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Osmosis Investigation

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Introduction

Osmosis Investigation Introduction Osmosis is defined as the diffusion of water molecules, down a water potential gradient, across a partially permeable membrane. If the solutions on each side of the partially permeable membrane are equally concentrated then there will be no net movement of water across the membrane. If the solution outside the cell has a low concentration of solute, this causes cells to become turgid as water flows into them, or if the solution outside the cell is of high concentration the cells become plasmolysed as the water flows out. Aim The aim of this investigation is to see what effect concentrated sugar solution has on the rate of osmosis on a vegetable. The vegetable chosen for this experiment is a potato. They have soaked in several concentrations of sucrose solution; these concentrations are 0.2, 0.4 and 0.6 and then the class concentrations of 0.2, 0.3, 0.35, 0.4, 0.5 and 0.6. These are the results I will observe and analyse. Hopefully if this method is successful, I will be able to observe osmosis at work. Equipment The equipment that I will require and will be using in this investigation, are: * Potatoes * Boiling Tubes * Weighing Scales * Ruler * Varying Concentrations of Sucrose * Water * Potato Borer * Stopwatch * Test tube rack Method My method to carry out this investigation is shown below in step by step instructions: 1. ...read more.

Middle

This means that the water from the cells will diffuse out into the surrounding solution which will balance the water and sucrose concentration. As the cells lose water through diffusion, the potato chips become plasmolysed, causing the chips to collapse, which will then obviously cause the chips to change in mass and length. The above can be reversed when the concentration in the potato chip is greater than the surrounding solution. Instead of the water diffusing out, it diffuses into the cell causing the chip to become turgid, making the potato chip swell. Using this principle, we will be able to find out the concentration of the potato cell, so when the mass or length of the potato is unchanged we know that no water has diffused in or out, so this means the concentration of the sucrose is equal to that inside of the potato chip. Diagram This diagram explains the experiment we are carrying out, when the solution outside the cell has a greater concentration than the cell inside. Results Table Solution Trial Before After Change %Change Av. % Change Water 1 2 3 20 20 20 22 20 21 2 0 1 10% 0% 5% 5% Sucrose 0.2M 1 2 3 20 20 20 22 22 21 2 2 1 10% 10% 5% 8.3% 0.4M 1 2 3 20 ...read more.

Conclusion

So the osmotic potential of the potato chip is 0.305m. Evaluation The results and graphs obtained are roughly in line with my predictions. Although the results were fairly accurate, I still think the investigation went fairly well and they were good enough to prove our hypothesis. The accuracy of the investigation was adequate, however there are some improvements that could be made if we were to do the experiment again; * Firstly carrying out more tests will enable us to obtain a more accurate average. * We did not take the potato chips out at the same time allowing some chips more time in the sucrose; this could have affected the results and so should be taken into consideration if there were to be a next time. * Use a wider range of sucrose solutions. * When the potato was dried to remove surface liquid it was not necessarily done the same on each potato, allowing some to weigh more. * Although the osmotic potential for this investigation was estimated, a more scientific approach would have been better. * Selecting a better root vegetable to see how the results differ. These points can all be taken into consideration for a re- test, but I believe this experiment went well and we obtained the results that proved my hypothesis and prediction. Mustaq Miah 11G Ms Chugtai Biology Coursework - 1 - ...read more.

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