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Osmosis is the diffusion of water through a partially permeable membrane.

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Introduction

BIOLOGY COURSEWORK PREDICTION AND PLANNING Osmosis is the diffusion of water through a partially permeable membrane. It is the movement of water from a dilute solution to a concentrated solution through a partially permeable membrane. If a dilute solution such as water is separated from a concentrated solution such as sugar solution, by a partially permeable membrane, water diffuses across the membrane from the dilute to the concentrated solution. Diagram of Osmosis I am planning to do the investigation on the amount of sugar in the water and see how it will affect the rates of osmosis and the change in mass inside the potato tissues. I think the mass of the potatoes will decrease when the concentration of sugar is higher because when the concentration of sugar in the sugar solution is high; there will be less free water molecules in the solution and comparing to the potato, there are more free water molecules in the potato. So according to what I have said, osmosis will occur and the free water molecules will diffuse through the semi-permeable membrane into the concentrated sugar solution. Apparatus � Knife � 5 beakers � Electronic balance � Measuring cylinder � Tiles � Stop watch I am going to an experiment to find out whether my prediction is correct. ...read more.

Middle

contain dissolved substances. So water tends to diffuse into cells by osmosis if they are surrounded by a weak solution, e.g. distilled water. If the cells are surrounded by a stronger solution, e.g. sugar solution; the cells may lose water by osmosis. ANALYSIS The results of the experiment are: Original mass (g) Final mass (g) Percentage changed (%) 25% of sugar solution 1 0.56 0.55 -1.79 2 0.5 0.48 -4 3 0.57 0.56 -1.75 50% of sugar solution 1 0.48 0.46 -4.17 2 0.55 0.54 -1.82 3 0.59 0.56 -5.08 75% of sugar solution 1 0.51 0.49 -3.92 2 0.57 0.52 -8.77 3 0.56 0.54 -3.57 100% of sugar solution 1 0.5 0.47 -6 2 0.45 0.4 -11.11 3 0.56 0.52 -7.14 After I have got the data, I am going to plot a graph and draw a best-fit line but before that I am going to find the mean of the changed percentage of the mass to make the graph more accurate. Concentration of the solution Mean of the changed percentage of the mass (g) 25% of sugar solution -2.51 50% of sugar solution -3.69 75% of sugar solution -5.42 100% of sugar solution -8.08 After I have plotted the graph and drawn the best-fit line, I found that the best-fit line is a curve line. ...read more.

Conclusion

This is because when the concentration of sugar in the solution is higher which means it has a low concentration of free water molecules, but the potatoes have a higher concentration of free water molecules, so when osmosis occurs, the free water molecules in the potatoes diffuse into the concentrated sugar solution that makes the potatoes' mass decreases. EVALUATION I think the experiment is quite successful apart from the easily squash potatoes which I have to throw them into the bin. I have got the results I need. Then, I drew the graph by the mean of the data I got which makes them more accurate and reliable; this gives me a very good graph. To make the experiment more accurate and reliable, I can put the potatoes in the solutions for a longer period of time because this can let osmosis occurs a longer period of time which let more free water molecules pass into the solutions and the mass of the potatoes will have a more dramatic change. After I take the potatoes out of the solutions, I have to make sure I dry them very thoroughly, or else it will increase the mass of the potatoes when I weigh them. Next time when I have to do experiments with potatoes again, I have to hold them more carefully, or else they will get squash again. ...read more.

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