloric acid) have low pH; strong alkalis (e.g., sodium hydroxide) have high pH.
可用通用指示剂或 pH 计测量 pH。强酸（如盐酸）pH 低；强碱（如氢氧化钠）pH 高。
9. Neutralisation Reaction | 中和反应
Neutralisation occurs when an acid reacts with an alkali to produce a salt and water. The ionic equation for neutralisation is:
中和反应是酸与碱作用生成盐和水的反应。中和反应的离子方程式为：
H⁺(aq) + OH⁻(aq) → H₂O(l)
Example: hydrochloric acid + sodium hydroxide → sodium chloride + water
HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)
示例：盐酸 + 氢氧化钠 → 氯化钠 + 水
HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)
Naming the salt: the first part comes from the metal (or base), the second part from the acid. Sulfuric acid gives sulfates; nitric acid gives nitrates.
盐的命名：前一半来自金属（或碱），后一半来自酸。硫酸生成硫酸盐，硝酸生成硝酸盐。
10. Reactivity Series of Metals | 金属活动性顺序
The reactivity series lists metals from most reactive to least reactive. A more reactive metal can displace a less reactive metal from its compound.
金属活动性顺序按反应活泼程度由高到低排列。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。
A common order for KS3: Potassium > Sodium > Calcium > Magnesium > Aluminium > Zinc > Iron > Lead > Copper > Silver > Gold.
KS3 常用顺序：钾 > 钠 > 钙 > 镁 > 铝 > 锌 > 铁 > 铅 > 铜 > 银 > 金。
- Zn + CuSO₄ → ZnSO₄ + Cu (zinc displaces copper) | 锌置换出铜
- Cu + ZnSO₄ → no reaction | 铜不能置换出锌
Reactions with water and acids also follow the series: only more reactive metals than hydrogen react with dilute acids to produce hydrogen gas.
与水、酸的反应同样遵循活动性顺序：只有活泼性在氢以上的金属才能从稀酸中置换出氢气。
11. Types of Chemical Reactions | 常见化学反应类型
Several reaction types appear at KS3:
KS3 阶段涉及以下几种反应类型：
- Combustion 燃烧: Substance + oxygen → oxides + energy. E.g., CH₄ + 2O₂ → CO₂ + 2H₂O
- Thermal decomposition 热分解: One compound breaks down into simpler substances when heated. E.g., CaCO₃ → CaO + CO₂
- Displacement 置换: ore reactive element takes the place of a less reactive one. E.g., Fe + CuSO₄ → FeSO₄ + Cu
- Oxidation 氧化: Gain of oxygen or loss of electrons. Rusting is oxidation: 4Fe + 3O₂ + xH₂O → 2Fe₂O₃·xH₂O
Recognising these patterns helps predict products and write equations.
识别这些反应模式有助于预测产物和书写方程式。
12. States of Matter & Separating Mixtures | 物质状态与混合物分离
Substances exist as solid, liquid or gas, depending on temperature and pressure. Changes of state are physical changes: melting, freezing, boiling, condensing, sublimation.
物质根据温度和压强可呈固态、液态或气态。状态变化属于物理变化：熔化、凝固、沸腾、冷凝、升华。
Mixtures can be separated using physical techniques based on differences in properties:
混合物可根据物质性质差异采用物理方法进行分离：
- Filtration 过滤 – separates an insoluble solid from a liquid (e.g., sand from water).
- Evaporation/Crystallisation 蒸发与结晶 – separates a dissolved solid from a liquid (salt from salt water).
- Simple distillation 简单蒸馏 – separates a solvent from a solution (pure water from salt water).
- Fractional distillation 分馏 – separates liquids with different boiling points (e.g., ethanol and water).
- Chromatography 色谱法 – separates dissolved substances based on their attraction to a medium (e.g., ink dyes).
Understanding these techniques is essential for practical chemistry and for explaining how pure substances are obtained.
理解这些分离方法是实验化学的基础，也是解释如何获得纯净物质的关键。
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