📚 Year 8 CCEA Chemistry: Formulas and Theorems Quick Reference Handbook | Year 8 CCEA 化学：公式定理速查手册
This quick reference handbook covers the essential formulas, rules and key theorems you will meet in Year 8 CCEA Chemistry. Use it to check chemical symbols, write balanced equations, recall particle theory and revise acids, metals and separation methods. Every rule is explained with an English–Chinese pair to support your bilingual learning.
这本速查手册涵盖了 Year 8 CCEA 化学中的基本公式、规则和重要定理。你可以用它查阅化学符号、书写配平方程式、回顾粒子理论，并复习酸、金属和分离方法。每条规则都以中英双语配对说明，帮助你开展双语学习。
1. States of Matter and Particle Theory | 物质状态与粒子理论
The three states of matter are solid, liquid and gas. Solids have a fixed shape and volume, liquids have a fixed volume but take the shape of the container, and gases have no fixed shape or volume.
物质有三种状态：固态、液态和气态。固体有固定的形状和体积，液体有固定体积但形状随容器而变，气体没有固定的形状和体积。
Particle theory states that all matter is made of tiny particles that are constantly moving. The amount of energy the particles have determines the state.
粒子理论指出，所有物质都由不断运动的微小粒子组成。粒子能量的大小决定了物质的状态。
- Solids: particles vibrate in fixed positions, closely packed. | 固体：粒子在固定位置上振动，排列紧密。
- Liquids: particles move around each other, still close together. | 液体：粒子相互滑动，仍然比较靠近。
- Gases: particles move rapidly in all directions, far apart. | 气体：粒子沿各个方向快速运动，彼此相距很远。
Changing state involves adding or removing energy: melting (solid → liquid), freezing (liquid → solid), boiling / evaporation (liquid → gas), condensing (gas → liquid).
状态变化涉及能量的增加或减少：熔化（固 → 液）、凝固（液 → 固）、沸腾/蒸发（液 → 气）、冷凝（气 → 液）。
2. Atoms and Subatomic Particles | 原子与亚原子粒子
An atom is the smallest particle of an element that can take part in a chemical reaction. Atoms are made of three subatomic particles: protons, neutrons and electrons.
原子是能参与化学反应的元素最小粒子。原子由三种亚原子粒子构成：质子、中子和电子。
The nucleus contains protons (positive charge, +1) and neutrons (no charge, 0). Electrons (negative charge, −1) orbit the nucleus in shells.
原子核包含质子（带正电，+1）和中子（不带电，0）。电子（带负电，−1）在电子层中绕核运动。
| Particle 粒子 | Relative mass 相对质量 | Relative charge 相对电荷 |
|---|---|---|
| Proton 质子 | 1 | +1 |
| Neutron 中子 | 1 | 0 |
| Electron 电子 | 1/1840 (negligible 可忽略) | −1 |
Key rule: In a neutral atom, number of protons = number of electrons.
关键规则：在中性原子中，质子数等于电子数。
Atomic number (Z) = number of protons. Mass number (A) = number of protons + number of neutrons.
原子序数（Z）= 质子数。质量数（A）= 质子数 + 中子数。
3. Elements, Compounds and Mixtures | 元素、化合物与混合物
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 consists of two or more substances (elements or compounds) that are not chemically combined.
元素是仅由一种原子组成的物质。化合物是由两种或两种以上不同原子通过化学键结合而成的物质。混合物是由两种或多种物质（元素或化合物）物理混合而成，没有发生化学结合。
Compounds have a fixed composition and their formation involves a chemical change. Mixtures can be separated by physical means and their composition can vary.
化合物有固定的组成，其形成涉及化学变化。混合物可以通过物理方法分离，其组成可以变化。
Examples: Oxygen (O₂) is an element; water (H₂O) is a compound; air is a mixture of gases.
示例：氧气（O₂）是元素；水（H₂O）是化合物；空气是气体混合物。
4. Chemical Symbols and Formulae | 化学符号与化学式
Each element is represented by a one- or two-letter symbol. The first letter is always capitalised; the second, if present, is lowercase.
每种元素用一个或两个字母的符号表示。首字母必须大写，第二个字母（若有）必须小写。
A chemical formula shows the types and numbers of atoms in a compound. Subscript numbers indicate the number of atoms of that element in one molecule or formula unit.
