(1) The liquid in the big beaker is water, and the liquid in the small beaker is alcohol. A small beaker filled with alcohol must be heated with water. This is because alcohol is flammable and volatile, and direct heating is easy to cause the danger of burns. Use water to heat alcohol to control the temperature and avoid the danger of alcohol burning.
(2) Put the leaves in a small beaker filled with alcohol and heat them in the absence of water. The purpose is to dissolve chlorophyll in leaves with alcohol, and the leaves turn yellow and white, which is convenient for observing the color reaction of starch turning blue when it meets iodine.
(3) The purpose of dropping iodine solution into leaves is to test whether starch is produced according to the characteristics that starch turns blue when it meets iodine.
So the answer is: (1) water; Alcohol; (2) dissolving the pigment in the leaves; (3) starch.