Leaf Chromatography

Leaves contain different pigments, which give them their color. Green chlorophyll is the most common type of pigment, but there are also cartenoids (yellow, orange) and anthocyanins (red). Chlorophyll, which is essential for photosynthesis, usually hides the other pigments, except when autumn comes along and it begins to break down. This is why leaves turn different colors in the fall. Do this project to see the hidden colors in a green leaf and predict what color it will be in the fall! (Adult supervision recommended.)

Materials:

• Green leaves from several different trees (Trees with a dramatic color change, like maples, work best)
• Beaker or drinking glass
• Isopropyl (rubbing) alcohol
• Plastic wrap
• Chromatography or filter paper (you can use coffee filters)
• Pencil

What to do:

Keep leaves from different trees separate and follow the steps below for each set of leaves, so you can compare results.

1. Tear the leaves into several pieces and place them in a beaker or glass, then add just enough rubbing alcohol to cover them. Cover the beaker with plastic wrap to keep the alcohol from evaporating.
2. Put the beaker in a dish of hot tap water for about 30 minutes, until the alcohol turns green as the pigments from the leaves are absorbed into it.
3. Cut a strip of filter paper about a half inch wide and tape it to a pencil. Suspend the pencil across the beaker and let the strip just barely touch the alcohol and pigment mixture.

What's happening?

A bit of the mixture will travel slowly up the paper. After about 30-90 minutes you should be able to see the "green" color break up into several different colors as the different pigments begin to separate. You'll see different shades of green, and perhaps other colors as well. Which leaves had the most colorful pigments? Based on your experiment, which trees' leaves do you think will turn the brightest and least brightest colors this fall?

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