How will you test leaf for starch and precautions you will take?
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Hey friend ^_^
Here is your answer:
Test to check for starch in a leaf :-
• Pour some boiling water into a large beaker.
• Using forceps, pick up the leaf and hold it in the hot water for about one minute.
• Using forceps, remove the leaf from the boiling water and note how it has changed.
• Drop the leaf into a boiling tube and push it to the bottom with a glass rod. Label this tube with your initials if you will be placing it in a hot water bath. Put on your eye protection.
• Add enough ethanol to cover the leaf, and stand the boiling tube in your beaker of hot water, or in the hot water bath.
• Watch as the ethanol boils and the green colouring (chlorophyll) is removed from the leaf. This will take a few minutes.
• Replace the hot water with freshly-boiled water from the kettle after 5 minutes if there is still some green colour in the leaf.
• Using forceps, remove the leaf from the boiling tube and rinse the leaf in cold water.
• Put the leaf in a Petri dish.
• Add iodine solution to the leaf from the dropper bottle. Make sure the leaf is completely covered with iodine.
• Watch for a few minutes to see if a blue-black colour develops in any part of the leaf. A blue-black colour with iodine solution indicates that starch is present.
Precautions to be taken :-
• Ensure the ethanol is kept away from naked flames.
• Wear eye protection when working with ethanol or iodine solution.
• Take care with hot liquids.
• Be aware that plant sap may irritate the skin. Wash your hands to remove any traces of plant sap, or the chemicals that you have used.
Hope it helps u.
Here is your answer:
Test to check for starch in a leaf :-
• Pour some boiling water into a large beaker.
• Using forceps, pick up the leaf and hold it in the hot water for about one minute.
• Using forceps, remove the leaf from the boiling water and note how it has changed.
• Drop the leaf into a boiling tube and push it to the bottom with a glass rod. Label this tube with your initials if you will be placing it in a hot water bath. Put on your eye protection.
• Add enough ethanol to cover the leaf, and stand the boiling tube in your beaker of hot water, or in the hot water bath.
• Watch as the ethanol boils and the green colouring (chlorophyll) is removed from the leaf. This will take a few minutes.
• Replace the hot water with freshly-boiled water from the kettle after 5 minutes if there is still some green colour in the leaf.
• Using forceps, remove the leaf from the boiling tube and rinse the leaf in cold water.
• Put the leaf in a Petri dish.
• Add iodine solution to the leaf from the dropper bottle. Make sure the leaf is completely covered with iodine.
• Watch for a few minutes to see if a blue-black colour develops in any part of the leaf. A blue-black colour with iodine solution indicates that starch is present.
Precautions to be taken :-
• Ensure the ethanol is kept away from naked flames.
• Wear eye protection when working with ethanol or iodine solution.
• Take care with hot liquids.
• Be aware that plant sap may irritate the skin. Wash your hands to remove any traces of plant sap, or the chemicals that you have used.
Hope it helps u.
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