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Investigate the effects of varying concentration of sucrose solutions on the amount of osmotic activity between the solution and a potato chip of a given size.

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Introduction

Osmosis in Plant Cells Aim The aim of this experiment is to investigate the effects of varying concentration of sucrose solutions on the amount of osmotic activity between the solution and a potato chip of a given size. Variables In order to create a fair test, certain aspects of the experiment will have to be kept the same whilst one key variable is changed. In my experiment, I have chosen to vary the concentration of the sucrose solution. This should give me a very varied set of results from which I hope to make a reasonable conclusion. I must make sure that all of the controlled variables (listed below) are kept constant or else it would mean it would not be a fair test. For instance, if one of the potato chips was slightly longer than the others, the surface area of the potato chip would be larger and therefore there would be more space for osmosis to occur. Controlled Variables: Controlling variables such as the ones below means that the experiment will be fair. * Temperature - for the purpose of my experiment I am going to do all my experiments at room temperature. I will make sure the temperature is constant by doing each experiment in the same room, and ensure that no other factors (such as open windows or strong lights) will change this. * Type of potato - the potato chips should all be cut from potatoes of similar size and weight, using the same tool and without being washed or peeled, to ensure that my experiment is fair. * Size of potato chips - the mass of the potato should be measured throughout the experiment, and should be measured in grams. ...read more.

Middle

* 1 Potato Borer - for making the potato tubes. * 1 Ruler - to measure the length of the potato tubes. * 1 Stopwatch - to measure the length of time the potato tubes were left in their solutions for. * 1 Set of Scales - to measure mass of potato tubes before and after being put in the solutions. * Sheets of blotting paper - to blot off any excess solution after removing the potato tubes from their solutions. * 1 roll of cling film - to put on top of the test tubes to prevent the solutions from evaporating. Changes in Method Due to the questionable results in the pilot experiment, the following method was adapted and corrected. The subsequent changes were made: * The total amount of solution was increased from 10 ml to 25 ml, in order to have enough solution to properly cover each potato chip. * More tests were added, so that three test tubes of each concentration of sucrose solution were tested instead of just one. This way, an average result can be obtained for each concentration. * Cling film was placed over the top of each test tube before being left, in order to prevent any solution evaporating. * The total amount of time that the potato tubes were left in the solutions was decreased from 24 hours to 2 hours. This would give us a better and more accurate set of results. * More accurate scales were used. Final Method 1. The experiment started with a range of sucrose solutions with concentrations of 0 molar, 0.1 molar, 0.2 molar, 0.3 molar and 0.4 molar being prepared. ...read more.

Conclusion

* The reading on the scales may have been read incorrectly. To prevent such anomalies occurring in the future, I can improve the accuracy of my experiment. This can be done in the following ways: * The range in the size of the potato chips should be decreased. This should be done by more accurately measuring each potato tube. Using a more accurate way of cutting the potato pieces, other than just a ruler and scalpel, could also do it, as this method was relatively imprecise. * The accuracy of each concentration should be improved. Being more careful when mixing up the sucrose solutions, and using the measuring equipment such as pipettes and measuring tubes more accurately should do this. * The reading on the scales should be read more accurately. This could be achieved by making sure that no other interferences (such as standing to close to the scales) impair the results. * The scalpel could be sharper. Other experiments that could be carried out involving potatoes could be: * Using higher concentrations of sucrose to put the potato tubes in. This could expand the range of results, and see how much higher sucrose concentrations affect the potato cells. * Using different types of potatoes. This would allow me to determine if different types of potato have a higher or lower water potential than others. * Using different vegetables. This would allow me to determine if different types of plant tissue have a higher or lower water potential than others. * Varying the temperatures of each solution. This would allow me to observe how varying temperatures affect the rate of osmosis in plant cells. Despite the slightly anomalous results in my experiment, I think that it was a fairly reliable experiment and my results were relatively precise and accurate. ...read more.

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