Design

Research Question (Aim):

The aim of this lab was to determine the point of incipient plasmolysis of onion (Allium cepa) cells using Sodium Chloride (NaCl) concentrations of 0.1M, 0.2M, 0.3M, 0.4M, 0.5M, 0.6M.

Hypothesis:

When the water concentration of a solution outside the cell is lower than the concentration inside the cell, water will move from the inside to the outside of the cell due to osmosis. As we increase the concentration of the NaCl solutions we have used (0.1M to 0.6M), more moles of NaCl are dissolved in the solution. Thus, the solutions increases in solute concentration but decreases in water concentration. We can therefore assume; the higher the concentration of the NaCl solution, the higher the number of plasmolysed cells as water moves outside the cell in order to dilute the NaCl concentration.

Data Collection and Processing

Table 1:

The number of plasmolysed onion cells (out of 30) ±1 for each of the 6 NaCl concentrations (0.1M, 0.2M, 0.3M, 0.4M, 0.5M, 0.6M) for three trials

|Concentration (in M) |Trial 1 (Number of Plasmolysed |Trial 2 (Number of Plasmolysed |Trial 3 (Number of Plasmolysed | | |Cells ±1) |Cells ±1) |Cells ±1) | |0. 1 |0 out of 30 |0 out of 30 |0 out of 30 | |0. 2 |2 out of 30 |0 out of 30 |0 out of 30 | |0. 3 |6 out of 30 |4 out of 30 |3 out of 30 | |0. 4 |6 out of 30 |12 out of 30 |13 out of 30 | |0. 5 |6 out of 30 |16 out of 30 |19 out of 30 | |0. 6 |6 out of 30 |30 out of 30 |30 out of 30 |

Qualitative Data:

In general, it was hard to keep an overview of the cells one has counted yet and one has not as one only counted the cells at random. To this, it was hard to determine visually whether a cell was plasmolysed or not so that one could have assumed some cells to be plasmolysed although they were not. Finally, as the results of our first trial show, we did not allow enough time for the cells to plasmolyse so that the results became inaccurate.

Table 2:

The percentage of plasmolysed onion cells ±3.33% for all of the six solute concentration (0.1M, 0.2M, 0.3M, 0.4M, 0.5M, 0.6M) for three trials, including the average percentage of plasmolysed cells for the second and third trial only*, as well as for all three trials together

|Concentration (in M) |Trial 1 (Percentage of |Trial 2 (Percentage of |Trial 3 (Percentage of |Average Percentage of |Average Percentage of | | |Plasmolysed Cells |Plasmolysed Cells |Plasmolysed Cells |Plasmolysed Cells for |Plasmolysed Cells for | | |±3.33%) |±3.33%) |±3.33%) |second and third trial |all three trials ±3.33%| | | | | |±3.33% | | |0. 1 |0. 00% |0. 00% |0. 00% |0. 00% |0. 00% | |0. 2 |6. 67% |0. 00% |0. 00% |2. 22% |0. 00%...