📚 Year 8 SQA Chemistry: Quick-Reference Formula & Theorem Handbook | SQA 化学：公式定理速查手册
This comprehensive revision guide gathers every essential formula, definition, and law you will encounter in the SQA Chemistry course at Year 8 level. Use it to quickly refresh calculations for the mole, concentration, gas behaviour, electrolysis, and more – all explained with worked-example logic and clear notation.
这本综合复习手册汇集了 Year 8 SQA 化学课程中必须掌握的每一个核心公式、定义和定律。你可以用它快速重温摩尔、浓度、气体行为、电解等计算——所有内容均配有示例逻辑和清晰的符号标注。
1. Atomic Structure & Particle Properties | 原子结构与粒子属性
Every atom consists of a tiny, dense nucleus surrounded by moving electrons. The three key subatomic particles are protons, neutrons and electrons. The nucleus contains the protons (positive charge) and neutrons (no charge), while electrons (negative charge) orbit in shells.
每个原子都由一个微小致密的原子核和绕核运动的电子构成。三种关键亚原子粒子是质子、中子和电子。原子核内含有带正电的质子和不带电的中子，而电子（带负电）则在电子层中运动。
| Particle / 粒子 | Relative mass / 相对质量 | Relative charge / 相对电荷 | Location / 位置 |
|---|---|---|---|
| Proton / 质子 (p⁺) | 1 | +1 | Nucleus / 原子核 |
| Neutron / 中子 (n⁰) | 1 | 0 | Nucleus / 原子核 |
| Electron / 电子 (e⁻) | 1/1840 (negligible) | -1 | Shells / 电子层 |
mber (A) = protons + neutrons. In a neutral atom, number of electrons = number of protons.
原子序数 (Z) = 质子数；质量数 (A) = 质子数 + 中子数。在中性原子中，电子数 = 质子数。
2. Writing Chemical Formulae | 书写化学式
A chemical formula shows the types and numbers of atoms in a substance. The valency (combining power) of an element or ion tells us how many bonds it can form or how many charges it carries. To write the formula of an ionic compound, swap the valencies and reduce to the simplest ratio.
化学式表明物质中原子的种类与数目。元素或离子的化合价（结合能力）告诉我们它能形成多少个化学键或携带多少电荷。书写离子化合物的化学式时，交换化合价并化简为最简整数比。
ts if more than one unit is needed: calcium sulfate → CaSO₄; ammonium sulfate → (NH₄)₂SO₄.
例如，铝离子 Al³⁺ 和氧离子 O²⁻ → Al₂O₃。对于硫酸根 SO₄²⁻ 等多原子离子，若需要多个单元则加括号：硫酸钙 → CaSO₄；硫酸铵 → (NH₄)₂SO₄。
Covalent compounds use prefixes (mono‑, di‑, tri‑, etc.) to indicate the number of each atom, e.g. CO₂ is carbon dioxide, N₂O₄ is dinitrogen tetroxide.
共价化合物使用前缀（单、二、三等）表示每个原子的数目，例如 CO₂ 为二氧化碳，N₂O₄ 为四氧化二氮。
3. Balancing Chemical Equations | 配平化学方程式
A balanced equation obeys the Law of Conservation of Mass: atoms are neither created nor destroyed in a chemical reaction. The same number of each type of atom must appear on both sides of the arrow.
配平的化学方程式遵循质量守恒定律：化学反应中原子既不会凭空产生也不会凭空消失。箭头两侧每一种原子的数目必须相等。
State symbols are added in brackets: (s) solid, (l) liquid, (g) gas, (aq) aqueous solution. Steps: write the word equation, then the skeleton formula equation, and adjust coefficients only – never change subscripts inside a formula.
需在括号中标注状态符号：(s) 固体，(l) 液体，(g) 气体，(aq) 水溶液。步骤：先写出文字表达式，再写出骨架化学式方程，然后只调整系数——绝不更改化学式内部的下标数字。
Example: H₂(g) + O₂(g) → H₂O(l) is unbalanced. Balanced: 2H₂(g) + O₂(g) → 2H₂O(l).
