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by Procheta Mallik

Introduction

Leaves are supposed to produce energy (food!). Here we test that theory by performing the starch test on it!

    • Alcohol is volatile, so make sure that the container it is in is closed if not using

    • Also, make sure the alcohol is not exposed to a naked flame

    • Be careful while boiling water and alcohol

    • Handle breakable materials like the test tube with care

  1. Boil about 500ml of water in a utensil
    • Boil about 500ml of water in a utensil

    • Pluck any leaf from a tree/plant and place it in the boiling water

    • Let the leaf boil for 3 mins

    • Take 5 ml of alcohol in a test tube

    • Put the leaf in the test tube and dip the test tube in the boiling water

    • Hold the test tube till the alcohol boils

    • The alcohol will slowly turn green as the chlorophyll in the leaf dissolves in the alcohol

    • Keep shaking the test tube till the liquid gets darker and the leaf turns pale

    • Take the leaf from the test tube with a tong and put it in the hot water and wait for 2 minutes

    • Remove the leaf from the water with a tong and put 2 drops of iodine solution on the leaf and leave it for 2 minutes

    • The leaf should turn a deep blue, confirming a positive test for starch!

    • Why is it necessary to boil the leaf in alcohol?

    • Why does chlorophyll have to be removed before performing the starch test?

    • Do all leaves respond the same way for the starch test? Try the same experiment with leaves from different plants, or of different age/colour

    • The alcohol should be of good quality and high concentration

    • It is possible that up to 10 minutes are required to adequately remove the chlorophyll from the leaf while it is boiling in the alcohol

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