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The purpose of this investigation is to test the movement of water into and out of potatoes from different strengths of sucrose solution via osmosis.

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Introduction

Osmosis Practical. Plan. The purpose of this investigation is to test the movement of water into and out of potatoes from different strengths of sucrose solution via osmosis. Osmosis is a special case of diffusion when water passes through a semi-permeable membrane from an area of high concentration to an area of low concentration. The sucrose solutions will have a smaller concentration of water than the potato, and I will be testing to see the effects of different strengths of solution on the amount of osmosis taking place. I will be using six different strengths of sucrose solution: 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0, 0.0 having no sucrose in it - simply water, and 1.0 being made up completely of sucrose. I will put 20ml of each strength solution into six different boiling tubes ready for me to put the potato pieces into. Before adding the potato pieces, I will weigh each piece, recording the values so that I will be able to see any change later in the experiment, and make sure that they are all roughly the same size. Then I will insert a piece of potato into each boiling tube to allow osmosis to occur. After 25 minutes I will take all of the pieces of potato out and weigh them again, recording the results before returning them to their boiling tubes and solutions. I will repeat this process one hour later, and 3 hours later, recording the results for each. ...read more.

Middle

-12 0.4 1.90 2.80 47 2.97 56 2.46 29 0.4 2.50 2.40 -4 2.30 -8 2.20 -12 0.6 3.11 2.90 -7 2.44 -22 2.37 -24 0.6 2.81 2.62 -7 2.23 -21 2.23 -21 0.6 2.83 2.58 -9 2.15 -24 2.10 -26 0.8 2.71 2.44 -10 1.99 -27 1.97 -27 0.8 2.65 2.36 -11 1.93 -27 1.89 -29 0.8 2.62 2.30 -12 1.86 -29 1.90 -27 1.0 2.76 2.39 -13 1.88 -32 1.87 -32 1.0 2.76 2.38 -14 1.89 -32 1.89 -32 1.0 2.72 2.40 -12 1.92 -29 1.92 -29 Average Results. Boiling Tube Concentration Weight at Start (g) Weight at 25mins (g) % Increase (From Start) Weight at 85mins (g) % Increase (From Start) Weight at 205mins (g) % Increase (From Start) 0.0 3.67 3.93 7 3.86 5 2.97 -19 0.2 3.10 3.10 0 3.11 0 2.84 -8 0.4 2.57 2.70 5 2.73 6 2.52 -2 0.6 2.92 2.70 -7 2.27 -22 2.23 -23 0.8 2.66 2.37 -11 1.93 -28 1.92 -28 1.0 2.75 2.39 -13 1.90 -31 1.89 -31 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. ...read more.

Conclusion

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. ...read more.

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