Login

An experiment to test the presense of starch in green leaves.

You will need : A green leaf ,test tube , beaker, dropper, water, alcohol, bunsen burner, and iodine solution. 

What to do :

 1. Take a green  leaf and put it in boiling water for about 3 minutes to soften it. This will destarch the leaf.

  2. Take some alcohol in a test tube and heat it by placing it in hot water. Make sure that you do not heat  the alcohol directly  as it will cath fire.

  3. Now put the leaf in the alcohol to remove the green colour.

  4. Take the leaf and drop iodine on it using a dropper.

  What will happens: The leaf turns black.

  You Have learnt : Iodine turns staech blue black. The change in colours shows the presence f starch in green leaves. 

 

  • 2
View Full Answer

APPARATUS/MATERIALS :

 

 

  • bunsen burner, tripod stand, wire gauze (OR 90oC electric water bath OR hot plate)
  • 250 cm3 beaker
  • boiling tube
  • anti- bumping granules
  • forceps
  • test tube holder-white tile
  • leaf to be tested (hibiscus leaves are excellent)
  • 90% ethanol
  • iodine/potassium iodide solution

  1. Remove a green leaf fom a plant that has been exposed to sunlight for a few hours
  2. Half-fill a 250cm3 beaker with water. Heat the water until it boils. Keep the water at boiling point.
  3. Use the forceps to place the leaf in the boiling water. Boil for 2 minutes.
  4. Turn off the Bunsen Burner. (If you are using a heat source without a naked flame - electric water bath or hot plate - this step is uneccesary.)
  5. Place the boiled leaf in a boiling tube containing 90% ethanol.
  6. Place the boiling tube in hot water and boil for 10 minutes or until the leaf decolourizes. ( It may be necessary to replace the ethanol)
  7. Gently remove the leaf and wash with a fine trickle of cold tap water.
  8. Spead the leaf evenly on a white tile.
  9. Add a few frops of iodne/potassium iodide solution to the leaf and note any observations.

OBSERVATIONS/RESULTS:

 

  • The leaf was flaccid (soft) after being boiled in water

     

     

  • The ethanol changed from colourless to green

     

     

  • The leaf was brittle after being boiled in ethanol

     

     

  • The leaf become flaccid once more after being rinsed in cold water

  1.  

  • 1

Take a leaf of a plant that has been exposed from sunlight for several hours. Boil it at least five minutes in water to soften it. Put in it a test tube in a with alcohol. Put test tube in a beaker of water. Now warm the water gently until the alcohol begins to boil. Mind water in the beaker should not be boil. The clorophyll will get dissolve into the alcohol and the leaf will lose its green colour.

Remove the alcohol from the leaf by washing it in warm water. Now spread the leaf on a dish and cover it with iodine solution. Take out leaf from iodine. Now wash it with water hold it up against light. A blue black colour will be seen if starch is present in it.

thumbs up please

  • 0

 take 2-3 drops of iodine solution and put it on a leave observe after some time leave indicates blue-black colour

  • 0

iodine test

  • 0
What are you looking for?