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Biology Lab Report-Osmosis

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Introduction

Shreya Shah IBD Year 11 Biology Lab Report: Osmosis Title: Osmosis in a potato chip. Aim: To investigate the effect of varying concentration of a certain sugar solution on the amount of osmotic activity between the solution and a potato chip of a given size. Hypothesis: The potato chips left in diluted solutions will increase in size, with the one kept in the solution of maximum dilution increasing in size the most. While the potato chips left in the concentrated solutions will decrease in size, with the one kept in the solution with the highest concentration decreasing in size the most. Osmosis is the movement of solvent molecules from their region of higher concentration to their region of lower concentration through a semi-permeable membrane, i.e. the molecules move down their concentration gradient. The process continues until the solutions on both sides of the semi- permeable membrane are of the same concentration. The potato chip cells and all the solutions used in the experiment each have their own concentration. Some solutions may have a higher concentration (lower osmotic potential) than the potato chip cells, while some will be at a lower concentration (higher osmotic potential) than the potato cells. This creates a concentration gradient. ...read more.

Middle

0.1M NaCl 3.21 3.35 44.0 44.0* 3. 0.2M NaCl 3.53 3.60 45.0 43.0 4. 0.3M NaCl 3.51 2.92 43.0 40.0 5. 0.4M NaCl 3.37 2.52 45.0 40.0 * This result appears to be anomalous Table 3: Percentage change in mass and length of potato chips in Trail 1:- Solution Calculations [(end mass - start mass) � start mass] x100 Percentage change in mass (in %) Calculations [(end length - start length) � start length] x100 Percentage change in length (in %) Distilled water [(2.92 - 2.51) � 2.51] x100 = 16.3 [(47.0 - 43.0) � 43.0] x100 = 9.30 0.1M NaCl [(3.35 - 3.21) � 3.21] x100 = 4.36 [(44.0 - 44.0) � 44.0] x100 = 0.00* 0.2M NaCl [(3.60 - 3.53) � 3.53] x100 = 1.98 [(43.0 - 45.0) � 45.0] x100 = -4.44 0.3M NaCl [(2.92 - 3.51) � 3.51] x100 = -16.8 [(40.0 - 43.0) � 43.0] x100 = -6.98 0.4M NaCl [(2.52 - 3.37) � 3.37] x100 = -25.2 [(40.0 - 45.0) � 45.0] x100 = -11.1 *This result appears to be anomalous Table 4: Results for Trial 2:- Solution Mass of chip- (in g �0.01g) Percentage change in mass (in %) Length of chip- (in mm �0.5mm) ...read more.

Conclusion

no change Slightly turgid Very slightly Hypo-osmotic 0.2M NaCl Increase Decrease Flaccid/ Plasmolysed Hyper-osmotic 0.3M NaCl Decrease Decrease Flaccid/ Plasmolysed Hyper-osmotic 0.4M NaCl Decrease Decrease Flaccid/ Plasmolysed Hyper-osmotic Thus, from Table 6 we can assume that the concentration of the solution in the cell is somewhere between 0.1M and 0.2M Evaluation: Despite taking several measures to prevent errors from occurring, a certain number of errors are unavoidable. These are mainly random errors which are caused by mistakes made while handling or reading equipment. These are probably the main reasons for the anomalies which have been discussed Special care was taken to ensure that the experiment was a fair test. All the chips were cut from the same potato, therefore eliminating any differences in absorbency. The flexibility of chips was tested after they had been weighed and measured so that it would not matter if pieces of the chips broke off since they had already been weighed and measured. To improve this experiment a wider range of concentrated solutions could be used to produce more varied results that would highlight, more clearly and accurately, the concentration of the solution inside potato cells. Overall, this experiment was quite accurate and successful in investigating the process of osmosis and concluding that the concentration of solution inside a potato cell is somewhere between 0.1M and 0.2M. ...read more.

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