化学式表示化合物中原子的种类和数目。下标数字表示一个分子或一个式单元中该元素原子的个数。
| Compound 化合物 | Formula 化学式 |
|---|---|
| Water 水 | H₂O |
| Carbon dioxide 二氧化碳 | CO₂ |
| Sodium chloride 氯化钠 | NaCl |
| Magnesium oxide 氧化镁 | MgO |
| Hydrochloric acid 盐酸 | HCl |
| Sulfuric acid 硫酸 | H₂SO₄ |
| Methane 甲烷 | CH₄ |
Rule: When balancing charges in ionic compounds, the total positive charge must equal the total negative charge. For simple compounds in Year 8, learn the common ion charges: Na⁺, Cl⁻, Mg²⁺, O²⁻, Al³⁺, etc.
规则：在离子化合物中配平电荷时，正电荷总数必须等于负电荷总数。对于 Year 8 的简单化合物，应熟记常见离子电荷：Na⁺、Cl⁻、Mg²⁺、O²⁻、Al³⁺ 等。
5. Writing Chemical Equations | 书写化学方程式
A word equation shows the names of reactants and products. Example: magnesium + oxygen → magnesium oxide.
文字方程式用物质名称表示反应物和生成物。示例：镁 + 氧气 → 氧化镁。
A symbol equation uses chemical formulae to show the reaction. State symbols show the physical state: (s) solid, (l) liquid, (g) gas, (aq) aqueous (dissolved in water).
符号方程式使用化学式表示反应。状态符号表示物理状态：(s) 固体，(l) 液体，(g) 气体，(aq) 水溶液。
Balancing equations: The number of atoms of each element must be the same on both sides of the equation. This follows the law of conservation of mass.
配平方程式：方程式两边每种元素的原子数目必须相同。这遵循质量守恒定律。
Example of a balanced equation:
配平方程式示例：
2Mg(s) + O₂(g) → 2MgO(s)
Another common reaction:
另一个常见反应：
CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)
6. Types of Chemical Reactions | 化学反应类型
Combination (synthesis): two or more substances combine to form a single product. A + B → AB
化合反应（合成）：两种或多种物质结合生成一种产物。A + B → AB
Decomposition: a compound breaks down into simpler substances. AB → A + B
分解反应：化合物分解成较简单的物质。AB → A + B
Combustion: a substance reacts with oxygen, releasing heat and light. Fuel + O₂ → CO₂ + H₂O (for hydrocarbons).
燃烧反应：物质与氧气反应，放出热和光。燃料 + O₂ → CO₂ + H₂O（适用于碳氢化合物）。
Neutralisation: acid + base → salt + water.
中和反应：酸 + 碱 → 盐 + 水。
Displacement: a more reactive element takes the place of a less reactive element in a compound. A + BC → AC + B
置换反应：较活泼的元素将化合物中较不活泼的元素置换出来。A + BC → AC + B
7. Acids, Bases and the pH Scale | 酸、碱与pH标度
An acid is a substance that produces hydrogen ions (H⁺) in water. Common laboratory acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃).
酸是在水中产生氢离子（H⁺）的物质。实验室常见酸有盐酸（HCl）、硫酸（H₂SO₄）和硝酸（HNO₃）。
A base is a substance that neutralises an acid to form a salt and water. An alkali is a soluble base that produces hydroxide ions (OH⁻) in water, e.g. sodium hydroxide (NaOH).
碱是能中和酸生成盐和水的物质。可溶性碱在水中产生氢氧根离子（OH⁻），如氢氧化钠（NaOH）。
The pH scale measures how acidic or alkaline a solution is:
pH 标度用于衡量溶液的酸碱度：
- pH < 7: acidic | 酸性
- pH = 7: neutral (e.g. pure water) | 中性（如纯水）
- pH > 7: alkaline | 碱性
Indicators change colour with pH: litmus turns red in acid and blue in alkali; universal indicator gives a range of colours across the pH scale.
指示剂随 pH 变化颜色：石蕊在酸中变红、在碱中变蓝；通用指示剂在 pH 标度上呈现一系列颜色变化。
8. Conservation of Mass | 质量守恒定律
The law of conservation of mass states that in a chemical reaction, the total mass of the reactants equals the total mass of the products. Atoms are neither created nor destroyed, only rearranged.
