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Osmosis - The aim of the practical was to find incipient plasmolysis using potato discsuss

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Introduction

Osmosis Aim The aim of the practical was to find incipient plasmolysis using potato discs. Apparatus Large potatoes- this was the sample I was using. 1.0 Molar solution- this was used to see when incipient plasmolysis takes place. Cork borer- this was used to provide consistency between the size of the potato discs. Petri dishes- to place the potato discs into. Filter paper- so the potato discs are dry before weighing otherwise the potato discs would weigh more than they should do. Razor blade- to cut the blocks of jelly up as accurate as possible. Stopwatches- To time 15 minutes when I would weigh the discs again. Method 1) From the 1m solution prepare the same volume of five different concentrations of sucrose solution. 2) I will use the cork borer to take cylinders of tissue from the same potato. ...read more.

Middle

Weight after second weigh. Weight difference. Concentration. Percentage change. Increase mass or decrease. 1.84g 1.31g -0.53g 0.6 -28% decrease 2.60g 2.02g -0.58g 0.2 - 22% decrease 3.83g 4.17g +0.34g 0.4 +8% increase 2.19g 2.16g -0.03g 0 -1% decrease 1.79g 2.05g +0.26g 1 +14% Increase 1.69g 1.42g -0.27g 0.8 -16% Decrease Analysis 0.2m The water is moving from the cells to the outside this means the outside of the cell has lower water potential, than inside the cell. 0.4m In this solution the water potential inside the cell is greater so the water moves into the cell increasing its mass. 0.6m This is the concentration at which incipient plasmolysis has taken place because this is when the mass has decreased the most. 0.8m The water potential inside the cell was greater than that on the outside so the water moved from inside the cell to outside. ...read more.

Conclusion

Evaluation My experiment did not go as well as I had hoped I had hoped to come up with some more accurate results. Nether the less I still found some results very useful. On the hole my results showed that as the concentration increased the weight of the potato discs increased. When the concentration as 1m the weight of the potato discs increased which proves my theory. Also I have read books which show when the concentration outside the cell is greater the weight should increase. Which brings me back to my theory that there were some inaccuracies in concentrations 0.6 and 0.8. I believe this because in the concentration 0.4m and 1m the weight increased which leads me to believe 0.6m and 0.8m were inaccuracies. To overcome the problems incounted I would probably try a different experiment. Like using a selectively permeable membrane with water in and sugar solution on the outside. ...read more.

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