Chemical Analysis

• pure substances is a single element of compound that is not mixed with any other substances

  they melt and boil at specific temperatures
• melting and boiling points can be used to distinguish between impure and pure substances
• formulations are mixtures that have been designed for a specific purpose
• examples of formulations:

  • fuels
  • cleaning agents
  • paint
  • medicine
  • alloys
  • fertilisers
  • food
• mixture = two or more elements/compounds combined together but not chemically bonded
• chromatography can be used to separate mixtures
• the two phases in chromatography:

  • mobile phase
  • stationary phase
• the mobile phase is where molecules can move
• stationary phase is where molecules cant move
• Rf is the distance moved by a compound
• different compounds have different Rf values, so they can be used to identify compounds
• during chromatography, compounds in a mixture can sperate into different spots

  pure compounds will produce a single spot
• test for hydrogen:

  • squeaky pop test
  • hold a lit splint at the opening of the test tube
  • if hydrogen is present, you'll hear a squeaky pop
  • the pop comes because hydrogen burns quickly
• test for oxygen:

  • place a glowing splint inside a test tube
  • if oxygen is present, the oxygen will relight the glowing splint
• test for carbon dioxide:

  • mix carbon dioxide with limewater
  • if carbon dioxide is present, solution will turn cloudy
• test for chlorine:

  • place damp litmus paper in solution
  • if chlorine is present, it will bleach the litmus paper which will turn white as chlorine is acidic