Pearson Edexcel · International A Level · WCH01–WCH04
Chemistry — Keywords & Key Terms — Definitions Glossary (2026)
Pearson Edexcel International A Level Chemistry
Topic-by-topic keywords, key terms and definitions for precise exam language—separate from our revision checklists (topic coverage) and formula sheets (equations).
Keywords & Key Terms — definitions
Examiner-style keywords and definitions organised by syllabus topic. Terms are tagged Essential (start here), Core (typical exam standard), and Advanced for harder distinctions — tick each row when you can recall it. Your progress is saved in this browser for this list.
Pearson Edexcel International A Level Chemistry (WCH01–WCH04)
Pearson Edexcel International A Level Chemistry (WCH01–WCH04)
Pearson Edexcel International A Level Chemistry
Pearson International A Level Chemistry (units WCH01–WCH04) covers advanced organic, physical and inorganic chemistry with practical skills. Topics include atomic structure, bonding, energetics, kinetics, equilibria, acids/bases, thermodynamics, electrochemistry, periodicity, transition metals, and organic synthesis including mechanisms and spectroscopic thinking at the level required by the specification.
Mark schemes: Mechanisms: curly arrows from lone pair or bond to electrophile; show dipoles where relevant. Physical chemistry: correct units for Kc; partial pressures for Kp; sign conventions for electrode potentials. Calculations: show moles route clearly. Organic synthesis: reagents and conditions must match the transformation (e.g. heat, catalyst).
Active recall: 0 / 39 terms ticked
| Recalled | Topic | Level | Keyword | Definition |
|---|---|---|---|---|
| Structure, bonding & periodicity | Core | First ionisation energy | Trends across period and down group — nuclear charge, shielding, distance. | |
| Structure, bonding & periodicity | Core | Electronegativity | Pauling scale — bond polarity. | |
| Structure, bonding & periodicity | Core | Shapes of molecules | VSEPR — electron pairs repel; bond angles. | |
| Structure, bonding & periodicity | Core | Lattice enthalpy | Born–Haber cycles for ionic compounds. | |
| Structure, bonding & periodicity | Core | Polarisation | Covalent character in ionic compounds — Fajans’ rules. | |
| Structure, bonding & periodicity | Core | Metallic bonding | Cations in sea of electrons — conductivity, malleability. | |
| Energetics & thermodynamics | Core | Enthalpy change | ΔH — measured at constant pressure. | |
| Energetics & thermodynamics | Core | Hess’s law | State function — route independent. | |
| Energetics & thermodynamics | Core | Bond enthalpy | Average values — use carefully in cycles. | |
| Energetics & thermodynamics | Core | Entropy | Disorder — S increases with moles of gas, temperature increase. | |
| Energetics & thermodynamics | Advanced | Gibbs free energy | ΔG = ΔH − TΔS; spontaneity when ΔG < 0. | |
| Kinetics & equilibria | Core | Rate equation | Experimentally: rate = k[A]^m[B]^n. | |
| Kinetics & equilibria | Core | Order | Exponent of concentration in rate equation. | |
| Kinetics & equilibria | Core | Half-life | For first order independent of initial concentration. | |
| Kinetics & equilibria | Core | Arrhenius | k increases with T — exponential dependence on Ea. | |
| Kinetics & equilibria | Core | Kc & Kp | Equilibrium constants — stoichiometric powers. | |
| Kinetics & equilibria | Core | Le Chatelier | Qualitative response to concentration, pressure, temperature changes. | |
| Kinetics & equilibria | Advanced | Equilibrium constant units | Derived from expression for homogeneous systems. | |
| Acids, bases & buffers | Core | Brønsted–Lowry definitions | Acid = proton donor; base = proton acceptor. | |
| Acids, bases & buffers | Core | pKa | −log Ka — compares acid strength. | |
| Acids, bases & buffers | Core | Buffer | Resists pH change — conjugate acid–base pair. | |
| Acids, bases & buffers | Advanced | Henderson–Hasselbalch | pH = pKa + log([base]/[acid]). | |
