Cambridge International · IGCSE · 0620
Chemistry — Keywords & Key Terms — Definitions Glossary (2026)
Cambridge IGCSE Chemistry (0620)
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.
Cambridge International IGCSE Chemistry (0620)
Cambridge International IGCSE Chemistry (0620)
Cambridge IGCSE Chemistry (0620)
Topic groups follow Cambridge IGCSE Chemistry 0620 (2026): states of matter, atomic structure, bonding, stoichiometry, reactions, organic chemistry, etc.
Mark schemes: Use correct chemical symbols and state symbols (s), (l), (g), (aq) when required. Observation questions need specific detail (colour change, effervescence, temperature change). Explanation questions should use particle or bonding ideas from the syllabus.
Active recall: 0 / 93 terms ticked
| Recalled | Topic | Level | Keyword | Definition |
|---|---|---|---|---|
| Subatomic particles & atomic structure | Essential | Proton | Positively charged particle in the nucleus; relative mass ≈ 1; relative charge +1. | |
| Subatomic particles & atomic structure | Essential | Neutron | Uncharged particle in the nucleus; relative mass ≈ 1; relative charge 0. | |
| Subatomic particles & atomic structure | Essential | Electron | Negatively charged particle outside nucleus; very small mass; relative charge −1. | |
| Subatomic particles & atomic structure | Core | Nucleus | Dense centre of atom containing protons and neutrons. | |
| Subatomic particles & atomic structure | Core | Atomic number (proton number) | Number of protons in an atom — defines the element. | |
| Subatomic particles & atomic structure | Core | Mass number (nucleon number) | Total protons + neutrons in one atom of an isotope. | |
| Subatomic particles & atomic structure | Core | Isotope | Atoms of the same element with the same number of protons but different numbers of neutrons. | |
| Subatomic particles & atomic structure | Core | Electronic structure / electron configuration | Arrangement of electrons in shells (energy levels) around the nucleus. | |
| Subatomic particles & atomic structure | Core | Shell | Energy level that holds electrons; inner shells fill first (2, 8, 8… at IGCSE). | |
| Subatomic particles & atomic structure | Advanced | Relative atomic mass (Ar) | Weighted mean mass of an element’s isotopes compared to 1/12 of a carbon-12 atom. | |
| Particles, elements, compounds & bonding | Essential | Atom | Smallest part of an element that can take part in a chemical reaction. | |
| Particles, elements, compounds & bonding | Essential | Element | Substance made of only one type of atom. | |
| Particles, elements, compounds & bonding | Essential | Compound | Substance formed from two or more elements chemically bonded in fixed ratio. | |
| Particles, elements, compounds & bonding | Essential | Molecule | Two or more atoms chemically bonded (can be elements or compounds). | |
| Particles, elements, compounds & bonding | Core | Mixture | Two or more substances physically mixed — composition variable; separated by physical methods. | |
| Particles, elements, compounds & bonding | Core | Ion | Charged atom or group of atoms formed when electrons are lost or gained. | |
| Particles, elements, compounds & bonding | Core | Cation | Positive ion (e.g. Na⁺, Ca²⁺). | |
| Particles, elements, compounds & bonding | Core | Anion | Negative ion (e.g. Cl⁻, O²⁻). | |
| Particles, elements, compounds & bonding | Core | Covalent bond | Strong electrostatic attraction between a shared pair of electrons and the nuclei bonded. | |
| Particles, elements, compounds & bonding | Core | Ionic bond | Electrostatic attraction between oppositely charged ions in a giant lattice. | |
| Particles, elements, compounds & bonding | Core | Metallic bonding | Positive metal ions arranged in a lattice surrounded by a ‘sea’ of delocalised electrons. | |
| Particles, elements, compounds & bonding | Advanced | Giant ionic lattice | Regular 3D array of alternating positive and negative ions. | |
| Particles, elements, compounds & bonding | Advanced | Simple molecular substance | Small molecules with weak intermolecular forces between them (e.g. iodine, water vapour). | |
| Particles, elements, compounds & bonding | Advanced | Giant covalent structure | Many atoms covalently bonded in a lattice (e.g. diamond, graphite, silicon(IV) oxide). | |
| Particles, elements, compounds & bonding | Core | Electronegativity | Relative attraction of an atom for the shared pair of electrons in a covalent bond. | |
| Particles, elements, compounds & bonding | Core | Polar covalent bond | Shared electrons pulled toward the more electronegative atom — partial charges. | |
