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Chemistry HKDSE English Knowledge Base
Paper 1 (75%, MC + structured) | Paper 2 Elective (25%) | SBA. All definitions must follow official HKEAA wording.
Topic 1 Atomic Structure & Periodic Table ★★★
| Term | Official English Definition | 中文注解 |
|---|---|---|
| Isotopes | Atoms of the same element with the same number of protons but different numbers of neutrons | 同位素 |
| Relative atomic mass | The weighted average mass of the isotopes of an element on the ¹²C = 12.00 scale | 相对原子质量 |
| Ionisation enthalpy | The energy required to remove one mole of electrons from one mole of gaseous atoms | 电离焓 |
Periodic trends（必背）：
- Across a period: atomic radius ↓, electronegativity ↑（核电荷增加，同层屏蔽不变）
- Down a group: atomic radius ↑, ionisation enthalpy ↓（电子层数增加）
- Group I 金属活性向下递增；Group VII 卤素氧化性向下递减
Topic 2 Bonding & Structure ★★★
| Bond type | Definition | Example |
|---|---|---|
| Ionic bond | The electrostatic attraction between oppositely charged ions | NaCl |
| Covalent bond | The electrostatic attraction between shared electrons and the two nuclei | H₂O, CO₂ |
| Metallic bond | The attraction between delocalised electrons and metal cations | Cu, Fe |
Structure–property 判断表（MC 每年必考）：
| Structure | Melting point | Electrical conductivity | Example |
|---|---|---|---|
| Giant ionic | High | Only when molten or in aqueous solution | NaCl |
| Giant covalent | Very high | No (except graphite) | Diamond, SiO₂ |
| Simple molecular | Low | No | I₂, CO₂ |
| Giant metallic | Usually high | Yes (solid & molten) | Fe, Al |
标准句式：NaCl has a high melting point because a large amount of energy is required to overcome the strong electrostatic attractions between oppositely charged ions in its giant ionic structure.（禁止写 "break the ionic bond molecules" —— ionic 无 molecule！）
Topic 3 Metals ★★
- Reactivity series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu > Hg > Ag > Au（口诀自编背熟）
- Extraction method matches reactivity: electrolysis (K–Al) / carbon reduction (Zn–Cu) / found native (Ag, Au)
- Displacement: a more reactive metal displaces a less reactive metal from its salt solution
- Corrosion of iron needs both oxygen and water; sacrificial protection uses a more reactive metal (Zn/Mg)
Topic 4 Acids & Bases ★★★
| Term | Official English Definition | 中文注解 |
|---|---|---|
| Acid | A substance which produces H⁺(aq) / hydrogen ions as the only positive ions when dissolved in water | 酸 |
| Alkali | A base that is soluble in water, producing OH⁻(aq) | 碱（可溶） |
| Strong acid | An acid which completely ionises in water | 强酸=完全电离 |
| Neutralisation | Acid + base → salt + water only | 中和反应 |
| pH | pH = −log[H⁺(aq)] | pH 定义式 |
Concentration vs Strength 陷阱：strong/weak 指电离程度，concentrated/dilute 指浓度——两组概念不可混用。
Volumetric analysis 计算模板：
text
Step 1 Write the balanced equation
Step 2 n = CV (mol) for the known solution
Step 3 Use mole ratio from the equation
Step 4 C = n/V for the unknown; state the answer with units (mol dm⁻³)Topic 5 Redox, Chemical Cells & Electrolysis ★★★
- Oxidation = loss of electrons / increase in oxidation number（OIL RIG: Oxidation Is Loss, Reduction Is Gain）
- Oxidising agent 自身被还原；reducing agent 自身被氧化（每年 MC 陷阱）
- Chemical cell: the more reactive metal is the negative electrode (anode inside cell)
