Sylvan Park Super Scientists Activity #6: Chromatography

What you will do – Discover how to separate colors using chomatography

Vocabulary words:      chromatography     chromatogram    capillary action    

Materials needed: (Get these things together first)
A black marker –It needs to be a water-based marker. NOT a sharpie.  Sharpies are permanent markers and the ink will not “travel” with water.
A pencil
A container to hold water
A sheet of paper towel

Have you ever mixed 2 colors to make a different color?

JOURNAL:  Write down what happened when you mixed colors. 

Scientists can separate colors in a mixture.  One way to do this is by using chromatography. Let’s find out what happens.

Experiment 1:

  1. Cut a 4 inch by 1 inch strip from a paper towel. (picture 1)
  2. Draw a line with a pencil across the bottom of the strip about 1 inch from the bottom. (picture 2)
  3. Put the strip of paper on top of another piece of paper or plate (to protect the table top) and make 2 heavy dots on the line with a black marker. (picture 3)
  4. Put about ¼ inch water into the container.
  5. Carefully place the bottom edge of the strip into the water.  Hold the top of the strip and be careful that only the bottom edge is in the water.  Keep the paper away from the sides. The black dots must never be in the water.  (picture 4)
  6. Watch the water rise up the paper.

JOURNAL:  What happens?
Wait about five or six minutes for development of the chromatogram.

What colors are now on the paper strip?
How many colors can you see?
Did any of the color move down from the line or just up?
Is the pencil line still there or did it move?

After the water has finished moving up the paper, place it on a sheet of paper towel to dry.  This is called a chromatogram.

Liquids can climb up paper, string, and other substances through the process of capillary action.  This is the same action that you looked at last week when colored water move up a celery stalk, leaves or flowers.
The liquid moves upward through small pores, or capillaries, that are found in paper towels, filter paper, chromatography paper, and other porous materials; this is what makes these materials absorbent.  
Scientists use this process to separate mixtures, including colors.  Chromatography is a physical way to separate mixtures.

Try this with different black markers and other colored markers.   

JOURNAL:  Do all black markers have the same colors in them? Predict what colors make up a marker color.  For instance, what colors would you predict are in a green marker?  In a purple marker? Do your chromatograms fit your predictions.  What are the surprises?

Look at the youtube video

Experiment #2
Materials you will need:
Coffee filters – either white or natural add (picture 5).
Water based colored markers
Container for water
For a round coffee filter:
Fold the coffee filter in half and then half again and press gently.  It should look like a cone. Open it up and locate the center point.
Use a pencil and draw a circle about 1 inch around the center. (Picture 6)
Put the filter on top of another piece of paper or plate (to protect the table top). Use your marker to drawer a heavy line on top of the pencil line.  Or you can use several marker colors on the pencil line. (Picture 7)
Fold the coffee filter back into its cone shape. (Picture 8)
Put about 1/8 inch water into a container.  Good containers would be a measuring cup, a wide small jar, a wide small cup, anything that will support the coffee “cone”.
Put JUST the bottom tip of the cone in the water. Spread the cone out so it fits the glass.  Watch the colors separate. (Picture 9)
When water has risen to the top of the filter, take the filter out of the water and put it on a paper towel for it to dry.

For a cone-shaped coffee filter:
Draw a heavy black line about 1 inch up from the bottom edge of the filter. (Picture 10)
Place filter in a container with about ¼ inch water and watch what happens.(Picture 11)
When water has risen to the top of the filter, take the filter out of the water and put it on a paper towel for it to dry.
Note – if you don’t have coffee filters you can cut a paper towel into a circle and use it like the round coffee filter.

Describe what happened when water rose up through the filters.  Did your black pen separate into the sane colors?
Try to find out how scientists use chromatography.