| Particles, elements, compounds & bonding | Core | Dot-and-cross diagram | Shows outer-shell electrons only to illustrate bonding. | |
| Periodic table, trends & groups | Essential | Period | Horizontal row in the periodic table — same number of occupied shells. | |
| Periodic table, trends & groups | Essential | Group | Vertical column — same number of outer-shell (valence) electrons in main groups. | |
| Periodic table, trends & groups | Core | Alkali metals (Group 1) | Soft reactive metals; form +1 ions; reactivity increases down the group. | |
| Periodic table, trends & groups | Core | Alkaline earth metals (Group 2) | Form +2 ions; less reactive than Group 1; trends in reactivity. | |
| Periodic table, trends & groups | Core | Halogens (Group 17) | Reactive non-metals; diatomic molecules; displacement reactions — reactivity decreases down the group. | |
| Periodic table, trends & groups | Core | Noble gases (Group 18) | Unreactive — full outer shell (stable electron arrangement). | |
| Periodic table, trends & groups | Advanced | Transition metals | Central block; often high density, variable oxidation states, coloured compounds, catalysts. | |
| Stoichiometry & calculations | Essential | Avogadro constant | 6.02 × 10²³ particles per mole. | |
| Stoichiometry & calculations | Core | Mole | Amount of substance containing Avogadro’s number of particles (atoms, molecules, ions, etc.). | |
| Stoichiometry & calculations | Core | Molar mass | Mass of one mole of substance in g/mol (numerically equal to Ar or Mr for many purposes). | |
| Stoichiometry & calculations | Core | Relative formula mass (Mr) | Sum of relative atomic masses in a formula unit. | |
| Stoichiometry & calculations | Core | Empirical formula | Simplest whole-number ratio of atoms in a compound. | |
| Stoichiometry & calculations | Core | Molecular formula | Actual numbers of atoms of each element in one molecule. | |
| Stoichiometry & calculations | Advanced | Limiting reactant | Reactant completely used up first — limits amount of product formed. | |
| Stoichiometry & calculations | Core | Theoretical yield | Maximum mass of product calculated from balanced equation. | |
| Stoichiometry & calculations | Core | Actual yield | Mass of product obtained experimentally. | |
| Stoichiometry & calculations | Core | Percentage yield | (Actual yield ÷ theoretical yield) × 100%. | |
| Stoichiometry & calculations | Core | Concentration | Amount of solute per unit volume — often mol/dm³. | |
| Stoichiometry & calculations | Core | Molar gas volume | Volume occupied by one mole of gas at stated temperature and pressure. | |
| Reactions, energetics & rates | Essential | Exothermic reaction | Transfers thermal energy to the surroundings — temperature of surroundings rises. | |
| Reactions, energetics & rates | Essential | Endothermic reaction | Absorbs thermal energy from the surroundings — temperature of surroundings falls. | |
| Reactions, energetics & rates | Core | Bond breaking | Requires energy input. | |
| Reactions, energetics & rates | Core | Bond making | Releases energy. | |
| Reactions, energetics & rates | Core | Catalyst | Increases reaction rate; unchanged in mass at the end; provides alternative route with lower activation energy. | |
| Reactions, energetics & rates | Core | Rate of reaction | Change in amount of reactant or product per unit time. | |
| Reactions, energetics & rates | Advanced | Collision theory | Reaction occurs when particles collide with sufficient energy (≥ activation energy) and suitable orientation. | |
| Reactions, energetics & rates | Core | Activation energy | Minimum energy particles must have to react successfully. | |
| Reactions, energetics & rates | Core | Reversible reaction | Products can react to reform reactants under the same conditions. | |
| Reactions, energetics & rates | Core | Dynamic equilibrium | In a closed system, forward and reverse reactions occur at equal rates. | |
| Reactions, energetics & rates | Core | Oxidation | Loss of electrons or gain of oxygen (in many IGCSE contexts). | |
| Reactions, energetics & rates | Core | Reduction | Gain of electrons or loss of oxygen. | |
| Reactions, energetics & rates | Core | Redox | Oxidation and reduction together. | |
| Reactions, energetics & rates | Core | Reactivity series | Metals ordered by tendency to lose electrons — predicts displacement reactions. | |
| Acids, bases, salts & electrolysis | Essential | Acid | pH below 7; produces H⁺(aq) in aqueous solution. | |
| Acids, bases, salts & electrolysis | Essential | Alkali | Soluble base; pH above 7; produces OH⁻(aq) in water. | |
