EXPERIMENT 3 Objective. To demonstrate osmosis by potato osmometer.

                            EXPERIMENT 3

Objective. To demonstrate osmosis by potato osmometer.

REQUIREMENTS

A large potato, knife, 10-20% sugar solution, petridish, beaker, water, pins etc.

PROCEDURE

1.Peel off the outer skin of the potato. Cut one end flat and make a cavity in the centre of the potato opposite to the flat side almost upto the bottom.

2.Now place the potato on its flat cut end in a petridish half full of water.

3.Fill half of the cavity of the potato with 10-20% sugar solution, and mark the level of sugar solution in the cavity with the help of a pin. It functions as an osmometer.

4.Leave the osmometer undisturbed for about one hour and then mark the rise in the level of sugar solution in the cavity with another pin.

OBSERVATION AND RESULT

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 potato osmosis.

CONCLUSION

The movement of water from the petridish occurs because of the difference in the concentration of solvent(water) molecules in the two regions. i.e., in the sugar solution in the cavity and water in the petridish. The cell membranes enclosing the cells of potato act as selectively permeable membrane for the movement of water.

PRECAUTIONS

1.The cavity should be deep enough to keep only a thin layer of tissues at the base.

2.The lower end of the potato should be flat so as to the keep the potato stable in the petridish.

3.The sugar solution should be of sufficiently high osmotic concentration as compared to the cell sap of potato cells.