Question

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 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.

Answer 1

(i) Water accumulates in the hollowed portions of B and C as a difference in the water concentration is observed. Thereby, endosmosis occurs as the cells act as a semipermeable membrane.

(ii) Potato A is essential in this experiment as it is significant to compare different scenarios seen in potato cups B, C and D. The potato A in this experiment clearly shows that the potato cavity on its own cannot bring about water movement.

(iii) Cup in A does not show any change in the water flow concentration for osmosis to occur, which requires the concentration to be higher than the other. Cells in cup D are dead, thus there is no existence of a semipermeable membrane for water flow. Consequently, osmosis does not occur.