In an experiment, a leaf that is partly green and partly yellow is plucked from a tree and the leaf is
I boiled for a minute,
II dipped in warm alcohol,
I washed in cold water,
I dipped in iodine solution.
One part of the leaf turns blue-black after the dipping in iodine solution while the other part remains unchanged.
(i)
Explain why each of the processes I, II and III
(ii)
Which part of the leaf turns blue-black? Explain.
(iii)
Why does the other part of the leaf not change colour?
(iv)
What conclusion can you draw from the experiment?
The table below gives the steps that were followed in an experiment to test for starch in a green leaf freshly taken from a tree.
| Stages in the test for starch |
|
I. Leaf is put into boiling water for 1 minute II. Leaf is dipped in alcohol warmed in a hot water bath III. Leaf is washed in cold water IV. Leaf is dipped into iodine solution |
(i)
State the reason for carrying out each of the activities in stages I, II and III.
(ii)
What happens when the leaf is dipped in iodine solution?
(iii)
Give the colour changes of the leaf from the beginning of the experiment to the end of the experiment.
(iv)
Why is the alcohol warmed indirectly in a water bath?
(vi)
Explain what will be observed if the test is carried out on a leaf taken from a plant kept in a dark room for 1 day
In an experiment, the following activities were carried out on two green leaves A and B.
Leaf A was from a plant placed in the sunlight for sometime while leaf B was from a plant placed in a dark cupboard for 24 hours.
| Activity |
|
I. Leaves dipped in boiling water for 1 minute II. Leaves dipped in warm alcohol III. Leaves washed in cold water IV. Leaves dipped into iodine solution |
After dipping the iodine solution, it was observed that leaf A changed colour while leaf B did not change colour.
Answer the following questions:
(i)
Explain why each of the activities I, II, III and IV was carried out.
(ii)
State the colour change of leaf A.
(iii)
Explain why leaf A changed colour but leaf B did not.
(iv)
Suggest an aim for the experiment.
In an experiment, the following activities were carried out on two green leaves A and B.Leaf A was taken from a plant placed in the sunlight for some time while leaf B was taken from a plant placed in a dark cupboard for 24 hours.
Activity
I. Leaves dipped in boiling water for 1 minute;
II. Leaves dipped in warm alcohol;
III. Leaves washed in cold water;
IV. Leaves dipped in iodine solution.
After dipping in the iodine solution, it was observed that leaf A changed colour.
Study the activities carefully and answer the questions that follow.
i)
Suggest an aim for the experiment.
ii)
Explain briefly why each of the following activities were carried out:
(α) I;
(β) II;
(γ) III.
iii)
State the colour change of leaf A.
iv)
Explain why leaf A changed colour?
v)
Why is it necessary to de-starch the plant before starting the experiment?
vi)
From the above experiment, what conclusion(s) can be drawn.
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