Frugal Chemistry Experiment with Children (100% safe)

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Picture by Dr. Dodd @ OCCC

For this experiment you will need:

  • Washable markers – preferably the bold or classic colors made by Crayola or RoseArt
  •  coffee filters (Cut in 2 inch by 4 inch rectangles)
  • a tall clear glass
  •  water
  •  table salt
  •  a 1 teaspoon measuring spoon
  •  an 8 oz measuring cup
  •  pencil (a pen or marker is not good for this experiment)
  •  scissors (parents should use these)
  •  a ruler
  •  paper towels
Procedure:
1.      Select 6 different washable markers to test in this experiment. (My suggestions would be any of the following colors: brown, black, green, purple, teal, azure, blue, orange, and red but feel free to pick your favorite colors. The results obtained with pale shades like pink or yellow are not as dramatic.)
2.      Use a ruler to draw a light pencil line on a piece of coffee filter about 1/2 to 3/4 of an inch from the bottom edge of the paper. (DO NOT USE A PEN OR MAKER TO DRAW THIS LINE.)
3.      Fold the paper in half lengthwise and then open it and place it on a double layer of paper towels. (This will protect your counter or table.)
4.      Select the first two markers that you will use in the experiment.
5.      Make two small dots with the pencil on the line drawn in step 4. Place one dot on each side of the paper. Below each dot, use the pencil to label the marker color that will be used.
6.      Using the markers you have chosen, carefully make a small spot of color directly on top of the appropriate pencil spot. Try to keep the spot no bigger than 1/16 to 1/8 of an inch in diameter.
7.      Next we will make the developing solution . Add 1 teaspoon of table salt (measure this with a kitchen measuring spoon) to 1 cup (8 ounces) of tap water (measure this with your measuring cup). Mix thoroughly until all of the salt dissolves.
8.      Pour the salt solution into the tall clear glass to a depth of about ¼ inch. The level of the solution should be low enough so that when you put the coffee filter in the glass, the dots will initially be above the water level. Hold the coffee filter with the dots at the bottom and set it in the glass with the salt solution.
 9. The salt solution climbs up the paper, moving through it by a process called capillary action. Notice that the color spots move up the paper as well with some colors beginning to separate into different bands of color.  If your color spots do not move up from the original dots (see picture in the next step), then you have used the wrong type of marker.
10. When the salt solution is about 1 to 1.5 inches from the top edge of the paper, remove the coffee filter from the solution. Lay the coffee filter on a double layer of clean paper towels to dry.
11. While this coffee filter is drying, repeat steps 2 through 10 with the other 4 markers you have selected. At the end of the experiment, you should have 3 chromatograms, each prepared using two different markers.
Explanation: 

Some markers contain more than one dye. These mixtures of dyes separate into separate bands of color as the dyes move up the paper. The mixtures of dyes separate because some dyes are more strongly attracted to the paper while other papers are more strongly attracted to the salt solution. These differences cause the dyes to end up at different heights on the paper.

This process is called chromatography. (The word “chromatography” is derived from two Greek words: “chroma” meaning color and “graphein” meaning to write.) The salt solution is called the mobile phase, and the chromatography paper is called the stationary phase. We use the word “affinity” to refer to the tendency of the dyes to prefer one phase over the other. The dyes that travel the furthest from the point where you “spotted” the marker (i.e. where you drew the 1/16 to 1/8 inch spot of marker in step 6) have more affinity for the salt solution (the mobile phase); the dyes that travel the least have more affinity for the paper (the stationary phase).   The filter paper that contains the dyes which have separated into the various bands of color is referred to as a chromatogram.
(This is taken from an experiment in Princess Karen’s Chemistry Around Us -Chem1103 Class at OCCC with Dr. Dodd)

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