📚 KS3 CAIE Chemistry: Quick Reference for Formulas and Theorems | KS3 CAIE 化学：公式定理速查手册
This handbook provides a concise summary of essential formulas, equations, and key principles for KS3 CAIE Chemistry. It is designed to help you revise quickly and reinforce your understanding of fundamental chemical concepts, from atomic structure to reaction rates.
本手册简要总结了 KS3 CAIE 化学的重要公式、方程式和关键原理。旨在帮助你快速复习，巩固从原子结构到反应速率等基本化学概念的理解。
1. Atoms, Elements and Compounds | 原子、元素与化合物
An atom is the smallest particle of an element that can take part in a chemical reaction. It consists of a nucleus containing protons and neutrons, surrounded by electrons in shells.
原子是能参与化学反应的元素最小粒子。它由包含质子和中子的原子核以及核外分层排布的电子组成。
The atomic number (Z) is the number of protons in the nucleus of an atom. It determines the identity of the element.
原子序数 (Z) 是原子核内质子的数目，它决定了元素的种类。
The mass number (A) is the total number of protons and neutrons in the nucleus.
质量数 (A) 是原子核内质子数与中子数之和。
A = Z + number of neutrons
An element is a pure substance that cannot be broken down into simpler substances by chemical means. A compound is a substance formed when two or more elements are chemically bonded together.
元素是不能通过化学方法分解成更简单物质的纯净物。化合物是由两种或两种以上元素通过化学键结合而成的物质。
2. Chemical Formulae and Equations | 化学式与方程式
A chemical formula shows the types and numbers of atoms present in a substance. The subscript after a symbol indicates how many atoms of that element are in one unit.
化学式表示物质中原子的种类和数目。元素符号后的下标表示该元素在一个单元中的原子个数。
To write a formula, use the valencies (combining powers) of elements or ions. Swap the valency numbers and write them as subscripts, then simplify if needed.
书写化学式时，使用元素或离子的化合价。交换化合价数值并写成下标，必要时进行约简。
Examples: Sodium chloride: Na⁺ and Cl⁻ → NaCl. Magnesium oxide: Mg²⁺ and O²⁻ → Mg₂O₂ simplified to MgO. Aluminium oxide: Al³⁺ and O²⁻ → Al₂O₃.
示例： 氯化钠：Na⁺ 与 Cl⁻ → NaCl。氧化镁：Mg²⁺ 与 O²⁻ → Mg₂O₂ 简化为 MgO。氧化铝：Al³⁺ 与 O²⁻ → Al₂O₃。
A balanced chemical equation has the same number of each type of atom on both sides. This follows the law of conservation of mass.
配平的化学方程式两边每种原子的数目相等。这遵循质量守恒定律。
State symbols show the physical state of reactants and products: (s) solid, (l) liquid, (g) gas, (aq) aqueous solution.
状态符号表示反应物和生成物的物理状态：(s) 固体，(l) 液体，(g) 气体，(aq) 水溶液。
| Common Ion | Formula | Valency |
|---|---|---|
| Sodium | Na⁺ | 1 |
| Chloride | Cl⁻ | 1 |
| Magnesium | Mg²⁺ | 2 |
| Oxide | O²⁻ | 2 |
| Aluminium | Al³⁺ | 3 |
| Sulfate | SO₄²⁻ | 2 |
| Nitrate | NO₃⁻ | 1 |
| Carbonate | CO₃²⁻ | 2 |
| Ammonium | NH₄⁺ | 1 |
| Hydroxide | OH⁻ | 1 |
3. Relative Atomic Mass and Relative Molecular Mass | 相对原子质量与相对分子质量
The relative atomic mass (Aᵣ) is the average mass of an atom of an element compared to 1/12th of the mass of a carbon‑12 atom. It has no units.
相对原子质量 (Aᵣ) 是元素一个原子的平均质量与一个碳‑12 原子质量的 1/12 的比值。它没有单位。
Aᵣ = (average mass of one atom of element) / (1/12 × mass of one ¹²C atom)
The relative molecular mass (Mᵣ) is the sum of the relative atomic masses of all atoms in a molecule. For ionic compounds, we use relative formula mass.
相对分子质量 (Mᵣ) 是分子中所有原子的相对原子质量之和。对于离子化合物，我们使用相对式量。
Example: H₂O: Aᵣ of H = 1, O = 16 → Mᵣ = (2 × 1) + 16 = 18. CO₂: Mᵣ = 12 + (2 × 16) = 44.
示例：H₂O：H 的 Aᵣ = 1，O = 16 → Mᵣ = (2×1)+16 = 18。CO₂：Mᵣ = 12+(2×16) = 44。
4. The Mole and Molar Mass | 摩尔与摩尔质量
A mole is the amount of substance that contains 6.02 × 10²³ particles (atoms, molecules, ions). This number is called the Avogadro constant.
摩尔是包含 6.02 × 10²³ 个粒子（原子、分子、离子）的物质的量。这个数字称为阿伏伽德罗常数。
The molar mass (M) of a substance is the mass of one mole of that substance. Its unit is g/mol. Numerically, it equals the relative atomic or formula mass.
