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An investigation to demonstrate osmosis using a potato

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Introduction

An investigation to demonstrate osmosis using a potato Aim I am going to investigate osmosis when potato is placed in different concentrations of sucrose. I am aiming to witness osmosis in 6 different concentrations of sucrose. I will use 6 varying concentrations so that I have a wider spread to compare the results, and check that I don't have any anomalies. Prediction Osmosis is the process of diffusion of water molecules from a weaker solution into a stronger solution, through a semi permeable membrane. The tiny pores in the membrane of the potatoes will allow the water molecules to go in and out of the potato cell, depending on the concentration gradient between the potato and the sucrose solution. If the water concentration is lower in the potato than in the sucrose solution, then water will pass from the sucrose solution into the potato, and it will gain weight. If there is a higher concentration of water in the potato, then the water will go out of the potato and into the sucrose solution, as osmosis is the movement of water molecules from a region of high concentration to a region of low concentration, through a semi permeable membrane. So, I predict that the higher the concentration of sucrose, the lower the weight of the potato as water from the potato diffuses into the sucrose solution. Predicted graph of results: Apparatus * 6 test tubes * 6 different concentrations of sucrose solutions * Potato * Potato cutter/core * Digital measuring scales * Measuring cylinders * Knife * Test tube racks * Coloured felt pens * Tissue paper Method I will need 3 pieces of potato in each tube. ...read more.

Middle

The weight taken at the beginning is also not correct, so I may have made a mistake right from the start. TABLE 1 I repeated the whole investigation, as the ones above were incorrect. This is my second attempt, and the results are correct this time. TABLE 2 Conclusion I found out that as the concentration of sucrose increases, the weight of the potato decreases. In water it gained 1.26 grams, but in 1 Molar sucrose, it lost 0.16 grams. My prediction supports my conclusion. I have calculated the average change in weight to have a simple, clear idea where the experiment is leading me to. Instead of having a large number of weights, I combined them into one by averaging them. I found the average by adding the weight gain/loss for each tube and divided it by three. To find the percentage, I multiplied that decimal by 100. I drew a line graph, and then a line of best fit, which is sloping downwards, negatively. This proves that the weight is getting lower as the percentage of the sucrose concentration is getting higher. In my investigation I found a definite relationship between the 2 variables - weight and concentration of sucrose. Any increase in sucrose concentration led to a decrease in weight. The prediction is supported by the evidence of the graph. Although there is one anomaly, all the other results stand out and give a straight line of best fit - exactly as I predicted. ...read more.

Conclusion

This would have a more spread to the results, and therefore, results can be compared and evaluated more thoroughly. They would be very accurate as well as reliable. As I have an anomaly, my evidence may not be extremely correct. I would have to do more research to what I have already done (in the conclusion) on osmosis, and see what actually happens, and see if it occurs in plant cells all the time. If I were to repeat the experiment, I would use a very accurate scale, so that results would come out accurately and then I would have a nice average. The graph will be fairly accurate. I would also make sure that the scale and the potato slices are properly wiped. This is because if they are not wiped, the weight would increase, and will not be accurate. I could use a syringe or a burette to measure the 10ml of sucrose solution, because those two apparatus are very accurate. I would do several more experiments with bigger sizes of potatoes to obtain more evidence to support my conclusion. I will also some research on osmosis, and this will make me certain of my evidence if I have many to compare with. I will agree with the majority. Overall, I am very pleased with these results and with the evidence I have so far, that osmosis occurs when there is a high concentration and a low concentration, both aside a semi-permeable membrane. The lower concentrated substance diffuses through the membrane to where there is the higher concentrated substance. ?? ?? ?? ?? Mariyah Zainuddin ...read more.

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