SEPARATING MIXTURES
Mr Walkley
WHAT IS A MIXTURE?
• A mixture contains two or more substances. That have not reacted
chemically with each other. Therefore they can be separated physically.
• What do we mean by being separated physically?
Hint: there are four of them, you’ve already studied some of them before
half term.
PHYSICALLY SEPARATING MIXTURES
• Chromatography: Separating a mixture by solubility.
• Distillation: Separating two liquids in a mixture by boiling point.
• Evaporation: Separating a solid and liquid by boiling off the liquid.
• Filtration: Separating a solid that has not dissolved in a liquid.
RETARDATION FACTOR (RF)
Rf = Distance travelled by component
Distance travelled by solvent
Example: If the red ink has travelled 4 cm up the paper and the solvent front is at 20cm,
what is the retardation factor of the red ink?
EVAPORATION AND FILTRATION
• They are both about separating solids from liquids. Here the similarities end!
• Evaporation boils away the liquid in the mixture, leaving you the solid behind.
• Filtration separates solids that haven't dissolved in the liquid. You end up with
the solid and liquid apart.
• Practical