📚 Formula & Theorem Quick-Reference Handbook for Year 7 Cambridge Chemistry | 剑桥七年级化学：公式定理速查手册
This comprehensive handbook brings together all the essential formulas, laws and key principles you need to master Year 7 Cambridge Chemistry. Use it as a quick revision tool to check your understanding of particle theory, atomic structure, reactions, acids and alkalis, and separation techniques.
本手册汇集了你掌握剑桥七年级化学所需的所有基本公式、定律和关键原理。将其作为快速复习工具，检查你对粒子理论、原子结构、化学反应、酸碱以及分离技术的理解。
1. Particle Theory of Matter | 物质粒子理论
All matter is made of tiny, constantly moving particles. The energy of these particles and the forces between them determine whether the substance is a solid, liquid or gas. In solids, particles are tightly packed in a regular pattern and vibrate in fixed positions. In liquids, particles are close together but can slide past each other. In gases, particles are far apart and move rapidly in all directions.
所有物质都是由不断运动的微小粒子组成的。粒子的能量和它们之间的作用力决定了该物质是固体、液体还是气体。在固体中，粒子紧密地排列成有规则的结构，并在固定位置上振动。在液体中，粒子彼此靠近但可以相互滑动。在气体中，粒子相距很远，并向各个方向快速运动。
Particle model key concept: Arrangement, movement and energy of particles explain the properties of solids, liquids and gases.
粒子模型核心概念：粒子的排列、运动和能量解释了固体、液体和气体的性质。
When a substance changes state, the particles themselves do not change; only their arrangement and energy change. Melting, freezing, boiling, condensation, sublimation and deposition are reversible physical changes that can be explained by the particle model.
当物质发生状态变化时，粒子本身不变，改变的只是它们的排列方式和能量。熔化、凝固、沸腾、冷凝、升华和凝华都是可以用粒子模型解释的可逆物理变化。
The key state changes and their energy transfers: melting (solid to liquid, energy taken in), freezing (liquid to solid, energy given out), boiling/evaporation (liquid to gas, energy taken in), condensation (gas to liquid, energy given out).
关键的状态变化及其能量转移：熔化（固态变液态，吸收能量），凝固（液态变固态，放出能量），沸腾/蒸发（液态变气态，吸收能量），冷凝（气态变液态，放出能量）。
2. Atomic Structure | 原子结构
Atoms are the smallest particles of an element that can take part in a chemical reaction. Each atom consists of a central nucleus containing protons and neutrons, surrounded by electrons orbiting in shells. Protons carry a positive charge (+1), electrons carry a negative charge (−1), and neutrons have no charge (0).
原子是能够参与化学反应的元素最小粒子。每个原子由一个包含质子和中子的原子核以及围绕原子核分层排布的电子组成。质子带正电荷（+1），电子带负电荷（−1），中子不带电（0）。
For a neutral atom, the number of protons equals the number of electrons. The atomic number (Z) is the number of protons, which determines the identity of the element. The mass number (A) is the total number of protons and neutrons in the nucleus.
对于中性原子，质子数等于电子数。原子序数（Z）是质子数，它决定了元素的种类。质量数（A）是原子核内质子数和中子数的总和。
Atomic number (Z) = Number of protons
原子序数（Z）= 质子数
Mass number (A) = Number of protons + Number of neutrons
质量数（A）= 质子数 + 中子数
Electrons are arranged in shells around the nucleus. The first shell can hold up to 2 electrons, the second shell up to 8, and the third shell also up to 8 in simple models for elements up to calcium. The electron arrangement determines how an element reacts.
电子围绕原子核分层排列。第一层最多容纳2个电子，第二层最多容纳8个，对于钙之前的元素，第三层也最多容纳8个（根据简单模型）。电子排布方式决定了元素的反应特性。
3. Elements, Compounds and Mixtures | 元素、化合物与混合物
An element is a pure substance made of only one type of atom. Each element has a unique chemical symbol, such as O for oxygen and Fe for iron. All elements are listed on the Periodic Table. A compound is a pure substance formed when two or more different elements chemically combine in fixed proportions. The properties of a compound are different from the elements it contains.
