Thursday, September 23, 2010

Theory Thursday: Leaf Chromatography

I thought it would be neat to see what colors the leaves of our trees will be changing to in a few weeks. The colors or pigments are already present, but are hidden by the chlorophyll needed for photosynthesis. It begins to break down though during the fall. We used chromatography, the separation of mixtures, to speed up the process.

We collected 2-3 large leaves from several different trees, making a pit stop 
at the garden to snack on cherry tomatoes. We used leaves from an unknown tree, 
and birch, cottonwood, lilac, and maple trees.

Cut the leaves into several small pieces and place them in a jar.

 Add enough rubbing alcohol to each jar to cover the leaves. Jake hated the smell!
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, 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.

 Remove jars from water and uncover. Place a strip of paper towel into each jar 
so that one end is in the alcohol. Bend the other end over the top of the jar.

The alcohol will travel up the paper, bringing the colors with it. After 30-90 minutes, 
the colors will travel different distances up the paper as the alcohol evaporates. 

 Remove the strips of paper, let them dry. You should be able to see different shades of green, possibly some yellow, orange or red, depending on the type of leaf.

Our strips were mostly green surrounded by a bit of yellow. The kids were completely unimpressed. I must admit, so was I. I was hoping to see some red and orange. Maybe we'll just have boring trees this fall. Only time will tell.

 Yep, we just have boring trees in our yard. {pout} We'll just have to try it again with pretty trees. 

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