KS3 OCR Chemistry: Formula and Theorem Quick Reference Handbook | KS3 OCR 化学：公式定理速查手册

📚 KS3 OCR Chemistry: Formula and Theorem Quick Reference Handbook | KS3 OCR 化学：公式定理速查手册

Welcome to your essential quick reference guide for KS3 OCR Chemistry. This handbook distills the fundamental formulas, theorems, and key equations you need to master the subject, from particle theory to reaction rates. Use it alongside your class notes to clarify concepts, memorise relationships, and tackle assessment questions with confidence.

欢迎使用 KS3 OCR 化学必备速查手册。本手册从粒子理论到反应速率，提炼了您需要掌握的基本公式、定理和关键方程式。配合课堂笔记使用，可以理清概念、记住关系式，自信地应对评估题目。

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1. Particle Model and States of Matter | 粒子模型与物质状态

All substances are composed of tiny particles (atoms, molecules, or ions) in constant motion. The energy and arrangement of these particles dictate whether the substance exists as a solid, liquid, or gas. Higher energy leads to greater particle movement and separation.

所有物质都由微小、持续运动的粒子（原子、分子或离子）构成。这些粒子的能量和排列方式决定了物质以固态、液态还是气态存在。能量越高，粒子运动越剧烈，间距越大。

In solids, particles are tightly packed in a regular lattice and can only vibrate around fixed positions. In liquids, particles are close but disordered, allowing them to slide past one another. In gases, particles are widely spaced with no regular arrangement and move rapidly in straight lines until they collide.

固体中，粒子紧密堆积成规则晶格，只能在固定位置振动。液体中，粒子彼此靠近但排列无序，能相对滑动。气体中，粒子间距很大，排列无规则，沿直线快速运动直至碰撞。

The transformation between states is a physical change driven by energy transfer. The general reversible pathway is:

状态之间的转变是由能量传递驱动的物理变化。普遍的可逆路径为：

Solid ⇌ Liquid ⇌ Gas

Melting (solid to liquid) and boiling/evaporating (liquid to gas) are endothermic processes: energy is absorbed to overcome attractive forces between particles. Freezing and condensing are exothermic: energy is released as forces strengthen.

熔化（固→液）和沸腾/蒸发（液→气）为吸热过程：吸收能量以克服粒子间的吸引力。凝固和冷凝为放热过程：粒子间作用力增强，能量得以释放。

At a state change, temperature remains constant even though heating or cooling continues. The energy input goes into breaking or forming inter-particle bonds rather than raising kinetic energy. This plateau is known as the latent heat of fusion or vaporisation.

在状态变化中，即使持续加热或冷却，温度仍保持不变。输入的能量用于断裂或形成粒子间键，而非提高动能。这个温度平台被称为熔化潜热或汽化潜热。

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2. Atomic Structure and Element Symbols | 原子结构与元素符号

An atom is the smallest unit of an element that retains its chemical properties. It consists of three sub-atomic particles: protons, neutrons, and electrons. The nucleus contains protons (+1 charge) and neutrons (0 charge), while electrons (−1 charge) orbit the nucleus in shells or energy levels.

原子是保持元素化学性质的最小单位。它由三种亚原子粒子组成：质子、中子和电子。原子核包含质子（+1 电荷）和中子（0 电荷），电子（−1 电荷）在核外的壳层（能级）中绕核运动。

Particle	Relative Mass	Relative Charge
Proton	1	+1
Neutron	1	0
Electron	1/1836	-1

The identity of an element is fixed by its atomic number (Z), which equals the number of protons in the nucleus. The mass number (A) is the total number of protons and neutrons. This relationship is fundamental:

元素的种类由其原子序数（Z）决定，Z 等于原子核内的质子数。质量数（A）则是质子数和中子数的总和。这个关系是根本性的：

A = number of protons + number of neutrons

Electron configuration follows the 2,8,8 rule for the first 20 elements. The first shell holds up to 2 electrons, the second up to 8, and the third up to 8 (for KS3). The electronic arrangement determines an element’s chemical reactivity and its position in the periodic table.

