Rate of Diffusion of Different Solutions

The lab report will describe the rate of diffusion of different solutions used in the experiment conducted by five groups using different solutions of distilled water, aluminum solution, glucose, sodium chloride and sucrose. Diffusion is the process, through which molecules or particles move from region of high concentration to the region low concentration. The hypothesis of the experiments was that the all the solutions were hypertonic, except distilled water, which is isotonic.

Material Used

The following list of materials was used in the experiments: dialysis tubing, beaker, sucrose, albumin, sodium chloride, glucose, distilled water, clips, beam balance, and test strips.

Procedures

Five 15 cm strips of presoaked dialysis tubing were obtained. A knot was tied in one end of each piece of the tubing to form five bags. Then, approximately 10 ml of glucose, distilled water, albumin, sucrose and sodium chloride solutions were poured into separate dialysis bags. The bags were then rinsed gently with distilled water in order to remove traces of solution that might have spilled during the refilling process. The outside of each bag was then carefully blotted and then the mass of each bag was measured and recorded. Each bag was then placed in an empty beaker and then labeled in order to indicate the solution in the dialysis bag. Each beaker was then 2/3 filled with distilled water and then the bags were completely submerged in the solution. The submerged bags were then left to stand for half an hour. At the end of the thirty minutes, the bags were removed from the water, carefully blotted and then the mass of each bag was measured. The percentage change in weight was then determined using the formula below:

% change in mass =

The group data was then recorded in Table 1.2 and then the data was obtained from other groups.

Data/Results

Sources of Errors

The sources of errors during the experiment could have been then rounding off of the different masses. The second error that could have risen was the fact that during the process of removing the bags, there was possible delaying, which could have affected the masses.

Discussion/Conclusion

One of the environmental factors that affect the rate of diffusion is the temperature. The rate of diffusion increases with an increase in temperature due to the fact that it raises the kinetic energy of the molecules. Diffusion is exhibited when plant cells with higher water potential release it to the surrounding where the concentration is relatively low. In order to determine whether glucose solution has crossed the dialysis membrane, a glucose test strip will be used after the tubing has been placed in water for a while. The presence of diffusion of glucose particles will be positive if the test strip turns green within one minute after being dipped into the water from the beaker.

There was no change in the mass in the beaker that was dipped with dialysis tubing that had distilled water. Since the two solutions were isotonic to each, the movement of water molecules across the semipermeable membrane did not cause any change in the concentration of the water particles on either side. The two solutions are said to be isotonic to each other since they have the same osmotic pressure across the dialysis tubing. The cells from the plant move to the solution due to the fact that their concentration is low compared to the high concentration of the solution (see Fig.1).

Fig. 1. What happens to plant cells when placed in hypertonic solutions