Cambridge IGCSE Chemistry (0620) Extended-Level – Keywords and Definitions
Chapter 1: The Particulate Nature of Matter
• Atom – Smallest particle of an element that retains its chemical properties.
• Molecule – Two or more atoms chemically bonded.
• Ion – Charged particle formed when an atom or molecule loses or gains electrons.
• Solid – Fixed shape and volume; particles vibrate in fixed positions.
• Liquid – Fixed volume, no fixed shape; particles move past each other.
• Gas – No fixed shape or volume; particles move freely.
• Diffusion – Movement of particles from high to low concentration.
• Density (ρ) – Mass per unit volume; ρ = m/V.
Chapter 2: Experimental Techniques
• Filtration – Separating insoluble solids from liquids.
• Crystallization – Separating a soluble solid from solution.
• Simple distillation – Separating a liquid from a solution.
• Fractional distillation – Separating liquids with different boiling points.
• Paper chromatography – Separating substances based on solubility and adsorption.
• Rf value – Ratio of distance moved by substance ÷ distance moved by solvent.
Chapter 3: Atoms, Elements, and Compounds
• Element – Substance made of only one type of atom.
• Compound – Two or more elements chemically combined.
• Mixture – Physical combination of substances.
• Empirical formula – Simplest ratio of atoms in a compound.
• Molecular formula – Actual number of atoms in a compound.
• Valency – Combining power of an element.
Chapter 4: Atomic Structure
• Proton – Positively charged particle in the nucleus.
• Neutron – Neutral particle in the nucleus.
• Electron – Negatively charged particle orbiting the nucleus.
• Atomic number (Z) – Number of protons.
• Mass number (A) – Protons + neutrons.
• Isotope – Same element, different number of neutrons.
• Relative atomic mass (Ar) – Weighted average mass relative to 1/12 of carbon-12.
Chapter 5: The Periodic Table
• Period – Horizontal row; number of electron shells.
• Group – Vertical column; similar chemical properties.
• Metal – Usually shiny, malleable, ductile, conducts heat/electricity.
• Non-metal – Usually dull, brittle, poor conductor.
• Transition metal – Variable oxidation states, colored compounds, good catalysts.
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Chapter 6: Ionic Bonding
• Ionic bond – Electrostatic attraction between oppositely charged ions.
• Cation – Positively charged ion.
• Anion – Negatively charged ion.
• Giant ionic lattice – 3D arrangement of ions held by ionic bonds.
Chapter 7: Covalent Bonding
• Covalent bond – Sharing of electron pairs.
• Simple molecular substance – Small molecules, weak intermolecular forces.
• Giant covalent structure – Large network of atoms (diamond, SiO₂).
• Delocalized electrons – Electrons free to move; responsible for conductivity (graphite).
Chapter 8: Metallic Bonding
• Metallic bond – Attraction between positive ions and delocalized electrons.
• Malleability – Can be hammered into sheets.
• Ductility – Can be drawn into wires.
Chapters 9 & 10: Formulae, Equations, and Moles
• Mole (mol) – 6.02 × 10²³ particles.
• Molar mass (M) – Mass of 1 mole (g/mol).
• Concentration (C) – Amount of solute per volume of solution (mol/dm³).
• Stoichiometry – Calculations of relative amounts of reactants/products.
Chapter 11: Electrolysis
• Electrolysis – Decomposition using electricity.
• Anode – Positive electrode; oxidation occurs.
• Cathode – Negative electrode; reduction occurs.
• Half-equation – Shows electrons gained or lost.
• Faraday (F) – Charge per mole of electrons = 96500 C/mol.
Chapter 12: Chemical Reactions
• Exothermic – Releases energy.
• Endothermic – Absorbs energy.
• Activation energy – Minimum energy needed for a reaction.
• Catalyst – Speeds up reaction without being consumed.
• Bond enthalpy – Energy needed to break a bond.
Chapter 13: Acids, Bases, and Salts
• Acid – Produces H⁺ ions.
• Base – Produces OH⁻ ions.
• Alkali – Soluble base.
• Neutralization – Acid + base → water + salt.
• Titration – Method to determine concentration.
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Chapter 14: Periodic Table – Patterns
• Reactivity – Tendency to undergo chemical reactions.
• Displacement reaction – More reactive element displaces a less reactive one.
Chapter 15: Metals
• Reactivity series – Metals ordered by reactivity.
• Alloy – Mixture of metals to improve properties.
• Corrosion – Gradual destruction of metal (e.g., rusting).
• Sacrificial protection – Using a more reactive metal to prevent corrosion.
Chapter 16: Air and Water
• Air composition – Mostly N₂ (78%), O₂ (21%), others.
• Pollutant – Harmful substance in air or water (CO, SO₂, NOₓ).
• Water treatment – Filtration, sedimentation, chlorination.
• Haber process – Industrial production of ammonia (N₂ + H₂).
• Flame test – Identifies metal ions by flame color.
• Glowing splint test – Tests for O₂.
• Limewater test – Tests for CO₂.
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