Variables and Fair Testing:
The control variables are kept constant to ensure a fair test. I will also use a pure water solution as a control in this experiment.
- 5 beakers of 500ml
- Electronic scale to 2 d.p.
- Distilled water
- Cutting board
- Paper towel
- Cut potato into strips by borer to 3.0cm long. Prepare 25 of them.
- Prepare 5 different concentration of salt solutions with NaCl and 50ml of distilled water each in the beakers and label them as below:
Table 1 - NaCl-H2O Dilutions
- Repeat Step 4. for 1.00M, 2.00M, 3.00M and 4.00M concentration solutions with 5 strips each.
- After 24 hours, place the potato strips again on the scale and work out the percentage change.
Table 2- Raw Data Table – Mass of Potato Strips – Pre- & Post-Experiment
Qualitative Data - Before Experiment
The potato strips are generally rigid in structure.
All the potato strips appear similar
Qualitative Data - After Experiment
All the potato strips have shrunken in size and have reduced lengths.
Strips immersed in 4.00M NaCl solution have become very soft and soggy.
The data I collected from the experiment is shown below where it shows the percentage change in mass of the potato strips after they are immersed in different concentration of salt solutions.
Table 3 - Processed Data Table – Difference between % Change in Mass and Average % Change in different concentration of salt solutions
Graph 1- The above average and standard deviation are plotted in the graph below to show the relationship to the percentage change in the mass of potato strips.
In conclusion, the results indicate that the concentration of salt solution have a correlation with the percentage change in mass. Graph 1 supports this theory.
The higher the concentration of salt solution, the larger the percentage change in mass of potato strips. (The y-xis is in negative figures).
The results for my control experiment did not turn out as I predicted. Instead of swollen, the strips also shrank after 24 hours in distilled water.