📚 Year 7 WJEC Chemistry: Formula & Theorem Quick Reference Handbook | Year 7 WJEC 化学：公式定理速查手册
This concise handbook brings together all the essential formulas, theorems and key concepts you need to master Year 7 WJEC Chemistry. Use it for quick revision, homework support and exam preparation. Each section pairs a clear English explanation with a Chinese translation to reinforce understanding.
这本速查手册汇集了 Year 7 WJEC 化学必须掌握的所有基本公式、定理和核心概念，适合快速复习、作业辅助和备考。每个知识点都配有清晰的中英文对照解释，帮助你巩固理解。
1. States of Matter & Changes of State | 物质状态与状态变化
Matter exists as solid, liquid or gas. The particle model explains how particles are arranged and how they move in each state. Solids have closely packed, vibrating particles; liquids have particles that can slide past each other; gases have widely spaced, fast-moving particles.
物质以固态、液态或气态存在。粒子模型解释了三态中粒子的排布和运动方式：固体粒子紧密排列，仅在固定位置振动；液体粒子可以相互滑动；气体粒子间距大，快速运动。
The key changes of state and their names are:
重要的状态变化及其名称：
- Melting (solid → liquid) | 熔化（固态 → 液态）
- Freezing (liquid → solid) | 凝固（液态 → 固态）
- Boiling / Evaporation (liquid → gas) | 沸腾/蒸发（液态 → 气态）
- Condensation (gas → liquid) | 液化/冷凝（气态 → 液态）
- Sublimation (solid → gas, e.g. dry ice) | 升华（固态直接变为气态，如干冰）
Melting point and boiling point are fixed temperatures for a pure substance. The melting point of pure water is 0 °C and the boiling point is 100 °C at standard pressure.
纯物质有固定的熔点和沸点。在标准大气压下，纯水的熔点为 0 °C，沸点为 100 °C。
2. Atoms, Elements & 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. Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons.
原子是元素参与化学反应的最小粒子。原子由含质子和中子的原子核以及绕核运动的电子构成。
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
In a neutral atom, the number of electrons equals the number of protons. Electrons are arranged in shells: the first shell holds up to 2 electrons, the second and third shells hold up to 8 electrons. The electronic configuration is written as, for example, 2,8,1 for sodium.
中性原子中，电子数等于质子数。电子分层排布：第一层最多容纳 2 个电子，第二层和第三层最多容纳 8 个电子。电子构型用数字记录，例如钠的电子构型为 2,8,1。
An element is a substance made of only one type of atom. A compound is a substance made of two or more different types of atom chemically bonded together. A mixture contains two or more substances not chemically combined.
元素是由同种原子组成的物质。化合物是由两种或多种不同元素的原子通过化学键结合而成的物质。混合物包含两种或多种没有发生化学结合的物质。
3. The Periodic Table | 元素周期表
The Periodic Table arranges all known elements in order of increasing atomic number. Rows are called periods and columns are called groups. Elements in the same group have similar chemical properties because they have the same number of electrons in the outer shell.
周期表按原子序数递增排列所有已知元素。横行为周期，竖列为族。同一族元素因外层电子数相同而具有相似的化学性质。
Key groups to know for Year 7:
Year 7 需要了解的重要族：
- Group 1: Alkali metals – soft, very reactive with water, stored under oil.
- 第 1 族：碱金属 – 质地柔软，与水反应非常剧烈，保存在油中。
- Group 7: Halogens – reactive non-metals, exist as diatomic molecules (F₂, Cl₂, Br₂, I₂).
- 第 7 族：卤素 – 活泼的非金属，以双原子分子存在（F₂, Cl₂, Br₂, I₂）。
- Group 0 (or 8): Noble gases – unreactive, full outer shell, used in lighting.
- 第 0 族（或第 8 族）：惰性气体 – 化学性质极不活泼，最外层全满，用于照明。
Metals are on the left and in the centre; non-metals are on the right. The zigzag line separates metals from non-metals.
金属位于周期表左侧和中部，非金属位于右侧。锯齿形线区分金属和非金属。
4. Chemical Formulae | 化学式
A chemical formula uses element symbols and subscript numbers to show the type and number of atoms in a substance. The subscript indicates how many atoms of the element directly before it are present. For example, H₂O means two hydrogen atoms and one oxygen atom.
