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Osmosis Experiment Aim: To investigate the factors which affect osmosis in potatoes and to investigate one in detail.

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Introduction

Osmosis Experiment Aim: To investigate the factors which affect osmosis in potatoes and to investigate one in detail. Introduction: Osmosis is the net movement of water from a high concentration to a low concentration through a semi permeable membrane. This diagram demonstrates it. In plants osmosis takes place between the cytoplasm and the solution outside of the cell. The effects of osmosis on the plant cell are visible to the eye. When a plant cell is placed in a less concentrated sugar solution the water passes through the cell wall, cell membrane and cytoplasm and into the central vacuole. The increased pressure in the central vacuole pushes out on the walls of the cell which gives the cell rigidity. When the plant cell is in this state it is known as being turgid. Sometimes plants cells can be placed in more concentrated sugar solutions, although this is unlikely in nature. If this happens the water passes out through the central vacuole, through the cytoplasm, the cell membrane and the cell wall into the solution outside the cell. This causes the pressure inside the central vacuole to decrease. The cell looks visibly deflated and limp. This state is known as plasmolysed. The solution which has a higher osmotic pressure is known as being hypotonic. ...read more.

Middle

Pot Number. Morality of solution 1 1Molar = 30ml 340g/l sugar solution 2 0.75Mola r= 22.5 340g/l sugar solution 7.5 distilled water 3 0.5 Molar = 15ml 340g/l sugar solution 15 ml distilled water 4 0.25Molar = 7.5 340g/l sugar solution 22.5ml distilled water 5 0Molar= 30ml 340g/l distilled water 5. I will cover each pot with cling film. 6. I Will leave the solutions for 24 hours 7. I will weigh the potato pieces using the balance. 8. I will calculate the difference in potato mass, recording my results. Diagram Prediction: I predict that pot one, with the highest concentration of sugar solution, will have the lowest mass after 24 hours. I think that pot five, with the lowest sugar concentration, will have the greatest mass after 24 hours. I think this is because in pot five there is no sugar outside of the potato cells. Inside the cells there is a weak sugar solution inside the central vacuole know as sugary sap, therefore the sugar concentration inside the cell is greater than outside the cell. This means that outside the cell there is a higher water potential and therefore the majority of the water will move into the cell causing the potatoes mass to increase. ...read more.

Conclusion

There will be no change in mass if the solution is approximately 0.15 Molar, because the concentration of sugar solution will be equal inside and outside of the potato cells i.e. an isotonic state. Evaluation: I feel my experiment was quite successful. I obtained a good range of results which enabled me to come to a reasoned conclusion. However I had one outlier, as indicated on the graph. I think that this could be eradicated by using three different pots for each molarity of solution, each containing one piece of potato, rather than one pot per molarity of solution each containing three pieces of potato. This would mean that if one of the pots some how became contaminated and the concentration of the solution was changed we would still be able to use the other two pots to find an accurate average of that molarity. I tried hard to ensure that I kept the experiment a fair test and although I had one outlier I think I kept the conditions constant. If I were to continue this experiment I could look at different factors that affect the rate of osmosis in this variety of potato. Alternatively I could look at different varieties of potatoes and compare my results. I could also look at the rate of osmosis in other root vegetables such as carrots and compare these results. ...read more.

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