The purpose of this project is to determine if chlorophyll is present in a leaf that is normally green, but has turned brown.
In the fall, deciduous trees lose their leaves. This is a brilliant display of gold, red, yellow, and orange put on by Mother Nature. During the spring and summer, these leaves are green.
We know that plants use a process called photosynthesis to make food. They use chlorophyll, water, minerals, carbon dioxide, and, most importantly, sunlight in the photosynthesis process. From experience, you have no doubt observed that photosynthesis stops when sunlight is cut off from a plant. Looking under a board that was thrown on a patch of grass reveals the grass has lost its green color.
When a leaf falls from a tree and turns brown, is chlorophyll still present?
Hypothesize that even though photosynthesis has ceased, some chlorophyll still remains in a brown leaf.
- Two test tubes
- Two test-tube holders
- One house plant
- Use of a stove burner
- Small cooking pot
- Adult supervision
Chlorophyll can be extracted from a leaf by placing it in a boiling bath of alcohol. If chlorophyll is present, the alcohol will begin to turn green. As a comparator, the more green the color of the alcohol, the greater the quantity of chlorophyll.
Alcohol is highly flammable, and must be handled with care around heat. Because alcohol boils at a lower temperature than water, we can use a double-boiler system that will make it safer to handle for this project.
On a house plant, locate two leaves that are as close as possible to being the same size. Using scissors, cut one leaf off the plant. Let it sit for several days until no green coloring is left in the leaf. To identify the other leaf of the plant, loosely tie a piece of string around its stem.
Gather two test tubes. Fill each one half-full of alcohol. In one test tube, place the brown leaf. Clip the leaf from the live plant (which you previously identified with a string) and place it into the other test tube.
Bring a small cooking pot filled with water to a rapid boil on a stove burner. Turn off the burner.
Using test-tube holders, lower both test tubes into boiling water. Position the holders and tubes, so the test tubes rest upright in the pot, or at least at a steep enough angle so no water gets into the tubes. An oven mitt may offer additional safety and comfort when you work around the pot. Let the test tubes remain in the water for 10 to 15 minutes.
Remove the test tubes and observe the color of the alcohol. Is green present in both test tubes? If so, does one test tube contain more green than the other?
Write down the results of your experiment. Document all observations and data collected.
Come to a conclusion as to whether or not your hypothesis was correct.
- Is any chlorophyll present in grass that has turned white because of sunlight deprivation?
- Are vegetables that are green (peas, string beans, lima beans, lettuce, spinach, kale, mint, and so forth) that color because they contain chlorophyll? Check for the presence of chlorophyll in green vegetables. Spinach and mint are leaves. Are your results different for these than for peas and beans?