化学式用元素符号和下标数字表示物质中原子的种类和数目。下标数字表示它前面紧邻的元素原子个数。例如 H₂O 表示两个氢原子和一个氧原子。
Common formulae you must learn:
必须记住的常见化学式：
| Substance 物质 | Formula 化学式 |
|---|---|
| Water 水 | H₂O |
| Carbon dioxide 二氧化碳 | CO₂ |
| Sodium chloride 氯化钠 | NaCl |
| Hydrochloric acid 盐酸 | HCl |
| Sulfuric acid 硫酸 | H₂SO₄ |
| Sodium hydroxide 氢氧化钠 | NaOH |
| Magnesium oxide 氧化镁 | MgO |
| Methane 甲烷 | CH₄ |
When writing formulae of ionic compounds, the positive ion (metal) always comes before the negative ion (non-metal). The overall charge must be zero. For example, magnesium chloride is MgCl₂ because Mg²⁺ needs two Cl⁻ to balance.
书写离子化合物化学式时，阳离子（金属）总是在阴离子（非金属）之前，总电荷必须为零。例如氯化镁写作 MgCl₂，因为 Mg²⁺ 需要两个 Cl⁻ 才能使电荷平衡。
5. Chemical Equations & Conservation of Mass | 化学方程式与质量守恒
s the names of reactants and products to summarise a chemical reaction. An arrow (→) means 'produces'. For example:
字方程式用反应物和生成物的名称概括化学反应。箭头（→）表示“生成”。例如：
methane + oxygen → carbon dioxide + water
甲烷 + 氧气 → 二氧化碳 + 水
A symbol equation replaces names with chemical formulae. It must be balanced so that the number of atoms of each element is the same on both sides of the arrow.
符号方程式用化学式代替物质名称。方程式必须配平，使得箭头两边每种元素的原子总数相等。
CH₄ + 2O₂ → CO₂ + 2H₂O
CH₄ + 2O₂ → CO₂ + 2H₂O
The Law of Conservation of Mass states that the total mass of the reactants equals the total mass of the products. Atoms are rearranged, not created or destroyed.
质量守恒定律：反应物的总质量等于生成物的总质量。原子重新组合，没有原子被创造或毁灭。
Total mass of reactants = Total mass of products
反应物总质量 = 生成物总质量
In a closed system, mass stays the same. If you observe a mass change in an open system, it is often because a gas has entered or escaped.
在封闭系统中，质量保持不变。若在开放系统中观察到质量变化，通常是因为有气体进入或逸出。
6. Separation Techniques | 分离技术
Mixtures can be separated by physical methods that exploit differences in physical properties.
混合物可通过利用物理性质差异的物理方法进行分离。
| Technique 方法 | What it separates 分离对象 | Principle 原理 |
|---|---|---|
| Filtration 过滤 | Insoluble solid from liquid | Particle size difference (filter paper retains solid residues) |
| Evaporation 蒸发 | Soluble solid from solution | Solvent evaporates, solid crystals remain |
| Distillation 蒸馏 | Solvent from a solution or liquids with different boiling points | Boiling point difference; solvent vapour is condensed and collected |
| Chromatography 色谱法 | Coloured substances, e.g. inks | Different solubilities cause components to travel different distances on paper |
In paper chromatography, a substance that is more soluble in the solvent travels further up the paper. An Rf value can be calculated (but is not required in Year 7).
在纸色谱法中，在溶剂中溶解度越大的物质在纸上移动的距离越远。可以计算 Rf 值（但 Year 7 不作要求）。
7. Acids, Alkalis & pH Scale | 酸、碱与 pH 标度
Acids have a pH lower than 7. Common laboratory acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃). Alkalis are soluble bases; they have a pH greater than 7. Sodium hydroxide (NaOH) is a typical alkali.
酸的 pH 小于 7。实验室常见的酸有盐酸 (HCl)、硫酸 (H₂SO₄) 和硝酸 (HNO₃)。碱是可溶于水的碱性物质，pH 大于 7。氢氧化钠 (NaOH) 是一种典型的碱。
The pH scale runs from 0 (strongly acidic) to 14 (strongly alkaline). A pH of 7 is neutral, e.g. pure water.
pH 标度从 0（强酸性）到 14（强碱性）。pH 7 为中性，如纯水。
Indicators change colour to show the pH:
指示剂通过颜色变化显示 pH：
- Litmus: red in acid, blue in alkali | 石蕊：酸中变红，碱中变蓝
- Phenolphthalein: colourless in acid, pink in alkali | 酚酞：酸中无色，碱中变粉红
- Universal indicator: gives a full range of colours (red – orange – yellow – green – blue – violet)
- 通用指示剂：显示全色系（红 – 橙 – 黄 – 绿 – 蓝 – 紫）
A neutralisation reaction occurs when an acid reacts with an alkali:
酸与碱发生中和反应：
acid + alkali → salt + water
酸 + 碱 → 盐 + 水
For example: hydrochloric acid + sodium hydroxide → sodium chloride + water.
