Method: The apparatus was firstly brought together. Look at apparatus diagram.
Preliminary work: I firstly did preliminary to give me a impression on the change of the potatoes length when it is put into certain concentrations. In this work I used distilled water and 0.5 molar of sucrose.
The results follow:
Full experiment:
A range of sucrose sugar solutions will be prepared. Sections of potato will be cut using a scalpel 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. I will use 30ml of each solution in separate test tubes, and then each test tube will be labeled. 5 chips will be placed in each test tube. The experiment will then be left for 24 hours and the results will then be taken.
Steps of process:
- I took two potatoes checking that they were healthy and hard
- I then inserted the cork bora, and took out cylinder shaped potato pieces.
- I then proceeded to measure them carefully and cut them into 2cm pieces.
- I did this 5 times for each solution.
- I then measured out 30ml of each solution and put them into their test tube.
- I then added the pieces of potato to each test tube, remembering to add 5 pieces, which measured 2 cm each.
Fair testing should play a big part in this experiment. If this experiment isn’t a fair test, we will be obtaining the wrong results, which could lead us to the wrong conclusions.
First of all, and most importantly, we will have to get the measurements of the potatoes and the measurements of the solutions right. We will try and get the measurements of the potatoes as accurate as possible for every single potato, evenly cutting the potato pieces 2cm per piece. But I believe one of the most important steps in the fair testing is to make sure that the potato is fully covered by the solution. This is because the potato should fully submerge, by having total contact with the solution. Getting and experimenting with the exact measurements of molars and water is vital to this task. If the volume of one solution in a test tube is higher or lower than another, will affect the pattern of results later on. Small things such as a dirty test tube, and a slightly cracked measuring cylinder could still affect the results, and therefore we will take these into account as well.
I couldn’t repeat this exercise due to not having enough time but I made sure that I compared my results with other groups doing this experiment so I could get a wider view of the out comings.
Other sources I used where the Internet where I compared my observations with other peoples. I also read some science books to research on osmosis. These sources were very helpful because I could then have wider knowledge on this subject, therefore making more accurate observations.
Results:
Graph on graph paper
Conclusions: My conclusions are that as the concentration of sucrose was increased then the length of the potato also decreased. This was due to there being a higher concentrated solution on the outside of the potato so the water diffused from a region of low concentration to a region of high concentration. The only real pattern in my results was that they were always decreasing in length, e.g. at 0.1 sucrose concentration the average length of the potato was 2.2cm and then at 0.2 sucrose the average length went down to 2.16. The theory I used was the movement theory which states that the movement of H2O from a region of low concentration to a region of high concentration. My results show that this theory is true because in the theory it states that water moves from a region of high concentration to a region of low concentration. In my experiment this did happen resulting in the length of the potato decreasing. My results support my prediction very well because I stated in my prediction that the length will decrease, I also gave a scientific theory. My results came out just as I said they would. My final conclusion is, yes the concentration of sucrose does affect the length of a potato.
Evaluation: I think my method was suitable enough because my prediction corresponded to my results via having a suitable method. A problem with my method could be that I didn’t repeat the exercise enough times to get more reliable results. I think that my observations and measurements were not the best because I was underneath a certain time limit to get the experiment done, the variations in length would have been at maximum 2mm. There were four anomalous results that didn’t go through the line this was due to me not cutting the potatoes to the exact size. Also because all the potatoes were not of the same mass.
To make this experiment better, I believe that we could have done one test at a time. Using more types of molar sucrose solutions would have helped us obtain better results, and more accurate results, so that we can make sure the results are totally correct. Experimenting with one set for a longer period of time, for each set, would lead us to better results, because the osmosis action would reach its maximum capability, and therefore tell us how much water could be transferred for each solution. I could have extended my investigation by doing more research on osmosis and by spending more time on the actual experiment. Overall I was pleased that my prediction was right although getting a few anomalous results due to human fault, however my results still supported my prediction and I came to my conclusion.
