Experiments provided by Dr Audrey Matthews, Department of Applied Science, De Montfort University

Salt will help you separate the colours

1. What you need
Food colourings, cocktail sticks, coffee filter paper, salt, saucer, water.

You don't have to wear a white coat to be a scientist

2. What to do
Open up the filter paper envelope to make a skirt which stands on its own. Dip the cocktail stick in a food colour and draw a line with it at the bottom of the skirt. Rest the paper in a saucer containing a thin puddle of salty water. Watch to see if the colours separate.

Also use the lemon juice and cocktail stick to write a secret message on a piece of paper. Reveal the secret message by warming the paper over a radiator.

You can do the same experiment with Smarties

3. What’s happening?
This is what us scientists call chromatography. The colours should separate to make a pattern with bands of each of the colours used to make the colour on the bottle.

Some food colours, like red, are made up of one colour. Others like black or green are made up of two or more colours. Chemists use chromatography to identify or find out how much compound is present. Sometimes a powder or liquid is used instead of paper. Liquids or even gases can be used instead of the salty water.

Want to investigate some more?
Try comparing how far each individual colour travels up the paper. Do they move the same distance? Do you think that the colours will always be separated in the same order?

This experiment can also be carried out with gobstoppers or Smarties. First lick it and wipe the colour at the bottom of the filter paper. Continue to do this until your the sweet turns white and then eat it! Repeat with a few more sweets of the same colour and dip in a saucer of salty water as before.