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Osmosis Internal Assessment – Biology Higher Level

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| The effect of salinity on osmosis of solanum tuberosum L. (potatoes)| Biology HL Internal Assessment – Year 10| | Teresa Nguyen| | Table of Contents 1 DESIGN2 1. 1 Defining the problem2 FOCUS QUESTION2 HYPOTHESIS2 BACKGROUND INFORMATION2 INVESTIGATION VARIABLES3 1. 2 Controlling Variables3 TREATMENT OF THE CONTROLLED VARIABLES3 CONTROL EXPERIMENT4 1. 3 Experimental Method4 MATERIALS4 RISK ASSESSMENT5 METHOD5 2 DATA COLLECTION and PROCESSING7 2. 1 Recording Raw data7 QUANTITATIVE RAW DATA7 QUALITATIVE RAW DATA7 2. 2 Processing Raw Data8 Processed Data Table9 3 Conclusions and Evaluation11 3.

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1 Conclusion11

CONCLUSION STATEMENT11 CONCLUSION EXPLANATION11 3. 2 Evaluation Procedures12 RELIABLITY12 LIMITATIONS/WEAKNESSES/ERROR IN LABORATORY INVESTIGATIONS13 3. 3 Improving the Investigation14 MODIFICATION TO THE EXPERIMENT14 Bibliography15 Appendixes16 Appendix A – Risk Assessment16 Appendix B – Turnitin Receipt19 Appendix C – Journal19 1 DESIGN 1. 1 Defining the problem FOCUS QUESTION What is the effect of osmosis on the mass (g) of solanum tuberosum L. (potatoes) after duration of 24 hours in varying concentration levels (2%, 5%, 10%, 20% and 25%) of sodium chloride (table salt)? HYPOTHESIS Solanum tuberosum L. inal masses will decline as the concentration (2%, 5%, 10%, 20% and 25%) of sodium chloride increases. Potato slices placed in distilled water will have higher mass percentage due to the cells becoming turgid. BACKGROUND INFORMATION Diffusion is the movement of molecules from a hypertonic (high concentration solute) to the hypotonic (low concentration of solute). There are different types of diffusion one of which is osmosis. Osmosis is the movement of water molecules through a semipermeable membrane that allows only smaller molecules such as water to pass through and prevent larger molecules to enter such as glucose or sodium chloride. Bozeman Biology, 2012) Within osmosis comparison between the different solutions standard terminology are used to describe the differences such as Isotonic, hypertonic and hypotonic as mentioned earlier. Isotonic is when the solution has equal concentration of solutes. Hypertonic is when the solution has concentration of the solute. In contrast, hypotonic is when the solution has lower concentration of the solute. (Bowen, 2002) Plant cells are known to have strong cell walls that when osmosis allows water to be taken up it swells. However, to prevent the cell from bursting the cells become turgid.

The pressure within the cell rises and gradually the internal pressure has increased to an extent which even water molecules cannot enter. (Nigel D Purchon, 2012) This is convenient for plants as they do not have skeletons, thus their leaves and stems are supported by the pressure of the water. Loss of water by osmosis causes the plant to become flaccid which the plasma membrane withers from the cell wall. (BBC, 2012) INVESTIGATION VARIABLES TABLE 1 – Practical Investigation Variables Type of Variable| Identified Variable | Independent | The varied concentration level of Sodium Chloride (2%, 5%, 10%, 20% and 25%). Dependent | The differentiation of masses of the different potato pieces (final – initial mass) in each Sodium Chloride concentrations (2%, 5%, 10%, 20% and 25%) after 24 hours. | Controlled| Each trial is from the same potato. The quantity of solution given in each trial. The size of potato slices. Source of biological material. Potato pieces in distilled water. The duration of the investigation. The size of the test tubes. | Uncontrolled | Rate of osmosis. The initial salt concentration in the potato. Change in room temperature. | 1. 2 Controlling Variables TREATMENT OF THE CONTROLLED VARIABLES

TABLE 2: Control Treatment of Variable Control Variables | Treatment | Each trial is from the same potato. | Each trial used pieces of potatoes from the same source. Thus, limits the variation of sources used. | The quantity of solution given in each trial. | Every test tube contained 25cm3 of solution. | The size of potato slices. | All potato pieces used were cut to a size of 2 cm in length. | The duration of the investigation. | All the trials were conducted in the same time duration of 24 hours. | Source of biological material. | All sources (potatoes) were purchased from the same producer. | The size of the test tubes. All trials used the same sized large test tubes. | CONTROL EXPERIMENT The control of this investigation is the potato pieces placed in distilled water over 24 hours. By being left in distilled water allows the no contamination of the unknown substances or sodium chloride to affect the osmosis process within the potato cells. According to theory, the potato slices in distilled water should increase in mass as the osmosis process would allow water to move through the semipermeable membrane of the potato cells. This control variable will allow the comparison of the masses of the potato pieces in sodium chloride.

