Testing a leaf for starch. Image credit taskermilward.org.uk

Testing a leaf for starch. Image credit taskermilward.org.uk

ZIMSEC O Level Integrated Science: The test for starch

Testing for Starch.

Materials: Iodine solution, dropper, alcohol, test tube, beaker, burner, tripod, gauze, white tile, leaf which was has been in the light.

The test for starch experiment

The test for starch experiment

Method

  1. Dip the leaf in a beaker of hot water to kill and soften it.
  2. Place the leaf in boiling alcohol to remove the chlorophyll as shown above.
  3. Alcohol is highly flammable and should never be heated by a direct flame as it will catch fire. The test tube containing alcohol must be placed in a beaker of boiling water instead.
  4. Remove the leaf from the alcohol and dip it into hot water to soften it. You can use a pair of tongs to do this.
  5. Place the leaf on a white tile. The white tile offers greater colour contrast that will allow you to more easily observe any colour changes.
  6. Using a dropper, cover the leaf with iodine solution.

Results

Results of starch test. Image credit taskermilward.org.uk

Results of starch test. Image credit taskermilward.org.uk

  • If starch is present the leaf will turn blue-black as shown above.
  • If starch is absent the leaf’s colour will remain unchanged.

 

To access more topics go to the Integrated Science Notes page.