m&m’s chromatography

Chromatography is a technique that scientists use to separate things. A good analogy for this is to picture bees and wasps flying in a pack over a flower bed. The bees will be attracted to the flowers, but the wasps will just keep moving. If you were standing just at the end of the flower bed, you would see the wasps fly by first (unattracted to the flowers) and the bees second (their attraction to the flowers slowed them down). [Credit wikipedia] Scientists in a lab will often use similar techniques to separate things. Today we are going to try to separate the colors in m&m;‘s. Did you know that there is more than one color in your brown m&m;? How many colors do you think there will be? Some colors will stick to the paper more than other colors, thus, just like the wasps and bees, the colors will separate.

This experiment is safe; no special precautions.

Brown m&ms;(other colors optional)
Small vial with lid
Water
Filter paper
Tall cup
Toothpick or q-tip
Pencil
Scissors
Hair dryer

Put four or five brown m&ms;in a vial and add a few drops of water—just enough to start to wash off the candy coating. Shake the m&ms;for a few minutes until you see the brown coloring come off into the water. Prepare a piece of filter paper with a line at the bottom and using the q-tip, blot some of the water/candy coating slurry onto the filter paper. Only do a little bit at a time, drying with the hair dryer for a minute between applications. If you get the filter paper too wet it will fall apart, and the colors will separate too much before you get them into the developing chamber/cup. Once you can clearly see the coloring on the paper, take a cup and fill it 1/2 inch full with water. Place the paper standing up against the side of the cup with the m&m;color near the bottom, but not submerged in water. Wait a few minutes as the water travels up the paper, carrying the various colors in the m&m;dye with it.

Like ink pens and colored images, m&m;candy colors are often made up of a combination of dyes. Test other colors to see which dyes are used in which m&m;coatings.

Chromatography was invented in 1910 by Russian botanist Mikhail Tsvet. He used it for separating the pigments that made up plant dyes. This technique provides an easy way to separate the components of a homogeneous mixture. Chromatography uses two phases (states of matter) to separate a homogeneous mixture because each component of the mixture has different affinities to each phase. We have a stationary phase (solid material), and a mobile phase (liquid or a gas). Some components of the mixture will stick to the solid better than others so each component will move at different rates so we can separate them. The rate at which a compound moves depends on the size of the molecule and the solubility in the solvent.

No special clean up required.