To ensure this was a fair test, I had to make sure that each beaker had exactly 100ml of sucrose solution in them, they were the same temperature, that each potato chip was left in the beakers for the same amount of time and that there were no grooves in the potato chips because grooves would affect the surface area of the chips which can cause more or lees osmosis to take place.
I have planned this experiment in this way with six beakers and six potato chips in with six different concentrations of sucrose from experience of past work such as the experiment were glucose was tested with potato chips. Were it was set out in the same way.
Results
Conclusion
Osmosis is defined as 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. It is measured in the change of mass of the partially permeable membrane.
As we know, sucrose molecules can not pass through a cell wall, but it does affect osmosis in potato cells, because if there is a high concentration of sucrose in a solution then there will be a low concentration of water molecules. So in order for the solution to become dilute the water molecules in the potato cell which have a higher concentration than the solution, move to the less concentrated solution of water molecules. This decreases the mass of the potato chip because it has lost water molecules. But if there is a low concentration of sucrose in the solution then there will be a high concentration of water molecules. So the high concentration of water molecules moves to the lower concentration of water molecules in the potato cell causing the potato chip to increase in mass. For instance in my results I put a potato chip weighing 3 grams into a sucrose solution of 0 molecule per dm³ concentration, so it had a high water molecule concentration and a low sucrose concentration. After leaving it over night I took the potato chip out and weighed it, the end mass was 5.4 grams so it had increased in mass considerably. On another result I put a potato chip weighing 2.6 grams into a sucrose solution of 1 molecule per dm³. So it had a high concentration of sucrose and a low concentration of water. The end mass was 1.6 grams so it lost water molecules causing the mass to reduce.
There is a relationship in the results obtained all results from the sucrose concentration of 0 to 0.4, the potato chips mass increases and concentrations of 0.6 to 1, the potato mass decreases.
The graph gives the line of best fit for the percentage change in mass of the potato chips over the course of the experiment. The graph is a curve that slopes downwards and does not go through the origin. Because the line is not straight and does not pass through the origin, it means that the percentage gain and loss in mass and concentration are not the same. However, there is a pattern on my graph, and this is, as the concentration of the sucrose increases, the percentage change in mass decreases. The gradient does change in my graph. It gets less steep as the X axis gets bigger. This is because the potato chip is becoming as flaccid as it possibly can, and so the change in mass of each molar concentration is becoming closer and closer together. From the line of best fit that has been added in, it can be seen that all of my points were very close to creating a perfectly smooth curve. This shows that my results are fairly reliable. My graph fits in with my prediction.
In my original prediction I said that the lower the concentration of the sugar solution, the larger the mass of the potato will increase because the cell wall of the potato chip will allow the smaller molecules such as the water molecules to pass through but won’t allow bigger molecules to pass through such as the sugar molecules. So if there is a high concentration of sucrose in the solution then their will be less water molecules to diffuse into the potato chip, so more water molecules are needed to dilute the solution, therefore the potato chip will decrease in mass because the water molecules have passed from a higher concentration of water molecules to the lower concentration of water molecules. Therefore a potato chip put into a higher concentration of water than sugar in the solution will increase in mass, but a chip put into a solution which has a higher sugar solution than water solution will decrease in mass. My prediction was correct because in my results the sucrose concentrations of 0 to 0.4, the potato chips mass increased and the concentrations of 0.6 to 1, the potato mass decreased.
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 a very informative graph with no anomalous results. There is enough evidence to make a firm conclusion.
How ever if I was to repeat the experiment again I might well increase the time of the results to allow more osmosis to happen and possibly find out the saturation point of the chips. Also the range of concentrations was adequate but I could possibly create more concentrations if I repeated the experiment so that I would have more varied results such as concentrations above 1.
The cutting of the potatoes could have affected 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 could have increased or decreased. So if I was to repeat the experiment again I could have used a machine to cut the potato as it would ensure that all potatoes would be the same weight and dimensions. For more accurate results I could have also weighed each chip on a more accurate scale not at 0.0grams but to about 0.0000grams. When the potato chips were removed from the beakers and dried I may well have dried some potato chips more thoroughly than others and so some could have had more excess water increasing the mass.