质量守恒定律指出，在化学反应中，反应物的总质量等于生成物的总质量。原子既不会凭空产生也不会凭空消失，只是重新排列。
This is why chemical equations must be balanced. If a reaction appears to lose mass (e.g. a gas escapes), the mass change is due to the gas leaving the reaction vessel, not the destruction of atoms.
这就是化学方程式必须配平的原因。如果反应看似质量减少（如气体逸出），质量变化是由于气体离开反应容器，而不是原子被消灭。
In a closed system, the total mass stays exactly the same before and after the reaction.
在封闭系统中，反应前后总质量完全不变。
9. Separation Techniques | 分离技术
Mixtures can be separated by physical methods. The choice of technique depends on the properties of the substances involved.
混合物可以通过物理方法分离。选择哪种技术取决于所涉及物质的性质。
- Filtration: separates an insoluble solid from a liquid, e.g. sand from water. | 过滤：分离不溶性固体与液体，如从水中分离沙子。
- Evaporation: removes a solvent from a solution, leaving the solute behind, e.g. salt from salt water. | 蒸发：将溶剂从溶液中除去，留下溶质，如从盐水中得到盐。
- Distillation: separates a solvent from a solution by boiling and condensing, useful when both components are needed, e.g. pure water from salt water. | 蒸馏：通过沸腾和冷凝将溶剂从溶液中分离，适用于两种组分都需要的情况，如从盐水中获得纯水。
- Chromatography: separates dissolved substances based on their different solubilities and attraction to a stationary phase, e.g. separating coloured inks. | 色谱法：基于不同溶解度和对固定相的吸引能力分离溶解物质，如分离彩色墨水。
10. Metals and Non-metals | 金属与非金属
Elements can be broadly classified as metals or non-metals based on their physical and chemical properties.
根据物理和化学性质，元素大致可分为金属和非金属。
| Property 性质 | Metals 金属 | Non-metals 非金属 |
|---|---|---|
| Appearance 外观 | Shiny (lustrous) 有光泽 | Dull 暗淡 |
| Conductivity 导电导热性 | Good conductors 良导体 | Poor conductors (insulators) 不良导体（绝缘体） |
| Malleability & ductility 展性和延性 | Malleable and ductile 有展性、延性 | Brittle when solid 固体时易碎 |
| Reaction with acid 与酸反应 | Many produce hydrogen gas 许多产生氢气 | Do not react with acids (usually) 通常不与酸反应 |
| Oxides 氧化物 | Basic or amphoteric 碱性或两性 | Acidic or neutral 酸性或中性 |
The reactivity series lists metals in order of their tendency to lose electrons and form positive ions. A more reactive metal can displace a less reactive metal from its compound.
金属活动性顺序按金属失去电子形成阳离子的趋势排列。较活泼的金属能从化合物中置换出较不活泼的金属。
11. Introduction to the Periodic Table | 周期表入门
The periodic table organises all known elements in order of increasing atomic number. The vertical columns are called groups; elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell.
周期表将所有已知元素按原子序数递增的顺序排列。竖列称为族；同一族元素具有相似的化学性质，因为它们最外层电子数相同。
Horizontal rows are called periods. Across a period, the number of electron shells stays the same, but the number of outer electrons increases gradually.
横行称为周期。在同一周期中，电子层数相同，但最外层电子数逐渐增加。
Key groups for Year 8:
Year 8 应掌握的关键族：
- Group 1: alkali metals – very reactive, soft metals, 1 outer electron. | 第1族：碱金属 – 非常活泼的软金属，最外层1个电子。
- Group 7: halogens – reactive non-metals, 7 outer electrons. | 第7族：卤素 – 活泼的非金属，最外层7个电子。
- Group 0 (or 8): noble gases – unreactive, full outer shell. | 第0族（或第8族）：稀有气体 – 不活泼，最外层电子已满。
Between groups 2 and 3 lies a block of transition metals, which have typical metallic properties and often form coloured compounds.
第2族和第3族之间是过渡金属区，它们具有典型的金属性质，往往能形成有色化合物。
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