Experiment #1

Leaf Chromatography Experiment

1. It’s important to read the instructions on this one before starting to ensure that you get a great result.
2. Cut a long rectangular strip of filter paper long enough to use inside your cups/glasses/jars. It needs to be long enough to hang in the jar without touching the bottom.
3. Tape the paper strip to a fork, spoon, straw or pencil. It needs to hang inside the glass and be stable, but not touch the bottom.
4. Separate the leaves by color so that you will get the strongest result.
5. With each set of leaves, tear or cut the leaves into small pieces to cover the bottom of one of the cups.
6. Pour the alcohol in the cup just enough to cover the leaves.
7. Use a spoon to smash and grind the leaves in the alcohol. You want a solution with the most color from the leaves that you can extract with crushing and grinding. The stronger the color, the stronger the result you will see.
8. You will complete these same steps for each color set of leaves into their own cup of solution so that you will have a variation of solutions and colors to test. (Try green, red, orange, yellow and maybe even brown!)
9. You can let the leaves sit in the alcohol for some time to allow the alcohol to extract the most color from the leaves as possible. You can leave it to soak overnight, covering the jar or glass to avoid evaporation of the alcohol.
10. You can strain the liquid off the leaves to see how concentrated the solution has become, but it is not necessary.
11. Now, carefully place your filter paper strip attached to the pencil or utensil across the jar or cup and let the strip dangle into the liquid from the leaves.
12. Let the strip soak within the solution and watch for the results.
13. You will see the color start moving up the strip and the colors will start breaking apart depending upon how strong the solution color is. This could take 30 min to an hour for total result.

The Science Behind the Experiment

First, you noticed we used alcohol in this experiment instead of water. Why? Alcohol is a much better solvent (dissolves solutions) for natural colors and will break down and extract the pigments into stronger solutions faster than regular water.

When you added the strip to the solution, the paper began absorbing and the solution began creeping up the paper. This is called Capillary Action and it is the same action that allows water and nutrients to spread throughout plants and trees. The capillary action is carrying the pigment molecules up the paper. Some pigments have smaller molecules than others and will travel the paper farther and faster than others. The larger ones will stay towards the bottom while the smaller ones will gravitate towards the top.

What color breakdowns do you see?

Did the pigment movement vary based upon the color variation?

Did some colors perform better than others?  (The colors break down based upon their chemical make-up.)

So Why Do Leaves Change Color in the Fall?

Leaves change color due to Photosynthesis. Photosynthesis is when the bright green chemical called Chlorophyll (already in the plant) helps the plant absorb the sunlight. When the sun and carbon dioxide in the air mixes with the water from the soil, it changes the sunlight, carbon dioxide and water into oxygen and glucose. The glucose (a form of sugar) feeds the plant making it green and the oxygen is released into the air “feeding” us by helping us breathe.

In the fall, Chlorophyll starts breaking down because of shorter days (less sunlight) and colder ground (harder to travel through the roots). As photosynthesis decreases, the color of the leaves lose their green “masks” and the true color of the leaves will be seen, like orange, red and yellow and some will stay green. As the photosynthesis continues to decrease, the food supply to the leaves begin to stop and the leaves will dry and fall off the trees.

In spring, new leaves will sprout and grow as the photosynthesis process begins again.

Pine trees will stay green because they have needles instead of leaves and require much less nutrients and glucose to survive. They will stay green all year round and survive well in colder climates because of this.

Experiment #2

Color Chromatography

1. It’s important to read the instructions on this one before starting to ensure that you get a great result.
2. Cut a long rectangular strip of filter paper about 4-6”. It needs to be short enough to hang in the jar, but not too long.
3. Mark a horizontal ½” solid black line using a washable or water-soluble marker about 1” from the bottom of the paper strip.
4. Tape the paper strip to a fork, spoon, straw or pencil. It needs to hang inside the glass and be stable, but not touch the bottom.
5. Put enough water inside the glass to cover the bottom of the glass. About 1-2” of water.
6. Carefully place the taped strip across the top of the glass allowing the strip to dangle inside the glass, touching the water but not touching the bottom of the glass. We want the water to creep up to the black line. Do not submerge the line as it will dilute the line and your reaction will be much weaker visually.
7. Sit back and watch to see what happens. The changes should happen quickly and be finished in about 20-30 minutes.
8. What happened?

The Science Behind the Experiment

Chromatography is simply the separation of components of a mixture. Chromatography is used in all sorts of industries, including forensic science, food and beverage industries and even companies that investigate chemical safety.

So today, we are separating the pigments from a specific color by using a form of paper chromatography. This means the paper (filter paper) will show the component breakdown. This breakdown of pigments is called a Chromatogram. The components, in this case, the pigments, pull across the paper at different rates based on their solubility (how fast or slow they dissolve in the liquid).

The paper contains Cellulose, a compound found in trees and plants that allows its nutrients to move through its leaves. The cellulose in the paper pulls the water through the paper using Capillary action. As the water reaches the color, it begins breaking it down into its different pigments. The pigments will then separate and pull through the paper based upon each pigment’s particle make-up and solubility. The smaller and lighter the particle weight will allow the pigment will move faster and therefore farther than others. This does not mean the lighter pigments, only the lightest weight pigments.

Which color traveled the farthest for you? It’s typically cool colors such as blues, reds and pinks will move the farthest, while the yellows and orange and browns will stay closer to the original mark.

What’s Next?

Try different color markers using this same method on different types of paper. Try a paper towel, construction paper, other types of coffee filters. As long as it is a “washable” marker, you should see results. Try a primary color such as red, blue or yellow and then try a non-primary color like brown, purple or green.

What differences did you see?