| Acids, bases & buffers | Core | Strong vs weak acid | Degree of dissociation in water. | |
| Electrochemistry & redox | Core | Standard electrode potential | Measured vs SHE under standard conditions. | |
| Electrochemistry & redox | Core | Cell potential | E°cell = E°red − E°oxid (or right − left in cell). | |
| Electrochemistry & redox | Core | Electrolysis | Ion discharge at electrodes — preferential discharge rules. | |
| Electrochemistry & redox | Core | Faraday | m = QMr/nF for mass deposited. | |
| Inorganic & transition metals | Core | Periodicity | Trends in atomic radius, ionisation, electronegativity. | |
| Inorganic & transition metals | Core | Group 2 trends | Reactivity, thermal stability of carbonates/nitrates. | |
| Inorganic & transition metals | Core | Group 7 trends | Oxidising power; displacement. | |
| Inorganic & transition metals | Core | Transition metals | Variable oxidation states, complex ions, colour, catalysis. | |
| Inorganic & transition metals | Core | Ligand exchange | Substitution in complexes — colour changes. | |
| Organic mechanisms & synthesis | Core | Electrophilic addition | Alkenes + electrophiles — carbocation stability. | |
| Organic mechanisms & synthesis | Core | Nucleophilic substitution | SN1 vs SN2 — substrate, nucleophile, solvent. | |
| Organic mechanisms & synthesis | Core | Elimination | Forms alkene — competition with substitution. | |
| Organic mechanisms & synthesis | Core | Electrophilic aromatic substitution | Nitration, halogenation — mechanism with NO₂⁺, X⁺. | |
| Organic mechanisms & synthesis | Core | Nucleophilic addition–elimination | Acyl chlorides with nucleophiles. | |
| Organic mechanisms & synthesis | Core | Carbonyl reactions | Nucleophilic addition to aldehydes/ketones; reduction, identification. | |
| Organic mechanisms & synthesis | Advanced | Aromatic directing groups | Activating vs deactivating; ortho/para vs meta directors. |
Pair this with our revision checklists, formula sheets hub and past paper finder.
Chemistry (WCH01–WCH04) — Keywords & Key Terms FAQ
- What is on this Pearson Edexcel International A Level Chemistry keywords and key terms list?
- It is a topic-organised glossary of important chemistry terms with short, exam-style definitions aligned to Pearson Edexcel International A Level Chemistry (WCH01–WCH04). It is designed for “define”, “state”, “outline” and “explain” questions where precise vocabulary earns marks.
- How should I use this Chemistry glossary alongside past papers?
- Tick terms when you can recall them without reading the answer, then check your wording against mark schemes. Pair vocabulary practice with past papers for International A Level Chemistry (WCH01–WCH04) so you apply terms in context.
- Is this the same as a revision checklist or a formula sheet?
- No. Revision checklists help you track which syllabus topics you have covered and your confidence—separate pages on Tutopiya. Formula sheets summarise equations and quantitative relationships. This page is only a definitions and key-terms glossary for Chemistry. Quantitative relationships belong on formula sheets; this list emphasises language and concepts.
- Can I download this Chemistry keywords and key terms list for free?
- Yes. After a quick free sign-up you can download a UTF-8 CSV (opens in Excel or Google Sheets) or open a print-friendly page and save as PDF. Browsing the list on the page is free.
- Is this Chemistry list aligned to the WCH01–WCH04 specification?
- Topic groupings and wording follow Pearson Edexcel International A Level Chemistry for Pearson Edexcel International A Level. Always confirm final learning objectives and any regional options in your official specification and recent examiner reports for your exam session.
- Why focus on definitions instead of full notes?
- Mark schemes reward correct technical terms and clear links between ideas. A compact glossary lets you drill the exact language examiners expect for Chemistry at International A Level, separate from longer notes or topic trackers.