Thus, revealing the effects of saline substances in plant osmosis. 1. 3 Experimental Method MATERIALS TABLE 3: List of apparatus Apparatus Required | Quantity Required | solanum tuberosum L. (Potatoes) | 1 Bud| Cork Borer| 1 | Fat Test tubes| 30| Sodium Chloride solution (2%, 5%, 10%, 20% and 25% )| 200cm3 (25cm3 per test tube)| Marker | 1| Paper towel roll| 1| Distilled Water| 200cm3 (25cm3 per test tube)| Ruler (30cm)| 1 | Electronic Scales (±Distilled Water(0. 00)1g)| 1 | Weigh Tray (70cm3) | 1| Tweezers | 1| Test tube stand (for 40 test tubes)| 1| RISK ASSESSMENT Refer to appendix. METHOD 1.

Collect required apparatus. 2. Label five test tubes Distilled Water and place in one column in the test tube stand. 3. Repeat step 2 for 2%, 5%, 10%, 20% and 25%. Place them side-by-side in chronological order. Each row is now the number of trials. Label all the test tubes in the first row “1” then repeat with the other rows with, 2, 3, 4, and 5. 4. Set up the scale. 5. Cut the potato with the cork borer and use the metal rod with to push the potato onto a piece of paper towel. Using the ruler measure cut the pieces into 2cm. 6. Place the weigh tray on the scale then press “Tare”. Place the potato piece on the scales.

Record results for ‘Initial Mass’. Repeat for every piece of potato. 7. Repeat step 6 and 7 for all the potatoes. 8. Pour 25cm3 of distilled water into each of the Distilled Water labelled test tubes. 9. Pour 25cm3 of 2% solution into each of the 2% labelled test tubes. 10. Repeat step 8 for 10%, 15%, 20% and 25%. 11. Place one piece of potato into a test tube with distilled water. Repeat using potato pieces from the same pile for the other trials. 12. Repeat step 12 with 2%, 5%, 10%, 20% and 25%. 13. Leave for 24 hours. 14. Record observations. 15. Place the weigh tray on the scale then press “Tare”. 16.

Use tweezers to remove the potato piece from a “distilled test tube” and place it on the weigh tray. Record the mass for ‘Final Mass’. 17. Repeat step 16 before weighing each piece of potato. 18. Repeat step 17 for the rest of the trials and for 2%, 5%, 10%, 20% and 25%. Diagram 1: Experimental Set-up 2 DATA COLLECTION and PROCESSING 2. 1 Recording Raw data QUANTITATIVE RAW DATA Table 4: Raw Data of Potato Pieces’ masses (±0. 001g) after 24 hours in Various Sodium Chloride Solutions Trials | Concentrations (±0. 5%)| Initial Mass (±0. 001g)| Final Mass (±0. 001g)| 1| Distilled Water(0. 0) CONTROL| 1. 71| 1. 387| | 2. 0| 1. 181| 0. 885| | 5. 0| 1. 091| 0. 877| | 10. 0| 1. 196| 1. 058| | 20. 0| 1. 149| 1. 054| | 25. 0| 1. 094| 0. 995| 2| Distilled Water(0. 0) CONTROL| 1. 258| 1. 453| | 2. 0| 1. 160| 0. 805| | 5. 0| 1. 158| 0. 899| | 10. 0| 1. 186| 1. 002| | 20. 0| 1. 243| 1. 085| | 25. 0| 1. 166| 1. 060| 3| Distilled Water(0. 0) CONTROL| 1. 135| 1. 314| | 2. 0| 1. 254| 0. 856| | 5. 0| 1. 244| 1. 041| | 10. 0| 1. 079| 0. 936| | 20. 0| 1. 244| 1. 047| | 25. 0| 1. 109| 0. 942| 4| Distilled Water(0. 0) CONTROL| 1. 176| 1. 323| | 2. 0| 1. 247| 0. 902| | 5. 0| 1. 260| 1. 034| | 10. 0| 1. 225| 0. 992| 20. 0| 1. 160| 1. 021| | 25. 0| 1. 267| 1. 102| 5| Distilled Water(0. 0) CONTROL| 1. 151| 1. 345| | 2. 0| 1. 263| 0. 986| | 5. 0| 1. 173| 0. 894| | 10. 0| 1. 207| 1. 024| | 20. 0| 1. 163| 1. 017| | 25. 0| 1. 165| 1. 068| QUALITATIVE RAW DATA During the investigation it was noted the potato pieces were tinged with yellow and had firm textures to them. After the twenty four hours the texture of the potato pieces had changed from firm to mushy. Also, there was a drastic change in the physical appearance of the potato pieces from a fully yellow tinged to partially brown. Potato pieces in 2% were the ushiest and were darkest in colour. As the concentration of Sodium Chloride increased the changes of the brown colouring and mushiness decreased. However, the control remained firm and did not go mushy or change in colour. This change in colour could be due to decay of the potato tissues as more and more cells become hypertonic. Trial 1, 25% – Visible physical change in appearance from yellow to brown Trial 1, 25% – Visible physical change in appearance from yellow to brown 2. 2 Processing Raw Data Table 5: Statistical Processing Calculations | Formulae| Solution| Calculation| Results (g)|

