Lab Manual: Osmosis in Raisins | Extra Documents & Tests for Class 9 PDF Download

Objective

Theory

• Imbibition: It is a special type of diffusion in which movement of water takes place due to difference in water molecule concentration between the adsorbant and the imbibant. For e.g., the dry plant part or dry seeds when placed in water increases in size or swells.
  Mass percentage of water imbibed by raisins can be calculated as:Mass % of water imbibed=
• Osmosis: When the solution of higher water concentration moves into the solution of lower water concentration through a semipermeable membrane, till the concentration on both the sides of the membrane is equal. This process is called osmosis.
• Hypotonic solution: When a cell (dry raisin) is dropped in water, the cell has a less water concentration than the medium in which it is kept. The water molecules will flow into the cell, and it will swell up or even can burst as in case of animal cells. Such a solution is called hypotonic solution. This is Endosmosis.
• Isotonic solution: If the medium has exactly the same water concentration as that of the cell, the water does not move either in or out of the cell, the size of cell remains the same. Such solution is called isotonic solution.
• Hypertonic solution: If the medium has lower concentration of water than the cell, the cell will lose water by osmosis and become smaller in size. Such a solution is called hypertonic solution. This is Exosmosis.
• Plasmolysis: When a cell loses water through osmosis and contracts, the contraction of the contents of the cells is away from the cell wall. This phenomenon is known as plasmolysis.

Materials Required

Procedure

• Take 5 dry raisins and weigh it.
• Place these raisins in a beaker containing water. Allow all the raisins.
• Next day remove all the raisins and place them on filter paper.
• Gently dry the outer surface of raisins by using filter paper.
• Weigh the raisins which are swollen.

Observations

• Weight of raisins taken = 10 g.
• Weight of swollen raisins = 13 g.

Calculations

• Weight of water absorbed by the raisins = (13- 10) = 3 g.
• The percentage of water absorbed by the raisins =

Conclusion
The percentage of water imbibed (absorbed) by raisins is 30 %.

Precautions

• Raisins should be with intact stalks, dry and clean.
• While soaking raisins in water, they should be properly immersed in water.
• Soaking should be for sufficient time.
• Before weighing, gently dry the raisins with the help of filter paper.