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The effect of concentration on the mass of potato cylinders.

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Introduction

Aim: The effect of concentration on the mass of potato cylinders. Background information: Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. Cell membranes are completely permeable to water, therefore, in the environment the cell is exposed to can have a dramatic effect on the cell. There are three types of solution; hypertonic solutions contain a high concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel. Hypotonic solutions contain a low concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly burst. Isotonic solutions contain the same concentration of solute as another solution (e.g. the cell's cytoplasm). When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. ...read more.

Middle

This is because the water molecules pass from a high concentration, i.e. in the water itself, to a low concentration, i.e. in the potato chip. Therefore, the chips in higher water concentrations will have a larger mass than in higher sugar concentrations. Method: Apparatus: Sugar solution, distilled water, potato, cork borer, mass balance, boiling tubes, knife, labels and a measuring cylinder. Plan: A range of sugar solutions will be prepared with concentrations from 0.0M to 0.8M, in intervals of 0.2M, by adding varying amounts of distilled water. Sections of potato will be cut using a cork borer and knife to equal lengths of 5cm each, this will keep the surface area constant. 10 ml of each concentration of sugar will be placed in five test tubes and labelled. To each test tube the 5cm piece of potato will be added and its mass recorded. These will be left for 24 hours. Then the potato pieces will be removed, the surface solution removed using paper towels and weighed. ...read more.

Conclusion

It shows that the potato cells increase mass in solutions with a high water concentration and decrease in mass in solutions with a low water concentration. At concentrations above 0.6 M, there appears to be no further water loss, suggesting that the cell is fully plasmolysed. Evaluation: The graph obtained in the results has a strong resemblance to the one in the prediction. This suggests that the experiment was fairly accurate. The accuracy of the investigation was adequate, however the concentrations were measured using a measuring cylinder and could be made more accurate using titration, also when the potato was dried to remove surface liquid it was not necessarily done the same on each potato, a more accurate and uniform way of drying would improve the accuracy further. Although 2 repetitions of each concentration are sufficient, there was no anomalous result. Further work could be carried out to include concentrations that increased in 0.1 M rather than 0.2 M. This would increase the accuracy and improve the results and graph. Other investigations could include using different varieties of potato or different plant tissues e.g. carrot. ?? ?? ?? ?? Declan Gervin Page 1 ...read more.

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