Purpose : to separate and identify colour pigments in leaves.
Things Required:
Alcohol green leaf
Coffee filter
Pencil
Baby food jar
Ruler
Directions:
Place the leaf, top side down, on the edge of the coffee filter. Rub the pencil lead back and forth ten times over the leaf about one half inch (13 mm) from the edge of the paper. Rotate the leaf and repeat step two. Continue moving and marking on the leaf until a single dark green spot forms on the filter paper.
Cut a one-half inch (13 mm) strip to the centre of the filter. Bend the strip down to form a tab. Place the filter on top of the jar with the bent tab inside the jar. Lift the filter and slowly pour alcohol into the jar to a depth that allows the bottom of the paper tab to touch the liquid.
Important: Be sure the alcohol level is below the green dot on the paper. Allow the paper to sit undisturbed for 30 minutes.
This Is What Happens:
The alcohol starts to move up the paper tab, and the green dot dissolves in it. As the green alcohol solution climbs up the paper, the green colour stops and a yellow streak forms.
Science Behind It:
Plants contain several colour pigments that are necessary in the energy production reaction called photosynthesis. The green pigment is the most abundant, causing most plant leaves to appear green in colour. Another pigment is present, but in smaller quantities. It is called carotenoid and ranges in colour from red to yellow. Carotenoid is responsible for the colour of fruits and flowers. The beautiful colours of autumn leaves are due to the fact that chlorophyll stops being formed first, leaving carotenoid to display its colours.
Living things are composed of many different chemicals. You have just used the process called paper chromatography to separate and observe two of the many. Chromatography means “to write with colour”. The chemicals dissolve in the alcohol and move up the paper. The heavier material settles out first allowing the separation of the lighter substances from the heavier ones.