📚 Year 7 CCEA Chemistry: Formula & Theorem Quick Reference Handbook | CCEA 7年级化学：公式定理速查手册
This handbook provides a quick reference to essential formulas, laws, and key concepts in Year 7 CCEA Chemistry. Mastering these fundamentals is vital for understanding matter, reactions, and laboratory techniques.
本手册为CCEA 7年级化学的重要公式、定律和关键概念提供速查支持。掌握这些基础知识对理解物质、化学反应和实验技术至关重要。
1. The Particle Model | 粒子模型定理
Particle theory states that all matter is made up of tiny, constantly moving particles. The properties of a substance depend on the arrangement and motion of its particles.
粒子理论指出所有物质都由微小且不断运动的粒子构成。物质的性质取决于粒子的排列和运动方式。
The particles have spaces between them, and they attract each other. When a substance is heated, its particles gain kinetic energy and move faster.
粒子之间有间隙，并且相互吸引。当物质受热时，粒子获得动能，运动加快。
Kinetic energy of particles ∝ Temperature (in Kelvin)
粒子动能 ∝ 温度（开尔文）
2. States of Matter and Changes of State | 物质状态与状态变化
In a solid, particles are closely packed in a regular pattern and vibrate in fixed positions.
在固体中，粒子紧密排列成规则的结构，在固定位置振动。
In a liquid, particles are still close but can slide past each other; they have no fixed shape.
在液体中，粒子仍然靠近，但可以互相滑动；液体没有固定的形状。
In a gas, particles are far apart and move rapidly in all directions, filling the entire container.
在气体中，粒子相距很远，快速向各个方向运动，充满整个容器。
Changes of state involve energy transfer without changing temperature. The key transitions are:
状态变化涉及能量传递而温度不变。关键的转变有：
Solid → Liquid (Melting, endothermic)
固体 → 液体（熔化，吸热）
Liquid → Gas (Boiling/Evaporation, endothermic)
液体 → 气体（沸腾/蒸发，吸热）
Gas → Liquid (Condensation, exothermic)
气体 → 液体（冷凝，放热）
Liquid → Solid (Freezing, exothermic)
液体 → 固体（凝固，放热）
Sublimation (solid → gas) and deposition (gas → solid) also occur in some materials.
某些物质还会发生升华（固体 → 气体）和凝华（气体 → 固体）。
3. Elements, Compounds and Mixtures | 元素、化合物和混合物
An element is a pure substance made up of only one type of atom. It cannot be broken down into simpler substances by chemical means.
元素是仅由一种原子组成的纯净物，不能通过化学方法分解为更简单的物质。
A compound is a pure substance composed of two or more different elements chemically bonded in a fixed ratio.
化合物是由两种或多种不同元素以固定比例通过化学键结合而成的纯净物。
A mixture contains two or more substances (elements or compounds) that are physically mixed but not chemically joined. Mixtures can be separated by physical techniques.
混合物包含两种或多种物质（元素或化合物），它们只是物理混合而非化学结合，可通过物理方法分离。
Representations:
表示方法：
Element: single symbol, e.g., Fe, O₂
元素：单一符号，如 Fe、O₂
Compound: fixed formula, e.g., H₂O, CO₂
化合物：固定化学式，如 H₂O、CO₂
Mixture: no fixed composition, e.g., air, seawater
混合物：没有固定组成，如空气、海水
4. Atoms and Chemical Symbols | 原子与化学符号
An atom is the smallest particle of an element that can take part in a chemical reaction.
原子是元素参与化学反应的最小粒子。
Each element is represented by a one- or two-letter chemical symbol. The first letter is capitalised; the second, if present, is lowercase.
每种元素用一个或两个字母组成的化学符号表示。首字母大写，若有第二个字母则小写。
| Symbol | English Name | 中文名称 |
|---|---|---|
| H | Hydrogen | 氢 |
| He | Helium | 氦 |
| C | Carbon | 碳 |
| N | Nitrogen | 氮 |
| O | Oxygen | 氧 |
| Na | Sodium | 钠 |
| Mg | Magnesium | 镁 |
| Al | Aluminium | 铝 |
| Si | Silicon | 硅 |
| P | Phosphorus | 磷 |
| S | Sulfur | 硫 |
| Cl | Chlorine | 氯 |
| K | Potassium | 钾 |
| Ca | Calcium | 钙 |
| Fe | Iron | 铁 |
| Cu | Copper | 铜 |
| Zn | Zinc | 锌 |
5. Chemical Formulae | 化学式
A chemical formula shows the number and type of atoms bonded together in a compound. Subscript numbers indicate how many atoms of each element are present (the number 1 is omitted).
化学式表示化合物中原子的种类和数目。下标数字显示每种元素原子的个数（数字1省略不写）。
Examples of common formulae:
常见化学式举例：
Water: H₂O (2 hydrogen atoms, 1 oxygen atom)
水：H₂O（2个氢原子，1个氧原子）
Carbon dioxide: CO₂ (1 carbon, 2 oxygen)
二氧化碳：CO₂（1个碳原子，2个氧原子）
Sodium chloride: NaCl
氯化钠：NaCl
Methane: CH₄
甲烷：CH₄
Sulfuric acid: H₂SO₄
硫酸：H₂SO₄
When a formula contains brackets, the subscript outside multiplies everything inside, e.g., Ca(OH)₂ means one calcium, two oxygen and two hydrogen atoms.
化学式中若有括号，括号外的下标会乘以括号内所有原子，如 Ca(OH)₂ 表示1个钙、2个氧和2个氢原子。
6. Word Equations and Simple Reactions | 文字方程式与简单反应
A word equation describes a chemical reaction using the names of reactants and products. It follows the general pattern:
文字方程式用反应物和生成物的名称描述化学反应，遵循以下基本格式：
Reactant(s) → Product(s)
反应物 → 生成物
The arrow (→) means ‘yields’ or ‘produces’.
箭头 (→) 表示“生成”或“产生”。
Common word equations for Year 7:
7年级常见的文字方程式：
Magnesium + Oxygen → Magnesium oxide
镁 + 氧气 → 氧化镁
Methane + Oxygen → Carbon dioxide + Water
甲烷 + 氧气 → 二氧化碳 + 水
Sodium + Water → Sodium hydroxide + Hydrogen
钠 + 水 → 氢氧化钠 + 氢气
These equations represent the law of conservation of mass – atoms are rearranged, not created or destroyed.
这些方程式体现了质量守恒定律——原子只是重新排列，既没有被创造也没有被消灭。
7. Law of Conservation of Mass | 质量守恒定律
Law of Conservation of Mass: In any chemical reaction, the total mass of the reactants equals the total mass of the products. No atoms are lost or gained.
质量守恒定律：在任何化学反应中，反应物的总质量等于生成物的总质量。没有原子损失或增加。
Total mass of reactants = Total mass of products
反应物总质量 =
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