chemical analysis

• a pure substance contains only one type of element or compound.
• pure substances

  • melt and solidify at one fixed temperature.
  • boil and condense at one temperature
• impure substances change state at a range of temperatures.
• formulations are mixtures designed to have specific properties.
• examples of formulations:

  • fuels
  • cleaning agents
  • paints
  • medicines
  • fertilizers
• chromatography involves:

  • a stationary phase
  • a mobile phase (moving)
• in paper chromatography:

  • the stationary phase is the absorbent paper.
  • the mobile phase is the solvent, often water.
• during chromatography

  • mixtures are separated into their components.
  • the solvent dissolves the samples and carries them up the water.
  • each component moves a different distance up the paper, depending on the attraction to the paper and solvent.
• chromatography:

  1. draw a start line in pencil
  2. put samples of food coloring
  3. unknown substance (x)
  4. dip the paper in the solvent
  5. wait
  6. identify the unknown substance.
• hydrogen test: squeaky pop.
• hydrogen test:

  1. hold a lit splint over a tube with the gas in
  2. if its hydrogen it will make a squeaky pop.
• chlorine test:

  1. dunk litmus paper in substance
  2. if chlorine litmus paper will turn white.
• oxygen:

  1. hold a glowing splint over a test tube of gas.
  2. if oxygen the splint will relight.
• carbon dioxide:

  1. bubble through limewater
  2. if carbon dioxide, limewater will turn cloudy.