Mass Changed (±0. 001g)| Final Mass- Initial Mass=Mass Changed| Distilled Water – 0. 00% (Control) Trial 1| 1. 387g-1. 171g=0. 216g| 2. 36g| Mean (±0. 001g)| x =X n mean=(Sum of all the products)(Number of prouducts)| Distilled Water – 0. 00% (Control)| 0. 186g=0. 216g+0. 195g+0. 179g+0. 147g+0. 194g5| 0. 186g| Standard Deviation (±0. 001g)| s = x- x2 n-1 Standard Deviation=Sum of (each value-mean)2Number of values-1| Distilled Water – 0. 00% (Control)| 0. 026g= (0. 216-0. 186)2+(0. 195-0. 186)2+(0. 179-0. 186)2(0. 147-0. 186)2+(0. 194-0. 186)25-1 | 0. 026g| Percentage Change| Mass Changed Initial Mass? 00=percentage change| Distilled Water – 0. 00% (Control) Trial 1| 0. 2161. 171? 18. 4%| 18. 4%| Processed Data Table Table 6: The Differences between the Initial Mass (g), Final Mass (g) of the Potato Pieces after 24 hours in Sodium Chloride Solution Trials | Concentrations (± 0. 05%) | Initial Mass (±0. 001g)| Final Mass(±0. 001g)| Changes in Mass(±0. 002g)| Percentage Change (0. 02%)| 1| Distilled Water(0. 0) CONTROL| 1. 171| 1. 387| 0. 216| 18. 45| | 2. 0| 1. 181| 0. 885| -0. 296| -25. 06| | 5. 0| 1. 091| 0. 877| -0. 214| -19. 62| | 10. 0| 1. 196| 1. 058| -0. 138| -11. 54| | 20. 0| 1. 49| 1. 054| -0. 095| -8. 27| | 25. 0| 1. 094| 0. 995| -0. 099| -9. 05| 2| Distilled Water(0. 0) CONTROL| 1. 258| 1. 453| 0. 195| 15. 50| | 2. 0| 1. 160| 0. 805| -0. 355| -30. 60| | 5. 0| 1. 158| 0. 899| -0. 259| -22. 37| | 10. 0| 1. 186| 1. 002| -0. 184| -15. 51| | 20. 0| 1. 243| 1. 085| -0. 158| -12. 71| | 25. 0| 1. 166| 1. 060| -0. 106| -9. 09| 3| Distilled Water(0. 0) CONTROL| 1. 135| 1. 314| 0. 179| 15. 77| | 2. 0| 1. 254| 0. 856| -0. 398| -31. 74| | 5. 0| 1. 244| 1. 041| -0. 203| -16. 32| | 10. 0| 1. 079| 0. 936| -0. 143| -13. 25| | 20. 0| 1. 244| 1. 047| -0. 197| -15. 84| | 25. | 1. 109| 0. 942| -0. 167| -15. 06| 4| Distilled Water(0. 0) CONTROL| 1. 176| 1. 323| 0. 147| 12. 50| | 2. 0| 1. 247| 0. 902| -0. 345| -27. 67| | 5. 0| 1. 260| 1. 034| -0. 226| -17. 94| | 10. 0| 1. 225| 0. 992| -0. 233| -19. 02| | 20. 0| 1. 160| 1. 021| -0. 139| -11. 98| | 25. 0| 1. 267| 1. 102| -0. 165| -13. 02| 5| Distilled Water(0. 0) CONTROL| 1. 151| 1. 345| 0. 194| 16. 85| | 2. 0| 1. 263| 0. 986| -0. 277| -21. 93| | 5. 0| 1. 173| 0. 894| -0. 279| -23. 79| | 10. 0| 1. 207| 1. 024| -0. 183| -15. 16| | 20. 0| 1. 163| 1. 017| -0. 146| -12. 55| | 25. 0| 1. 165| 1. 068| -0. 097| -8. 33|

