Chromatography

Chromatography is a method of separation. The most common form of it is paper chromatography with black ink. When a piece of filter paper with drops of ink (or other solution) is put in eluting solution (NaCl solution works for food dye), the eluting solution rises up the paper through capillary action. The most polar ions in solution are most easily dissolved and carried along with the eluting solution, so they 'win' the 'race' to the top of the filter paper.

This mural is funny because it was painted on a series of poles/columns in the science hallway, and the 'most pole-ar wins.'