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Summer Science Series: Candy Chromatography

If your family is like ours, summer means more sweet treats and more candies in the cupboard! Here’s an opportunity to put those candies to another use. Using a scientific technique called CHROMATOGRAPHY, this experiment uncovers the different mixtures of dyes that make up colorful candy coatings.

Chromatography is the chemistry of separating a mixture into its individual components. Mixtures are made up of two or more substances that keep their original properties when combined. For this reason, they can be separated or un-mixed!

There are many different kinds of chromatography. Scientists use chromatography in the lab to separate and analyze all sorts of different mixtures, including liquids, gases, proteins, and carbohydrates. Chromatography is also used as a tool in forensic science to identify substances from crime scenes.

In this experiment, you will use coffee filters and water to separate the dyes in candy coatings.

WHAT YOU’LL NEED

  • M&Ms, Skittles, or other candies with colored coating
  • pipette or dropper
  • small bowl of water
  • flat piece of aluminum foil
  • pencil
  • white coffee filters cut into 6” X 4“ rectangles
  • toothpicks
  • piece of tape
  • small clear drinking glass filled with a small amount of water (about ¼ inch)
  • piece of white paper

 LET’S GET STARTED

(See photos below for experimental set-up.)

  1. Sort the candies by color. You need one candy of each color.
  2. Using a dropper or pipette, place a single drop of water – one for each different color of candy, onto the piece of foil. Leave some space between each drop.
  3. Place one candy on each of the water drops. Wait 1-2 minutes, then remove the candy. (You can eat the candy, or throw it away!) The dye from the candy will dissolve in the water, leaving a colored drop of dye.
  4. Using a pencil, write each color on the bottom of a piece of filter paper (on the long side). For example, for M&Ms, write “red   orange   yellow   green   blue   brown”.
  5. Dip the toothpick into the drop of dye and apply it to the filter paper – about ½ inch from the bottom, above the corresponding color. For example, dip the toothpick in the red dye and then touch the filter paper above where you wrote “red”.
  6. Repeat for each color. Use a clean toothpick for each new color.
  7. Let the spots of dye dry and then apply 3-4 more drops of color to each spot. The more dye you apply to the filter paper, the better your chromatogram will turn out!
  8. Once the spots of color have dried, connect the ends of the filter paper to create a tube, using a small piece of tape to hold the tube together.
  9. Place the tube into the drinking glass of water. Don’t let the filter paper touch the sides of the drinking glass. Also make sure the water level is below the spots of dye.
  10. The filter paper will soak up the water and the water will move up the paper, carrying the dye along with it. Remove the filter paper when the water gets close to the top.
  11. Carefully remove the tape and lay the filter paper flat on a piece of white paper to dry.
  12. Observe the pattern of dyes on the filter paper.

What did you see? Did different colors give different patterns? How did the patterns from the primary colored candies (red, yellow, blue) compare to the other colors? Why do you think this is?

WHAT’S GOING ON?

In this experiment you used paper chromatography to separate the mixture of dyes that make up candy coatings. The filter paper is called the stationary phase. The water is the mobile phase. Water moves up the filter paper by a process called capillary action. As the candy coating dissolves in the water, the pigment molecules from the dye are pulled along with the water and move up the paper. The pattern of colors on the filter paper is called a chromatogram.

You probably saw that some of the candy dyes were a mixture of several different pigments or colors. In our experiments at Yellow Scope, we saw that the brown and green candies were made up of several different pigments, but the dyes of the primary colored candies, like red and yellow, showed only one color.

You also may have noticed that some pigments moved farther up the filter paper than others. How far they move depends on the size of the molecule and how attracted they are to the paper. Some pigment molecules stick to the paper, so they don’t move as fast or far up the paper. Smaller molecules tend to move farther up the paper than larger molecules.

MIX IT UP!

Try more chromatography experiments with other dyes like colored markers. We find that brown and black washable markers show the most interesting pattern of colors. Compare different brands of markers. You also can use chromatography to separate the dyes in food coloring, powdered gelatin, or powdered drink mixes 

For another variation, try adding salt to the water to see if salt affects the pattern of colors. Some pigments may interact with the ions in the salt water and to produce a different separation of colors.

Let us know what you find. Share your photos and results with us on Facebook, Twitter, or send us an email to info@yellow-scope.com. We love getting your messages!

For more exciting chemistry experiments, check out our Foundation Chemistry Kit at www.yellow-scope.com.

Happy experimenting!

     The Yellow Scope Team




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