2 PURITY

2 PURITY

1. Definitions

   • Mixture: Two or more substances mixed together, not chemically bonded
     • Homogeneous Mixtures (Solutions)
       • Every part of the solution has the same composition. Same all the way through
     • Heterogeneous Mixture
       • When a mixture is not the same all through (that is, when different parts of a mixture have different compositions)
   • Solution: The end result of solute and solvent
   • Solute: A substance that has another substance dissolved in it
   • Solubility: Whether the substance can be dissolved or not
   • Miscible: The ability to mix together
   • Pure Substances: A substance made from the same type of atom (definite melting and boiling points)
   • Impure Substances: A substance made not from the same type of atom

2. Methods of Separation

   • Paper Chromatography
     • 1. Take a piece of chromatography paper. Draw a pencil line across 1cm from one end
       • 2. Place a drop of unknown substance along the line. Allow the spots of colour to dry
         • 3. Set up the chromatography paper around a glass rod, secured with paperclips. Dip the paper in the solvent, making sure the pencil line doesn't touch the solvent
           • 4. Observe and allow the water to rise up the paper until almost at the top and see solvent spread on the paper
             • 5. Remove paper from the solvent before it reaches the top. Mark where the water reached and hang to dry.
               • 6. When dried, measure the distance moved by spots and solvent front. Identify the unknown and calculate Rf.
   • Filtration
     • Separates solid from a liquid
   • Crystallisation
     • Separates a solute from its solution
   • Simple Distillation
     • Separates a solvent from a solution
   • Fractional Distillation
     • Separates liquids from each other