示例：H₂(g) + O₂(g) → H₂O(l) 未配平。配平后：2H₂(g) + O₂(g) → 2H₂O(l)。
4. The Mole Concept | 摩尔概念
nt of substance that contains exactly 6.022 × 10²³ specified elementary entities (Avogadro's constant, Nₐ). This number is used to count atoms, molecules, ions or formula units.
一摩尔（mol）是包含恰好 6.022 × 10²³ 个指定基本单元（阿伏伽德罗常数, Nₐ）的物质的量。这个数值用于计量原子、分子、离子或化学式单元。
n = m / M and N = n × Nₐ
ays find the molar mass from the relative formula mass (sum of relative atomic masses Aᵣ).
其中 n = 物质的量 (mol)，m = 质量 (g)，M = 摩尔质量 (g mol⁻¹)，N = 粒子数，Nₐ = 6.022 × 10²³ mol⁻¹。摩尔质量始终由相对化学式质量（相对原子质量 Aᵣ 之和）得出。
ne CH₄. Mᵣ of CH₄ = 12 + (4×1) = 16, so M = 16 g mol⁻¹. n = 8.0 g / 16 g mol⁻¹ = 0.50 mol.
示例：计算 8.0 g 甲烷 CH₄ 的物质的量。CH₄ 的 Mᵣ = 12 + (4×1) = 16，因此 M = 16 g mol⁻¹。n = 8.0 g / 16 g mol⁻¹ = 0.50 mol。
5. Concentration of Solutions | 溶液浓度
The concentration of a solution tells us how much solute is dissolved in a given volume of solvent. The most common unit in SQA is moles per litre (mol L⁻¹) or moles per cubic decimetre (mol dm⁻³).
溶液的浓度表示在一定体积的溶剂中溶解了多少溶质。SQA 中最常见的单位是摩尔每升 (mol L⁻¹) 或摩尔每立方分米 (mol dm⁻³)。
c = n / V
³. Remember: 1 dm³ = 1000 cm³, so volume in cm³ must be divided by 1000 to convert to dm³.
c = 浓度 (mol dm⁻³)，n = 物质的量 (mol)，V = 溶液体积 (dm³)。请记住：1 dm³ = 1000 cm³，因此以 cm³ 为单位的体积需除以 1000 转换为 dm³。
L⁻¹. Use both relationships to prepare standard solutions or to interpret titration data.
也可使用质量浓度：ρ = m / V，其中 ρ 的单位为 g dm⁻³ 或 g L⁻¹。运用这两个关系可以配制标准溶液或解析滴定数据。
6. Empirical and Molecular Formulae | 经验式与分子式
The empirical formula is the simplest whole‑number ratio of atoms in a compound. The molecular formula shows the actual number of atoms of each element in one molecule. It is always a whole‑number multiple of the empirical formula.
经验式（最简式）是化合物中原子个数的最简整数比。分子式则表示一个分子中各原子的实际数目，它始终是经验式的整数倍。
To determine empirical formula from experimental data: (i) convert % or mass of each element to moles, (ii) divide all mole values by the smallest, (iii) adjust to the simplest integer ratio, multiplying by a common factor if needed.
根据实验数据确定经验式的步骤：(i) 将每种元素的质量或质量百分数转换为摩尔数，(ii) 将所有摩尔数除以最小值，(iii) 调整为最简整数比，必要时乘以公倍数。
Example: a compound is 27.3% carbon and 72.7% 2.275 → C₁O₂, so empirical formula is CO₂. If the Mᵣ is 44, the molecular formula is CO₂.
