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Investigating Osmosis In Potato Cores

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Introduction

Investigating Osmosis In Potato Cores Scientific Knowledge Water potential is the measure of free kinetic energy within a system and the capacity of a system to lose water. Water molecules move from an area of high water potential to an area of lower water potential. If you change the water potential of a solution an effect should be seen on cells placed in the solution. The effect should be that the lower the water potential of the surrounding substance the more flaccid the cells placed in the substance become. So the more concentrated the sugar solution is, the more flaccid the potato cores in it will be. The whole subject of osmosis is to do with water potential. Water has a water potential of zero, sugar solution has negative water potential. The rule is that the water molecules move from a more positive water potential to a more negative water potential. Definition of osmosis: The movement of water molecules across a partially permeable membrane from a region of high water concentration to a region with low water concentration. (From: GCSE Double Science Revision Guide) Diagram of Osmosis: 1. 2. = A water molecule = A glucose molecule = A semi-permeable membrane The right hand part of diagram 1 is a sugar solution, which has a low water concentration. ...read more.

Middle

20ml Water 6.65 20ml 5 % sucrose 6.34 20ml 10 % sucrose 5.67 20ml 15% sucrose 5.24 20ml 20% sucrose 4.28 Here is a graph to show the change in mass of the potato cores before and after they were placed in different solutions Series 1 is the mass of each set of cores before they were placed into different solutions. Series 2 is the mass of each set of cores after they had been placed in different solutions. Experiment 2 For this set of results I changed the mass of the cores to 4 grams to see if there was any noticeable difference. AFTER BEFORE Solution Mass (g) 20ml Water 4 20ml 5 % sucrose 4 20ml 10 % sucrose 4 20ml 15% sucrose 4 20ml 20% sucrose 4 Solution Mass (g) 20ml Water 4.00 20ml 5 % sucrose 3.83 20ml 10 % sucrose 3.27 20ml 15% sucrose 2.63 20ml 20% sucrose 2.22 Here is a graph to show the change in mass of the potato cores before and after they were placed in different solutions. Series 1 is the mass of each set of cores before they were placed into different solutions. Series 2 is the mass of each set of cores after they had been placed in different solutions. ...read more.

Conclusion

However even if I did employ these techniques into my investigation I would still have loots of other sources of error. For example I would have to try and keep the same potato. I did do this where I could and I did use the same type of potato but could not use the exactly the same potato. I didn't use the same weighing machine each time either so there could have been unnoticed errors in my results. Drying the potatoes was a huge source of error. If I had time I would make sure that each core was dried as much as the next one. The temperature of the room was not under my control and as temperature increases the rate of osmosis I would have to make sure that the temperature stayed the same if I had time. The concentrations may not have been exactly the right concentration and may have changed slightly from day to day. If I had more time I would also attempt to look at different types of potato or go past the 20% concentration level and look at plasmolysis. Or I would investigate the things I didn't change like different surface areas (therefore smaller and larger sites for osmosis) or different temperatures or variable light intensity or even smaller changes in the concentration of sucrose Satch Patel Biology Coursework 02/05/2007 1of3 ...read more.

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