Why do leaves change color in the fall?
Plants need several things to live. They take water from the ground through their roots. They also take a gas called carbon dioxide from the air. Plants use sunlight to turn water and carbon dioxide into glucose. Glucose is a kind of sugar which plants use as food for energy and as building blocks for growing. The way plants turn water and carbon dioxide into sugar is called photosynthesis. A chemical called chlorophyll helps make photosynthesis happen. Chlorophyll is what gives plants their green color. During winter, there is not enough light or water for photosynthesis. The trees will rest, and live off the food they stored during the summer. They stop making food so the green chlorophyll disappears from the leaves. As the bright green fades away, we begin to see yellow and orange colors. Small amounts of these colors have been in the leaves all along. We just can't see them in the summer, because the green chlorophyll covers them up. This is the reason leaves change color in the fall.
Since leaves do not have the materials they need to survive in the winter and fall, their leaves die and loose the green color.
"Separate the colors of a green leaf using chromatography"
- leaves, small jars
- covers for jars or aluminum foil or plastic wrap
- rubbing alcohol, paper coffee filters
- shallow pan, hot tap water, tape, pen
- plastic knife or spoon, clock or timer.
- Collect 2-3 large leaves all from different trees. Cut the leaves into very small pieces and put them into small jars labeled with the name or location of the tree.
- Add enough rubbing alcohol to each jar to cover the leaves. Using a plastic knife or spoon, carefully chop and grind the leaves in the alcohol.
- Cover the jars very loosely with lids or plastic wrap or aluminum foil. Place the jars carefully into a shallow tray containing 1 inch of hot tap water.
- Keep the jars in the water for at least a half-hour, longer if needed, until the alcohol has become colored (the darker the better). Twirl each jar gently about every five minutes. Replace the hot water if it cools off.
- Cut a long thin strip of coffee filter paper for each of the jars and label it.
- Remove jars from water and uncover. Place a strip of filter paper into each jar so that one end is in the alcohol. Bend the other end over the top of the jar and secure it with tape.
- The alcohol will travel up the paper, bringing the colors with it. After 30-90 minutes (or longer), the colors will travel different distances up the paper as the alcohol evaporates. You should be able to see different shades of green, and possibly some yellow, orange or red, depending on the type of leaf.
- Remove the strips of paper, let them dry and then tape them to a piece of plain paper.