The Science of Chromatography
Chromatography
The food coloring is mixed with the water and it can be splits up into colors on paper. This is called paper chromatography. Scientists called Chemists use this to help them identify mystery materials at a crime scene. The colors mixed in water creep slowly along the paper towel liquid (the ink) dissolved in water or another solvent creeping over the surface of a solid (the paper). As the mixture moves or spreads out over the paper towel some of colors stay attached to the paper towel (less soluble) while some move along and separate out later because they are more soluble in water. The colored dyes are made of different molecules and some stay dissolved in water longer (more soluble) than other molecules that are less soluble. This lets chemists identify different molecules that might be part of a mixture.
Resources
Scientific American
Teaching Engineering for classroom chromatography!