ZIMSEC O Level Combined 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.
- Dip the leaf in a beaker of hot water to kill and soften it.
- Place the leaf in boiling alcohol to remove the chlorophyll as shown above.
- 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.
- 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.
- 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.
- Using a dropper, cover the leaf with iodine solution.
- 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 Combined Science Notes page.