电子排布遵循前 20 号元素的 2,8,8 规则。第一壳层最多容纳 2 个电子，第二层 8 个，第三层 8 个（KS3 阶段）。电子排布决定了元素的化学活泼性及其在元素周期表中的位置。

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3. Chemical Formulae: Using Combining Power | 化学式：运用化合价

Chemical formulae represent the types and numbers of atoms in a compound. The combining power (valence) of an ion or group tells you how it bonds. For ionic compounds, the total positive charge must equal the total negative charge.

化学式表示化合物中原子的种类和数目。离子或原子团的化合价（结合能力）告诉您它如何成键。对于离子化合物，总正电荷必须等于总负电荷。

Simple ions from groups: Group 1 metals form +1 ions (Na⁺, K⁺), Group 2 metals form +2 ions (Mg²⁺, Ca²⁺), Group 7 halogens form −1 ions (Cl⁻, Br⁻), and Group 6 elements often form −2 ions (O²⁻, S²⁻).

常见族的简单离子：第 1 族金属形成 +1 离子（Na⁺、K⁺），第 2 族金属形成 +2 离子（Mg²⁺、Ca²⁺），第 7 族卤素形成 −1 离子（Cl⁻、Br⁻），第 6 族元素常形成 −2 离子（O²⁻、S²⁻）。

Polyatomic ions are groups of atoms that carry an overall charge. You must memorise them:

多原子离子是带有整体电荷的原子团。你必须记住它们：

• Sulfate SO₄²⁻
• Carbonate CO₃²⁻
• Nitrate NO₃⁻
• Hydroxide OH⁻
• Ammonium NH₄⁺

• 硫酸根 SO₄²⁻
• 碳酸根 CO₃²⁻
• 硝酸根 NO₃⁻
• 氢氧根 OH⁻
• 铵根 NH₄⁺

To write a correct formula, swap the numerical values of the combining powers and place them as subscripts. The ‘cross-over’ method works reliably:

要写出正确的化学式，交换化合价的数值并将其作为下标。交叉法始终有效：

Al³⁺ + O²⁻ → Al₂O₃

If the charges are equal, they cancel (e.g., Ca²⁺ + O²⁻ → CaO). Brackets are needed when more than one polyatomic ion is present, such as Ca(OH)₂ not CaOH₂, and Mg(NO₃)₂ not MgNO₃₂.

如果电荷数相等，则相互抵消（如 Ca²⁺ + O²⁻ → CaO）。当存在多个多原子离子时，需要使用括号，例如 Ca(OH)₂ 而非 CaOH₂，Mg(NO₃)₂ 而非 MgNO₃₂。

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4. Writing and Balancing Chemical Equations | 书写与配平化学方程式

A balanced chemical equation obeys the law of conservation of mass. Every atom present in the reactants must appear in the products. We balance equations by placing coefficients (large numbers) in front of chemical formulae; we never change the subscripts inside a formula.

配平的化学方程式遵循质量守恒定律。反应物中的每一个原子都必须出现在生成物中。我们通过在化学式前添加系数（大数字）来配平方程式；绝不改变化学式内部的下标数字。

Start by writing the word equation, then replace it with correct formulae. Count atoms of each element on both sides and add coefficients to balance them. Leave hydrogen and oxygen to balance last.

从写出文字表达式开始，然后将其替换为正确的化学式。数一数两边每种元素的原子数，添加系数来配平它们。最后再配平氢和氧。

Example 1: Hydrogen + Oxygen → Water. Stepwise: H₂ + O₂ → H₂O. On the right there are 2 hydrogen atoms but only 1 oxygen atom, while the left has 2 oxygens. Add coefficient 2 before H₂O to get 2 oxygen atoms on the right: H₂ + O₂ → 2H₂O. Now hydrogens are 2 on left but 4 on right. Add coefficient 2 before H₂: 2H₂ + O₂ → 2H₂O.

