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To investigate how osmosis in potatoes is affected by varying the concentration of a salt solution.

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Introduction

Investigation into the effect of Concentration on the Rate of Osmosis Aim: To investigate how osmosis in potatoes is affected by varying the concentration of a salt solution. Introduction: Osmosis is the movement of water molecules between selectively permeable membranes. It takes place in all cells, at the surface of the organism. In order for osmosis to take place, a concentration gradient is needed on each side of the cell membrane. The water molecules move across the membrane during osmosis and always travel from a higher concentration to a lower concentration. If a potato chip is put into water, where the number of particles inside the potato is less than that compared to the number of particles outside the potato, the mass of the potato should increase, due to the fact that the water would be able to travel through it; the concentration outside the potato is less than that of the concentration inside the potato. However, if the water concentration was to be changed, i.e. salt was added, the concentration of the water would increase and the solution would become stronger than that of the potato, then the water molecules would be able to move out, rather than in, and so the potato would decrease in mass. ...read more.

Middle

This occurs when a concentration gradient is established. The water molecules which move across the membrane during osmosis always travel from the higher to the lower concentration. So if we leave a potato chip in distilled water, where the number of particles (water molecules) in the potato is less than the solution outside of the potato than that inside the potato, water should travel into it and its mass should increase. Now if the distilled water were replaced with 0.5 molar (0.5M) salt solution, the concentration of water in the potato would become higher than that of the solution to which it is being compared and therefore, water molecules would move out of the potato and its mass would decrease. When an identical potato chip is then placed in a weak solution of 0.5M, the concentration of water would be higher in the potato chip and therefore the rate of water loss in the potato chip would be greater than the rate of water entering the potato chip and therefore the cells in the potato chip would become flaccid (when the contents of the cell pull away from the cell wall, the process is called plasmolysis and the cells have become plasmolysed) this is because of osmosis as the concentration gradient has tried to be lessened. ...read more.

Conclusion

* Do not distract others while they conduct their experiment. Preliminary Experiment: To ensure that my experiment would be carried out without any problems and inconveniences, I conducted a preliminary experiment prior to my actual experiment. Concentration (Mole, M) Mass of Chip 1 Mass of Chip 2 Mass of Chip 3 Average mass Change in mass (Gram, g) (Gram, g) (Gram, g) (Gram, g) Before After Before After Before After Before After g % 0 1.02 1.2 1.11 1.33 0.99 1.35 1.04 1.29 0.25 24.01 0.5 1.2 1.19 1.15 1.13 0.98 0.95 1.11 1.09 -0.02 -1.08 1 1.09 0.98 1.03 0.99 1.10 0.92 1.07 0.96 -0.11 -10.28 1.5 0.99 0.81 1.03 0.85 1.10 0.82 1.04 0.83 -0.21 -20.19 2 1.04 0.70 1.00 0.65 0.98 0.59 1.00 0.65 -0.35 -0.35 I will now plot the results I have on a piece of graph paper. This will enable me to read the results more clearly and to draw a definite conclusion as to whether my prediction was correct or not. I will also be able to see which changes I need to make, where I will have an anomalous result, which I will be able to change during the actual experiment. Graph (on next page): Analysis of Preliminary results: As evident by the graph, my prediction has been proved; as the concentration gradient increases the amount of osmosis will also increase. ?? ?? ?? ?? - 1 - Naaila Haq 10g1 Biology Coursework-Osmosis ...read more.

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