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osmosis

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Introduction

GCSE BIOLOGY COURSEWORK BY AASIM GALAL Biology Coursework The aim of this investigation is to find the effect of varying concentration of sucrose solution on the rate of osmotic activity between the solution and the potato chips. Planning The definition of the term Osmosis is the net movement of water from a region in which the water molecules are highly concentrated to a region in which they are less concentrated. This movement must therefore take place across a partially permeable membrane such as a cell wall, which only lets smaller molecules such as water through, but does not allow bigger molecules such as sugar to pass through. In Osmosis, the molecules will continue to diffuse through the cell until the area in which the molecules are found in a large concentration reach a state of equilibrium, which means the molecules become randomly distributed, with no area having a higher or lower concentration than any other. Plant cells are different from animal cells although they both have certain similarities. They both contain a nucleus, cytoplasm, cell membrane and mitochondria. But plant cells are unique in the sense that, only they have a cell wall, vacuole and chloroplasts. This is what makes a plant cell unique from animal cells. The cell wall of a plant is the structure that surrounds each and every plant cell. the cell wall is made of cellulose and it helps to give the plant cell strength and support. When plant cells take up water by osmosis, the pressure inside the cell rises and the cells start to swell, but it is the cell wall that prevents the cell from bursting. When plant cells are placed in dilute solutions (or in this case a weak sugar concentration), they start to become turgid. ...read more.

Middle

5. I tied each of the potato chips to a piece of string. The string was attached to a clamp stand. I now had 6 pieces, one for each beaker. 6. I got a stopwatch and lowered the chips into their beakers at the same time. I left them for one hour. 7. Whilst waiting for the experiment to conclude, I prepared paper towels with which to dry the excess water of the chips. 8. After the hour had elapsed, I pulled the pieces out from the beakers using the string. They were placed on paper towels and each was labelled with the molarity the chip just came out from. This is to avoid any confusion. Each chip was dried using the paper towels. 9. Each potato chip was then placed on an electronic scale and the mass of each chip was carefully recorded. I will also calculate the percentage change in mass. This can be done using the following formula: Change in mass (g) Original mass (g) *100 To ensure my results are going to be precise, I am going to obtain two sets of results which could help me calculate the average. Precautions For my experiment to be fair and for my results to be accurate, I had to make sure that I kept all the non-variables the same. * I had to take extreme caution whilst cutting the potato using the corer, as it was extremely sharp. * I had to be sure that the molarities of the solutions were accurate as these may change the outcome of the experiment. It may cause a change in the results. * My hands had to be dry and clean whilst I was handling the potato chips. ...read more.

Conclusion

A special type of machine could be used in this case. By looking at my graph, there doesn't seem to be any anomalous results. But if I were to repeat the experiment, I could have found another way to dry the chips. Because I may have dried some chips more thoroughly than others this may have altered my results. My results reflect my earlier predictions stated in my planning. I was able to obtain a sufficient amount of results and from which I was able to plot a graph. I calculated the average of all my results including the average percentage change in mass, the average initial mass, and the average mass after and so on. The average was easily calculated by adding my two sets of results and then dividing them by 2. The apparatus used was sufficiently reliable. None of the apparatus was faulty. However, I do think that my experiment was successful and I was pleased with the results I obtained. I was also pleased that my results reflected my initial prediction. There is however one result in my experiment that doesn't seem to fit the general trend or pattern. This anomalous result occurred in the first reading of my results. This may have been caused due to a misread on the weighing balance or just human error. If this experiment were to be repeated, I will make sure that not even one anomalous result will be achieved. The evidence gathered in this experiment is sufficient as I was able to obtain two sets of results which also helped me find the averages of all my results. I managed to draw three line graphs showing my results. I also managed to draw a line of best fit that almost went through all the points on the graph which suggests that the results are sufficiently accurate. ?? ?? ?? ?? 1 ...read more.

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