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The effect of sugar concentration on potato tubers.

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Introduction

The effect of sugar concentration on potato tubers Aim; I will be carrying out this experiment to investigate the effects reflected on a potato tuber; which is left in sugar solutions of various concentrations. Prediction; Diagram 1. I predict that the more dilute (the solution with more water than sugar in it) will result with the potato's mass increasing. I base this prediction on the knowledge I have about osmosis. Osmosis is the term given for the process of water passing through a semi-permeable membrane from the less concentrated solution to a more concentrated solution. If, as in diagram 1, the potato tuber has a higher sugar concentrate than the sugar solution surrounding it, osmosis will take place into the potato, causing the potato in the solution to swell. This is because the plant cells; which make up the potato have become turgid, So that the cytoplasm is pushing outwards onto the cell wall. (Please refer to diagram 2 on separate sheet) To find out how much water the potato is able to take in you may use a simple potometer. The potato takes up water through a capillary tube as shown in diagram 4. The rate of up take can be measured by allowing a small air bubble to enter the tube. ...read more.

Middle

6. Come back to the experiment; pour the solution through a filter to make sure you don't loose the potato you are examining. 7. Reweigh the potato and record the weight 8. Redo the experiment above. 9. Compared the two differences in weights. * How to work out how much of each liquid you have to put in: You want to make 20ml of 0.0M 0ml (sugar) + 20ml (distil water) = 20ml of 0.0M You want to make 20ml of 0.2M 4ml (sugar) + 16ml (distil water) = 20ml of 0.2M You want to make 20ml of 0.4M 8ml (sugar) + 12ml (distil water) = 20ml of 0.4M You want to make 20ml of 0.6M 12ml (sugar) + 8ml (distil water) = 20ml of 0.6M You want to make 20ml of 0.8M 16ml (sugar) + 4ml (distil water) = 20ml of 0.8M You want to make 20ml of 1M 20ml (sugar) + 0ml (distil water) = 20ml of 1M Safety; Although this is a fairly safe experiment we have to be aware of the potential dangers. When using the razor blades we will have to be very cautious, as it is easy to slip and cut your self. We will make sure that we know where the blade is at all times and return it to the place where we got it from. ...read more.

Conclusion

Osmosis is the movement of water from a low concentration to a high concentration through a semi-permeable membrane. When there is more sugar, in ratio to the water, weight is lost. This is because the water that is already present in the potato is passed through to the solution. This is called plasmolysis, the reverse action to osmosis. These two processes are shown in diagram 2. We can also tell that the point in where no transaction is made is between 0.2M and 0.4M of sucrose solution. I have marked out the rough estimate of this point on the graph. If a solution is separated from the pure solvent by a membrane that is permeable to the solvent but not the solute, the solution will tend to become more dilute by absorbing solvent through the membrane. This process can be stopped by increasing the pressure on the solution by a specific amount, called the osmotic pressure- but we have not studied this variable yet. (Information obtained from Britannica CD 1999) Conclusion; My prediction is correct. We did not obtain any anomalous results. I think the results that we obtained clearly show that there is a marked difference in the process; which takes place within the potato when put in different concentrations of sucrose solution. The consistency in the results suggests that the apparatus selected for this experiment was appropriate. I have already suggested a way to find out the approximate intake of water by the potato in my prediction. ...read more.

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