What could be simpler?
Warning! Only under adult supervision
- paper coffee filter;
- brown felt-tip pen;
- citric acid;
- cotton wool;
Place a paper coffee filter on a suitably-sized plate. Use a brown felt-tip pen to draw and fill in a circle in the middle of the filter. Dissolve a teaspoon of citric acid in a glass of water and dip a piece of cotton wool in the resulting solution. Put the wet cotton wool on the circle. Watch as the brown spot turns into multicolored rings!
It would seem that the brown marker is filled with brown dye, but it isn’t! And chromatography can help you prove this! Chromatography is a method of separating and analyzing substances based on the different mobility of substances between two phases – a stationary phase (in this case, the coffee filter) and a mobile phase (the citric acid solution). Due to the capillary effect, the citric acid solution evenly wets the paper and carries the brown dye with it, which divides into several colors as it moves farther from the center! The dyes comprising the brown dye in the pen differ from each other in their chemical nature, and move through the paper at different speeds.
Cool experiments await you in the MEL Chemistry subscription!