If you mix one substance with another substance you get a mixture. Lemonade would be an example. Or cookie dough! Pen ink is also a mixture. It has more than one substance in it. In this experiment you will see that it is possible to UNmix a mixture too. This is called chromatography. Chromatography is separating the parts of a mixture so that you can see each one by itself.
Watch the video below to see a demonstration of chromatography using some simple items you can find at home. Then try it yourself with paper towels and markers. In this experiment you will find out something surprising about what mixes together to make black ink!
Try a Chromatography Experiment at Home:
What You Need:
Cut strips from the paper towel about 1 inch wide - one for each type of marker. Scribble across the bottom of one of the paper towel strips with each kind of marker. Scribble about one inch from one end of the paper towel strip. Tape the OTHER end of the strip to the maker you used to scribble on that strip. That will help you remember which marker goes with each paper towel strip.
Now hang the paper towel strips above the bowl of water so that only a little bit of the scribble end is in the water. Do not submerge the pen scribbles! Check on the paper towels in an hour. What has happened to the pen marks?
What you see happening on the paper towel strips is chromatography. The color of the ink in markers is made by mixing different pigments together. A pigment is a substance that makes color, like ink or dye. To make black, several pigments are mixed together. When the end of the paper towel strip is submerged in water the water soaks up through the paper towel. When the water passes through the black ink it takes the pigment colors with it. Some pigments dissolve in water easier and are pulled with the water farther up the paper. This is called chromatography - separating the parts of a mixture so that you can see them one at a time. Black ink actually looks like a rainbow!
Now set up an experiment using different kinds of paper to see what happens. Try a paper towel, a tissue, a square of toilet paper, and a piece of printer paper. Cut them all the same size. How does the ink act the same? What do you see that is different?
Or, set up an experiment with equally sized pieces of paper towels again, but test different colors of markers. Try black, purple, blue, green, and red. Can you predict what colors make up purple ink?
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