Q- Carry out the following osmosis experiment.
Take four potato halves and hollow out potatoes to make potato cups, on potato cup should be made out of boiled potato; put each potato cup in a trough containing water in such a way that the portion without peel is in contact with water:
Now,
(a) Keep cup A empty
(b) Put one teaspoon sugar in cup B
(c) Put one teaspoon salt in cup C
(d) Put one teaspoon sugar in boiled potato cup D
Keep these for two hours. Observe the four potato cups and answer the following:
(i) Explain in detail why water gathers in the hollowed portion of potato B and C.
(ii) Why is potato A necessary in this experiment.
(iii) Explain why water does not gather in the hollowed out portions of A and D.
Answer- (i) In potato cup B and C the water moves in the hollowed portions due to endosmosis as both B and C consists of hypertonic sugar and salt solutions.
(ii) Potato A as control experiment to confirm that water moves on the principle of osmosis.
(iii) Water does not gather in the hollowed out portions of A and D because hollowed portions of A does not contain any sugar or salt solution while the cells of potato cup D are killed when it is boiled so osmosis does not occur.