Overview
This lecture provides a comprehensive summary of core GCSE Chemistry topics, including states of matter, atomic structure, bonding types, calculations, chemical reactions, and key experimental techniques.
States of Matter & Particle Theory
- Solids: particles in fixed positions, strong forces, low kinetic energy.
- Liquids: particles less fixed, moderate forces, more kinetic energy.
- Gases: particles far apart, weak forces, high kinetic energy.
- Melting, boiling, condensation, freezing: key state changes.
- Diffusion: net movement from high to low concentration; passive process.
Atomic Structure & The Periodic Table
- Atom: smallest particle of an element.
- Element: substance with one type of atom.
- Compound: two or more elements chemically joined.
- Mixture: elements/compounds not chemically joined.
- Protons (+1), neutrons (0), electrons (-1); most mass in nucleus.
- Atomic number = protons; mass number = protons + neutrons.
- Groups = outer electron count; periods = electron shells.
Bonding: Ionic, Covalent, Metallic
- Ionic: metal + non-metal, electrons transferred, forms ions.
- Covalent: non-metal + non-metal, shared electron pairs.
- Metallic: metal atoms, sea of delocalized electrons.
- Giant ionic: high melting points, conduct when molten.
- Giant covalent: e.g. diamond, graphite; very strong bonds.
- Simple molecular: low melting/boiling, weak intermolecular forces.
Chemical Calculations
- Relative atomic mass (Ar): average mass compared to carbon-12.
- Moles = mass / Mr; mass = Mr × moles.
- Empirical formula: simplest ratio of atoms.
- Percentage yield = (actual/theoretical) × 100.
- Titrations: n = c × v; volumes in dm³.
Electrolysis & Redox
- Electrolysis: ions must be able to move (molten/solution).
- Cations to cathode (reduced); anions to anode (oxidized).
- Redox: oxidation = loss, reduction = gain of electrons (OIL RIG).
- Oxidation state rules help identify redox changes.
Acids, Bases, & Salts
- Acids: H⁺ donors; turn litmus red; pH <7.
- Bases: H⁺ acceptors, often OH⁻ donors; turn litmus blue; pH >7.
- Strong acids/bases fully dissociate; weak only partially.
- Salts form when H in acid replaced by metal/ammonium.
- Solubility rules: nitrates, group 1, ammonium, most sulfates soluble.
Separation Techniques & Analysis
- Filtration: separates insoluble solids.
- Evaporation: isolates solute from solution.
- Simple/fractional distillation: separates liquids by boiling point.
- Chromatography: separates dissolved substances; Rf = distance moved by solute/solvent.
- Flame tests: identify metal ions by flame colour.
- Precipitation reactions identify certain ions.
Organic Chemistry
- Hydrocarbons = C and H only.
- Alkanes (CnH₂n+2), alkenes (CnH₂n); alkenes have C=C.
- Alcohols (–OH), carboxylic acids (–COOH), esters, and polymers.
- Addition polymerization (no byproducts); condensation (water lost).
Key Terms & Definitions
- Diffusion — movement of particles from high to low concentration.
- Mole — amount containing 6.02 × 10²³ particles.
- Ionic Bond — electrostatic attraction between oppositely charged ions.
- Redox — reaction with simultaneous oxidation and reduction.
- Empirical Formula — simplest atom ratio in a compound.
- Electrolysis — decomposition using electricity.
- Functional Group — atom/group giving compounds characteristic reactions.
- Catalyst — substance speeding reaction, not used up.
Action Items / Next Steps
- Practice drawing particle and bonding diagrams.
- Memorize ion charges and solubility rules.
- Review formulas for moles, concentration, and yield.
- Complete homework on empirical formulas and titration calculations.
- Revise key practicals and flame test colours.