Experiment with Chlorophyll and Chromatography
In this science experiment, kids will explore the chlorophyll in plant leaves.
Photosynthesis is the process by which plants make their own food. Plants capture the energy from sunlight with their leaves and other green parts of the plant. The green color comes from a pigment called chlorophyll. Chlorophyll absorbs the energy from the sun, allowing the plant to use this energy to make its own food. Plants use carbon dioxide and water, along with this energy from the sun, to make glucose, which is a sugar. This is photosynthesis.
At the height of photosynthesis, during the summer when the days are long, plants continually make chlorophyll. The green from the chlorophyll covers up any other color that may be in the leaf. However, when the days become shorter and the temperatures become cooler, trees stop producing chlorophyll. Without chlorophyll present, the leaves change color as the other pigments are exposed. The yellow color that we see in the fall is a pigment called carotenoid. We also see carotenoids in carrots, corn, bananas and even canaries! The red color that we also see is called anthocyanin, and this is produced by the leaves only in the autumn when the days are short and the temperatures are cool, and only when chlorophyll is no longer being produced. Anthocyanins can also be found in cranberries, red apples, cherries and strawberries.
Safety Notes
The rubbing alcohol used in this experiment can be dangerous if consumed or splashed into the eyes.
Materials
- Flat coffee filters cut into 1 - 1 per student
- Small beakers or plastic cup - 1 per student
- Various large green leaves - 1 per student
- Rubbing alcohol - 2 tablespoon total
- Tape
Instructions
Cut a coffee filters into strips that are approximately 3 inches or so long and half an inch across.
Fold up a green leaf and rub firmly across the bottom of one of the filter strips (about 1" from the end) until there is a solid, thick green line. Younger children will likely need assistance with this.
Pour rubbing alchohol into your clear cup or beaker to a depth of about 1/2".
Place the piece of filter paper with the green leaf line into the alcohol, wetting it just under the leaf line.
With the bottom of the strip soaking in the alcohol, tape the strip to the side of the cup so that the alcohol can slowly soak up through the strip. Set aside for about 30 minutes. When finished, you should see at least two colors on your strip: the green chlorophyll and the true color of the leaf underneath (usually yellow).
Extension:
Repeat this experiment in the fall with colorful fall leaves. What happens?
