Chemistry: topic 2 states of matter and mixtures

• Physical changes: They involve forces between particles but the particles do not change
• Physical changes


  • Melting
  • Boiling
  • Freezing
  • Condensing
• Chemical changes where a new product has formed
• Mixture


  2 or more elements not chemically combined
• Mixture


  • Chemical properties of each substance are unchanged
• Pure substance


  Single element or compound not mixed with any other substance
• Simple distillation


  1. Heating solution

  2. Solvent vapour evaporates

  3. Vapour cools and condenses
• Simple distillation


  Used to separate solvent from a solution (producing water from a salt solution)
• Simple distillation


  • Dissolved solute has a much higher boiling point than the solvent
• Paper chromatography


  1. Separate components of a mixture

  2. Identify substances
• Rf value


  Distance moved by substance / distance moved by solvent
• Pure substance will produce a single spot in all solvents
• Fractional distillation


  1. Heat mixture

  2. Vapours with different boiling points condense at different temperatures
• Fractional distillation


  Used to separate pure liquids from a mixture of solutions
• Ethanol has a lower boiling point than water so it evaporates first
• Crystallisation


  1. Warm solution to evaporate solvent

  2. Allow to cool

  3. Solid crystals form and can be collected
• Potable water


  Drinkable water with low levels of microbes and contaminants
• Making potable water


  1. Sedimentation

  2. Filtration

  3. Chlorination
• If both spots are the same height in chromatography then the substance being tested is the same as the known substance
• Filtration leaves behind the precipitate (insoluble salt) on the filter paper