Question

Carry out the following osmosis experiment:

Take four peeled potato halves and scoos 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

NCERT Class IX
Sciences - Exemplar Problems

Chapter 5. The Fundamental Unit of Life

Answer 1

(i)Water gathers in B and C because of exosmosis in the cells of the peeled potato as the sugar with water is more concentrate.
(ii)To demonstrate that no osmosis takes place in the absence of a more concentrate solution as A is empty
(iii)As the process of osmosis is not carried out in these cups.

Answer 2

Answer:

Osmosis is the process responsible for the gathering of water

in the hollowed portion of B and C. Since, the concentration of solute

(sugar in cup Band salt in cup C) is higher inside the cup as compared to

the water, which is outside the cup. Hence, water from its higher

concentration (outside the cup) will move towards the lower

concentration (inside the cup). This process of osmosis (moving in of

solvent) is called endosmosis.

(ii) Potato A acts as a control for the experiment. This is required for

comparing the results of the experiment.

(iii) Water does not gather in the hollowed out portions of A and D because of the following reasons

The hollowed portion of potato A is empty. So, because of no

concentration difference, no osmosis can occur.

• The hollowed portion of potato D contains sugar in it but it is boiled.

So, osmosis cannot occur as its semipermeable membrane is destroyed

by boiling.