Study of Osmosis – MeitY OLabs
Study of Osmosis Osmosis is the process by which fluids move from a region of higher concentration to a region of lower concentration through a semi-permeable membrane. Osmosis occurs due to the free energy of the solvent molecule in two regions. The
free energy of the solvent or pure water is greater as compared to that present in the
solution. So, when osmosis occurs, the solvent moves from a region of its high free energy
to a region of its low free energy through a semi-permeable membrane. To do experiment we require: A large potato without peel, knife, 20 % sugar
solution, Petri dish, distilled water, pins and a tile. Procedure: Take a potato from the watch glass and place
it on the tile. Take a knife and cut both ends of the potato
to make it flat. Using the knife, make a cavity in the centre
of the potato from the flat side almost up to the bottom.
Take a beaker containing distilled water and pour the Petri dish half full of distilled
water. Now, place the potato on the Petri dish that
is half full of water. Take the beaker containing sugar solution
and fill half of the cavity of the potato with 20% sugar solution. Mark the level of sugar solution in the cavity with the help of a pin.
The potato now functions as an osmometer. Leave the osmometer undisturbed for about
two hours. Mark the rise in the level of sugar solution
in the cavity with another pin. Observation: The level of sugar solution in the potato
cavity rises after some time due to the entry of water into the sugar solution through selectively
permeable membrane of the cells of the potato. Conclusion: The movement of water from the Petri dish
to the potato cavity occurs because of the difference in the concentration of solvent
molecules in the two regions: sugar solution in the potato cavity and pure water in the
Petri dish. Precautions: The cavity should be deep enough to keep only
a thin layer of tissues at the base of the potato.
The sugar solution should be of sufficiently high osmotic concentration as compared to
the cell sap of potato cells.