Paper Towel Rainbows: Chromatography for Beginners

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Get ready for all the rainbow heart eyes in this easy and gorgeous introduction to chromatography. 🌈😍 Recommended age 3.5+

This activity focuses on the concept of solubility and how an appropriate solvent can carry molecules along a stationary phase. Read on for some basic science and how to make some jaw dropping art!

Materials

Method

  1. Cut squares from a paper towel (four from a large sheet or two from a select-a-size sheet).
  2. Find the center of sheet and using different color Sharpies, heavily color in dots around the center point. Make sure the dots have a lot of ink in them, but don’t puncture the paper towel.
  3. Using the eye dropper, drop isopropanol onto the center of the paper towel and watch as the ink radiates out from the center. Keep slowly adding isopropanol to grow your chromatograph.
  4. Use your science art to make new crafts or hang it up to display!

Extra Experiments and Questions

  • Try doing this with water instead of isopropanol. Does it work? What’s happening?
  • Try doing this with washable markers (like Crayola). Which works better- water or isopropanol?
  • Do you think this would work with crayons?
  • How does this relate to stain removal? Why can’t you wash Sharpie out of your clothes with water?
  • Try putting less ink on the dots and see if you can separate some of the colors within the ink. The success of this will vary on the markers/colors you use, but its worth a shot!

Discussion

Chromatography is used frequently in labs to separate compounds in a mixture. There are many types of chromatography but they are all based on a similar concept: a mobile phase carries your molecules of interest through a stationary phase, and based on the different interactions with the mobile and stationary phase, the different compounds can be separated. This experiment illustrates how a solvent (the isopropanol) can carry soluble molecules (the ink) through a stationary phase (the paper towel). After kids grasp this concept, you can move on to more delicate examples of chromatography like separating the components of fall leaves or a bouquet of flowers. See below for some key definitions to go over.

Definitions

Chromatography: A way to separate parts of a mixture by moving the mixture and a solvent (mobile phase) along a surface (stationary phase). Because the different parts of the mixture will “prefer” to be on the stationary phase or mobile phase differently, they travel at differing rates, causing the parts to separate.

Solubility: A demonstration really helps to explain this to kids. They first must know that everything is made up of smaller parts, like molecules, ions, or atoms. Mix sugar or salt into warm water and show them that it seemingly disappears into the water. Explain that the smaller parts are being broken off from the larger crystal and surrounded by water molecules, which keeps them suspended in the liquid. They are still there, we just can’t see them. Then try doing this with chalk or something else that is not soluble in water. They will be able to see the bulk either floating or sinking to the bottom. Explain that these things are insoluble. The sugar or salt have properties that make them want to associate with water, kind of like magnets sticking to each other, while the chalk molecules do not.

In this experiment, the ink from Sharpies is soluble in isopropanol but not in water. The isopropanol is called a solvent, and the ink molecules are called the solute.

Mobile Phase: In this experiment, the mobile phase is the isopropanol. It carries the ink molecules along the paper towel through capillary action.

Stationary Phase: In this experiment, the stationary phase is the paper towel. If solute molecules interact strongly with the stationary phase, they will stick to it earlier than molecules with less attraction to it.


Share the art you create with this project on Instagram and join our community! Tag us and use the hashtag #IBravedTheElements for a chance to be featured!

xoxo

 

Cara

Make your own pH strips with turmeric

This post is part of our 2017 Summer of Science series! Here you’ll find quick and easy projects and experiments you can do this summer to keep your kids’ brains active and curious! As always, you can go as much or as little into the science explained below based on age and interest. Enjoy!

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This project actually came about kind of by accident, but honestly that’s how lots of science discovery happens! I was washing the extract of turmeric from a bowl in my sink (we were making dye for tie-dye!) and realized the color changed from bright yellow to brownish-red when I added water. I googled the color change and found that curcumin, the main compound responsible for turmeric’s color, will turn red in solutions with pH greater than 7.5. I took out my (real) pH strips and clocked the pH of my tap water at 9. After making sure that it’s not big deal to drink pH 9 tap water, I decided to see if we could make some pH strips with the turmeric extract, and it worked splendidly!

Continue reading “Make your own pH strips with turmeric”

Painting with Chlorophyll: How to make your own fluorescent paint

This post is part of a series on chlorophyll, a molecule both plants and humans owe their lives to! This specific activity is a fun, easy, and art-inspired introduction to chlorophyll for children 2 years old and up where we will make paint from the chlorophyll in spinach leaves, then observe the fluorescence of the chlorophyll artwork with a black light! If you can paint, and not eat the paint, this activity is for you!

Continue reading “Painting with Chlorophyll: How to make your own fluorescent paint”