APPARATUS: -
- Potato
- Cork Borer
- Test Tubes
- Test tube stand
- Sugar Solution
- Water
Planned method: -
First of all I will make patato chips using a cork borer and a potato. After making 25 chips of potato of equal weight and length I will make sugar solutions of different concentration. For the 0.00 mole solution I will only take water. For the 0.25m (molar) solutions I mixed 2.5ml of sugar solution with 7.5ml of distilled water. For the 0.50m (molar) solutions I mixed 5.0ml of sugar solution with 5.0ml of distilled water. For the 0.75m (molar) solutions I mixed 7.5ml of sugar solution with 2.5ml of distilled water. For the 1.00m (molar) I will only take sugar solution.
Planned method: -
A range of sucrose sugar solutions will be prepared with concentrations 0 molar, 0.25 molar, 0.5 molar, 0.75 molar and 1 molar. This will be done by adding varying amounts of distilled water to varying amounts of sucrose solution. Sections of potato will be cut and will be measured 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 10 ml 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 test tubes and then left for 3 hours. Then the potato pieces will be removed, the
Surface solution removed using paper towels and then they will be re-weighed. If I then have time afterwards I will repeat this experiment again as to obtain a second set of results. This will hopefully produce more accurate results from which I will be able to draw a more accurate conclusion.
Method: - (in points form)
1. I took two average sized ground potatoes and checked that they were both healthy and hard.
2. Using a cork borer I cut the potato into chips, which were 5 cm long.
3. Taking a test tube rack I placed 5 test tubes and then labelled them 0 molar, 0.25 molar, 0.5 molar, 0.75 molar and 1 molar.
4. Using a measuring cylinder I measured out different amounts of sucrose solution and distilled water, which I then poured into the test tubes in a percentage ratio giving me the various molar concentrations.
5. I then weighed every potato chip on an electronic balance and recorded the weights.
6. I swiftly put 3 potato chips into each beaker and then started my stopwatch. Chips were used to create an average, which gave me a better set of results and more accurate graphs.
7. 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.
8. After 3 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.
9. I dried each chip with the paper towel and then placed each one on the scales so that I could weigh them.
10. Each potato was measured accurately on the electronic scales and then the weights were recorded.
11. As I had time after doing the first set of results I redid the experiment under exactly the same conditions. This gave me secondary set of results, which gave me a more accurate view on the changes.
Main Tables of Results: -
0.00m Solutions/Water
0.25m Solutions
0.5m Solutions
0.75m solutions
1.00m solutions
Table of Average mass of all 5 Solutions:-
Table of Average length of all 5 Solutions:-
Evaluation: -
The experiment was very successful in my opinion. I obtained a large quantity of
very accurate results from which I was able to create informative graphs. I
think I took easily enough results for the amount of concentrations that I was
using, and the time that I used for the experiment to last was enough to allow
sufficient osmosis to occur. However if I was to repeat the experiment I might
well increase the time of the result to allow more osmosis to happen. The range of concentrations was adequate but I would possibly create more concentrations if I repeated the experiment so that I would have more varied results, i.e. 0.10m, 1.15m, 1.20m, and so on. This way would have allowed me to also find out the isotonic point far more accurately as the one that I estimated is very approximate.
The cutting of the potatoes was the most difficult part of the experiment as
although I was recording my results by mass, it could well have affected the
surface area and so the overall rate of osmosis. As well as the potato I could have found a more accurate way to measure out the solutions and to determine the molar concentrations. Perhaps I could have used a burette.
This would ensure that I have an accurate amount of fluid in each test tube. I could also weigh each chip on a more accurate scale, e.g. not to 0.00g but to 0.0000g.There were not any out of the ordinary results, but some were not as close to the line as others. This may have been caused by human. When the potato chips were removed from the test tubes and dried I may well have dried some potatoes more thoroughly than others and so some would have more excess water, which would add to the mass. If the experiment was repeated I could find another way to dry the potatoes that would ensure that all were dried in the same way for the same time. However with all this said I think that the experiment was truly successful and I was very pleased with the complete comparison of my results with my initial prediction.