示例：某化合物含碳 27.3%、氧 72.7%（质量百分比）。C 的摩尔数 = 27.3/12 = 2.275；O 的摩尔数 = 72.7/16 = 4.544。除以 2.275 → C₁O₂，经验式为 CO₂。若 Mᵣ 为 44，则分子式即为 CO₂。
7. Gas Law Relationships | 气体定律关系
Under standard conditions, one mole of any gas occupies the same molar volume. At room temperature and pressure (rtp, 20 °C, 1 atm), the molar volume is approximately 24 dm³ mol⁻¹; at standard temperature and pressure (stp, 0 °C, 1 atm) it is 22.4 dm³ mol⁻¹.
在标准条件下，一摩尔的任何气体都占有相同的摩尔体积。在常温常压 (rtp, 20 °C, 1 atm) 下，摩尔体积约为 24 dm³ mol⁻¹；在标准温度与压力 (stp, 0 °C, 1 atm) 下为 22.4 dm³ mol⁻¹。
pV = nRT
the gas constant R = 8.31 J K⁻¹ mol⁻¹. Temperatures must be in kelvin: T(K) = T(°C) + 273.
理想气体状态方程将压力 p (Pa)、体积 V (m³)、物质的量 n (mol)、温度 T (K) 和气体常数 R = 8.31 J K⁻¹ mol⁻¹ 联系起来。温度必须使用开尔文：T(K) = T(°C) + 273。
For reacting gas volumes at the same temperature and pressure, Gay‑Lussac's law applies: volumes combine in simple whole‑number ratios corresponding to the coefficients in the balanced equation.
对于同温同压下发生反应的气体体积，适用盖‑吕萨克定律：气体体积以简单整数比进行化合，该比值与配平方程式中的系数对应。
8. Percentage Yield & Atom Economy | 产率百分比与原子经济性
al yield) with the maximum theoretical mass predicted by stoichiometry. It is always ≤ 100%.
产率百分比是将实际获得的产品质量（实际产率）与由化学计量预测的最大理论质量进行比较的结果，其值始终 ≤ 100%。
% yield = (actual yield / theoretical yield) × 100
Atom economy measures the efficiency with which reactant atoms are incorporated into the desired product. It is especially important in green chemistry.
原子经济性衡量的是反应物原子结合到目标产物中的效率，这一指标在绿色化学中尤为重要。
Atom economy = (Mᵣ of desired product / sum of Mᵣ of all reactants) × 100
A reaction with high atom economy produces less waste. Always check the balanced equation and consider only the reactants that appear on the left‑hand side.
原子经济性高的反应产生的废物较少。务必参照配平的化学方程式，仅考虑出现在左侧的反应物。
9. Acids, Bases & pH Scale | 酸、碱与pH标度
An acid releases H⁺ ions in aqueous solution; a base accepts H⁺ or releases OH⁻ ions. The pH scale measures the concentration of hydrogen ions, [H⁺], on a logarithmic scale from 0 (strongly acidic) to 14 (strongly alkaline), with 7 neutral.
酸在水溶液中释放 H⁺ 离子；碱接受 H⁺ 或释放 OH⁻ 离子。pH 标度以对数形式表示氢离子浓度 [H⁺]，范围从 0（强酸性）到 14（强碱性），7 为中性。
pH = –log₁₀[H⁺] and [H⁺] = 10⁻ᴾᴴ
Dilution by a factor of 10 raises the pH by 1. Neutralisation: acid + base → salt + water.
对于 HCl 等强一元酸，[H⁺] 等于酸的浓度。溶液稀释 10 倍，pH 升高 1。中和反应：酸 + 碱 → 盐 + 水。
Corrosive, irritant and toxic hazard symbols must be recognised and suitable safety precautions taken when handling acids and alkalis.
处理酸和碱时必须识别腐蚀性、刺激性及毒性危险标志，并采取相应的安全措施。
10. Electrolysis & Quantitative Electricity | 电解与电量计算
Electrolysis is the decomposition of an ionic compound, when molten or in solution, by passing an electric current. Cations move to the cathode (– electrode) and anions to the anode (+ electrode).