元素是仅由一种原子组成的纯物质。每种元素都有独特的化学符号，例如 O 代表氧，Fe 代表铁。所有元素都列在周期表中。化合物是由两种或两种以上不同元素以固定比例化学结合而成的纯物质。化合物的性质与其组成元素不同。
A mixture contains two or more substances (elements or compounds) that are not chemically combined. The components of a mixture retain their individual properties and can be separated by physical means. Air, salt water and muddy water are all mixtures.
混合物含有两种或两种以上未通过化学键结合的物质（元素或化合物）。混合物中的各组分保持各自原有的性质，并可通过物理方法分离。空气、盐水和泥水都是混合物。
Element: one type of atom → Compound: two or more elements chemically bonded → Mixture: not chemically combined
元素：一种原子 → 化合物：两种或以上元素化学键结合 → 混合物：未发生化学结合
4. The Law of Conservation of Mass | 质量守恒定律
During a chemical reaction, atoms are rearranged but no atoms are created or destroyed. This means the total mass of the reactants equals the total mass of the products. This principle is known as the law of conservation of mass, and it must be respected when writing word or symbol equations.
在化学反应过程中，原子重新排列，但没有原子被创造或消灭。这意味着反应物的总质量等于生成物的总质量。这一原则称为质量守恒定律，在书写文字方程式或符号方程式时必须遵循。
For example, when magnesium burns in oxygen to form magnesium oxide, the mass of the white powder produced is equal to the combined mass of magnesium and oxygen that reacted, provided all the product is collected.
例如，当镁在氧气中燃烧生成氧化镁时，只要收集了全部生成物，所产生的白色粉末的质量就等于参与反应的镁和氧的质量之和。
Total mass of reactants = Total mass of products
反应物总质量 = 生成物总质量
In practice, mass may appear to change if a gas is produced and escapes, or if oxygen from the air is added to the products. In a closed system, the mass remains constant.
在实践中，如果反应产生气体逸出，或从空气中吸收了氧气参与生成，质量可能会表现出变化。在密闭系统中，质量保持不变。
5. Writing Chemical Formulas and Word Equations | 化学式与文字方程式的书写
A word equation shows the names of reactants and products in a chemical reaction, with an arrow (→) meaning ‘reacts to form’. For instance: magnesium + oxygen → magnesium oxide. The substances on the left are reactants, those on the right are products, and the arrow represents the direction of the change.
文字方程式用名称表示化学反应中的反应物和生成物，箭头（→）表示“反应生成”。例如：镁 + 氧 → 氧化镁。左侧的物质是反应物，右侧的是生成物，箭头代表变化的方向。
Chemical formulas represent compounds using symbols and subscript numbers to show how many atoms of each element are present. Subscript numbers are written to the bottom right of the symbol, such as H₂O for water (two hydrogen atoms, one oxygen atom) and CO₂ for carbon dioxide. No subscript means one atom.
化学式用元素符号和下角标数字表示化合物，下角标数字标在符号右下角，表明各元素的原子个数，例如 H₂O 代表水（两个氢原子，一个氧原子），CO₂ 代表二氧化碳。没有下角标表示一个原子。
When naming simple compounds made of two elements, the metal is written first, followed by the non-metal with its ending changed to ‘-ide’. Example: sodium + chlorine → sodium chloride.
在命名由两种元素组成的简单化合物时，先写金属，再写非金属，将非金属词尾改为“-ide”。例如：钠 + 氯 → 氯化钠。
6. Acids and Alkalis: pH and Indicators | 酸与碱：pH 和指示剂
Acids are substances with a pH less than 7 that release hydrogen ions (H⁺) in water. Common laboratory acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃). Alkalis are soluble bases that release hydroxide ions (OH⁻) in water and have a pH greater than 7. Examples are sodium hydroxide (NaOH) and potassium hydroxide (KOH). A neutral solution has a pH of exactly 7.
