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Osmosis, What is the effect of sucrose concentration on the rate of osmosis in a potato cell? What is the concentration inside a potato?

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Introduction

Investigation - Biology Coursework What is the effect of sucrose concentration on osmosis in a potato cell? What is the concentration inside a potato? PLANNING 2 AIM 2 WHAT IS OSMOSIS? 2 FAIR TEST 3 PREDICTION 4 PREDICTION GRAPH 4 RISK ASSESSMENT 4 APPARATUS 4 DIAGRAM 5 METHOD 6 BLANK RESULTS TABLE 6 PILOT TEST 7 PILOT TEST RESULTS TABLE 7 PILOT TEST ANALYSIS 7 PILOT TEST GRAPH 8 OBTAINING EVIDENCE 9 RESULTS TABLE 9 GRAPH OF RESULTS 9 ANALYSIS 10 SCIENTIFIC EXPLANATION OF RESULTS 10 CONCLUSION 10 PREDICTION CONFIRMED? 10 EVALUATION 11 QUALITY OF RESULTS 11 ANOMALOUS RESULTS 11 QUALITY OF THE METHOD USED 12 METHOD IMPROVEMENTS 12 IDEAS FOR COLLECTING FURTHER EVIDENCE 12 BIBLIOGRAPHY 16 PLANNING Aim What is the effect of sucrose concentration on the rate of osmosis in a potato cell? What is the concentration inside a potato? What is Osmosis? Osmosis is the net movement of water from a high water concentration (high water potential, a dilute solution) to a place of lower water concentration (low water potential, a concentrated solution) through a partially permeable membrane. This is a diagram to show how osmosis works: When sugar dissolves in water... This diagram, I sourced from [www.gcsesciencehelp.co.uk/concepts/osmosis] I have edited it slightly Hypertonic Solution Hypotonic Solution Concentrated Sugar Solution - A low water concentration or low water potential Dilute Sugar Solution - A high water concentration or high water potential A low concentration of free water molecules A high concentration of free water molecules Sugar molecules pass through the pores more slowly Water molecules are free to move through the pores in the membrane Selectively permeable membrane Sugar molecules attract some of the water molecules and stop them from moving freely. This, in effect, reduces the concentration of water molecules. In the diagram above, the molecules on the left have "captured" about half of the water molecules. There are more free water molecules on the right of the membrane than on the left, so water will diffuse more rapidly from right to left across the membrane than from left to right. ...read more.

Middle

I cannot see any anomalous results in the pilot test graph, however I cannot be sure, due to there being only two points on the graph to justify this. On the other hand, the difference between original points (before averages were calculated) is minimal and signals to a much more reliable set of data. In the pilot test, just using 0.0M and 1.0 M, although providing a quite accurate set of results, is not reliable. In the real experiment, I will use other sucrose concentrations between 0.0M and 1.0M concentrations. These, I will create as in the table below: Sucrose (ml) Water (ml) Sucrose Concentration Created (Moles/Litre) 40 0 0 32 8 0.2 24 16 0.4 16 24 0.6 8 32 0.8 0 40 1.0 In the pilot test, I did not drain the excess sucrose/water from the outside of the potato pieces. This creates a higher mass than the actual, so the actual percentage mass change is lower. This means that the concentration I discovered, 0.38M, is actually slightly lower. In the pilot test, the pieces of potato were cut into cubes. This is a very crude way of preparing the experiment. The surface area cannot have been accurate and there was a difference in the masses. In the real experiment, I will use the cutting method shown in the fair test section using a corer and a scalpel. Pilot Test Graph OBTAINING EVIDENCE Results Table Sucrose Concentration (Moles/Litre) Mass Before (g) Mass After (g) Mass Change (g) % Mass Change (2 decimal points) 0 2.4 2.52 0.12 5.00% 0 2.56 2.67 0.11 4.30% 0.2 2.53 2.59 0.06 2.37% 0.2 2.52 2.54 0.02 0.79% 0.4 2.39 2.35 -0.04 -1.67% 0.4 2.55 2.52 -0.03 -1.18% 0.6 2.53 2.44 -0.09 -3.56% 0.6 2.64 2.53 -0.11 -4.17% 0.8 2.52 2.35 -0.17 -6.75% 0.8 2.43 2.27 -0.16 -6.58% 1 2.48 2.24 -0.24 -9.68% 1 2.51 2.27 -0.24 -9.56% Sucrose Concentration (Moles/Litre) ...read more.

Conclusion

Weighs the water and the sucrose 1 Beaker Holds the water/sucrose when being weighed Diagram Method 1) Set up the apparatus as shown in the diagram without placing the sucrose/water or the potato pieces in the test tubes. 2) Using the weighing scales and the concentration table below make up the different sucrose molarities and pour them into the test tubes Sucrose (ml) Water (ml) Sucrose concentration created (Moles/Litre) 20 20 1 24 16 1.2 28 12 1.4 32 8 1.6 36 4 1.8 40 0 2.0 3) Take the large potato and cut out twelve tubes using the corer. 4) Remove any pieces of potato skin from the tubes 5) Using the computer, make each tube into a 3 cm long cylinder 6) Use the micrometer to make sure that every potato has the same surface area. 7) Record the mass of each potato cylinder. When not weighing put the potato pieces on the tile to prevent moisture loss 8) Place the potato cylinders into the test tubes with the solutions and start the stopwatch 9) After 30 minutes, take all of the potato pieces out of the test tubes and place them on the tile 10) Leave them for the surface moisture to evaporate for 10 minutes 11) Calculate the mass change of each potato and their percentage mass change. 12) Calculate the average percentage mass changes 13) Create a graph of average sucrose concentration against average percentage mass change Blank Results Table Sucrose Concentration (Moles/Litre) Mass Before (g) Mass After (g) Mass Change (g) % Mass Change (2 decimal points) 0 0 0.2 0.2 0.4 0.4 0.6 0.6 0.8 0.8 1 1 Sucrose Concentration (Moles/Litre) Average % Mass Change (2 decimal points) 0 0.2 0.4 0.6 0.8 1 After drawing a scatter graph for these results I will analyse them and see whether or not this analysis confirms my prediction. I feel that I have investigated the independent variable fully and in the future, I would like to conduct a similar experiment for one of the controlled variables (type of cells, etc.) mentioned at the beginning of this coursework. ...read more.

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