Question 10
Boohji wanted to test the presence of starch in leaves. He performed the following steps:
(i) He took a leaf and boiled it in water.
(ii) He placed the leaf in a petri dish and poured some iodine over it.
He did not get the expected result. Which step did he miss? Explain.
Question 10
Boohji wanted to test the presence of starch in leaves. He performed the following steps:
(i) He took a leaf and boiled it in water.
(ii) He placed the leaf in a petri dish and poured some iodine over it.
He did not get the expected result. Which step did he miss? Explain.
Boohji did not get the expected results of his experiment because he missed an important step in the procedure.
The correct procedure is:
(i) Take a leaf and boil it in water.
(ii) Boil the leaf in alcohol or spirit to remove chlorophyll.
(iii) Place the leaf in a petri dish and pour some iodine over it.
He did not boil the leaf in alcohol or spirit to remove chlorophyll (green colour pigment) from the leaf. It is necessary to remove chlorophyll because it interferes with the test for starch. Only the decolourised leaf turns blue-black on adding iodine, showing the presence of starch.
Boohji did not get the expected results of his experiment because he missed an important step in the procedure.
The correct procedure is:
(i) Take a leaf and boil it in water.
(ii) Boil the leaf in alcohol or spirit to remove chlorophyll.
(iii) Place the leaf in a petri dish and pour some iodine over it.
He did not boil the leaf in alcohol or spirit to remove chlorophyll (green colour pigment) from the leaf. It is necessary to remove chlorophyll because it interferes with the test for starch. Only the decolourised leaf turns blue-black on adding iodine, showing the presence of starch.
