Question

Megha wanted to test the presence of starch in leaves. She performed the following steps:

Answer 1

Answer:

1 heat a plant leaf in boiling water for 30 seconds (this kills the leaf, stopping any chemical reactions)

2 add the leaf to boiling ethanol in a water bath for a few minutes (the boiling ethanol dissolves the chlorophyll and removes the green colour from the leaf - it turns white so it is easy to see the change in colour)

3 wash with water to rehydrate and soften the leaf and spread onto a white tile

4 add iodine solution from a dropping pipette

After a few minutes, the parts of the leaf that contain starch turn the iodine from brown to blue/black.