Paper Chromatography For 7th Grade Science Projects

Colors of a Leaf Experiment

Things You Will Need

• 1. Green leaf
• 2. Coffee filter
• 3. Plastic knife with blunt end
• 4. Rubbing alcohol
• 5. Small jar (baby food jar size)
• 6. Ruler

 

Do This

1. 1. Place a green leaf, topside down, on the edge of a coffee filter.

    

2. Rub the blunt end of the plastic knife firmly over the leaf in a small spot about one-half inch from the edge of the filter.
3. Move the leaf around and repeat step two until a single dark green spot forms on the filter paper.
4. Cut on either side of the green spot to form a tab in the filter. Do not cut the tab off the filter.
5. Bend and fold the tab downward.
6. Place the filter on top of the jar with the bent tab inside the jar.
7. Lift the filter and slowly pour alcohol into the jar to a depth that barely allows the bottom of the tab to touch the liquid. Be sure the alcohol level is below the green dot of the paper.
8. Let the paper sit undisturbed for at least 30 minutes.

 



What Should Have Happened

The green leaf pigment dissolves in the alcohol as the alcohol moves up the paper filter tab. The dark green pigment separates into various shades of green, yellow, and possibly orange and purple. Plants contain several color pigments that are required in the energy production reaction called photosynthesis.


The green pigment chlorophyll is the most abundant. Other pigments are also present, but in smaller quantities. Carotene pigments produce the red and yellow colors. The pigment chemicals from the leaf dissolve in the alcohol and move up the paper by a process called chromatography ("to write with color"). The heavier dissolved chemicals settle out first on the paper and the lighter dissolved chemicals rise higher on the paper. I hope you enjoyed this7th grade science projects experiment.