Is Your Marker a Mixture?

Mixtures are substances made by combining two or more different materials without a chemical reaction between them.  If needed, a mixture can usually be separated back into its original materials.  Tossed salad and mixed nuts are both examples of mixtures that contain a variety of ingredients.  If desired, each ingredient can be separated such as a picky eater who hates tomatoes might routinely do with their salad.

One substance that might seem pure but is often a mixture is the ink from a pen. Ink is usually a mixture of several colored dyes (or pigments).  When needed, we can separate these dyes by passing them through a material in which the dyes move at different speeds.  Black, brown, and gray ink are always mixtures of several dyes.  One method used to separate colored ink is called chromatography. When we place a piece of paper with a sample of ink on it in a liquid solvent, the ink dissolves and moves up the paper along with the solvent.  The different dyes in the ink move up the paper at different speeds and this causes them to become separated as part of the process.  In this activity we will use water as our solvent and water-based, washable markers. These markers contain ink and dyes that will dissolve in water.