酸是 pH 值小于7 并在水中释放氢离子（H⁺）的物质。实验室中常见的酸包括盐酸（HCl）、硫酸（H₂SO₄）和硝酸（HNO₃）。碱是可溶的并在水中释放氢氧根离子（OH⁻）的物质，pH 值大于7，如氢氧化钠（NaOH）和氢氧化钾（KOH）。中性溶液的 pH 值恰好为7。
Indicators are dyes that change colour depending on the pH of the solution. The colour changes of common indicators are summarised below:
指示剂是根据溶液 pH 值改变颜色的染料。常见指示剂的颜色变化总结如下：
| Indicator (指示剂) | Colour in acid (酸性中的颜色) | Colour in neutral (中性中的颜色) | Colour in alkali (碱性中的颜色) |
|---|---|---|---|
| Litmus (石蕊) | Red | Purple | Blue |
| Phenolphthalein (酚酞) | Colourless | Colourless | Pink |
| Universal Indicator (通用指示剂) | Red/orange/yellow | Green | Blue/purple |
The pH scale runs from 0 (very strong acid) to 14 (very strong alkali). The lower the pH, the more acidic the solution; the higher the pH, the more alkaline it is.
pH 标度从0（强酸）到14（强碱）。pH 值越低，溶液酸性越强；pH 值越高，碱性越强。
7. Neutralisation: The Core Reaction | 中和反应：核心反应
Neutralisation is the reaction between an acid and a base to form a salt and water. The hydrogen ions (H⁺) from the acid react with the hydroxide ions (OH⁻) from the alkali to produce water molecules. This is an exothermic reaction.
中和反应是酸与碱反应生成盐和水的过程。酸中的氢离子（H⁺）与碱中的氢氧根离子（OH⁻）结合生成水分子。这是一个放热反应。
acid + base → salt + water
酸 + 碱 → 盐 + 水
The name of the salt comes from the acid used: hydrochloric acid produces chlorides, sulfuric acid produces sulfates, nitric acid produces nitrates. Example: hydrochloric acid + sodium hydroxide → sodium chloride + water.
盐的名称来自所用的酸：盐酸产生氯化物，硫酸产生硫酸盐，硝酸产生硝酸盐。例如：盐酸 + 氢氧化钠 → 氯化钠 + 水。
When an acid reacts with a metal carbonate, the products are a salt, water and carbon dioxide gas. Word equation: acid + metal carbonate → salt + water + carbon dioxide.
当酸与金属碳酸盐反应时，产物是盐、水和二氧化碳气体。文字方程式：酸 + 金属碳酸盐 → 盐 + 水 + 二氧化碳。
8. The Reactivity Series of Metals | 金属活动性顺序
The reactivity series lists metals in order of their reactivity, from the most reactive to the least reactive. More reactive metals can displace less reactive metals from their compounds and react more vigorously with water and acids.
金属活动性顺序将金属按反应活性由强到弱排列。更活泼的金属可以从化合物中置换出较不活泼的金属，并与水和酸反应更剧烈。
| Metal (金属) | Symbol (符号) | Reaction with cold water (与冷水反应) | Reaction with dilute acid (与稀酸反应) |
|---|---|---|---|
| Potassium (钾) | K | Very violent | Explosive |
| Sodium (钠) | Na | Very vigorous | Very vigorous |
| Calcium (钙) | Ca | Vigorous | Vigorous |
| Magnesium (镁) | Mg | Very slow with steam | React rapidly |
| Zinc (锌) | Zn | Very slow with steam | Moderate reaction |
| Iron (铁) | Fe | Slow with steam | Slow reaction |
| Copper (铜) | Cu | No reaction | No reaction |
A displacement reaction occurs when a more reactive metal takes the place of a less reactive metal in a compound. For example, iron + copper sulfate → iron sulfate + copper. This proves iron is more reactive than copper.
当较活泼的金属取代化合物中较不活泼的金属时，就会发生置换反应。例如：铁 + 硫酸铜 → 硫酸亚铁 + 铜。这证明铁比铜更活泼。
9. Separation Techniques | 分离技术
Mixtures can be separated into pure substances using physical techniques that exploit differences in physical properties. The choice of method depends on the components present. Below is a summary of key separation methods:
混合物可以通过利用物理性质差异的物理技术分离成纯物质。方法的选择取决于所含组分。下面是主要分离方法的总结：
| Technique (技术) | Property used (利用的性质) | Example (实例) |
|---|---|---|
| Filtration (过滤) | Particle size ( insoluble solid from liquid) | Sand from water |
| Evaporation (蒸发) | Boiling point (solvent evaporates leaving solid) | Salt from salt water |
| Crystallisation (结晶) | Solubility changes with temperature | Pure copper sulfate crystals |
| Simple distillation (简单蒸馏) | Difference in boiling points | Pure water from salt water |
| Chromatography (色谱法) | Solubility in a solvent | Separating coloured inks |
In chromatography, substances travel different distances up the paper because they have different solubilities. The more soluble a substance, the further it moves. This can be used to identify unknown substances by comparing their Rf values (retention factor), though Year 7 may only require visual comparison.
