All of Edexcel iGCSE Chemistry in 45 mins - GCSE Science Revision

Key Concepts in Edexcel International GCSE Chemistry

Introduction

  • Focus on triple separate or double award.

  • Review quickly, pause if necessary.

Substances and Atoms

  • Atoms: Basic units of matter, represented by symbols in the periodic table.

  • Compounds: Substances made of two or more different types of atoms chemically bonded (e.g., H2O).

  • Mixtures: Combinations of different elements/compounds that are not chemically bonded (e.g., air, saltwater).

Chemical Reactions

  • Equations: Can be written as word equations or chemical equations with symbols.

  • Conservation of Mass: Same number of each type of atom on both sides of a reaction.

  • Balancing Equations: Start with atoms in compounds; you can't change small numbers in formulas but can modify coefficients.

Separation Techniques

  • Filtration: Separates insoluble solids from liquids (e.g., sand from water).

  • Crystallization: Evaporates solvent to leave behind a solute (e.g., salt from water).

  • Distillation: Separates liquids by heating and condensing based on different boiling points; fractional distillation improves separation of similar boiling point liquids.

  • Chromatography: Separates substances in a mixture using stationary and mobile phases, measured using RF values.

States of Matter

  • Three States: Solid (fixed positions), liquid (free to move), gas (far apart).

  • Physical Changes: Melting/evaporating involves adding energy, do not create new substances.

  • State Symbols: (s) solid, (l) liquid, (g) gas, and (aq) aqueous.

Atomic Structure

  • Historical models: Plum Pudding (Thompson), Rutherford's nucleus, Bohr's electron shells, Chadwick's neutrons.

  • Protons & Neutrons: Equal mass of 1 (relative mass), electrons are negligible.

  • Atomic Number: Number of protons; defines the element.

  • Mass Number: Number of protons + neutrons.

  • Ions vs. Atoms: Ions form when atoms gain or lose electrons.

  • Isotopes: Same element with different numbers of neutrons (e.g., carbon-12 and carbon-13).

The Periodic Table

  • Elements arranged based on atomic number.

  • Electron Configuration: Shows arrangement of electrons in shells (max 2, 8, 8, 2).

  • Metals vs. Nonmetals: Metals donate electrons (to left of staircase), nonmetals accept electrons (to right of staircase).

  • Groups: Indicate the number of electrons in the outer shell; Group 1 is alkali metals, known for donating one electron.