| Acids, bases, salts & electrolysis | Essential | Base | Substance that neutralises an acid — metal oxide, hydroxide, or ammonia solution. | |
| Acids, bases, salts & electrolysis | Core | Neutralisation | Acid + base → salt + water (and sometimes other products). | |
| Acids, bases, salts & electrolysis | Core | pH scale | 0 (strong acid) to 14 (strong alkali); pH 7 neutral at 25 °C. | |
| Acids, bases, salts & electrolysis | Core | Indicator | Substance that changes colour over a pH range (e.g. litmus, methyl orange, universal). | |
| Acids, bases, salts & electrolysis | Core | Strong acid | Fully ionised in water (e.g. HCl, H₂SO₄, HNO₃). | |
| Acids, bases, salts & electrolysis | Core | Weak acid | Partially ionised in water (e.g. ethanoic acid). | |
| Acids, bases, salts & electrolysis | Advanced | Electrolysis | Decomposition of an ionic compound (molten or in solution) by electrical energy. | |
| Acids, bases, salts & electrolysis | Core | Electrolyte | Ionic compound or solution that conducts electricity. | |
| Acids, bases, salts & electrolysis | Core | Cathode | Negative electrode — reduction (gain of electrons) occurs here. | |
| Acids, bases, salts & electrolysis | Core | Anode | Positive electrode — oxidation (loss of electrons) occurs here. | |
| Acids, bases, salts & electrolysis | Core | Ion movement in electrolysis | Positive ions (cations) attracted to cathode; negative ions (anions) to anode. | |
| Separating mixtures & analysis | Core | Filtration | Separate insoluble solid from liquid using filter paper. | |
| Separating mixtures & analysis | Core | Crystallisation | Obtain solid from solution by evaporating solvent slowly. | |
| Separating mixtures & analysis | Core | Distillation | Separate liquid from solution by boiling and condensing. | |
| Separating mixtures & analysis | Core | Fractional distillation | Separate miscible liquids with different boiling points. | |
| Separating mixtures & analysis | Core | Chromatography | Separate dissolved substances by different rates of movement in a solvent. | |
| Separating mixtures & analysis | Core | Rf value | Ratio of distance moved by spot to distance moved by solvent front. | |
| Organic chemistry basics | Essential | Hydrocarbon | Compound containing only carbon and hydrogen atoms. | |
| Organic chemistry basics | Core | Alkane | Saturated hydrocarbon — only single C–C bonds; general formula CₙH₂ₙ₊₂. | |
| Organic chemistry basics | Core | Alkene | Unsaturated hydrocarbon with at least one C=C double bond; general formula CₙH₂ₙ. | |
| Organic chemistry basics | Core | Alcohol | Contains the –OH functional group (general formula CₙH₂ₙ₊₁OH). | |
| Organic chemistry basics | Core | Carboxylic acid | Contains –COOH group. | |
| Organic chemistry basics | Core | Homologous series | Family of organic compounds with same functional group and trend in physical properties. | |
| Organic chemistry basics | Advanced | Structural isomerism | Same molecular formula but different structural arrangement. | |
| Organic chemistry basics | Core | Functional group | Atom or group of atoms that largely determines chemical properties. | |
| Organic chemistry basics | Core | Saturated | Only single bonds between carbon atoms (alkanes). | |
| Organic chemistry basics | Core | Unsaturated | Contains C=C double bond(s) (alkenes). | |
| Organic chemistry basics | Core | Cracking | Thermal decomposition of long-chain hydrocarbons into shorter, more useful molecules. | |
| Organic chemistry basics | Core | Combustion | Reaction with oxygen; complete combustion of hydrocarbons gives CO₂ and H₂O. | |
| Organic chemistry basics | Core | Addition polymer | Many unsaturated monomers add across double bonds to form a long polymer chain. | |
| Organic chemistry basics | Core | Ester | Formed from alcohol + carboxylic acid (often sweet smell — context dependent). |
Pair this with our revision checklists, formula sheets hub and past paper finder.
Chemistry (0620) — Keywords & Key Terms FAQ
- What is on this Cambridge International IGCSE Chemistry keywords and key terms list?
- It is a topic-organised glossary of important chemistry terms with short, exam-style definitions aligned to Cambridge IGCSE Chemistry (0620) (0620). 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 IGCSE Chemistry (0620) 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 0620 specification?
- Topic groupings and wording follow Cambridge IGCSE Chemistry (0620) for Cambridge International IGCSE. 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 IGCSE, separate from longer notes or topic trackers.