Preliminary Work
I used a core borer to cut out three potato chips. I measured and weighed them, recorded the information, and placed them in three different concentrations of glucose solution. The concentrations were zero moles, naught point four moles and four moles. I left them in solution for eighteen hours and then took them out of solution and weighed them. I then recorded the information in a table. The results are shown below:
Equipment list
Core borer; ten 100ml beakers; conical flasks; thirty potato chips; filter paper; ruler; scalpel; digital scales.
Risk assessment
When using the core borer, use away from your hands. Cut away from yourself when using the scalpel. Do not run with liquids or other equipment. When handling liquids, wear goggle. Wear an apron.
Variables
Type of potato, weight of the potato chips, the temperature that the experiment will take place at and the time in solution are all variables that may cause a variation in results. To prevent this from happening I will take several precautions. I will make sure the samples are the same by using a core borer to take them from the potato weigh them on some digital scales and cut them to the same length. The independent variable is the concentration of the glucose solution. The dependent variable is the mass of the potato sample. Other variables like: the type of potato, starting mass of the Sample, temperature of the solution and the time in the solution will all be controlled to make it a fair test.
Method
A range of glucose sugar solutions will be prepared with concentrations. This will be done by adding varying amounts of distilled water to varying amounts of glucose solution. Sections of potato will be cut using a scalpel and will be measured to thirty millimetres using a ruler. This part of the preparation must be done very accurately as a change in the surface area may allow more or less osmosis to occur. The mass of each chip will be measured as well so that more results can be obtained. Three chips will be placed in each test tube each time so that I can take an average for each tube. I will use ten millilitres of each concentration of sugar solution and once in the test tubes they each will be labelled. The potato pieces will then be placed in the different beakers and then left for fifty hours. Then the potato pieces will be removed, the surface solution removed using paper towels and then they will be re-weighed. This will hopefully accurate results from which I will be able to draw a more accurate conclusion. If there is an anomalous result, the experiment will be repeated.
Method
1. I took two average sized ground potatoes and checked that they were both healthy and hard.
2. I used a core borer with a radius of two point five millimetres, and cut the potatoes into cylindrical strips. I had to use the core borer away from my hands and body to avoid injury.
3. Using a scalpel and ruler I cut the potato into cylindrical chips, which were thirty millimetres long. I had to be very careful whilst cutting the potato, as the scalpel is exceptionally sharp. I then had thirty chips.
4. I labelled ten one hundred millilitre beakers from naught point zero moles to one mole, going up at intervals of naught point one moles.
5. Using a measuring cylinder I measured out different amounts of glucose solution and distilled water, which I then poured into the test tubes in a percentage ratio giving me the various molar concentrations.
6. I then weighed every potato chip on an electronic balance and recorded the weights.
7. I swiftly put 3 potato chips into each beaker and then started my stopwatch. 3 chips were used to create an average, which gave me a better set of results and more accurate graphs.
8. Whilst waiting I set out some paper towels with which I was going to dry the paper and I drew up a basic table for my results.
9. After fifty hours, I drained out the solutions in the sink and placed all the chips on the paper towel in the order I had put them in the test tubes as to not confuse myself as to which chip came from which solution.
10. I dried each chip with the paper towel and then placed each one on the scales so that I could weigh them.
11. Each potato was measured accurately on the electronic scales and then the weights were recorded.
Conclusion
From my graphs I can see that the potato chips absorb water from the solution at around a 2.5 mole solution. This is known as the isotonic concentration for my potato as it has the same osmotic pressure as the glucose solution. There is however, an anomaly. This value is very far away from the line of best fit and says that at a concentration of 1 mole, the potato chip gains weight. This result is void.
Evaluation
My method was good. My results were pretty reliable with the exception of an anomalous result. The results were reliable because they were very close to the line of best fit. It was expected that some of the results would be slightly out and it was expected that we could not collect and record the gas to an excellent degree of accuracy. The problem is that all the instruments were not to the highest standard. We could not effectively and efficiently collect 100% reliable results with basic school, equipment. This has affected the results but not very much. It would however be seen as an improvement if accurate cutters and more accurate digital scales would be used. It would also benefit the experiment if the potato chips were from a cloned potato. The potato would have to remove some tissue from the parent plant and transfer it into a culture tube, containing agar until it grows into stumps. This would take a long time to do and though it would result in accurate results, it is too time consuming and expensive to do.
