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The aim of this experiment is to investigate the effect that different concentrations of sucrose solution has on osmosis in potato chips.

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Introduction

Osmosis Coursework Aim The aim of this experiment is to investigate the effect that different concentrations of sucrose solution has on osmosis in potato chips. Scientific Knowledge Osmosis is the passage of water from a region of high concentration, through a semi -permeable membrane, to a region of low water concentration. A semi - permeable membrane (such as a cell wall) will allow small molecules such as water, Oxygen and Ammonia to pass through easily, but will prevent larger molecules, such as sucrose, starch and protein, from passing through. Osmosis generally tries to even the concentrations either side of the semi permeable membrane out, as shown in the picture to the left. This is also known as reaching equilibrium. Plant cells, such as those found in potatoes, can absorb water because the cell membrane is semi - permeable. When the cell absorbs the water it swells and becomes turgid. This is an essential in plant structure because it allows them to stand up by themselves without any aid. Eventually the pressure inside the cell will rise due to the excess amount of water and reach a point where no more will be able to enter. This is called hydrostatic pressure and it works against osmosis. Osmosis is an essential process in all-living things as it allows water to be passed from cell to cell, transporting it around the entire body or plant. When plant cells are placed in sugar solutions that have a lower content of water than the cell, the cells lose water and become flaccid. ...read more.

Middle

Results Concentration M 0 0.25 0.5 0.75 1 Mass before (g) 1.23 1.23 1.23 1.23 1.23 Mass after (g) 1.28 1.25 1.2 1.17 1.16 Difference (g) 0.05 0.02 -0.03 -0.06 -0.07 Percentage change 4.07 1.63 -2.44 -4.88 -5.69 Concentration M 0 0.25 0.5 0.75 1 Mass before (g) 1.37 1.35 1.35 1.35 1.35 Mass after (g) 1.47 1.38 1.35 1.39 1.31 Difference (g) 0.1 0.03 0 0.04 -0.04 Percentage change 7.29 2.22 0 2.96 -2.96 Concentration M 0 0.25 0.5 0.75 1 Mass before (g) 1.81 1.71 1.74 1.79 1.75 Mass after (g) 1.93 1.78 1.75 1.72 1.68 Difference 0.12 0.07 0.01 -0.07 0.105 Percentage change 6.63 4.09 0.57 -3.91 -4 To work out the percentage change I used the formula PC = Difference Mass before This will help me to put all of the three of the experiments into perspective and give them all a relative number. This will then allow me to calculate an average to get the most reliable result. So here is a table with the average percentage change for each concentration. Concentration (M) Average Percentage Change (%) 0 6 0.25 2.65 0.5 -0.62 0.75 -1.94 1 -4.12 I will now put this information into a graph to give me a better indication of any correlation that has emerged Analysing and considering evidence The graphs on the previous pages show simply that as the concentration of sucrose in the solution surrounding the potato increases the mass of the potato chip decreases. The fourth graph drawn was that of average percentage change across three experiments. ...read more.

Conclusion

However, the three individual experiments were carried out over a period of one week, running a risk of completely different temperatures and climates to work in. Additional experiments could be undertaken to investigate other possible factors affecting the amount of osmosis taking place in a potato chip. The first is that we could establish if temperature affects the amount of osmosis that takes place. I would do this by having two different concentrations of sucrose solution (such as 0M and 1M). Two potato chips would be submerged in 0M and 1M solutions at room temperature and two would be placed in heated solutions. After leaving them for a specified amount of time I would compare the weight after from the weight before. This would tell me whether the rate of osmosis can be changed by temperature and would also help me in the current investigation. I predict that in this investigation the temperature increasing would cause the rate of osmosis to increase. If the solution is heated, particles will be moving faster and reaching the semi-permeable membrane with more speed. The second experiment that could be undertaken is to investigate how different types of potato affect the rate at which osmosis occurs. No two types of potato will hold the same concentration of water molecules. If I were to investigate this I would use the same concentration of sucrose solution and five different types of potato, possibly with different origins. I would then leave the chips in the solution for a suitable amount of time before comparing the weight before and after. This further investigating may help to support my conclusion in this current investigation and may also help to explain the anomalies. Emma Lerway Biology Coursework 2003 ...read more.

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