C8 - Chemical Analysis

• Pure - a substance containing only atoms of one compound or element
• You can test purity by boiling/melting the sample and comparing with the known boiling point of the substance
• Formulation - a mixture with set quantities for a purpose e.g paint, shampoo
• Gas tests:

  • Chlorine - bleaches damp litmus paper
  • Oxygen - relight glowing splint
  • Carbon dioxide - limewater turns cloudy
  • Hydrogen - burning splint produces squeaky pop
• Chromatography uses two phases:

  • Mobile phase - molecules can move e.g solution
  • Stationary phase - molecules can't move e.g paper
• Chromatography:

  1. Draw pencil line on chromatography paper
  2. Dots of known inks and ink to be tested
  3. Dangle paper in a beaker just touching solvent
  4. Wait for solvent to soak 3/4 up the paper
  5. Calculate Rf value of each ink and compare
• Rf value = distance travelled by substance / distance travelled by solvent
• Rf value will change depending on the solvent used