Diffusion Experiment Essay

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 15cm 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 10ml 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 to from table 1.3

Table 1.2 shows changes in mass of the dialysis tubing with water solution after being dipped in distilled water

Solution

Initial Mass (grams)

Final Mass (grams)

% change of mass

Distilled water

10.3

10.3

0

Table 1.3 shows the changes in mass of the dialysis tubing with different solutions after being dipped in distilled water

Solution

Initial mass (grams)

Final mass (grams)

% change of mass

Sucrose

11.8

13.8

16.95

Glucose

10.4

11.5

10.58

Albumin

10.0

10.2

5.5

Sodium Chloride

10.8

11.4

2

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

What environmental factors affect diffusion?

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. Another environmental factor that affects the rate of diffusion is pressure. As the pressure increases, it upsurges the kinetic energy of the molecules, which in return increases the rate of diffusion.

Will water move into or out of a plant cell if the cell has a higher water potential than the surrounding environment?

When concentration of water molecules inside the plant cell has a higher water potential than the surrounding environment, water molecules will move out of the plant cells (Where they are highly concentrated), to the immediate environment (where water molecules are lowly concentrated).

How would you test for the diffusion of glucose?

 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.

Which pairs that you tested did not have a change in weight? How can you explain this?

There was no change in the mass in mass of the 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.

Based on your observations, can you predict the direction of diffusion in living cells when the cells are placed in various solutions?

When living cells are placed in sodium chloride solution (hypertonic), the water molecules inside the cell will move from it and bond with the solution. However, when the living cells are placed in distilled water solution (isotonic), there will be no diffusion since the concentration gradient will be the same. When the living cells are placed in albumin solution (hypertonic), the water molecules inside the plant cell will move from it and bond with the solution. Also, when living cells are placed inside a sucrose solution (hypertonic), the water molecules will move from the cell into the solution. Finally, when the living cells are placed inside the glucose solution, the water molecules will diffuse from the cells into the glucose solution.

An Illustration Diagram on What Happens to a Living Cell (plant cell) When Placed in Hypertonic Solutions

Diagram I