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An investigation into the isotonic point of Potatoes

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An investigation into the isotonic point of Potatoes P Introduction: In this experiment I will be trying to find out the isotonic point of potatoes. This is a point where the concentrations of water inside and outside the potato cells are equal. Water gets into or out of various cells by Osmosis. (Hypothesis) Osmosis is the net movement of water or any other solutions molecules from a region in which they are highly concentrated to a region in which they are less concentrated. This movement must take place across a partially permeable membrane such as a cell wall, which lets smaller molecules such as water through but does not allow bigger molecules to pass through. The molecules will continue to diffuse until the area in which the molecules are found reaches a state of equilibrium, meaning that the molecules are randomly distributed throughout an object, with no area having a higher or lower concentration than any other. Water potential is a measure of whether a solution is likely to gain or lose water molecules from another solution. A dilute solution, with its high proportion of free water molecules is said to have a higher water potential than a concentrated solution, because water will flow from the dilute to the concentrated solution (high water potential to a low water potential). Safety; The only safety precaution needed in this experiment is to be careful with various apparatus such as the tool used to get potato chips out of a full potato. Apparatus: Method: I set up the experiment as shown above. I cut out eight pieces of potato using the tool that cuts cylinders (chips) ...read more.


This will ensure that the most accurate isotonic point can be found. Reliability: The results will be made accurate by a repetition of results. This will definitely make the results more accurate and so therefore more reliable. I will repeat the whole experiment at least three times and then I will obtain more results after the isotonic point is found. I will also repeat any anomalous results. The end set of results will be reliable enough to draw up a good enough conclusion. Preliminary work: Experiments that I did before this current experiment included the experiment to illustrate turgor in a plant cell. This involved using a visking tube. Osmosis occurred as the visking tube acted as a semi permeable membrane. The point of doing this experiment is to show that there is a resemblance to the way a potato works and a visking tube. O Equipment: The equipment needed to make my measurements were measuring cylinders, a burette and accurate weighing scales. The weighing scale made my results that extra little bit more accurate as the scales were very, very sensitive and gave mass to at least one decimal place. The burette made sure that the correct volume was being used each time. Results: 1) Vol. Water ml Vol. Sugar ml Molarity Mass before g Mass after g % change % 7 1 0.1 3.4 4.2 23.5 6 2 0.2 3.6 4.1 13.9 5 3 0.3 3.5 3.8 8.5 4 4 0.4 3.1 3.1 0.0 3 5 0.5 3.4 3.3 -2.9 2 6 0.6 3.6 3.5 -3.0 1 7 0.7 3.1 2.9 -6.5 0 8 0.8 3.3 2.9 -12.1 2) ...read more.


If I had cut the potato into doughnuts, I would have only been using the out side of the potato, leaving out the middle. I could have also used a machine to cut the potato chips. My results did lie close to the line, and therefore were fairly accurate, but if I was doing the experiment again I could make changes, some as mentioned above. I also used a burette to measure out my solutions. This ensured that I had an accurate amount of fluid in each test tube. I could also weigh each chip on another digital but more accurate scale, e.g. not to 0.00 but to 0.0000g. There were not any anomalous results, but some results were not as close to the line as others. This may have been caused by human error, or one out of my results could have been inaccurate, and changed the average drastically. Or perhaps the potato chip was not cut accurately, or that part of the potatoes, cells did not loose/gain mass well. My results did vary a lot for the same concentration. The fact that a certain part of the potato may not be the same as another was shown as the chips all of the same length were not all the same weight. This is another reason to use cloned potatoes. My results were consistent, and there were no results that they were ignored. I could extend my enquiry by testing the percentage change in mass with morality using a different substance. By this I mean using a different vegetable, perhaps celery or cucumber. Then I could find out whether osmosis occurs with the same patterns and trends with any vegetable. ...read more.

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