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The aim of my experiment is to determine how potato tissue is affected by varying concentrations of water.

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Introduction

Contents Introduction Page 1 My prediction Page 1 Scientific Knowledge Primary Sources Page 2 Secondary Sources Page 4 Experiment List of Apparatus Page 6 Method Page 6 How to make it a safe test Page 8 How to make it a fair test Page 9 Graph and Results Graph and Results Page 10 Preliminary Experiment Page 10 Results: Preliminary Experiment Page 11 Results: Experiment 1 and 2 Page 12 Results: Experiment 1 and 2 Page 13 Results: Average of Experiment 1 and 2 Page 14 Analysis Page 15 Conclusion Page 16 Evaluation Page 17 Bibliography Page 19 Introduction The aim of my experiment is to determine how potato tissue is affected by varying concentrations of water. Distilled water will be used to provide the high water concentration and a further five solutions will be made using sugar to provide varying lower water concentrations. The six water concentrations will be 0, 0.2, 0.4, 0.6, 0.8 and 1 molar sucrose solutions. (1 molar sucrose solution is 34.2g of sugar per 100ml of water) I will carry out this experiment by comparing the volume of rods of potato before and after immersion in the solutions of varying water concentrations. By analysing the results, I hope to be able to determine the relationship between the concentration of water in sucrose solution and the change in volume of the potato tissues. My Prediction My prediction is that the potato tissue immersed in the one molar sucrose solution will shrink because water will leave their cells due to osmosis, which means that the cells (and therefore the potato tissue) will become plasmolysed and flaccid. This will happen because the potato tissue would be surrounded by a region where the concentration of water molecules is lower than that of the concentration inside the tissue. This will result in the passage of water out of the potato cells through the semi-permeable membranes (the cell membranes), which should result in a decrease in volume of the potato tissue. ...read more.

Middle

* Cut the potato cores perpendicular to their length If I did not cut the potato core perpendicular to their length then it is possible for a number of readings for the diameter to be obtained. By cutting the potato core perpendicular to their length then it is only possible for one true reading for the diameter to be obtained. The only factor that will be purposely inconsistent in this investigation is the water concentration. (The water concentrations will range from 0 molar to 1 molar of sucrose solution.) All of the other variables in the experiment must be eliminated! Graphs and Results The results obtained from my experiments are shown in tabulated form (see tables for experiment 1 and 2). These show volume change and percentage volume change between the initial and final readings. From the tables I have produced a bar chart of the volume change vs. molarity of sucrose solution illustrating the results of experiment 1 and 2. I have also created line graphs of percentage change in volume vs. molarity of sucrose solution illustrating the results of experiment 1 and 2, the average results and a best fit line. Preliminary Experiment I will first carry out a far simpler experiment where only the extremes are tested. I will do this because it will hopefully give me a greater understanding of the expected results in the main experiments and it will provide an opportunity to run through similar procedures to that of the main experiments. I will use the same method as the main experiments except that I will only prepare three water concentrations - 0.0 (distilled water), 0.5, and 1.0. The dilutions of the 1 molar sucrose solution for the concentrations are shown below. Results: Experiment 1and 2 Bar graph to show the change in volume of three potato cores immersed in varying concentrations of sucrose solutions for 24 hours Experiment 1 Initial Readings Final Readings Volume Change Sucrose Length Diameter Volume Length Diameter Volume Concentration (mm) (mm) (mm3) (mm) ...read more.

Conclusion

* Increasing the number of Experiments I could also have increased the number of times that I carried out the experiment. I would have more results to make the average graph so it would be more accurate. * Increasing the number of solutions in each experiments If I increased the number of solutions used in each experiment it would be far clearer to see any anomalous results and it would be far easier to draw the best-fit line. This would then help in the conclusion to estimate the point of equilibrium more accuracy and with greater certainty. * Extending the period of time the potato cores are immersed If the time period is increased then the change in volume maybe more profound. This would make observing and analysing the results easier. I think that to extend the investigation I could have: * Used different vegetables I could have used other vegetables such as beetroot, turnips or even another variety of potato. There might have been a more profound difference in the results making them easier to analyse. * Measure the weight of the potato core instead of the volume This may prove to be a more effective way of observing the relationship between the solute concentration and the mass change rather than the volume change. * Use onion tissue Since shells of onions are thin then I could cut a strip and place it in a petri dish with the solute concentrations in them. I could then simply measure the final and initial lengths of the samples rather than calculating they volume. Overall, I feel that the conclusion I have drawn from my experiments verifies the predictions I made prior to carrying out the investigation. Further more I am sure that if the experiments were carried out with the improvements and extensions of the investigation as outlined above, the results obtained would give further credence to my conclusion. 1 ...read more.

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