A food scientist is testing the food colouring used in cans of drink. She has to check that any colouring used does not contain any banned chemical. She places drops of the drink on chromatography paper. She allows the colouring to separate using water. She also makes another chromatogram, using drops of all the permitted chemical colourings. If she finds anything that does not match with these colourings, she will have to carry out further tests. The diagrams show her two chromatograms.
a) Why is the spot of drink placed above the water line at the start of the process?