Diffusion Osmosis Lab Part 1B

Part 1B:

Introduction / Purpose:

The purpose of this experiment was to explore the relationship between the solute concentration and the passage of water through a selectively permeable membrane by the natural process of osmosis. The solute concentration may be isotonic, hypotonic, or hypertonic. Isotonic solutions will have the same amount of solute concentration. There will be no net change in the amount of water in each solution. The two solutions are said to be hypertonic if there is more solute concentration inside of the cell than there is outside. A solution is said to be hypotonic when there is less solute concentration inside of the cell. For this experiment, a hypertonic solution was placed in a dialysis tubing bag and let to sit in a hypotonic solution for 30 minutes.

Procedure:

1.  Obtain six 30-cm strips of presoaked in water dialysis tubing.

2. Tie a knot in one end of each piece of dialysis tubing to form 6 bags. Pour approximately 15-25 mL of each of the following solutions into separate bags; (distilled water, 0.2M sucrose, 0.4M sucrose, 0.6M sucrose, 0.8M sucrose, 1.0M sucrose) Leave sufficient space for the expansion of the contents in the bag.

3. Rinse each bag gently with distilled water to remove any sucrose spilled during the filling.

4. Carefully blot the outside of each bag and record in Table 1.2 the initial mass of each bag, expressed in grams.

5. Place each bag in an empty 250-mL cup and label the beaker to indicate the molarity of the solution in the dialysis bag.

6. Now fill each beaker two-thirds full with distilled water. Be sure to completely submerge each bag.

7. Let them stand for 30 minutes.

8. At the end of 30 minutes remove the bags from the water. Carefully blot and determine the mass of each bag.

9. Record your group's data in Table 1.2 and fill Graph 1.1.

Conclusion/Analysis:

From the experiment, it is possible to conclude that when the bags were placed in a hypotonic solution, meaning that the solute concentration inside of the bag was greater than the solute concentration outside of the bag, the bags’ masses increased, as shown in Table 1.2. This may be due to water moving to the inside of the cell due to diffusion, water’s tendency to move from areas of high concentration to areas of low concentration. In the case of hypotonic solutions, water must rush into the bag since there is an increasingly less amount of water in each bag as the molarity increases. This would explain why bags with a higher molarity would experience a greater change in their mass, as noted in Table 1.2. Our graph may be skewed, however, due to human error, whether it be in performing the procedure or doing the calculations.