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IGCSE Chemistry Glossary

 

IGCSE Chemistry Glossary

IGCSE Chemistry Glossary for the latest revised syllabuses 0620 and 0971 (9–1) IGCSE Chemistry. Use this as a quick-reference companion while revising topics or practising exam-style questions.

  • Strengthens subject knowledge by clarifying precise meanings of key terms.
  • Builds conceptual links across topics (e.g., bonding ? energetics ? rates).
  • Improves exam responses with concise, specification-aligned definitions.
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No definite shape or volume; particles far apart, moving rapidly and randomly.
  • Solid
    A state of matter with fixed volume and definite shape; particles packed in an orderly arrangement with lowest kinetic energy.
  • Liquid
    Definite volume but no fixed shape; particles close but free to move past one another.
  • Gas
    A state of matter with no definite shape or volume, expanding to fill any container it occupies. Its particles are far apart and move rapidly and randomly, with negligible attractive forces between them. Gas particles possess the highest kinetic energy of the three main states.
  • Boiling point
    Temperature at which a liquid turns into a gas by boiling.
  • Condensation
    Change of state from gas to liquid.
  • Diffusion
    Particles spread from higher to lower concentration.
  • Evaporation
    Change of a liquid to a vapor below its boiling point.
  • Kinetic particle theory
    Matter is made of tiny particles in constant, random motion.
  • Melting point
    Temperature at which a solid turns into a liquid.
  • Sublimation
    Change of state directly between solid and gas.
  • Alloy
    Mixture of a metal with other element(s).
  • Atom
    Smallest particle of an element that can take part in a chemical reaction.
  • Atomic number (proton number)
    Number of protons in the nucleus.
  • Compound
    Substance formed when elements are chemically bonded.
  • Electron
    Negatively charged subatomic particle.
  • Element
    Only one type of atom; cannot be chemically broken down.
  • Isotopes
    Same element: same protons, different neutrons.
  • Mass number (nucleon number)
    Total protons + neutrons in the nucleus.
  • Molecule
    Two or more atoms held by covalent bonds.
  • Neutron
    Uncharged subatomic particle in the nucleus.
  • Nucleus
    Central part of an atom containing protons and neutrons.
  • Proton
    Positively charged subatomic particle in the nucleus.
  • Relative atomic mass (Ar)
    Average mass of an atom relative to 1/12 of carbon-12.
  • Covalent bonding
    Sharing of electron pairs between non-metals.
  • Giant ionic lattice
    3-D repeating structure of ions.
  • Giant metallic lattice
    Metal ions in a “sea” of delocalised electrons.
  • Ionic bonding
    Attraction between oppositely charged ions.
  • Avogadro constant
    6.02 × 10?2;?3; particles per mole.
  • Limiting reactant
    Reactant used up first; limits product formed.
  • Mole
    Amount containing Avogadro’s number of particles.
  • Molar mass
    Mass of one mole (g mol??1;).
  • Relative molecular mass (Mr)
    Sum of relative atomic masses in a molecule.
  • Anode
    Positive electrode (oxidation).
  • Cathode
    Negative electrode (reduction).
  • Electrolysis
    Decomposition of an ionic compound using electricity.
  • Electrolyte
    Molten/aqueous ionic compound that conducts.
  • Electroplating
    Coating a surface with metal via electrolysis.
  • Inert electrode
    Electrode that conducts but doesn’t react.
  • Activation energy
    Minimum energy to start a reaction.
  • Endothermic reaction
    Absorbs energy from surroundings.
  • Exothermic reaction
    Releases energy to surroundings.
  • Catalyst
    Speeds up a reaction without being consumed.
  • Combustion
    Burning in oxygen to form oxides.
  • Displacement reaction
    More reactive element replaces a less reactive one.
  • Dynamic equilibrium
    Forward and reverse rates are equal.
  • Neutralization
    Acid + base ? salt + water.
  • Oxidation
    Loss of electrons / gain of oxygen.
  • Rate of reaction
    Speed of reactant use or product formation.
  • Reduction
    Gain of electrons / loss of oxygen.
  • Reversible reaction
    Can proceed in both directions.
  • Acid
    Produces H? in water.
  • Alkali
    Soluble base producing OH? in water.
  • Amphoteric
    Acts as acid or base.
  • Base
    Metal oxide/hydroxide that neutralizes acids.
  • pH scale
    Measure of acidity/alkalinity.
  • Salt
    Acid H? replaced by metal or NH??.
  • Group
    Vertical column; indicates outer-shell electrons.
  • Halogens
    Group 17 elements; highly reactive.
  • Noble gases
    Group 18; unreactive (full outer shell).
  • Period
    Horizontal row.
  • Periodic Table
    Elements arranged by increasing atomic number.
  • Ductile
    Can be drawn into wires.
  • Malleable
    Can be hammered into shape without breaking.
  • Reactivity series
    Metals ranked by decreasing reactivity.
  • Rusting
    Corrosion of iron by oxygen and water.
  • Alkanes
    Saturated hydrocarbons, CnH2n+2.
  • Alkenes
    Unsaturated hydrocarbons (C=C), CnH2n.
  • Homologous series
    Same functional group; successive members differ by –CH2–.
  • Hydrocarbon
    Compound containing only C and H.
  • Isomers
    Same molecular formula, different structures.
  • Saturated
    Only single C–C bonds.
  • Unsaturated
    At least one C=C or C?C bond.
  • Chromatography
    Separates a mixture of soluble substances.
  • Filtration
    Separates an insoluble solid from a liquid.
  • Fractional distillation
    Separates liquids with different boiling points.
  • Simple distillation
    Separates a soluble solid from a liquid or a pure liquid from a solution.