AQA GCSE Chemistry Paper 1 Summary

Topics Covered

• Atoms
• Bonding
• Quantitative Chemistry
• Chemical Changes
• Energy Changes

Important Notes

• Applicable for higher and foundation tier, double combined trilogy, and triple separate chemistry.

Atoms & Periodic Table

• Atoms: Building blocks of substances, each element represented by a symbol on the periodic table.
• Compounds: Chemical combination of two or more types of atoms.
  • Example: H₂O for water.
• Mixtures: Combination of elements/compounds not chemically bonded (e.g., air, saltwater).
• Separation Techniques:
  • Filtration, Crystallization, Distillation, Fractional Distillation.
• States of Matter: Solid, Liquid, Gas.
  • Physical changes (not chemical): Melting, Evaporation.
• Atomic Models:
  • Plum Pudding Model (J.J. Thompson)
  • Nuclear Model (Ernest Rutherford)
  • Electron Shells (Niels Bohr)
  • Neutrons (James Chadwick)
• Periodic Table:
  • Atomic Number (protons), Mass Number (protons + neutrons).
  • Isotopes: Atoms with different neutrons.
  • Dmitri Mendeleev: Grouped elements by properties, predicted undiscovered elements.
  • Electron Configuration: Shells with 2, 8, 8, 2 electrons.
  • Metals vs Non-metals: Metals donate electrons, non-metals accept.
  • Groups: Alkali Metals (Group 1), Halogens (Group 7), Noble Gases (Group 0).

Bonding

• Metallic Bonding: Sea of delocalized electrons.
• Ionic Bonding: Metal to non-metal electron transfer.
  • Result: Ionic compounds (salts), high melting points, conduct electricity when molten.
• Covalent Bonding: Non-metals share electrons.
  • Simple Molecular: Low boiling points, do not conduct electricity.
  • Giant Covalent Structures (e.g., Diamond, Graphite).
  • Allotropes of Carbon: Graphene, Fullerenes, Nanotubes.

Quantitative Chemistry

• Conservation of Mass: Mass of reactants equals mass of products.
• Moles: Unit to measure substance quantity.
  • Calculation: Moles = grams/relative atomic mass (rams).
• Stoichiometry: Mole ratios in reactions.
• Percentage Yield & Atom Economy:
  • Yield: Actual vs theoretical product amount.
  • Atom Economy: Efficiency of mass usage.

Chemical Changes

• Reactivity Series: Metals compared to carbon and hydrogen.
• Displacement Reactions: More reactive metal displaces less reactive one.
• Extraction of Metals: Smelting, Oxidation/Reduction (OIL RIG mnemonic).
• Acid-Base Reactions: Neutralization, pH scale (logarithmic).
  • Titration: Determines unknown concentration.
• Electrolysis: Extracts metals, purifies substances.
  • Involves anions and cations moving to respective electrodes.

Energy Changes

• Exothermic vs Endothermic Reactions:
  • Exothermic: Releases energy (e.g., combustion).
  • Endothermic: Absorbs energy.
• Energy Profiles: Visual representation of energy changes in reactions.
• Cells/Batteries: Convert chemical energy into electrical energy.
  • Hydrogen Fuel Cells: Use electrolysis to generate electricity.