电解是指使熔融态或溶液中的离子化合物在外加电流作用下发生分解的过程。阳离子移向阴极（– 电极），阴离子移向阳极（+ 电极）。
The quantity of electricity (Q) is measured in coulombs (C). It links current (I, in amperes) and time (t, in seconds):
电量 (Q) 的单位是库仑 (C)，它将电流 (I，单位安培) 和时间 (t，单位秒) 联系起来：
Q = I × t
The amount of product formed is proportional to Q and follows Faraday’s laws. One mole of electrons carries 96 500 C (the Faraday constant, F). The number of moles of electrons required to discharge one mole of a substance depends on the half‑equation and the ion’s charge.
生成物的物质的量与 Q 成正比，遵循法拉第定律。1 摩尔电子携带 96 500 C 电荷（法拉第常数 F）。生成 1 摩尔物质所需的电子的物质的量取决于半反应式及离子所带电荷。
+ 3e⁻ → Al. To produce 1 mol of Al, 3 mol e⁻ are needed; charge required = 3F ≈ 289 500 C.
示例：Al³⁺ + 3e⁻ → Al。生成 1 mol Al 需要 3 mol e⁻；所需电荷 = 3F ≈ 289 500 C。
11. Enthalpy & Heat Calculations | 焓与热量计算
Enthalpy change (ΔH) is the heat energy transferred in a reaction at constant pressure. Exothermic reactions release heat (ΔH negative); endothermic reactions absorb heat (ΔH positive).
焓变 (ΔH) 是在恒压条件下反应中传递的热量。放热反应释放热量 (ΔH 为负)；吸热反应吸收热量 (ΔH 为正)。
q = m c ΔT
ater), ΔT = temperature change (°C). The experiment is often carried out in a calorimeter.
其中 q = 热量 (J)，m = 溶液质量 (g)，c = 比热容（通常水为 4.18 J g⁻¹ °C⁻¹），ΔT = 温度变化 (°C)。实验常在量热计中进行。
To find ΔH per mole: ΔH = – c convention). Watch the sign: if the temperature rises, q is positive but ΔH is negative.
求算每摩尔焓变：ΔH = –q / n（放热惯例）。注意符号：若温度升高，q 为正，但 ΔH 为负。
Bond enthalpy calculations: ΔH ≈ sum of bonds broken (endothermic) – sum of bonds formed (exothermic). This is an estimate based on average bond energies.
键焓计算：ΔH ≈ 反应物断裂键的总键焓 (吸热) – 生成物形成键的总键焓 (放热)。这是基于平均键能的估算值。
12. Key Laws & Theories | 重要定律与理论
Law of Conservation of Mass – mass is neither created nor destroyed in a chemical reaction (Lavoisier).
质量守恒定律 – 化学反应中质量既不会创生也不会消失（拉瓦锡）。
Law of Definite Proportions – a compound always contains the same elements in the same proportion by mass (Proust).
定比定律 – 化合物总是以相同的质量比含有相同的元素（普鲁斯特）。
Dalton’s Atomic Theory – all matter is made of indivisible atoms; atoms of the same element are identical; chemical reactions rearrange atoms.
道尔顿原子说 – 所有物质均由不可分割的原子构成；同种元素的原子完全相同；化学反应是原子的重新排列。
Avogadro’s Law – equal volumes of gases, at the same temperature and pressure, contain equal numbers of molecules.
阿伏伽德罗定律 – 相同温度与压力下，相同体积的气体含有相同数目的分子。
Collision Theory – rticles must collide with sufficient energy (≥ activation energy) and correct orientation.
碰撞理论 – 发生反应时，粒子必须以足够的能量（≥ 活化能）和正确的取向发生碰撞。
Le Chatelier’s Principle – if a system at equilibrium is subjected to a change in concentration, temperature or pressure, the equilibrium shifts to oppose the change.
勒夏特列原理 – 若平衡系统受到浓度、温度或压力的改变，平衡将向削弱该改变的方向移动。
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