The purpose of this experiment is to demonstrate that starch, a food substance, is produced in leaves.
Things Required:
Paper towels
Tincture of iodine
Leaf, pale green
Rubbing alcohol
Shallow dish
Pint (500 ml) jar with a lid
Measuring cup (250 ml)
Directions:
Place the pale green leaf in the jar. The paler the leaf, the easier it will be to extract the green pigment, chlorophyll. Pour 1 cup of alcohol into the jar. Put the lid on the jar. Allow the jar to stand for one day.
Remove the leaf and dry it by blotting with a paper towel. Lie the leaf in the shallow dish. Add enough iodine to cover the leaf.
This Is What Happens:
Dark areas appear on the leaf.
Science Behind It:
Photosynthesis is an energy-producing reaction that occurs in the leaves of plants. Starch, a food substance, is one of the products of this reaction. Soaking the leaf in alcohol removes the waxy coating on the leaf plus it partially removes the green pigment, chlorophyll. It is easier to see the results of the starch test without the presence of the green chlorophyll. Iodine combines with starch particles to form a dark purple to black colour.