物质的摩尔质量 (M) 是一摩尔该物质的质量，单位为 g/mol。在数值上等于其相对原子质量或式量。
The relationship among mass, moles, and molar mass is given by:
质量、摩尔与摩尔质量之间的关系如下：
moles = mass (g) / molar mass (g/mol)
mass (g) = moles × molar mass (g/mol)
Example: How many moles are in 36 g of water? Mᵣ of H₂O = 18, so n = 36 / 18 = 2 mol.
示例：36 g 水中有多少摩尔？H₂O 的 Mᵣ = 18，因此 n = 36/18 = 2 mol。
5. Acids, Bases and Salts | 酸、碱与盐
An acid is a substance that releases hydrogen ions (H⁺) when dissolved in water. A base is a substance that neutralises acids to form a salt and water. An alkali is a soluble base that releases hydroxide ions (OH⁻) in water.
酸是溶于水时释放氢离子 (H⁺) 的物质。碱是能中和酸生成盐和水的物质。可溶性碱是溶于水时释放氢氧根离子 (OH⁻) 的物质，称为碱溶液。
The pH scale measures how acidic or alkaline a solution is. Values below 7 are acidic, 7 is neutral, and above 7 are alkaline.
pH 标度衡量溶液的酸碱程度。小于 7 为酸性，7 为中性，大于 7 为碱性。
Neutralisation: acid + base → salt + water. The ionic equation for neutralisation is:
中和反应：酸 + 碱 → 盐 + 水。中和反应的离子方程式为：
H⁺(aq) + OH⁻(aq) → H₂O(l)
Common laboratory acids: hydrochloric acid (HCl), sulfuric acid (H₂SO₄), nitric acid (HNO₃).
常见实验室酸：盐酸 (HCl)、硫酸 (H₂SO₄)、硝酸 (HNO₃)。
Common alkalis: sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)₂).
常见碱溶液：氢氧化钠 (NaOH)、氢氧化钾 (KOH)、氢氧化钙 (Ca(OH)₂)。
| Indicator | Colour in acid | Colour in neutral | Colour in alkali |
|---|---|---|---|
| Litmus | Red | Purple | Blue |
| Methyl orange | Red | Orange | Yellow |
| Phenolphthalein | Colourless | Colourless | Pink |
6. States of Matter and Changes of State | 物质状态与状态变化
Matter exists in three main states: solid, liquid, and gas. Particles in a solid are closely packed in a regular arrangement, vibrating in fixed positions. In a liquid, particles are close together but can move past each other. In a gas, particles are far apart and move randomly at high speeds.
物质主要以三种状态存在：固态、液态和气态。固态粒子紧密排列，只能在固定位置振动；液态粒子相互靠近但能相对滑动；气态粒子相距很远，进行高速随机运动。
Changes of state are physical changes. Melting, boiling, freezing, condensing, and sublimation occur at specific temperatures.
状态变化是物理变化。熔化、沸腾、凝固、凝结和升华都在特定温度下发生。
Melting point: temperature at which a solid becomes a liquid. Boiling point: temperature at which a liquid becomes a gas throughout.
熔点：固体变为液体的温度。沸点：液体内部全面变为气体的温度。
During a change of state, temperature remains constant even though heat is being supplied. This energy is used to overcome the forces between particles.
状态变化期间，虽然继续加热，温度保持恒定。这份能量用于克服粒子间的作用力。
Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration. It is fastest in gases and slowest in solids.
扩散是粒子从较高浓度区域向较低浓度区域的运动。在气体中最快，在固体中最慢。
7. Separation Techniques and Rf Values | 分离技术与比移值
Mixtures can be separated using physical methods. Filtration separates an insoluble solid from a liquid. Evaporation recovers a dissolved solid from a solution by heating to dryness. Crystallisation obtains pure crystals by cooling a hot saturated solution. Simple distillation separates a solvent from a solution. Fractional distillation separates two or more liquids with different boiling points. Chromatography separates small amounts of dissolved substances.
混合物可通过物理方法分离。过滤将不溶性固体与液体分离。蒸发通过加热至干燥从溶液中回收溶解的固体。结晶通过冷却热的饱和溶液获得纯晶体。简单蒸馏将溶剂从溶液中分离出来。分馏分离两种或多种沸点不同的液体。色谱法分离少量溶解的物质。
In paper chromatography, the Rf value (retention factor) is used to identify a component:
在纸色谱法中，比移值 (Rf) 用于鉴定组分：
Rf = distance travelled by substance / distance travelled by solvent front
Rf is always between 0 and 1. It depends on the solvent and the paper used.
Rf 值总是在 0 到 1 之间，它取决于所用的溶剂和纸张。
8. Rates of Reaction | 反应速率
The rate of a chemical reaction is the speed at which reactants are converted into products. It can be measured by the change in mass, volume of gas produced, or colour change over time.
