Name ____________________________________________________________
Lab.Leaf Chromatography.2015
Activity Title: Why Do Leaves Change Color in Autumn?
Goal: To observe and describe the various pigments in
plants “masked” by chlorophyll by using paper
chromatography to separate the them.
Background Information: Leaves are nature's food factories. Plants take water from
the ground through their roots. They 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. Plants use glucose as food for energy and as a building block for growing. The
way plants turn water and carbon dioxide into sugar is called photosynthesis. That
means "putting together with light." A chemical called chlorophyll helps make
photosynthesis happen. Chlorophyll is what gives plants their green color.
As summer ends and autumn comes, the days get shorter and shorter. This is how the
trees "know" to begin getting ready for winter.
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 begin to shut down their foodmaking factories. 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 they
are covered up by the green chlorophyll.
The bright reds and purples we see in leaves are made mostly in the fall. In some trees,
like maples, glucose is trapped in the leaves after photosynthesis stops. Sunlight and
the cool nights of autumn turn this glucose into a red color. The brown color of trees like
oaks is made from wastes left in the leaves.
It is the combination of all these things that make the beautiful colors we enjoy in the
fall.
Paper chromatography is a process that uses a solvent like alcohol to pass through a
paper strip so that various pigments can be separated from a mixture. In this activity, we
want to separate the pigments that make up the green material found in plants.
Materials: rubbing/isopropyl alcohol, green leaves, coffee filter paper (paper
chromatography strips), thin straws, a penny, marker, tall clear plastic cups,
Procedure:
1. What I Know: Write two sentences describing what you know about why
leaves change color in autumn.
2. Write your name and period on a clear plastic cup using a marker.
3. Place a leaf on the filter paper strip about one half inch from the bottom. Rub
the edge of the penny back and forth over the leaf so that the green material
from inside the leaf is transferred onto the filter paper.
4. Wrap the edge of the filter paper without the green mark onto the middle of a
straw and hang it in the plastic cup.
5. Adjust the length of the filter strip so the edge with the green mark just
touches the bottom of the cup and the straw rests on the edge of the cup.
6. Pour enough alcohol in the bottom of the cup so that the filter paper touches
the alcohol, but the green mark is not dipping into the alcohol.
7. Leave the set-up for this activity undisturbed overnight.
8. What I Observed: Draw your set-up from Day 1. Label all parts of the setup. The next day remove the strip from the cup and allow it to dry. Draw the
paper chromatography strip from your Day 2 observations. Label the
pigments you observe. Write a caption that describes your observations.
a. Make a drawing of your set-up from Day 1. Label all parts of the setup.
b. Make a drawing of the paper chromatography strip from Day 2. Label
the pigments you can observe
9. Questions: Answer the following questions in complete statements.
a. What colors did you find on the filter paper strip after it was soaked in
the alcohol?
b. What purpose do you think the alcohol served in this experiment?
c. These colors are only visible in the Fall. Why can’t you see these
colors during the spring and summer months?
d. Why do the leaves of some trees and shrubs turn other colors in the
Fall?
10. What I Wonder: Pose a why or how question that you may have concerning
this topic.
How (is; did; can; would; will; might)
Why (is; did; can; would; will; might)
Question:
11. What I Learned: Complete the following writing prompts to explain what you
learned from completing this investigation. Use your CER Rubric to guide
your writing.
Goal: State the goal of this
lesson.
Claim: Describe what you
learned from this
investigation and be sure it
relates to the goal of the
lesson.
Evidence: Provide
evidence from the
investigation to support
your claim.
Reasoning/Explanation:
Explain the science that
supports your claim and
evidence.
Conclusion:
Reword the claim:
Make a connection to self,
text or world.