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The effect that different concentrations of salt solution in the water has on strips of potato, due to osmosis

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Introduction

Iestyn. Evans 11D Biology Coursework - Osmosis For my biology coursework a will be conducting an experiment to discover the effect that different concentrations of salt solution in the water has on strips of potato, due to the effect of osmosis. The experiment will be conducted by having different test tubes each filled with a different concentration of salt solution, and 2 strips of potato. Each test tube is then left for 24 hours and then the changes recorded. But for the changes to be recorded I must decide on a factor to record. I shall decide on a factor to record, to see what effect osmosis has on the factor, and to record any change in that factor from the start at the end of the experiment. I have decided that factor shall be mass (of the potato strip), because in my opinion that is the factor that can be recorded with the finest accuracy. So the potato strips will be weighed (separately) at the start of the experiment, and recorded, weighed after the experiment, then recorded again. Then the percentage change (in mass) of the potato strip worked out for each individual strip worked out. As there will be two strips for each tube, I will have two percentage changes, so the average percentage change will be worked out for each tube. The results will then be recorded in a table, and then a graph. Now I shall put forward my hypothesis, which is, a short statement saying what I think will happen - As the concentration of salt solution in the water increases, the mass of the potato strips in the water will decrease. ...read more.

Middle

There will be 2 test tubes for each concentration labelled A and B, so in all there will be 12 test tubes. 12 strips of potato shall be cut with a size 2 borer, and at a length of 3 cm, and a strip of potato placed in each test tube. But before being placed in the test tube each potato strip must be weighed on an electronic scale and recorded in a table. After the experiment is complete each piece of potato shall be dried and then re - weighed, and the new weight recorded. All in all I will have 4 weights for each concentration (2 weights per test tube, 2 test tubes for each concentration labelled A and B), one weight for test tube A before experiment, and one weight for test tube B before experiment = 2 weights. Ten we will have one weight for test tube A after experiment, and one weight for test tube B after experiment = 2 weights. I will be using 20 cc of solution, here is a table showing how I will be setting up all the different concentrations: Concentration (M) Water (cc) Salt Solution (cc) 0.0 20 0 0.2 16 4 0.4 12 8 0.6 8 12 0.8 4 16 1.0 0 20 List of apparatus: Salt solution, Water, Measuring Cylinder, Size 2 borer, Knife/scalpel, Potato, Cutting tile, 12 glass test tubes, Test tube holders (Rack), Sticky labels, Electronic Weighing scales, Ruler (For measuring length of potato). ...read more.

Conclusion

The measuring for concentration (cc), and Mass of potato strips, were done very accurately using a measuring cylinder for the concentration and electronic scales for the mass of the potato. The measuring was done to the most accurate degree possible, the only measuring were it was maybe slightly inaccurate was the cutting of the potato strips as there was no equipment to help us measure them accurately, so we relied on the accuracy of the naked eye, and a ruler. Conclusion - Overall the experiment was completed successfully, but if we were to re do the experiment we would ask for more time. As the time scale was very small it didn't allow the group to cut sufficient amount of potato strips. Also, if I was to repeat the experiment I would make sure that all the potatoes used in the experiment were the same age, and species/brand to get a greater degree of accuracy in the experiment for better results. I could have also used a more accurate scale, which again would have provided a greater degree of accuracy for the optimum results. When pushing through the potato with the borer I could have been pushing through a hole that had already been used, which could give an inaccurate when weighing. And as we relied upon the naked eye when cutting the potato strips to length a degree of accuracy has been lost. If we were to repeat this experiment again I would try to ensure that I had the best modern technology available to get the most accurate set of results possible. ...read more.

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