化学反应速率是反应物转化为产物的快慢。可通过质量变化、产生气体的体积或颜色随时间变化来测量。
Factors that affect the rate of reaction:
影响反应速率的因素：
- Temperature: Increasing temperature increases particle kinetic energy and collision frequency, so more particles have energy greater than the activation energy.
- 浓度： 增加温度使粒子动能增大，碰撞频率增加，因此更多粒子的能量超过活化能。
- Concentration / pressure: Higher concentration (for solutions) or higher pressure (for gases) increases the number of particles per unit volume, leading to more frequent collisions.
- 浓度/压强： 溶液浓度越大或气体压强越大，单位体积内粒子数越多，碰撞更频繁。
- Surface area: Breaking a solid into smaller pieces increases its surface area, allowing more particles to be exposed for collisions.
- 表面积： 将固体破碎成更小的颗粒增大表面积，使更多粒子暴露并发生碰撞。
- Catalyst: A catalyst increases the rate without being used up by providing an alternative pathway with lower activation energy.
- 催化剂： 催化剂通过提供活化能较低的替代路径来增大反应速率，而自身不被消耗。
Collision theory states that for a reaction to occur, particles must collide with sufficient energy (activation energy) and with the correct orientation.
碰撞理论指出，要发生反应，粒子必须以足够的能量（活化能）和正确的取向发生碰撞。
9. Redox Reactions | 氧化还原反应
Oxidation is the gain of oxygen by a substance. Reduction is the loss of oxygen.
氧化是物质得氧的过程，还原是物质失氧的过程。
A redox reaction is one in which both oxidation and reduction occur simultaneously.
氧化还原反应是同时发生氧化和还原的反应。
Example: In the reaction between magnesium and copper(II) oxide, Mg gains oxygen (oxidised) and CuO loses oxygen (reduced): Mg + CuO → MgO + Cu.
示例：镁与氧化铜反应中，Mg 得氧（被氧化），CuO 失氧（被还原）：Mg + CuO → MgO + Cu。
More broadly, oxidation can be defined as loss of electrons, and reduction as gain of electrons. The mnemonic OIL RIG is useful: Oxidation Is Loss, Reduction Is Gain (of electrons).
更广义的定义中，氧化是失电子，还原是得电子。记忆口诀 OIL RIG：氧化失电子 (Oxidation Is Loss)，还原得电子 (Reduction Is Gain)。
Oxidising agents accept electrons and are reduced. Reducing agents donate electrons and are oxidised.
氧化剂接受电子，自身被还原；还原剂给出电子，自身被氧化。
10. The Periodic Table | 元素周期表
The Periodic Table arranges elements in order of increasing atomic number. Vertical columns are called groups; horizontal rows are called periods.
元素周期表按原子序数递增的顺序排列。纵列称为族，横行称为周期。
Elements in the same group have the same number of electrons in their outer shell and therefore similar chemical properties.
同一族元素具有相同的最外层电子数，因此化学性质相似。
Group 1: Alkali metals – reactive metals, one outer electron, form 1⁺ ions. Group 2: Alkaline earth metals – two outer electrons, form 2⁺ ions. Group 17 (VII): Halogens – diatomic non‑metals, seven outer electrons, form 1⁻ ions. Group 18 (0): Noble gases – full outer shells, very unreactive.
第 1 族：碱金属 – 活泼金属，最外层 1 个电子，形成 1⁺ 离子。第 2 族：碱土金属 – 最外层 2 个电子，形成 2⁺ 离子。第 17 族 (VII)：卤素 – 双原子非金属，最外层 7 个电子，形成 1⁻ 离子。第 18 族 (0)：稀有气体 – 最外层全满，非常不活泼。
Across a period, the number of protons increases, so the electrostatic attraction between nucleus and electrons increases. This leads to trends such as decreasing atomic radius and increasing ionisation energy from left to right.
同一周期内，质子数增多，原子核与电子间的静电吸引力增强。这导致从左到右原子半径减小、电离能增大的趋势。
Metals are found on the left and centre; non‑metals are on the right. The dividing line is a staircase starting between boron and aluminium.
金属位于左侧和中部，非金属位于右侧。分界线为从硼和铝之间开始的阶梯线。
11. Density and Physical Properties | 密度与物理性质
Density is the mass per unit volume of a substance. It is a physical property that can help identify materials.
密度是物质单位体积的质量，是可用于鉴定材料的物理性质。
Density (ρ) = mass (g) / volume (cm³)
Common units for density are g/cm³ or kg/m³. Water has a density of 1 g/cm³ at 4 °C.
密度的常用单位是 g/cm³ 或 kg/m³。水在 4 °C 时的密度为 1 g/cm³。
Knowledge of density helps in explaining floating and sinking, as well as in separation techniques like using a separating funnel for immiscible liquids.
密度的知识有助于解释浮沉现象，以及用于分离技术，例如使用分液漏斗分离互不相溶的液体。
Other physical properties include melting point, boiling point, electrical conductivity, and thermal conductivity. These do not involve changing the chemical identity of the substance.
其他物理性质包括熔点、沸点、导电性和导热性。这些性质不改变物质的化学身份。
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