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Carry out the following osmosis experiment: Take four peeled ... - Science
Carry out the following osmosis experiment:
Take four peeled potato halves and scoops each one out to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup in a trough containing 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 the boiled potato cup D.
Keep these for two hours. Then observe the four potato cups and answer the following:
(i) Explain why water gathers in the hollowed portion of B and C.
(ii) Why is potato A necessary for this experiment?
(iii) Explain why water does not gather in the hollowed out portions of A and D.
(i) Water gathers in the hollowed portions of B and C due to osmosis. The concentration of water is higher in the trough than inside the potato cups containing sugar and salt. Therefore, water moves from the outside to the inside through the semi-permeable membrane of the potato cells.
(ii) Potato A acts as a control experiment. It is necessary to compare the results with the other cups and to prove that water does not enter the potato cup merely because it is hollow, but requires a solute (sugar/salt) to trigger osmosis.
(iii) Water does not gather in A because there is no solute (sugar or salt) inside it, so there is no concentration gradient to cause water movement.
Water does not gather in D because the potato was boiled. Boiling kills the cells and destroys the semi-permeable nature of the cell membrane, which is required for osmosis to take place.
