1.00- Take a measuring cylinder and place in 40ml of 1M Sugar Solution and 0mm of water,
1.25- Take a measuring cylinder and place in 5ml of 2M Sugar Solution and 35mm of water,
1.50- Take a measuring cylinder and place in 10ml of 2M Sugar Solution and 30mm of water,
1.75- Take a measuring cylinder and place in 35ml of 2M Sugar Solution and 5mm of water,
2.00- Take a measuring cylinder and place in 40ml of 2M Sugar Solution and 0mm of water.
∙ Now that you have got your potatoes cut, they are ready to weigh, dry them off as well as possible and place on scales, These are the following results: -
∙ Now you have everything you need to do the experiment, all you need to do now is place the potatoes in the right molar solutions.
∙ Place in with tweezers carefully; try not to disturb the solution.
∙ Now that the potatoes are in there are 2 things left to do: -
- Wait 20 minutes (This is a reasonable time to leave them for)
- Take the potatoes out of the solutions and place them on a piece of towel, but remember to keep trace of which one is which. Blot the potatoes as much as u can. (Relatively you should dab them for exactly the same amount of time as before you placed them in).
- Using the same scales weigh each one individually and write down the results: -
Fair test
In this experiment there should only be two changing variables: 1: Different moralities of sugar solution. 2: Changing weight of the potato samples. To keep these two variables the only variables in the experiment I must:
1: Keep the potato samples the same length (5cm). This is because if one potato sample is 1cm long and one is 6cm long then the 6cm long sample will have a larger surface area and will osmosis much more quickly.
2: Use the same potato. This is because many factors due to the potato may affect the experiment. For example the age, species e.g. King Edward, size and any imperfections in the potato can be kept to a minimum.
3: Stop the evaporation of any of the molar solution. This is because if the sugar solution evaporates past the level of the of the potato then the potato sample will have less surface area in the solution so may osmosis slower. To stop any solution evaporating a foil lid can be placed on top of the test tube.
4: Accurate amount of sugar solution: More Bathing solution may affect the rate of solution. To make the amount of solution placed in the test tube as accurate as possible a syringe will be used to measure out the exact amount needed.
5: Contamination: As each test tube is filled up with the different molar solutions the syringe which would measure the amount of solution placed in the test tube may become contaminated with different moralities. To stop this the beaker and syringe must be washed every time they are used.
6: Average: To make the experiment as accurate as possible an average will be taken out of 5 results taken. Also any clearly anomalous results will be ignored.
7:Temperature: The temperature may affect the reliability of the experiment for example at extreme temperatures the cells of the potato may die and at less extreme temperatures the experiment may be speeded up. To keep this from happening all the test tubes will be kept in the same place
Graph
Conclusion
The results in this experiment show a number of different things. Its shows that as the morality gets stronger, there is a greater decrease in the weight of the potatoes. This is due to the movement of water molecules from a region of high concentration of water molecules to a region of low concentration of water molecules. In other words with a morality of 0 the concentration is high and so the water molecules move into the potato.
Evaluation
I think that the experiment went very well, there were no 'odd' results and they produced a good graph. However there were a few areas where there could be improvement. Firstly, when I dried off the excess water on the potato cylinders after the experiment and before I weighed them, I used a paper towel. This might have either taken some water out of the potato or it might of left some excess water on the potato. This part of the experiment is difficult to come up with an accurate and fair method, as other ways would also lead to some slight mistakes. Also the potato itself was not definitely from the same potato and was not exactly the same size, although I did try to cut them to 5cm each. Another way of improving the results would have been to leave the experiment running longer, this would have enabled me to find the saturation point (when the potato can no longer take in any more water) and dehydration point (when the potato cannot lose any more water) and therefore get a more accurate result. Finally, I could extend the experiment to a more exact level by looking at the potato cylinders under a microscope, and then I would be able to see the cells in greater detail and draw some more observational results. In my opinion the experiment went well. I gained a good set of results and altogether I am pleased with the investigation. The graph obtained from the results has a strong resemblance to the one in the prediction. This suggests that the experiment was fairly accurate. Although 5 repetitions of each concentration are sufficient, there was a possible anomalous result. This part of the investigation would need to be repeated. A possible factor affecting my results is that although the cylinders were taken from the same potato there is no guaranteeing that the density remains the same throughout the potato. Another factor is that the potato from which the cylinders are taken could be abnormal - this could be prevented by amalgamating sets of results, for example of a whole class, where each experimenter used a different potato. I think that five sets of results was a good number. However, I think that in order to improve my results, the last concentration needs to be retaken, as it is an irregular result. Further work could be carried out to include concentrations that increased in 0.1 M rather than 0.2M. This would increase the accuracy and improve the graph. Other investigations could include using different varieties of potato or different plant tissues e.g. carrot.
By Aaron Shread 5 A.M.C
