Fair testing
Firstly, we are using six discs in each measuring beaker. This is because, when cutting up the potato cylinder into 0.5cm discs we are making sure that the surface area of 1 potato disc will measure out the surface area of another.
Then, we are going to leave them for 24 hours. This is to make sure that all the Osmosis that is going to happen will happen. Also they will be kept in the same place so that the temperature will alwayz be the same at every point of the 24 hours.
Thirdly, we are going to cover them with cling film so that the water will not evaporate.
Finally, we are going to towel off the discs before and after the experiments. This is so that all the excess moisture will be removed and we can get a more accurate mass for the discs.
Preliminary Work
Equipment list
Potato
Core Borer
5% sucrose solution
10% sucrose solution
15% sucrose solution
20% sucrose solution
Scalpel
Ruler
4 boiling tubes
White tile
Measuring cylinder
Method
- Bore the potato with the Core Borer
- Cut the potato into twenty four 0.5cm discs
- Towel the discs off to remove excess moisture.
- Weigh the discs
- Put six of the discs into each of the boling tubes.
- Measure 100cm³ of each of the concentrations of sucrose solutions into the boiling tubes.
- Cover them with cling film and then leave for twenty-four hours.
- Weigh them again
- Towel the discs off again to remove excess moisture.
Results
From this experiment I decided to use 5% solution for my main experiment.
Main work
Equipment list
Potato
Core Borer
5% sucrose solution
Scalpel
Ruler
5 boiling tubes
White tile
Measuring cylinder
Method
- Bore the potato with the Core Borer
- Cut the potato into thirty 0.5cm discs
- Towel the discs off to remove excess moisture.
- Weigh the discs
- Put six of the discs into each of the boling tubes.
- Measure 100cm³ of sucrose solutions into a boiling tube.
- Measure 80cm³ of the sucrose solution and 20cm³ of water in to one of the boiling tubes.
- Do the same for 60cm³ sucrose and 40cm³ water, 40cm³ sucrose and 60cm³ water and 20cm³ sucrose and 80cm³ water
- Cover them with cling film and then leave for twenty-four hours.
- Weigh them again
- Towel the discs off again to remove excess moisture.
Conclusion
At 20% sucrose concentration, the most dilute solution, the percentage mass change was 18.37, compared to the higher concentration of 100% sucrose concentration where the percentage mass change was 7.43. This represents a difference in mass of 10.94.
Evaluation
There were 3 out of 5 anomalies and the 40% sucrose solution point did not fit the expected pattern.
We tried to overcome the problem of anomalies by leaving the discs for 24 hours and the same environment to eliminate the problem of temperature, we used 6 discs and left it for 24 hours to eliminate the problem of incorrect surface area, we stopped water from evaporating by covering each boiling tube with cling film, and we towelled off the discs to remove excess moisture.
However, to eliminate the anomalies completely, we could have used a papet instead of a measuring cylinder because the measuring cylinder is not always accurate. Also we can’t be sure that all the osmosis that could have happened did happen. We could have eliminated this problem by weighing it in trials after every hour until the mass did not change. Finally, we might have destroyed the membrane while preparing the potato and to eliminate this problem we would do an experiment with visking tubing which would involve putting water into a testube and sugar solution into the visking tubing and then leave it for 24 hours.
The results I obtained lend some evidence to support the prediction, however since there were so many anomalies I would need more evidence to lead to a firm conclusion.
