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Osmosis on Potato Cylinders

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Introduction

Osmosis on Potato Cylinders Problem We are going to investigate the effect of varying the concentration of sucrose solution, and using deionised water on the amount of osmotic activity between the solution and a potato chip of a given size. In this investigation the pressure and temperature in each case has to be kept the same. We also know that the volume, size and surface area of each cylinder has to be kept the same. So the only variable is the concentration of sucrose solution. Prediction Osmosis is defined as 'The movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low concentration.' Osmosis occurs across a semi-permeable membrane whenever there is a difference between the water concentrations on the two sides of the membrane and when his happens to cells they will either become turgid (if water flows into them or plasmolysed (if water flows out of them). So I predict that when a cell is placed in high concentrated water, the water will move across the semi-permeable membrane in to the cell where there is lower concentrated water, buy osmosis and making the cell swell. ...read more.

Middle

and diameter. This would have to be done very accurately as a change in the surface area may allow more or less osmosis to occur. 2. Separate the six pieces of potatoes into six boiling tubes, five of them containing 25 cm3 of different concentrations of sucrose solutions, as shown in diagram. The test tubes would have to be labelled so there are no mistakes. 3. Use the other boiling tube to put 25 cm3 of deionised water into. 4. Leave them at room temperature for 24 hours. 5. Measure the new lengths of the potato cylinders. Safety Precautions This experiment is quite safe but we may have to consider handling the cork-borers and scalpel with care, as they are sharp objects. Results Concentrations of Sucrose solution/ Deionised water (cm3) Length of potato at beginning: 4cm 4cm 4 cm Average length Change in length Deionised water 4.4 4.2 4.2 4.3 0.3 0.1 4 4.05 4.2 4.1 0.1 0.2 4 3.95 3.9 4 0 0.3 3.9 3.6 3.8 3.8 -0.2 0.4 3.8 4.5* 3.7 3.8 -0.2 0.5 3.6 3.8 3.4 3.6 -0.4 *Anomaly Conclusion From my results I can see that deionised water and low concentrated sucrose solution affected the size of the potato. ...read more.

Conclusion

Evaluation I think that the experiment was very successful. I resulted with accurate enough to results from which I was able to plot two informative graphs. There was one anomaly in my results, which is highlighted. This was caused by a groove in one of the potato cylinders this affected my results and made them unreliable, but the anomaly was not used in the results. Other than that I think I took easily enough results for the amount of concentrations that I was using, and the time that I used for the experiment to last was enough to allow sufficient osmosis to occur. However if I was to criticize my experiment I would leave the potatoes in the liquids for a little while longer so that I could find the saturation and dehydration point and get more accurate and varied results. Another way to improve my results could be to use more accurate equipment for the investigation. For example using callipers for measuring and cutting the potatoes to 4 cm and then measuring the new height of the potatoes after the 24 hours. Callipers are more accurate than rulers; therefore they would give a more accurate result. Overall my investigation went well and my results matched my initial predictions. ...read more.

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