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Name: _______________________________
__________________
Group: 0405/0____
_______________________________
_____/27=_______%
I.
II.
Date:
Score:
Title: Leaf Pigment Chromatography
Purpose: To distinguish and study the various pigments in plants,
from chlorophyll to carotenes, through paper chromatography.
Research question: Do green leaves contain other pigments?
Write your hypothesis in the space below.
Hypothesis:
_______________________________________________________________ (2pts)
III. Background information
Plants carry out the process of photosynthesis, during which light
energy from the sun is converted into chemical energy (food). Light
energy is captured by molecules known as pigments, which are present
within the plant cells.
What are Pigments?
Pigments are chemical compounds that can reflect only a particular range
of wavelengths of visible light. Leaves of plants primarily contain
different types of pigments within their tissues. The four different
types of pigments are listed below in a tabular column, along with their
colors.
Pigment
Color
Chlorophyll A
Dark green
Chlorophyll B
Yellowish-green
Xanthophylls
Yellow
Carotenoids
Orange
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A simple technique known as chromatography can be used to view and
distinguish the primary four plant pigments.
What is Chromatography?
It is a technique that is used to distinguish between different
molecules. This differentiation is based on these attributes: shape,
size, charge, mass, adsorption, and solubility.
Some types of
chromatography: Column chromatography, Paper chromatography, Partition
chromatography, and Thin-layer chromatography
Mechanism of Paper Chromatography
In this technique, the interaction between three components is involved – a
solid phase (paper), separation of a mixture (pigment), and a solvent
(alcohol).
1. At first, the mixture is spotted on the paper and dried.
2. The solvent is made to flow through the capillary attraction.
3. While the solvent moves through the paper, the various components
of the mixture differentiate into varied colored spots.
4. Later, the paper is allowed to dry, and the position of various
compounds is viewed.
5. The substance that is the most soluble moves further on the paper
than the other substances that are less soluble.
IV.
V.
Materials
Isopropyl alcohol
Green leaf
Chromatography paper
Coin
Beaker
Ruler
Scissors
Pencil
Tape
Colored pencils or markers
Procedure
1. Obtain a strip of chromatography paper.
2. Use a ruler to measure and draw a light pencil line 2 cm above the
bottom of the paper strip.
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3. Place a leaf on top of the chromatography paper with the waxy side
of the leaf facing outward. Now, roll a quarter over the leaf
along the light pencil line on the paper strip (about 15 times)
until you make a dark green line. (See Figure 1)
Figure 1 DO NOT RUB THE LEAF ABOVE OR BELOW THE LINE. RUB THE LEAF ON
THE LINE ONLY.
4. Tape the top of the paper strip to a pencil so that the end of the
strip with the green line hangs down. The pencil should be able to
sit across the top of the beaker, with the bottom of the paper
strip barely touching the bottom of the beaker (See Figure 2). Cut
off any excess paper from the top of the strip if it is too long.
DO NOT CUT THE BOTTOM OF THE STRIP WITH THE GREEN LINE.
Figure 2 Paper chromatography setup
5. For now, remove the pencil/paper strip from the beaker.
6. Carefully add isopropyl alcohol to the beaker until it reaches a
depth of 1 cm in the beaker.
7. Lay the pencil across the top of the beaker with the paper strip
extending into the alcohol (See Figure 3).
Figure 3
MAKE SURE THAT THE LEVEL OF THE ALCOHOL IS BELOW THE GREEN
LINE ON YOUR PAPER STRIP. IF THE ALCOHOL IS GOING TO COVER THE GREEN
LINE, POUR OUT SOME ALCOHOL BEFORE YOU GET THE GREEN LINE WET.
8. Observe as the alcohol gets absorbed and travels up the paper.
This may take up to 20 minutes. Do not touch your experiment
during this time. (See Figure 4)
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Figure 4 Paper chromatography as time progresses.
9. Using colored pencils or crayons, draw your results on Data Table
1.
10.
Using a ruler, measure the distance traveled by pigments and
solvent and write the results on Data Table 2.
VI.
Data and Observations
Data Table 1: Draw your results. (6 pts)
Filter paper
Use colored pencils to draw your observations
Before paper
chromatography
After paper
chromatography
(make sure to include
measurements of the
distance traveled by
each pigment)
Any other observation:
Data Table 2: Distance traveled by pigment. (5pts)
Color of Pigment
Chlorophyll A
Distance traveled (mm)
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Chlorophyll B
Carotenoids
Xanthophylls
Distance traveled by solvent: _______ mm
VII. Conclusions
1. CLAIM: Did the leaf you tested contain different pigments? (2 pts)
________________________________________________________________________
________________________________________________________________________
______________________________
2. EVIDENCE: Refer to your results to support your answer. (3 pts)
a. __________________________________________________________________
__________________________________________________________________
__________________________
b. __________________________________________________________________
__________________________________________________________________
__________________________
c. __________________________________________________________________
__________________________________________________________________
__________________________
3. Why is paper chromatography an appropriate technique to determine
if different pigments are present in a leaf? (2 pts)
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
_____________________________________________
4. How does paper chromatography work? (2 pts)
________________________________________________________________________
________________________________________________________________________
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________________________________________________________________________
_____________________________________________
5. REASONING: Based on what you have learned, explain why leaves tend
to change color in the fall. (2 pts)
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
_____________________________________________
6. Research: Leaves in New England change color in the fall. However,
leaves in Puerto Rico do not change color in the fall. Why is this
so? (Hint: Think of a difference between the two locations that
might act as a trigger for leaves to change color in the fall.) (3
pts)
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
____________________________________________________________
References
Biology Junction. (n.d.). Chromatography lab. Retrieved from
https://biologyjunction.com/chromatography-lab/
BYJU'S. (n.d.). Separation of plant pigments through paper chromatography. Retrieved
from https://byjus.com/biology/separation-of-plant-pigments-through-paperchromatography/
Druce. (n.d.). Paper chromatography of a spinach leaf lab. SlideServe. Retrieved from
https://www.slideserve.com/druce/paper-chromatography-of-a-spinach-leaf-lab
Experiment Archive. (n.d.). Leaf pigments chromatography. Retrieved from
https://www.experimentarchive.com/experiments/leaf-pigments-chromatography/
KeyStageWiki. (n.d.). Chromatography. Retrieved from
https://keystagewiki.com/index.php/Chromatography
Royal Society of Chemistry. (n.d.). Leaf chromatography. Retrieved from
https://edu.rsc.org/experiments/leaf-chromatography/389.article
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