chromatography practical

• Why is it important we keep the food colouring spots small?

  This prevents the colours from spreading into each other later
• What is the solvent in this experiment?

  The water
• Why should the pencil line be above the water?

  Otherwise, the water will wash the ink off the line.
• Why should the paper not touch the

  sides of the beaker?

  It will interfere with the way that the water moves.
• Why do we put a lid on the beaker?

  To reduce evaporation of the solvent (water)
• What are the observations of this experiment?

  The water moves up the paper and the ink is also carried up.
• If the unknown colour has separated into 3 spots, what does this tell us?

  It tells us that this is a mixture of 3 colours.
• In order to work out what the unknown colour is...

  ... see which spots are horizontally aligned with the spots in the vertical line of the unknown.
• How would we identify the chemicals in these colours using the results from the experiment?

  Calculate the Rf values.
• How to measure Rf values

  1. Measure the distance from the pencil line to the centre of each spot
  2. Measure the distance the solvent travelled from the pencil line
  3. Calculate by doing distance chemical/distance solvent