- Electrolysis 优先放电规则：阳离子按活性逆序，阴离子浓度高者优先
- 常考电解产物：electrolysis of dilute NaCl → H₂ (cathode) + O₂ (anode)；concentrated NaCl → H₂ + Cl₂
Topic 6 Energetics & Rate of Reaction ★★
| Term | Official English Definition |
|---|---|
| Enthalpy change of neutralisation | The enthalpy change when an acid and an alkali react to form one mole of water under standard conditions |
| Enthalpy change of combustion | The enthalpy change when one mole of the substance is completely burnt in oxygen under standard conditions |
| Hess's Law | The enthalpy change of a reaction depends only on the initial and final states, independent of the route |
Rate factors + 解释句式（必须用 collision theory）： Increasing the concentration increases the number of reactant particles per unit volume, so the frequency of effective collisions increases and the reaction rate increases. （温度题必须写 "more particles possess energy ≥ activation energy" + 碰撞频率两点）
Topic 7 Chemical Equilibrium ★★
- Dynamic equilibrium: rate of forward reaction = rate of backward reaction; concentrations remain constant but not equal
- Kc 表达式书写：products over reactants, powers = coefficients；纯固体和纯液体不写入
- Le Chatelier: 系统倾向部分抵消外加改变（"partially offsets"，不是完全抵消）
- 升温使 Kc 改变；浓度/压强变化不改变 Kc（高频陷阱）
Topic 8 Organic Chemistry ★★★
Homologous Series Quick Table
| Series | General formula | Functional group | Example |
|---|---|---|---|
| Alkane | CnH₂n₊₂ | — | methane CH₄ |
| Alkene | CnH₂n | C=C | ethene C₂H₄ |
| Alkanol | CnH₂n₊₁OH | −OH | ethanol |
| Alkanoic acid | CnH₂n₊₁COOH | −COOH | ethanoic acid |
| Ester | — | −COO− | ethyl ethanoate |
Key Reactions
- Alkene + Br₂：decolorises brown bromine rapidly（烯烃检验）— addition reaction
- Alkane + Br₂：substitution only under UV light
- Ester 制备：alkanoic acid + alkanol ⇌ ester + water（concentrated H₂SO₄ catalyst, heat under reflux）
- Oxidation chain：ethanol → ethanal → ethanoic acid（acidified K₂Cr₂O₇, orange → green）
- Isomers: same molecular formula, different structural formulae — 画结构异构体是长题常客
Naming Rules (IUPAC)
最长碳链定主名 → 编号使支链/官能团位号最小 → 支链按字母序排列。
Topic 9 Practical Chemistry ★★★
实验描述四要素句式（Procedure / Observation / Conclusion / Precaution）：
| 要素 | Standard sentence pattern |
|---|---|
| Procedure | Add 2 cm³ of dilute HCl to the sample in a test tube. （祈使句+精确量） |
| Observation | Colourless gas bubbles evolve; the gas turns limewater milky. （只写看到的，不写结论词） |
| Conclusion | Hence the sample contains carbonate ions (CO₃²⁻). |
| Precaution | Perform the experiment in a fume cupboard as the gas is toxic. |
常考气体检验：H₂ — burning splint, 'pop' sound；O₂ — relights glowing splint；CO₂ — turns limewater milky；NH₃ — turns moist red litmus paper blue；Cl₂ — bleaches moist litmus paper。
Frequently Misspelled Words Checklist
separate (не seperate) · occurred · beaker · burette / pipette · desiccator · effervescence · precipitate · hydrochloric · sulphuric / sulfuric · ammonium · equilibrium
Unit Test Prompt
prompt
Act as an HKEAA Chemistry examiner. For the topic I specify, set 6 questions in English: 2 definitions + 2 MC + 1 calculation + 1 experiment-design question.
After I answer, check terminology spelling, definition wording against official HKEAA phrasing, calculation steps, and experimental description standardisation (procedure/observation/conclusion). List all missing scoring points.
Topic: [e.g. Acids & Bases]