在色谱法中，物质因溶解度不同而在纸上移动的距离不同。溶解度越大，移动得越远。这可用于通过比较 Rf 值（比移值）来鉴别未知物质，但七年级可能只要求目视比较。
10. Chemical Changes vs Physical Changes | 化学变化与物理变化
A physical change alters the form or appearance of a substance but does not produce a new substance. All changes of state, dissolving, and cutting are physical changes. They are usually easily reversed.
物理变化改变物质的形式或外观，但不产生新物质。所有状态变化、溶解和切割都属于物理变化，它们通常容易逆转。
A chemical change (chemical reaction) produces one or more new substances with different properties. Signs of a chemical change include colour change, temperature change, gas production (bubbles) without heating, formation of a precipitate, and a change that is difficult to reverse. Burning, rusting and cooking are chemical changes.
化学变化（化学反应）产生一种或多种性质不同的新物质。化学变化的迹象包括颜色变化、温度变化、无需加热即有气体产生（气泡）、生成沉淀物以及难以逆转的变化。燃烧、生锈和烹饪都是化学变化。
Key rule: In a chemical change, atoms rearrange to form new substances. In a physical change, no new substances are made.
关键规则：化学变化中，原子重新排列形成新物质。物理变化中没有新物质生成。
11. Key Properties of Metals and Non-metals | 金属与非金属的关键性质
Metals are typically shiny, good conductors of heat and electricity, malleable (can be hammered into shape) and ductile (can be drawn into wires). Most metals are solid at room temperature (except mercury) and have high melting points. Non-metals are often dull, brittle, poor conductors and have lower melting and boiling points.
金属通常具有光泽，是热和电的良导体，具有可锻性（可锤打成形）和延展性（可拉成细丝）。大多数金属在室温下为固态（汞除外），熔点高。非金属通常暗淡、脆性、非良导体，熔点和沸点较低。
Oxides of metals are usually basic, reacting with acids to form salt and water. Oxides of non-metals are often acidic, reacting with alkalis to form salt and water. This helps predict the nature of an unknown oxide.
金属的氧化物通常是碱性氧化物，与酸反应生成盐和水。非金属的氧化物通常是酸性氧化物，与碱反应生成盐和水。这有助于预测未知氧化物的性质。
12. Factors That Affect the Rate of a Reaction | 影响反应速率的因素
The rate of a chemical reaction tells us how quickly reactants are used up or products are formed. Four main factors can change the reaction rate: temperature, concentration (of solutions), surface area (of solids), and the use of a catalyst.
化学反应速率告诉我们反应物消耗或生成物产生的快慢。四个主要因素可以改变反应速率：温度、浓度（溶液的）、表面积（固体的）以及催化剂的使用。
Increasing the temperature increases the energy of particles, so they collide more often and with greater energy; more successful collisions per second mean a faster reaction. Water must be at boiling point to react rapidly with magnesium, but reacts slowly when cold.
升高温度增加了粒子的能量，使它们碰撞更频繁且能量更大；每秒更多有效碰撞意味着反应更快。水必须在沸腾时才能与镁快速反应，而冷水反应缓慢。
Higher concentration means more reactant particles in the same volume, leading to more frequent collisions and a faster reaction. Similarly, breaking a solid into smaller pieces increases its surface area, exposing more particles to react, which also speeds up the reaction.
浓度更高意味着相同体积内有更多的反应物粒子，导致碰撞更频繁、反应更快。同样，将固体破碎成更小的颗粒可增加其表面积，暴露出更多粒子参与反应，从而加快反应速率。
A catalyst is a substance that speeds up a reaction without being used up itself. It lowers the energy needed for the reaction to happen. For example, manganese dioxide (MnO₂) can speed up the decomposition of hydrogen peroxide.
催化剂是一种能加快反应速率而自身在反应中
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