Chemistry (revision)

• States of Matter

  • Solid
  • Liquid
  • Gas
• Solids


  • Strong forces of attraction between particles
  • Particles held in fixed positions in a regular lattice arrangement
  • Particles vibrate about their positions
• Liquids


  • Weak forces of attraction between particles
  • Particles randomly arranged and free to move past each other
  • Particles constantly moving with random motion
• Gases


  • Very weak forces of attraction between particles
  • Particles free to move and far apart
  • Particles move constantly with random motion
• Changing between states of matter

  1. Particles gain energy

  2. Particles break free from positions

  3. Melting (solid to liquid)

  4. Evaporating (liquid to gas)

  5. Subliming (solid to gas)
• Physical changes don't change the particles, just their arrangement or their energy
• Heating a substance


  Increases the energy of the particles
• Cooling a substance


  Decreases the energy of the particles
• Changing the energy of particles can cause a change of state
• Diffusion


  The gradual movement of particles from places where there are lots of them to places where there are fewer of them
• Diffusion experiments


  • Potassium manganate(VII) and water
  • Ammonia and hydrogen chloride
  • Bromine gas and air
• Solubility


  The ability of a substance to dissolve in a solvent
• Investigating how temperature affects solubility

  1. Make a saturated solution

  2. Pour solution into evaporating basin

  3. Evaporate water

  4. Weigh remaining solid

  5. Repeat at different temperatures
• The solubility of a substance can change with temperature
• It's important to ensure the solute is in excess to get a saturated solution
• Filtration


  Used to separate an insoluble solid from a liquid
• Filtration


  1. Pour mixture into filter paper

  2. Liquid runs through paper, leaving behind solid residue
• Filtration used for


  • Separating solid impurities from a reaction mixture
• Crystallisation


  Separates a soluble solid from a solution
• Crystallisation


  1. Pour solution into evaporating dish

  2. Gently heat to evaporate some water, increasing concentration

  3. Remove from heat and allow to cool, forming crystals

  4. Collect crystals and dry
• Crystallisation is for separating soluble solids
• The components of a mixture aren't chemically joined, so can be separated by physical methods