THE VERY HUNGRY CATERPILLAR
INTRODUCTION This experiment is
especially appropriate for Nursery through First Grade children, who love
to hear their favorite stories told time after time. Most young children
know and love this story, and many already know that it was written by
Eric Carle. While many teachers have used this story in the springtime
to introduce children to a unit on butterflies, this is a new way to create
a butterfly. The emerging butterfly is a delightful surprise for
the children.
PURPOSE This activity introduces
young children to the exciting world of science by using one of their favorite
stories as the backdrop to a science project. Chromatography is used
to show the children how to separate the colors present in water-soluble
marking pens, producing a beautiful, colorful "butterfly" from drawings
of the hungry caterpillar and some of the foods that he ate.
MATERIALS Water-soluble marking
pens - colors that are the same as some of the foods, which the caterpillar
eats (brown for chocolate cake, red for an apple, blue and yellow for the
lollipop, green for a pickle, etc.)
This experiment works best when you use water-soluble markers with a pretty color separation. Colors differ according to manufacturer so that, for example, some blue markers contain only blue ink, while others separate into blue and pink or other combinations of colors. To test the inks, cut a coffee filter into strips about 1/2" x 4" long. Keeping a record of which marker you use, draw a large dot about 1/2" from the bottom of a strip. Hang the strip in a glass by inserting a toothpick through the top of the strip and resting the toothpick on the rim of the glass. Carefully pour in enough water to just touch the bottom of the filter paper, being careful to not get water on the rest of the strip. Check to see how the colors have separated in about 5 minutes. Choose those markers that are appropriate for drawing the foods eaten by the caterpillar, but which also have the prettiest separation. Prior to beginning
the class, use water-soluble markers to draw a simple picture of the "hungry
caterpillar" (green caterpillar with a red head) about 2 cm from the bottom
of the cone coffee filter. Draw the same picture on the opposite
side of the filter.
PROCEDURE 1. Tell the children that you are going to read one of their favorite stories to them, and show them the book. Then explain that before reading the story, you need their help. You have already drawn a picture of the caterpillar (show them), but you also want to draw pictures on the filter of some of the foods the caterpillar ate. As they mention a food item, draw a simple picture of the item on both sides of the filter. Be sure to use several different colors of marking pens, especially those that have the prettiest separation (see "Preparation for the Activity"). The "pictures" should start 2 cm from the bottom of the filter and then more or less cover the bottom 1/3 of both sides of the filter, 2. Show the children the pictures you drew. Then cut off a very narrow strip of paper at the folded edges of the filter, so that you can open the filter. 3. Thread the 2 skewers through the filter, about 2" apart and about 2" from the top of the filter. Spread the filter apart and lay the skewers on top of a shallow bowl. Pour just enough water into the bowl so the bottom of the filter is in the water, but so the water does not touch the pictures you´ve drawn. Put the bowl aside, or sit in front of it as you read the story to the children. The chromatography process will probably take longer than reading the story, so you can spend some extra time talking about the author, caterpillars, butterflies, etc. Some fun and interesting facts about caterpillars that we discovered at Calloway Gardens in Georgia include: the caterpillar is often called a "world class eating machine" or "a stomach with legs". Some caterpillars have a 3000X increase in size, and if a baby grew at the same rate as a caterpillar, the baby would weigh 20 tons by his first birthday! 4. When you
are finished reading the story, remove the filter paper from the skewers,
and open the filter so the children can see the emerging butterfly.
If the colors have not spread to the top of the paper, put the butterfly
back on the skewers and let the process continue. Remove the filter
from the bowl when the water has carried some of the ink dyes to the top
of the paper, and there is a colorful mixture of dyes filling the center
of the filter. If you wait too long to remove the paper from the bowl,
all the colors will have been carried by the water up to the top of the
filter, and the butterfly will not be as colorful.
EXPLANATION Red, blue, and yellow
are the primary colors and are used in different combinations to make all
other colors. As the water travels up the paper, it carries the colors
out of the inks at different rates, depending on whether the attraction
of the ink to water or to paper was greater. Ink that has a greater
attraction to water will be carried up the paper by the water more quickly,
while ink with a greater attraction to paper will not climb as quickly.
Thus, the ink in the caterpillar and the food pictured on the filter paper
will spread out at different rates to create the effect of a beautiful
butterfly on the cone filter paper. This process is called "Chromatography"
and is used to separate the different substances that compose a compound,
just as different colors separated out at varying rates from the individual
markers in this experiment.
ADDITIONAL SUGGESTIONS When the filter paper
dries, you can put a clothespin on or tape pipe cleaners to the center
of the butterfly to give it a "body".
REFERENCES 1. Janice Smith,
editor, Super Science Connections,1995, a publication from The Institute
2. Notes from the Butterfly House in Callaway Gardens, Pine Mountain, Georgia 3. Eric Carle, The
Very Hungry Caterpillar, Philomel Books, NY, 1969.
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