Carry out the following osmosis experiment:

Take four peeled potato halves and scoop each one out to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup into 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 2 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 porato A necessary for this experiment?

(iii) Explain why water does not gather in the hollow out portion of A and D?

(i) Water gathers in the hollowed portion of B and C because the cells of potatoes gained water by endosmosis. Since the concentration of water in surrounding medium is higher than the cell, the water moves inside the cell by osmosis. Thus, water gathers in the hollowed portions of potato cup.

(ii) Potato cup A is necessary in the experiment as a ‘control’ for providing comparison with situations created in potato cups B, C and D. No water gathers in the hollowed portion of potato A.

(iii) Water does not gather in the hollowed portion of potato cup A because it is empty. It is a control set up in the experiment. Water is not able to enter into potato cup D because potato cup D is boiled potato cup. Boiling the potato disrupts the cell membrane which loses its permeability. Because of the disrupted membrane, osmosis will not occur and hence water does not come out from within the potato cells into the hollowed portion.