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. In this experiment you will find out something surprising about what mixes together to make black ink.
What You Need:
- Paper Towel or Coffee Filter
- Several different kinds of black markers
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 marks it takes the pigment colors with it. Different colors of pigments travel with the water at different rates because the molecules of some pigments stick to the paper more strongly than others. So, as the water travels it separates the colors. 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!
Websites, Activities, Printables:
Science in Context: Chromatography and Mixtures and Solutions is a database you can use in any IndyPL Library Branch or at home. Login using your IndyPL library card number. The Science in Context database will show you articles, images and videos to help you learn about chromatography.
You can also ask a math and science expert for homework help by calling the Ask Rose Homework Hotline. They provide FREE math and science homework help to Indiana students in grades 6-12.
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