Chromatography

Vermont is known for beautiful fall colors. Every Autumn, the green leaves change into a wonderful collage of oranges, yellows, and reds. It may seem like the colors just appear out of nowhere, but they are actually present in the leaves the entire time! During the spring and summer months, leaves work really hard to provide energy for the tree through photosynthesis. Chlorophyll, the pigment responsible for giving leaves their green color, is responsible for this process.

In the fall, as the days get shorter, trees don’t need their leaves to make energy so the green pigment is no longer necessary and the other hidden pigments get a chance to shine. Scientists used chromatography to figure out that the colors were there all along.

Chromatography is the process of separating different components from a mixture. The different parts are separated when the mixture is passed through a medium, trapping the different parts in different places as they move through the mixture. Why do the different parts get trapped in different places? Molecules! Everything in the world is made up of tiny things we cannot see called molecules. These molecules come in many different sizes. In chromatography, we can determine how big different molecules are by witnessing how far they travel. Are there colors that are hiding in objects in your home? Become a scientist and perform chromatography at home!

Materials: 1 glass, pencil, paper towel or coffee filter, black Crayola marker (or any color on hand — not permanent), tape.

Directions: Cut a strip out of the coffee filter or paper towel. Draw a line across the bottom with a black marker. Hang the coffee filter vertically in a glass by taping it to the pencil and hanging it over the glass. Add just enough water to be just below the black line. Wait and watch the colors separate!

How it works: This activity is done using paper chromatography. As the liquid moves, it carries the different colored molecules. Molecules of different sizes are deposited in different locations on the coffee filter.  Smaller molecules travel farther across the coffee filter than larger molecules. Which colors spread out the farthest?

Want more? Research it!: How might law enforcement use chromatography at crime scenes to help crack the case?