示例 1：氢气 + 氧气 → 水。逐步操作：H₂ + O₂ → H₂O。右边有 2 个氢原子但只有 1 个氧原子，左边有 2 个氧原子。在 H₂O 前添加系数 2 使右边有 2 个氧原子：H₂ + O₂ → 2H₂O。此时左边氢原子为 2 个，右边为 4 个。在 H₂ 前添加系数 2：2H₂ + O₂ → 2H₂O。

Example 2: Methane combustion. CH₄ + O₂ → CO₂ + H₂O. Balance carbon: 1 C each side. Balance hydrogen: 4 H on left, so add 2 before H₂O: CH₄ + O₂ → CO₂ + 2H₂O. Balance oxygen: right has 2 + 2 = 4 oxygens, so add 2 before O₂: CH₄ + 2O₂ → CO₂ + 2H₂O.

示例 2：甲烷燃烧。CH₄ + O₂ → CO₂ + H₂O。配平碳：两边各 1 个 C。配平氢：左边 4 个 H，因此在 H₂O 前添加 2：CH₄ + O₂ → CO₂ + 2H₂O。配平氧：右边有 2 + 2 = 4 个氧原子，因此在 O₂ 前添加 2：CH₄ + 2O₂ → CO₂ + 2H₂O。

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5. The Law of Conservation of Mass | 质量守恒定律

No atoms are created or destroyed during a chemical reaction. The total mass of the reactants equals the total mass of the products. This is a fundamental principle that governs all quantitative chemistry.

在化学反应中，原子既不会凭空产生，也不会凭空消失。反应物的总质量等于生成物的总质量。这是支配一切定量化学的基本原则。

Total mass of reactants = Total mass of products

If a reaction appears to gain or lose mass, it is usually because a gas is being exchanged with the surroundings. For example, burning magnesium in air appears to gain mass because oxygen from the air combines with the metal to form solid magnesium oxide: 2Mg + O₂ → 2MgO. The added oxygen mass makes the product appear heavier.

如果反应看起来质量增加了或减少了，通常是因为有气体与环境发生了交换。例如，在空气中燃烧镁，质量看起来增加了，因为空气中的氧与金属结合生成固态氧化镁：2Mg + O₂ → 2MgO。氧元素的加入使产物看起来更重。

When marble chips react with hydrochloric acid in an open beaker, the mass decreases because carbon dioxide gas escapes: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂. If the same reaction is carried out in a sealed container, the total mass stays the same.

当大理石碎片在敞开烧杯中与盐酸反应时，质量会减少，因为二氧化碳气体逸出：CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂。如果在密封容器中进行同样的反应，总质量保持不变。

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6. Types of Chemical Reactions | 化学反应类型

KS3 OCR Chemistry covers five main reaction patterns. Each has a characteristic general equation that helps you predict products.

KS3 OCR 化学涵盖五种主要的反应模式。每种都有其特有的通式，可帮助您预测产物。

Combustion: A fuel reacts with oxygen, releasing heat and light. Hydrocarbons burn in plenty of oxygen to form carbon dioxide and water.

燃烧：燃料与氧气反应，释放热和光。碳氢化合物在充足的氧气中燃烧，生成二氧化碳和水。

Hydrocarbon + O₂ → CO₂ + H₂O

Neutralisation: An acid reacts with a base (alkali or metal oxide/hydroxide) to produce a salt and water. The neutralisation ionic equation for strong acid–strong alkali is H⁺ + OH⁻ → H₂O.

中和：酸与碱（碱性溶液或金属氧化物/氢氧化物）反应，生成盐和水。强酸强碱中和的离子方程式为 H⁺ + OH⁻ → H₂O。

Acid + Base → Salt + Water

Metal + Acid: Reactive metals (above hydrogen in the reactivity series) displace hydrogen from dilute acids, forming a salt and hydrogen gas. Example: Zn + 2HCl → ZnCl₂ + H₂.

金属 + 酸：活泼金属（金属活动性顺序中排在氢之前）从稀酸中置换出氢，生成盐和氢气。示例：Zn + 2HCl → ZnCl

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