Question

Why do we boil the leaf in alchohol when we are testing it for starch

Answer 1

When we boil the leaf in alcohal, the leaf gets killed under heat and the alcohal breaks down the chlorophyll taking the green colour out of the leaf.

Since the presence of starch can only be deduced by iodine, we place this leaf in the iodine solution. If the leaf turns blue black it is indicative of the presence of starch and if it turns reddish brown it means that the leaf does not have starch.