📚 Year 8 AQA Chemistry: Formula & Theorem Quick Reference | Year 8 AQA 化学：公式定理速查手册
This handbook pulls together all the essential chemical formulas, laws and theorems from the Year 8 AQA Chemistry course. Use it to revise core ideas such as conservation of mass, atomic structure, valency, reactivity, neutralisation and reaction rates. The clear English–Chinese pairings make it ideal for bilingual revision and quick classroom reference.
本手册汇总了 Year 8 AQA 化学课程中所有关键的公式、定律与定理，涵盖质量守恒、原子结构、化合价、金属活动性、中和反应与反应速率等核心概念。清晰的中英文对照非常适合双语复习和课堂速查。
1. Law of Conservation of Mass | 质量守恒定律
During a chemical reaction, atoms are neither created nor destroyed. The total mass of the reactants always equals the total mass of the products.
在化学反应中，原子既不会被创造也不会被消灭。反应物的总质量永远等于生成物的总质量。
Total mass of reactants = Total mass of products
反应物总质量 = 生成物总质量
If a reaction is carried out in a closed system, the reading on a balance stays constant. In an open system, mass may appear to change –for example magnesium gains mass when it burns in air because it combines with oxygen from the surroundings.
若在密闭系统中进行反应，天平读数将保持不变。在开放系统中，质量似乎会发生变化——例如镁在空气中燃烧时质量增加，因为它与周围空气中的氧气发生了结合。
2. Atomic Structure and Key Numbers | 原子结构与关键数字
All substances are made from atoms. An atom contains a tiny nucleus of protons and neutrons, surrounded by electrons orbiting in shells.
所有物质均由原子构成。原子内部有一个由质子和中子组成的极小原子核，核外有电子分层排布。
The atomic number (Z) is the number of protons in an atom. In a neutral atom, the number of electrons equals Z. The mass number (A) is the total number of protons plus neutrons.
原子序数 (Z) 是原子中质子的数目。在中性原子中，电子数等于 Z。质量数 (A) 是质子数与中子数之和。
A = Z + number of neutrons
A = Z + 中子数
For example, a carbon atom with Z = 6 and A = 12 has 6 protons, 6 electrons and 6 neutrons.
例如，一个 Z = 6、A = 12 的碳原子含有 6个质子、6个电子和 6个中子。
3. Electron Configuration and the Periodic Table | 电子排布与周期表
Electrons occupy shells (energy levels) around the nucleus. The first shell holds up to 2 electrons, the second shell up to 8, and the third shell can also hold 8 for the first 20 elements.
电子在原子核外分层排布。第一层最多容纳 2 个电子，第二层最多容纳 8 个，前 20 号元素的第三层同样最多容纳 8 个。
The arrangement of electrons (e.g. sodium: 2,8,1) determines an element's chemical behaviour and its position in the periodic table.
电子排布方式（如 钠：2,8,1）决定了元素的化学性质及其在周期表中的位置。
Period number = number of occupied electron shells
周期数 = 已占据的电子层数
Group number = number of electrons in the outer shell (for main groups)
族数 = 最外层电子数（主族元素）
4. Valency and Writing Chemical Formulae | 化合价与化学式书写
Valency (or combining power) tells you how many bonds an atom can form. In an ionic compound, the total positive charge must exactly balance the total negative charge.
化合价（或称结合能力）表示一个原子能形成多少根化学键。在离子化合物中，正负总电荷必须恰好抵消，使化合物整体不显电性。
To write the formula of an ionic compound, use the cross-over rule: swap the valency numbers to become subscripts. For example, aluminium (Al³⁺) and oxygen (O²⁻) combine to give Al₂O₃.
书写离子化合物的化学式时，使用交叉规则：将化合价数值交换后作为下标。例如，铝离子 Al³⁺ 与氧离子 O²⁻ 结合，化学式为 Al₂O₃。
Sum of positive charges + sum of negative charges = 0
正电荷总和 + 负电荷总和 = 零
5. Balancing Chemical Equations | 化学方程式配平
A balanced symbol equation shows the same number of each type of atom on both sides. Atoms are only rearranged, never lost or gained.
配平的符号方程式表明方程式两边每种原子的数目相等。原子只是重新组合，不会凭空消失或增加。
Start with a word equation, then write the correct formulae. Count the atoms for each element and adjust the large numbers (coefficients) in front of the formulae until the atoms balance.
先写出文字方程式，再写出正确的化学式。数出每种元素的原子数，然后调整化学式前的大数字（系数），直到两边原子数相等。
Word equation: hydrogen + oxygen → water
文字方程式：氢气 + 氧气 → 水
Unbalanced: H₂ + O₂ → H₂O
未配平: H₂ + O₂ → H₂O
Balanced: 2H₂ + O₂ → 2H₂O
配平: 2H₂ + O₂ → 2H₂O
6. Relative Atomic Mass and Formula Mass | 相对原子质量与式量
The relative atomic mass (Ar) of an element is the average mass of its atoms compared with 1/12 of the mass of a carbon‑12 atom. For most elements, Ar is close to the mass number.
元素的相对原子质量 (Ar) 是其原子平均质量与碳‑12 原子质量的 1/12 之比值。对大多数元素，Ar 约等于质量数。
The relative formula mass (Mr) of a compound is found by adding together the Ar values of all the atoms in its formula.
