Chemical analysis

• Pure substance


  A single element or compound, not mixed with any other substance
• Pure substance


  • Melts and boils at specific temperatures
• Impure substance


  Melts and boils over a range of temperatures
• A pure substance is a single element or compound, not mixed with any other substance
• Pure substances melt and boil at specific temperatures
• Impure substances melt and boil over a range of temperatures
• Formulation


  A mixture that has been designed as a useful product
• Formulation


  • The quantity of each component is carefully measured so that the product has the properties needed
• Formulations


  • Fuels
  • Cleaning products
  • Paints
  • Medicines
• Pure substance


  (in everyday language) a substance that has had nothing added to it, in its natural state
• Paper chromatography


  Allows us to separate substances based on their different solubilities
• Paper


  • The stationary phase, as it doesn't move
• Solvent


  • The mobile phase as it does move
• A pure compound will produce a single spot in all solvents
• Compounds in a mixture separate into different spots depending on solvent
• The starting line is drown in pencil because if drawn in pen, the pen ink would move up the paper, with the solvent
• Rf value has NO unit
• Identifying unknown Substances


  Look up Rf value in database to find identity of substance
• Solvent distance
• Rf value= spot distance/ solvent distance
• several different substance may have the same RF Value, so experiment may need to be repeated with different solvent
• HYDROGEN TEST 


  Insert burning splint into test tube of hydrogen -hydrogen gas burns rapidly and produces a SQUEAKY POP
• OXYGEN TEST 


  glowing splint placed into test tube of oxygen

  -splint will RELIGHT
• CARBON DIOXIDE TEST 


  using pipette take carbon dioxide gas and bubble it through limewater

  -limewater will turn CLOUDY if carbon dioxide present
• CHLORINE TEST


  insert damp litmus paper into mouth of chlorine gas test tube

  -chlorine BLEACHES litmus paper turning it WHITE
• HYDROGEN- SQUEAKY POP

  OXYGEN- glowing splint RELIGHTS

  CARBON DIOXIDE- LIMEWATER turns CLOUDY

  CHLORINE- damp LIMTUS PAPER BLEACHES WHITE