Studying the Impact of Solute Concentration on the Rate of Osmosis - Lab Report Example

In animal cells, when the solute concentration is equal on both sides of the membrane, there will be no movement of water molecules. Solutions with this property are said to be isotonic. Hypertonic solutions have higher solute concentrations. When an animal cell is placed in this solution the water molecules will move out of the cell, causing it to shrink. On the other hand, placing an animal cell in hypotonic solutions will cause water molecules to move into the cell, causing it to swell. This is because hypotonic solutions have lower solute concentrations (Freeman, 2010). This forms the basis for the hypothesis of the study: the weights of the dialysis tubings with different solute concentrations will change, showing that osmosis is dependent on the concentration of the solute.

Method:
Six dialysis tubings were soaked for five minutes in a beaker containing 400 ml of water to soften them. One end of every tubing was tightly tied using floss. Two of the tubings were then each filled with 10 ml of water through the untied end. These were taken to be the control tubings. Two other tubings were each filled with 10 ml of 15% sucrose solution and two others with 10 ml of 45% sucrose solution in the same way as the control tubing. The untied ends on the tubings were tied using floss and then appropriately labeled. The weight of each tubing was measured and recorded.

150 ml of water was put in six separate beakers. The six tubings were then placed separately in the six beakers at the same time. After ten minutes, the dialysis tubings were removed from the beakers and their weights were measured and recorded. They were then placed in the beakers again. This step was repeated three more times.
Results:
The weights recorded during the experiment indicated that the weights of the dialysis tubings with sucrose solutions increased as the experiment progressed as shown in the table below. The table also shows that the average weight of the control tubings changed by a small fraction.

The percentage changes in weights of the tubings as their weights increased or reduced are shown below. The results show that the tubings with 45% sucrose gained the most weight while the control tubings reduced in weight. The data in the table was used to plot the graph below. It shows visually how the weight of the dialysis tubings changes over time.

The experiment showed that as the concentration of sucrose increased, the mass of the dialysis tubings also increased. In the control tubing, the weight change was very small compared to the change in the tunings with sucrose. The beaker in which the control dialysis tubings were immersed contained an isotonic solution: there was water on both sides of the tubing. Therefore there was no great movement of water molecules. The small change (0.489 grams) in the weight of the control dialysis tubings can be attributed to possible experimental errors resulting from incorrect weight measurements or contamination.

In the dialysis tubings with sucrose solutions, the increase in weight was because the concentration of sucrose was higher in the tubings than in the surrounding water. Therefore water moved into the tubings to equalize the water potential in the two regions. This caused the dialysis tubings to swell up and increase in weight. The water in which the tubings with sucrose were placed was hypotonic; and the sucrose solutions were hypertonic (Freeman, 2010).
The tubings with 45% sucrose solutions had the highest sucrose concentration. Consequently, more water moved into them compared to the tubings with 15% sucrose solutions.

Conclusion:
The experiment successfully proved that the hypothesis was right. By studying the weights of the dialysis tubings after the experiment was over, the conclusion arrived that the rate of osmosis between two solutions separated by a selective membrane is heavily dependent on the solute concentration in the two solutions. Errors in the experiment may have arisen from the use of contaminated glassware in the preparation of the control dialysis tubings; this beaker containing the water in which the tubing was immersed may have been inadequately cleaned before the experiment began, resulting in the mixing of residual solute particles with the water once the experiment began. This can be avoided in future experiments by ensuring that the glassware used is adequately cleaned before the experiment starts. Read More