Question

Why is the leaf boiled in alcohol before the test for starch in iodine solution??

Answer 1

The hot water kills the leaf and
disrupts/destroy the cell membranes and softens the cuticle and cell walls.
The alcohol breaks down the chlorophyll, taking the green color out of the leaf. When you put iodine on the leaves, one of them will turn blue-black and the other will be a reddish-brown. Iodine is an indicator that turns blue-black in the presence of starch.