Pearson Edexcel · GCSE · 1CH0
Chemistry — Keywords & Key Terms — Definitions Glossary (2026)
Pearson Edexcel GCSE (9-1) Chemistry (1CH0)
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 GCSE Chemistry (1CH0)
Pearson Edexcel GCSE Chemistry (1CH0)
Pearson Edexcel GCSE (9-1) Chemistry (1CH0)
Topics follow the Pearson Edexcel GCSE Chemistry 1CH0 specification covering atomic structure, the periodic table, bonding, quantitative chemistry, chemical changes, energy changes and organic chemistry.
Mark schemes: Pearson Edexcel chemistry mark schemes reward linked reasoning chains that connect particle behaviour to observable change using discriminator language. Symbol equations must be balanced with appropriate state symbols and calculations need correct units.
Active recall: 0 / 28 terms ticked
| Recalled | Topic | Level | Keyword | Definition |
|---|---|---|---|---|
| 1. Atomic structure & periodic table | Essential | Atom | Smallest particle of an element that retains the chemical identity of the element. | |
| 1. Atomic structure & periodic table | Essential | Isotope | Atoms of the same element with equal protons but different neutron numbers. | |
| 1. Atomic structure & periodic table | Core | Relative atomic mass (Ar) | Mean mass of an atom of an element relative to 1/12 of a carbon-12 atom. | |
| 1. Atomic structure & periodic table | Core | Group | A vertical column in the periodic table; elements share similar chemical properties. | |
| 1. Atomic structure & periodic table | Advanced | Electronic configuration | Arrangement of electrons in shells, e.g. 2,8,1 for sodium. | |
| 2. Bonding, structure & properties | Essential | Ionic bond | Electrostatic attraction between oppositely charged ions formed by electron transfer. | |
| 2. Bonding, structure & properties | Essential | Covalent bond | Shared pair of electrons between two non-metal atoms. | |
| 2. Bonding, structure & properties | Core | Metallic bond | Attraction between positive metal ions and a sea of delocalised electrons. | |
| 2. Bonding, structure & properties | Core | Giant covalent structure | Network of covalently bonded atoms, e.g. diamond, with very high melting points. | |
| 2. Bonding, structure & properties | Advanced | Simple molecular substance | Small covalent molecules held together by weak intermolecular forces. | |
| 3. Quantitative chemistry | Essential | Mole | Amount of substance: n = mass / Mr; one mole contains Avogadro's number of particles. | |
| 3. Quantitative chemistry | Core | Avogadro constant | 6.02 × 10²³ particles per mole of substance. | |
| 3. Quantitative chemistry | Core | Concentration | Amount of solute per unit volume of solution: C = n/V (mol/dm³). | |
| 3. Quantitative chemistry | Core | Percentage yield | (Actual yield ÷ theoretical yield) × 100%; measures reaction success. | |
| 3. Quantitative chemistry | Advanced | Atom economy | (Mr of useful products ÷ Mr of all reactants) × 100%; measures reaction efficiency. | |
| 4. Chemical changes | Essential | Neutralisation | Reaction between an acid and a base producing a salt and water. | |
| 4. Chemical changes | Core | Electrolysis | Decomposition of an ionic compound, molten or in solution, using electrical energy. | |
| 4. Chemical changes | Core | Reduction | Gain of electrons or loss of oxygen during a chemical reaction. | |
| 4. Chemical changes | Core | Oxidation | Loss of electrons or gain of oxygen during a chemical reaction. | |
| 4. Chemical changes | Advanced | Reactivity series | Ranking of metals by how readily they lose electrons to form positive ions. | |
| 5. Energy changes | Essential | Exothermic reaction | Reaction that transfers thermal energy to the surroundings, raising temperature. | |
| 5. Energy changes | Essential | Endothermic reaction | Reaction that takes in thermal energy from the surroundings, lowering temperature. | |
| 5. Energy changes | Core | Activation energy | Minimum energy required for colliding particles to react successfully. | |
| 5. Energy changes | Advanced | Bond energy calculation | ΔH = energy to break reactant bonds − energy released forming product bonds. | |
| 6. Organic chemistry | Essential | Hydrocarbon | Compound containing only carbon and hydrogen atoms. | |
| 6. Organic chemistry | Core | Alkane | Saturated hydrocarbon with general formula CnH2n+2; only single C–C bonds. | |
| 6. Organic chemistry | Core | Alkene | Unsaturated hydrocarbon with general formula CnH2n; contains a C=C bond. | |
| 6. Organic chemistry | Advanced | Cracking | Thermal decomposition of long-chain alkanes into smaller, more useful molecules. |
Pair this with our revision checklists, formula sheets hub and past paper finder.
Chemistry (1CH0) — Keywords & Key Terms FAQ
- What is on this Pearson Edexcel GCSE 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 GCSE (9-1) Chemistry (1CH0) (1CH0). 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 GCSE Chemistry (1CH0) 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 1CH0 specification?
- Topic groupings and wording follow Pearson Edexcel GCSE (9-1) Chemistry (1CH0) for Pearson Edexcel GCSE. 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 GCSE, separate from longer notes or topic trackers.