例如：盐酸 + 氢氧化钠 → 氯化钠 + 水。
8. Reactions of Metals | 金属的反应
Metals can be placed in a reactivity series from most reactive to least reactive. A typical Year 7 series is: potassium, sodium, lithium, calcium, magnesium, aluminium, zinc, iron, copper, silver, gold.
金属可根据活泼性排列成活动性顺序，从最活泼到最不活泼。Year 7 常见的顺序为：钾、钠、锂、钙、镁、铝、锌、铁、铜、银、金。
salt formed depends on the acid used: hydrochloric acid produces chlorides, sulfuric acid produces sulfates.
金属 + 酸 → 盐 + 氢气。生成的盐取决于所用的酸：盐酸生成氯化物，硫酸生成硫酸盐。
Mg + 2HCl → MgCl₂ + H₂↑
Mg + 2HCl → MgCl₂ + H₂↑
Very reactive metals (e.g. potassium, sodium) react vigorously with cold water, producing a metal hydroxide and hydrogen. Less reactive metals like magnesium react slowly with water but readily with steam. Unreactive metals such as copper do not react with water at all.
极活泼金属（如钾、钠）与冷水剧烈反应，生成金属氢氧化物和氢气。活泼性较低的金属（如镁）与冷水反应缓慢，但与水蒸气反应迅速。不活泼金属（如铜）不与水反应。
n oxidation reaction. For example, magnesium burns with a bright white flame to form magnesium oxide (MgO).
金属 + 氧气 → 金属氧化物。这是氧化反应。例如，镁燃烧发出耀眼白光，生成氧化镁 (MgO)。
9. Combustion & Oxidation | 燃烧与氧化
Combustion is a rapid reaction between a fuel and oxygen that releases heat and light. For complete combustion to occur, three things are needed: a fuel, oxygen (usually from air) and an ignition temperature. This is often called the fire triangle.
燃烧是燃料与氧气发生的快速放热、发光反应。完全燃烧需要三个条件：燃料、氧气（通常来自空气）和达到着火温度。这三者常被称为火三角。
Complete combustion of hydrocarbons (such as methane) produces carbon dioxide and water:
碳氢化合物（如甲烷）完全燃烧生成二氧化碳和水：
fuel + oxygen → carbon dioxide + water (+ energy)
燃料 + 氧气 → 二氧化碳 + 水（+ 能量）
Oxidation is a more general term for a reaction in which a substance gains oxygen. Rusting is the slow oxidation of iron in the presence of oxygen and water, forming hydrated iron(III) oxide. Rusting can be prevented by painting, oiling or galvanising.
氧化是一个更广义的术语，指物质与氧结合的反应。生锈是铁在氧气和水存在下的缓慢氧化，生成水合氧化铁。可通过涂漆、涂油或镀锌来防止生锈。
10. Key Definitions & Theorems | 关键定义与定理
This section lists the fundamental definitions and theorems that underpin Year 7 Chemistry.
本节列出支撑 Year 7 化学的基本定义和定理。
- Element: A substance that cannot be broken down into simpler substances by chemical means. | 元素：无法通过化学方法分解为更简单物质的纯净物。
- Compound: A substance formed when two or more elements chemically combined in fixed proportions. | 化合物：两种或多种元素按固定比例通过化学结合形成的物质。
- Mixture: Two or more substances not chemically combined that can be separated by physical methods. | 混合物：两种或多种未发生化学结合的物质，可通过物理方法分离。
- Particle Model: All matter is made of tiny particles; particles are in constant motion; there are forces between particles; temperature affects particle motion. | 粒子模型：所有物质由微小粒子组成；粒子不断运动；粒子间存在作用力；温度影响粒子运动。
- Proton number = atomic number. | 质子数 = 原子序数。
- Relative charge: proton +1, neutron 0, electron −1. | 相对电荷：质子 +1，中子 0，电子 −1。
- Conservation of mass: In a chemical reaction, the total mass of reactants equals the total mass of products. | 质量守恒：化学反应中，反应物总质量等于生成物总质量。
- Diffusion: The movement of particles from an area of higher concentration to an area of lower concentration. | 扩散：粒子从高浓度区域向低浓度区域运动的过程。
Mastering these definitions and theorems gives you a solid foundation for all future chemistry learning.
掌握这些定义和定理，为未来的化学学习打下坚实基础。
Published by TutorHao | WJEC Chemistry Revision Series | aleveler.com
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