化合物的相对式量 (Mr) 等于其化学式中各原子的 Ar 相加之和。
Mr (H₂O) = 2 × Ar(H) + 1 × Ar(O) = 2×1 + 16 = 18
Mr (H₂O) = 2 × Ar(H) + 1 × Ar(O) = 2×1 + 16 = 18
This concept helps to explain why one mole of a substance has a mass equal to its Mr in grams, even if mole calculations are studied later.
这个概念有助于理解为何 1 摩尔物质的质量等于其 Mr 以克为单位的值，尽管摩尔计算将在之后深入学习。
7. Reactivity Series of Metals | 金属活动性顺序
The reactivity series lists metals in order of how vigorously they react. A more reactive metal can displace a less reactive metal from its compound.
金属活动性顺序按反应剧烈程度排列。较为活泼的金属能把较不活泼的金属从其化合物中置换出来。
K > Na > Ca > Mg > Al > Zn > Fe > Sn > Pb > (H) > Cu > Ag > Au
钾 > 钠 > 钙 > 镁 > 铝 > 锌 > 铁 > 锡 > 铅 > (氢) > 铜 > 银 > 金
+ water → metal hydroxide + hydrogen (for reactive metals); metal + oxygen → metal oxide.
反应通式：金属 + 酸 → 盐 + 氢气；活泼金属 + 水 → 金属氢氧化物 + 氢气；金属 + 氧气 → 金属氧化物。
8. Acids, Bases and Neutralisation | 酸、碱与中和反应
An acid is a substance that releases hydrogen ions (H⁺) in water. A base can neutralise an acid; an alkali is a soluble base that releases hydroxide ions (OH⁻) in water.
酸是在水中能释放氢离子 (H⁺) 的物质；碱能中和酸；可溶于水的碱称为碱溶液，它在水中释放氢氧根离子 (OH⁻)。
Neutralisation is the reaction of an acid with a base to form a salt and water. The ionic equation for the reaction between H⁺ and OH⁻ is:
中和反应是酸与碱作用生成盐和水的过程。H⁺ 与 OH⁻ 反应的离子方程式为：
H⁺(aq) + OH⁻(aq) → H₂O(l)
H⁺(aq) + OH⁻(aq) → H₂O(l)
hydrochloric acid + sodium hydroxide → sodium chloride + water (HCl + NaOH → NaCl + H₂O).
常见实例：盐酸 + 氢氧化钠 → 氯化钠 + 水 (HCl + NaOH → NaCl + H₂O)。
9. The pH Scale and Indicators | pH 标度与指示剂
The pH scale measures how acidic or alkaline a solution is. It runs from 0 (very acidic) to 14 (very alkaline), with 7 being neutral.
pH 标度用于衡量溶液的酸碱程度，范围从 0（极强酸性）到 14（极强碱性），7 为中性。
Indicators change colour according to pH. Litmus turns red in acid and blue in alkali. Universal indicator gives a full range of colours from red (pH 0‑3) through green (pH 7) to purple (pH 12‑14).
指示剂根据 pH 变色。石蕊在酸性中变红，在碱性中变蓝；通用指示剂能显示从红 (pH 0‑3) 经绿 (pH 7) 到紫 (pH 12‑14) 的完整色谱。
| pH 0‑6 | 酸性 Acidic |
| pH 7 | 中性 Neutral |
| pH 8‑14 | 碱性 Alkaline |
10. Factors Affecting Reaction Rate | 影响反应速率的因素
For a chemical reaction to occur, particles must collide with enough energy (activation energy). The rate depends on the frequency of successful collisions.
化学反应发生的条件是：粒子必须发生碰撞且有足够的能量（活化能）。反应速率取决于有效碰撞的频率。
Four main factors increase the rate of a reaction:
能加快反应速率的四个主要因素：
Increasing temperature – particles move faster and collide more often and with more energy.
升高温度 – 粒子运动加快，碰撞更频繁且能量更高。
Increasing concentration of a solution – more particles per volume, so more collisions.
增大溶液浓度 – 单位体积内粒子增多，碰撞次数增加。
Increasing surface area of a solid – breaking a solid into smaller pieces exposes more particles to react.
增大固体的表面积 – 将固体破碎成更小的颗粒，使更多粒子暴露出来参加反应。
Using a catalyst – a substance that lowers the activation energy without being used up.
使用催化剂 – 一种能降低活化能而自身不被消耗的物质。
11. States of Matter and Changes of State | 物态与状态变化
Substances exist as a solid, liquid or gas depending on the arrangement and movement of their particles. Changes of state are physical changes, not chemical reactions.
物质以固态、液态或气态存在，取决于其粒子的排列和运动方式。状态变化属于物理变化，不是化学反应。
aporation (liquid → gas), condensation (gas → liquid), sublimation (solid → gas directly).
关键术语：熔化（固→液）、凝固（液→固）、沸腾/蒸发（液→气）、凝结（气→液）、升华（固→气）。
During a change of state, the temperature stays constant while the substance absorbs or releases energy. The melting point and boiling point are characteristic properties of a pure substance.
状态变化期间，物质吸收或释放能量时温度保持恒定。熔点和沸点是纯净物质的特征性质。
12. Separation Techniques – Principles | 分离技术原理
Mixtures can be separated using physical methods that exploit differences in properties such as particle size, boiling point or solubility.
可利用混合物的物理性质差异（如粒径、沸点、溶解度）来分离混合物。
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（如沙子与水）。
Evaporation and crystallisation – separate a soluble solid from its solution by removing the solvent.
蒸发与结晶 – 通过除去溶剂从溶液中分离可溶性固体
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