AQA GCSE Chemistry Paper 1 Overview

Introduction

• Covers topics 1 to 5:
  • Atoms
  • Bonding
  • Quantitative Chemistry
  • Chemical and Energy Changes
• Applicable for Higher and Foundation Tier, Combined Trilogy, and Triple separate chemistry.
• Indications for Triple only or Higher tier only topics will be provided.

Atomic Structure and the Periodic Table

Atoms and Elements

• Substances are made of atoms, represented by symbols on the periodic table.
• A compound contains two or more types of atoms chemically bonded.
  • Example: Water (H₂O) is made of hydrogen and oxygen.

Chemical Reactions

• Represented by word and chemical equations.
• Law of Conservation of Mass: Atoms aren't created or destroyed in reactions; equations must be balanced.
• Tips for balancing:
  • Start with atoms in compounds.
  • Balance elements last.

Mixtures and Separation Techniques

• Mixtures consist of different elements and compounds not chemically bonded.
• Techniques:
  • Filtration (separates insoluble particles from liquids)
  • Crystallization (evaporates solvent to leave solute)
  • Distillation (separates liquids by boiling points)
  • Fractional Distillation (separates mixtures by boiling points)

States of Matter

• Solid, Liquid, Gas
• Changes between states involve energy transfer but are physical changes, not chemical.

Development of Atomic Models

• JJ Thompson: Plum pudding model
• Ernest Rutherford: Discovery of the nucleus
• Niels Bohr: Electrons in shells
• James Chadwick: Discovery of neutrons

The Periodic Table

• Atomic Number: Number of protons, determines element.
• Mass Number: Protons + Neutrons.
• Isotopes: Atoms with the same number of protons, different neutrons.
• Historical Development:
  • Mendeleev arranged elements by properties, predicted undiscovered elements.

Chemical Bonding

Ionic Bonding

• Metals and non-metals bond by transferring electrons to achieve full outer shells.
• Ionic compounds form repeating lattice structures, have high melting/boiling points, conduct electricity when molten or dissolved.

Covalent Bonding

• Non-metals share electrons to form molecules.
• Simple covalent structures have low boiling points, don't conduct electricity.
• Giant covalent structures (e.g., diamond) have high boiling points.

Metallic Bonding

• Metals bond through a lattice of ions with delocalized electrons.
• Good conductors of electricity and heat.

Allotropes of Carbon

• Diamond: Hard, high melting point due to strong bonds.
• Graphite: Conducts electricity, layers can slide over each other.
  • Graphene: Single layer of graphite.
  • Fullerenes: 3D carbon structures, e.g., nanotubes.

Quantitative Chemistry

Conservation of Mass and Moles

• Mass is conserved in reactions.
• Moles: Amounts of substances; use relative atomic/molar mass to calculate.
• Calculating moles: ( \text{Moles} = \frac{\text{Mass (g)}}{\text{RFM}} )

Empirical and Molecular Formulas

• Use moles to determine ratios of elements in compounds.

Concentrations of Solutions

• Expressed in g/dm³ or mol/dm³.
• Calculations involve converting between mass, moles, concentration.

Chemical Changes

Reactivity Series

• Metals ranked by reactivity.
• Displacement reactions: More reactive metal displaces a less reactive one.
• Extraction of metals using carbon (smelting).

Acid-Base Reactions

• Acids react with bases to form salts and water (neutralization).
• pH scale measures acidity/alkalinity.
• Strong acids fully dissociate; weak acids partially dissociate.

Electrolysis

• Process of using electricity to cause chemical change.
• Used for extracting metals, purifying them.

Energy Changes

Exothermic and Endothermic Reactions

• Exothermic: Release energy, increase temperature.
• Endothermic: Absorb energy, decrease temperature.
• Energy profiles visualize energy changes.

Calculating Energy Changes

• Bond energy calculations determine energy changes in reactions.

Cells and Batteries (Triple Only)

• Produce electricity through chemical reactions.
• Hydrogen fuel cells: Combine hydrogen and oxygen to generate electricity.