RAINBOW CROW
INTRODUCTION This is a simple experiment which delights young children from pre-K through grade 3 and is integrated with children's literature. We believe that integration with childrenís literature is particularly important for stimulating younger children because they love to hear the stories. Children seem to prefer stories that they have never heard or stories that they know very well. This is one that many children have not heard. Integration of a story with an activity allows the teacher to use class time more efficiently because language arts are being considered at the same time as science. We first read about this experiment in Science Grasp1, and later in Super Science Connections2. We introduce this story by asking the children what color a crow is,
and also what kind of a "song" the crow has. A long time ago,
we tell them, a Lenape Indian chief looked out and saw a crow in the sunlight.
He noticed that in the bright sunshine, he could see flecks of several
different colors shining amongst the crowís black feathers.
So the chief made up this story of RAINBOW CROW to tell his grandson
why we can see flecks of colors in the crow´s black feathers.
That story has been passed down from grandfather to grandson through many
years, and is what we now call a legend. (Note that a legend is a
story passed down through the ages. It may be true but frequently
is not true.)
PURPOSE The purpose of this activity is to have students separate the colors
that are present in a black, water-soluble, wet-erase, marking pen, and
thus to make a "Rainbow Crow."
MATERIALS (for one demonstration or individual, or for each group of four students) Black Vis-a-Vis, water-soluble, wet-erase, marking penPROCEDURE 1. Before reading or telling the story, draw a simple picture of a flying crow with a black Vis-a-Vis, wet-erase, marker about 2 cm up from the bottom of the 5 cm x 18 cm strip of filter paper. 2. Pour about 5 cm of water into a plastic tennis ball container or tall glass. 3. Put a short wooden skewer through the top of the filter paper so that you can hang the filter paper in the tennis ball container or glass. The water should touch the bottom of the filter paper, but do not let the water touch the drawing of the crow. 4. Put the tennis ball container or glass aside where it can't be seen easily, and then read or tell the story. 5. At the end of the story, lift the filter paper out of the tennis
ball container or glass, and show it to the children. They will be
delighted to see a large "Rainbow Crow" on the filter paper, as the black
ink will have separated into several different colors.
EXPLANATION The color pigments used in water-soluble marking pens appear to be made
up of only one color. However, most pigments, except the primary
colors, are made up of mixtures of colors. For example, the color
black is made up of all the colors of the rainbow. As water travels
up the filter paper, it carries all of the colors out of the black ink,
but at different speeds. Each color has a different attraction for
the water and the filter paper. How fast or slow a color moves
depends upon its attraction for water versus the filter paper. Colors
that bind more tightly to the water travel upward faster whereas colors
that bind more tightly to the filter paper travel upward slower.
As a result the crow grows much larger as it separates upward into Rainbow
Crow. This process is called "Chromatography," and scientists use
this process to separate the different substances which compose a mixture,
just as we have separated the different colors from the color "black".
ADDITIONAL SUGGESTIONS A tall drinking glass or plastic drinking cup can be used in place of the tennis ball container. Increase or decrease the length of the filter paper accordingly. Coffee filter paper works fine in this activity. White paper towels may also be used, but paper towels do not give as good a separation of colors. Janice Smith from York College in Pennsylvania wrote to us about an
ingenious adaptation of this activity. 3
She wanted a crowd of more than 150 third grade students to perform this
activity in a hands-on mode in a new music recital hall where she could
not tolerate a mess of any kind. She prepackaged for each student
a styrofoam plate and a coffee filter with a crow drawn in the center with
a water-soluble black marker as well as several water soaked cotton balls
in a separate Zip-loc bag. The plate and filter paper were passed
through the rows of students. Then the cotton balls were distributed
during instructions to squeeze the water onto the crow in the center of
the filter paper. She read the story, using colored transparencies
of pictures from the book, while the separation occurred. Finally,
they examined the rainbow crows. Zip-loc bags of cotton balls were
collected as the children left the auditorium. As Janice put it,
"third graders, teachers, I, the custodians, and nervous musicians were
all smiles!"
REFERENCES 1. Bonnie Barger, "The Colors of the Crow," Science Grasp 92, The Upjohn Company, IV.2-IV.3. 2. Janice Smith, editor, Super Science Connections, 1995, a publication from The Institute for Chemical Education (ICE), University of Wisconsin - Madison, 1101 University Ave, Madison, WI 53706. 3. Janice Smith, Physical Science Department, York College, York, PA 17405-7199, personal communication. 4. Rainbow Crow: A
Lenape Tale, retold by Nancy Van Laan, A Dragonfly Book, Alfred A.
Knopf, NY, 1989.
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