I will keep this experiment fair by using an accurate electronic balance to measure each potato, and by drying each piece with a towel before weighing them to make sure that I’m not weighing any solution that might be clinging to the potato piece. I will measure each solution with a measuring cylinder before putting them into the boiling tubes, as well as making sure that the general temperate of the room stays the same throughout the experiment. I will do each test three times to make sure that any irregular results can be distinguished, and to eliminate other problems, like the differing surface areas of the potato pieces.
This means I will need these pieces of equipment for the experiment:
Boiling tubes (x18)
Electronic Balance
Pipettes
Test Tube Rack
Stop Watch
Distilled Water
Measuring Cylinder
I predict that water from the lower concentrations of sucrose solutions will diffuse into the potato because the concentration of water will be higher outside the potato that inside it. Since osmosis is the movement of water from an area of high concentration to an area of low concentration, the potatoes in the weaker sucrose solutions (0.0, 0.2 and perhaps 0.4) will gain weight. I think that the opposite will happen with the high concentration solutions (1.0, 0.8 and perhaps 0.6) because there will be a larger amount of water inside the potato than outside, so water will move out of the potato. Therefore potatoes in the higher concentrations of sucrose solution will lose weight.
Results.
Average Results.
Evaluation.
The experiment was successful. I decided to measure amounts of liquid to one millilitre, making sure that I measured to the top of the meniscus (curve of a liquid in a container due to friction against its sides and the surface tension of the liquid), as there needed to be an exact amount of sucrose solution in each boiling tube for it to be a fair test. I used an electronic balance when measuring the potato chips, and ‘dried’ all of the chips evenly to remove any sucrose solution by letting the clinging solution drip back into the boiling tube for 5 seconds before weighing. The results obtained from the experiment are conclusive with, and support my original prediction.
My original prediction was that the potatoes in the weaker sucrose solutions will gain weight and that potatoes in the higher concentrations of sucrose solution will lose weight. I converted all of my results into percentages to make them easier to compare, as many of the potatoes were of different sizes, and had different surface areas, meaning that possible rates of osmosis occurred. By taking averages of the three sets of results that I took, as well as converting them into percentage increase or decrease, I find my results easier to compare.
Looking at my graphs, I see that the three graphs that I made from my results prove my prediction. The potato chips in the weaker solutions did gain weight to start with, but as I left the potato chips in their solution for longer periods of time, I saw that they began to lose weight because the opposite began to happen. They had become so saturated with water that the concentration of water was more in the potatoes than in the solution, and I found that some of the water from the solutions had evaporated. This made the concentration less in the solutions than in the potatoes, and water moved by osmosis from the potatoes to the solution and the potatoes lost weight. The difference between the weaker solutions was the total amount of water gain before water started to move out of the chips, the weakest solution gaining the most water.
The potato chips in the stronger solutions did lose weight as I predicted, but when I left them for longer period of time, their weight loss decreased and eventually stopped. This was because the amount of water in the potatoes had become even to the amount of water in the solutions, and since osmosis is the movement of water from an area of high concentration to an area of low concentration, there could be on osmosis is the concentrations were the same. The difference between the stronger solutions was the speed and amount of water loss, the strongest solution losing water the most water the fastest.
I think that the experiment would have benefited from taking more results. There were large gaps between some of the results that I took, and I would have been able to assess what happened to the potatoes more exactly if I knew precisely what happened between the times I took readings. If I were to do the experiment again, I would take more readings at regular intervals of time, as well as taking precautions against evaporation. I would also find a more effective way of removing the potato chips from the solutions in the boiling tubes for weighing. I took the potato chips out by scooping them out with a metal rod, and sometimes a little of the solution in the boiling tube escaped. I would perhaps attach the potatoes to a piece of nylon string so that I could easily remove them for weighing. I think that using some other plant tissues would prove and interesting comparison to that of potatoes. Perhaps pieces of carrot or apple might work with this experiment and show how osmosis differs between plants or if it is the same.
In conclusion, I think that this was an effective experiment in assessing the process of osmosis in potatoes. I was able to predict what might happen, and prove my predictions with my results.
