Chemistry C2 GCSE AQA - UNIT 2

Follow on to 'Chemistry C2 GCSE AQA - UNIT 1'.

Everything you need to know about UNIT 2 for AQA higher GCSE


Ionic Compounds

Ionic Compounds

  • Already covered in UNIT 1, but if you missed that or want to go over it again its here (In more detail as well) :)
  • STRONG electrostatic forces, holds the ions tightly together.
    • Means SOLIDS at room temperature
    • A LOT of energy is needed to over come these, so HIGH melting/boiling points
  • HOWEVER, when melted the ions are FREE to move, allows them to carry ELECTRICAL CHARGE, so liquid ionic compounds can CONDUCT electricity
  • Some ionic compounds can DISSOLVE in water
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Simple Molecules

Simple Molecules

  • Held together by STRONG COVALENT BONDS
  • Bonds act only between atoms WITHIN the molecule, so simple molecules have LITTLE attraction for each other.
    • LOW melting/boiling points
  • Molecules have no OVERALL CHARGE and CANNOT carry an electric current, so do not CONDUCT electricity
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Giant Covalent Substances

Giant Covalent Substances

  • Several covalent bonds can be formed by atoms of some elements.
  • Join together in GIANT COVALENT STRUCTURES, sometimes known as MACROMOLECULES (not sure if you specifically need to know this word, but it may be mentioned on the paper, so it will help if you recognise it).
  • Every atom is joined to SEVERAL other atoms, by STRONG covalent bonds.
  • Takes A LOT of energy to break these, so HIGH melting points
  • DIAMOND and SILICA are examples of regular, three-dimensional giant structures
    • Very hard
    • Transparent
  • GRAPHITE is a form of CARBON.
    • WEAK forces between the layers, slide over eachother making it SLIPERY and GREY
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Giant Metallic Structures

Giant Metallic Structures

  • Arranged in LAYERS
  • Layers can SLIDE over eachother
  • Can move into a new position WITHOUT breaking
  • Useful for making WIRES, ROADS or SHEET materials
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Nanoscience and Nanotechnology

Nanoscience and Nanotechnology

  • VERY SMALL particles
  • 10(-9)m
  • Nanoparticles are a few nanoparticles in size
  • Behave differently to materials in bulk
  • LARGE surface area-volume ratio
  • Electrons can move through them more EASILY
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