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To observe how water and sugar solution affect potato cells. This will show how potato cells take up water by osmosis and cause an increase in weight.

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Introduction

An investigation into the Osmosis of a Potato Aim: To observe how water and sugar solution affect potato cells. This will show how potato cells take up water by osmosis and cause an increase in weight. Scientific Knowledge: Osmosis is the movement of water or any other solutions' molecules from a region of high concentration to a region of low concentration. This movement must take place across a semi-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 reaches a state of equilibrium. This means that the molecules are randomly distributed throughout an object, with no area having a higher or lower concentration than any other. In my experiment, the tiny holes in the membrane of the potatoes will allow the water molecules to pass through in and out of the solution and the potato. When the concentration gradient is lower in the potato, the water will transfer from the solution to the potato and vice versa. The potato tissues, being surrounded by a weak solution, will be most likely to swell up and become turgid; taking in all the water it can possibly take in. ...read more.

Middle

Method: 1.) Collect all equipment needed. 2.) Using a cork borer, cut out 18 cylindrical shaped potato cells. 3.) Weigh them using the same scales all the time so they are 1.62 grams. (Cut or re-make if too less or too much.) 4.) Dry the potatoes off using a paper towel. 5.) Using a measuring cylinder, measure out 10 cm3 of sucrose solution. 6.) Place the liquid into a test tube, and label "100%." 7.) Then repeat steps 5 and 6 twice for the same amount of each liquid. 8.) Then repeat steps 5, 6 and 7 for 80%, (2 cm3 of water and 8 cm3 of sucrose solution), 60%, (4 cm3 of water and 6 cm3 of sucrose solution), 40%, (6 cm3 of water and 4 cm3 of sucrose solution), and 20%, (8 cm3 of water and 2 cm3 of sucrose solution). 9.) Also produce three test tubes of just water (10 cm3.). 10.) Place all dried potato shapes into the test tubes and set the stop clock for 30 minutes. 11.) After 30 minutes, dry the potatoes and weigh them. (Be careful not to mix the potatoes up.) Diagram: Conclusion: The graph on the previous page shows the osmosis of a potato using the axes, mass and % concentration. ...read more.

Conclusion

Two are below the line of best fit while another is above. Also, 1.46 and 1.49 grams are lower than the 100% concentration. Experimental errors were also made, some being random and some being systematic. A systematic error was that we didn't record the start mass of each potato. They were roughly measured at 1.62 grams but not everyone was this weight. This will affect the graph and results as the percentage change will not be accurate as it will be taken from the average. The occasional errors occurred in the solution measurement but wouldn't have affected the results to a noticeable extent. As I had quite a few anomalous results I would carry out a few more trials but concentrate particularly on the 80% concentration as I was surprised with the results. If I repeated this experiment, I would make sure that I included the start mass as this would give me a more accurate measure of percentage change. I would also carry the experiment out over the full 30 mins and this would mean that my results would be precise. I would also make sure that the potatoes were dry before measuring them. To extend this experiment I would add more concentrations to have a wider spread of results and I would use different time scales. This would further my prediction. Hannah Bennett 31 May 2002 ...read more.

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