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Osmosis Coursework

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Introduction

GCSE Osmosis Coursework Strand S Aim: We are trying to find out how sucrose concentration affects the mass and length of potato chips. Osmosis is very important to plants because they absorb water through their roots by osmosis. Plant cells become turgid when they absorb water, this is important because it makes the leaves erect to absorb more light from the sun for photosynthesis. When plant cells have lost water it becomes flaccid or plasmolysed. Water stops entering plant cells when the cell becomes turgid, because the cell wall rejects water. Osmosis in animal cells is very different as animal cells don't have a cell wall. Therefore the cells burst if there is too much water. If the cell doesn't have enough water it shrivels up. Prediction: I predict that the potatoes in a weak concentrated sucrose solution will increase in mass and length. I also predict that potatoes in a highly concentrated sucrose solution will decrease in mass and also length. The rate that it passes depends on pressure, concentration and temperature of the molecules or solutes on either side. If the solution is a sucrose solution then the mass of the potatoes will decrease. This is because more water will be moving out of the potato than entering it. A semi-permeable membrane allows small molecules through, this means that water molecules are able to move freely, however the sucrose molecules are too big and will not be able to go through. ...read more.

Middle

I will change the concentration of sucrose solution from 0.0 (water) to 0.8. This is to see the affect on potatoes when put in different concentrations. Safety: Method ? A range of sucrose solutions will be prepared with concentrations from 0.2 M to0.8M, in intervals of 0.2M, as well as one test tube filled with distilled water. ? Sections of potato will be cut using a cork borer as this is the most accurate way of getting the lengths equal. ? About 15 ml of each concentration of sucrose will be placed in three test tubes and labelled. ? To each test tube a cut piece of potato will be added and its mass added to the label. These will be left for about 1 hour ? Then the potato pieces will be removed, the surface solution removed using paper towels and weighed. ? Three readings are taken for each concentration in order to get an average and reduce the effect of inconsistent results. ? As it is difficult to get the cut potato pieces to the same mass it was decided that a percentage change in mass will be used to compare the data in the results, as this would be far more accurate. Results Concentration of sucrose solution and water Initial mass of potato chips(g) ...read more.

Conclusion

If the experiment was repeated I could find another way to dry the potatoes that would ensure that all were dried in the same way for the same time. Another way of improving the results would have been to leave the experiment running longer, this would have enabled me to find the point when the potato can no longer take in any more water and when the potato cannot lose any more water and therefore get a more accurate result. There also another problem that could have gained a less accurate result this was the fact that the cork borers kept on overlapping and causing some chips to not be the same size as the others Further work To find out whether or not this investigation could have investigated the effect other factors had on the rate of osmosis. The temperature of the water in the sucrose solution is one. It would prove that the protein in the potato membrane stops after the optimum temperature which is about 37 degrees and osmosis would no longer take place as the membrane is ruined. We could also investigate how sucrose concentration affects the mass of other vegetables or foods as this could give us an entire view on the affect of osmosis in potatoes. Furthermore we could try and change the sucrose solution from sucrose to fructose and see if the different types of sucrose have diverse changes to the potatoes. ?? ?? ?? ?? Jamil Nwoko 11CMC ...read more.

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