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The aim of this experiment is to investigate the movement of water into and out of plant cells by osmosis. The cells chosen for study will be taken from potato as they provide a ready supply of homogeneous material.

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Introduction

Osmosis Aim - The aim of this experiment is to investigate the movement of water into and out of plant cells by osmosis. The cells chosen for study will be taken from potato as they provide a ready supply of homogeneous material. Osmosis is the diffusion of water molecules across a partially permeable membrane from a high concentration of water to a low concentration of water. Movement of substances takes place through the cell membrane, which separates the different substances in the cell from its surroundings. This type of membrane allows small molecules such as water to pass through it, but it denies entry to large particles, such as glucose, to pass. This membrane is called a partially permeable membrane. The amount of water inside a cell is called water potential. Variables that may affect the experiment (rate of osmosis) - * Concentration of Salt Solution * Size of the potato * Temperature of surroundings * Time Prediction - Osmosis is the movement of water molecules, where water molecules diffuse from a highly concentrated region, to a region in which they are less concentrated. ...read more.

Middle

Weight of potatoes Before Experiment (g) Salt Concentration (%) A B C 0 0.67 0.73 0.77 0.5 0.75 0.80 0.67 1 0.73 0.68 0.72 1.5 0.64 0.60 0.67 2 0.78 0.64 0.73 2.5 0.74 0.74 0.71 3 0.68 0.64 0.70 Weight of potatoes After Experiment (g) Salt Concentration (%) A B C 0 0.87 0.78 0.89 0.5 0.71 0.79 0.63 1 0.71 0.64 0.71 1.5 0.58 0.54 0.58 2 0.58 0.51 0.59 2.5 0.51 0.53 0.50 3 0.40 0.42 0.46 Observations: 0 - Hard, 0.5 - Fairly Hard, 1 - Hard, 1.5 - Soft, 2.0 - Slightly Soft, 2.5 - Very Soft and 3 - Very Soft. Change In Mass (g) Concentration Of Salt Solution (%) A B C Average Change In Mass (X) Average Start Mass (Y) Percentage Change In Mass (X/Y *100) 0 0.2 0.05 0.12 0.123 0.723 17.01% 0.5 0.04 0.01 0.01 0.02 0.73 -2.73% 1 0.2 0.04 0.01 0.023 0.71 -3.23% 1.5 0.06 0.06 0.09 0.07 0.636 -11.01% 2 0.2 0.13 0.15 0.16 1.663 -9.62% 2.5 0.23 0.21 0.21 0.216 1.72 -12.55% 3 0.28 0.22 0.24 0.246 1.553 -14.30% The graph clearly shows as I increase the concentration of the salt solution, the weight change (%) ...read more.

Conclusion

would expect the beaker which contains plant tissue of 5% salt to decrease slightly compared to the plant tissue which decreases more in size and mass because it was placed in a solution of 10% salt. This is because water molecules move from a high concentration i.e. the solution, to a low concentration i.e. the plant tissues. Therefore, the potatoes cylinders in higher water concentrations will become swollen and increase in mass compared to the salt concentrations. After a certain period of time I predicted that the plant tissue will not be able to increase in size any further this is because the plant tissue is completely swollen. And the opposite will happen if I place the plant tissue in a solution with higher salt concentration than water concentration. I predict that the potato tissue will have become soft and weak, and its size will decrease more according to the concentration. This is because osmosis is the diffusion of water from a region of high concentration of water i.e. plant tissue, to a region of low concentration i.e. salt solution. Using this I can say that my prediction was correct. ?? ?? ?? ?? By David Pryse ...read more.

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