Criteria for purity

Criteria for purity

1. Appropriate apparatus for measuring

   • Time
     • Stopwatch
     • Clock
   • Temperature
     • Thermometer
   • Mass
     • Balance
   • Volume
     • Measuring cylinder
     • Burette
     • Pipette

2. Paper chromatography

   • Used to seperate mixtures and give information to help identify
   • Involves a stationary phase and a mobile phase
   • Separation depends on the distribution of substances between the phases
   • To carry it out
     • Place substances on line near bottom of paper
       • Place in solvent and observe how far the substances travel up the paper
         • Rf Value: distance moved by substance/distance traveled by solvent
           • Different compounds have different solvents which can be used to help identify the compounds
             • Pure compounds will produce a single spot in all solvents

3. Pure substances

   • Melt and boil at specific temperatures
   • A single element or compound, not mixed with any other substance
   • Impurities could be dangerous, even in small amounts

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