Table 7: Average percentage masses of Sodium Chloride Solutions (±0. 5%) and Distilled Water Trials| Distilled Water (Control)| 2. 0%| 5. 0%| 10. 0%| 20. 0%| 25. 0%| 1| 18. 45| -25. 06| -19. 62| -11. 54| -8. 27| -9. 05| 2| 15. 50| -30. 60| -22. 37| -15. 51| -12. 71| -9. 09| 3| 15. 77| -31. 74| -16. 32| -13. 25| -15. 84| -15. 06| 4| 12. 50| -27. 67| -17. 94| -19. 02| -11. 98| -13. 02| 5| 16. 85| -23. 79| -23. 79| -15. 16| -12. 55| -8. 33| Mean| 15. 81| -27. 77| -20. 00| -14. 90| -12. 27| -10. 91| Trials| Distilled Water (Control)| 2. 0%| 5. 0%| 10. 0%| 20. 0%| 25. 0%| 1| 0. 216| -0. 296| -0. 214| -0. 38| -0. 095| -0. 099| 2| 0. 195| -0. 355| -0. 259| -0. 184| -0. 158| -0. 106| 3| 0. 179| -0. 398| -0. 203| -0. 143| -0. 197| -0. 167| 4| 0. 147| -0. 345| -0. 226| -0. 233| -0. 139| -0. 165| 5| 0. 194| -0. 277| -0. 279| -0. 183| -0. 146| -0. 097| Averages| 0. 186| -0. 334| -0. 236| -0. 176| -0. 147| -0. 127| Standard Deviation| 0. 026| 0. 048| 0. 032| 0. 038| 0. 037| 0. 036| Table 8: Average percentage masses (±0. 02%) of various Sodium Chloride Solutions (±0. 5%) and Distilled Water Graph 1: The relationship between the varied sodium chloride solutions and the control over 24 hours GRAPH COMMENTARY

It appears that Graph 1 represents the relationship between the mass changes and the sodium chloride concentrations (0%, 2%, 5%, 10%, 20% and 25%). The graph displays that there was a major decrease in size mainly in the 2% and only potato pieces in the distilled water were able to increase in mass. 3 Conclusions and Evaluation 3. 1 Conclusion CONCLUSION STATEMENT The aim of this investigation was to test the effect of the varied sodium concentration on the osmosis of potato. This aim of the investigation was accomplished as there were significant differences on the effect of the varied sodium chloride solutions.

Although the data has proven the hypothesis to be false. CONCLUSION EXPLANATION Data produced from this investigation reveals that the hypothesis suggested earlier is incorrect. As shown in Graph 1, the average for 2% concentration had a more drastic decrease than the 25% concentration. Thus, disproving the hypothesis which states as the concentration level of sodium chloride increases the masses will decrease in relation. On the contrary the results suggested decrease in concentration of the solution will greater the decrease in mass after a period of time.

For example, the average percentages change for the 2% concentration decreased by approximately 27. 77% in comparison to the average percentages change of 10. 91% of the 25% concentration of sodium chloride. This would suggest that any concentration higher than 2% concentration of sodium chloride would cause the potato cell to become turgid and hypotonic as a result of the higher concentration of water entering the potato cell. By becoming turgid the cell is no longer allowing the diffusion of any molecules into the cell thus preventing osmosis to occur.

The higher the percentage the faster the occurrence of the osmosis causing the cell to become turgid faster and preventing the water molecules enter. With this in mind, questions the reliability of the data despite the evidence of the balanced error bars. The effects of “sodium chloride concentration had decreased the mass as the concentration levels increased. ” (Roberts, et al. , 2009) This investigation supports the hypothesis stated earlier. In this investigation the results as the researchers were able to conclude on the results of their 0. % decreasing the lease and with their maximum concentration of 2% giving the largest change in mass. However, this investigation was conducted in the time from of only 30 minutes not 24 hours. On the other hand, a research “The Effect of Salinity on Osmosis in Solanum tuberosum (potatoes)” provided much similar results and was also conducted in a similar environment. This investigation supports the results obtained in this experiment justifying “0. 1% and 0. 5% declined in mass with a rapid rate” and “10% and increasing, the rate was much slower” (Holler, 2012) . 2 Evaluation Procedures RELIABLITY Measurements were measured with by only one researcher and thus eliminated the possible chances of human error that may occur if the measurements were recorded by multiple people. The trials of this investigation were conducted in a chronological order and one-by-one. This process was also repeated five times for the each concentration to increase the reliability. The standard deviation displayed quite minimal and well balanced which shows there were minimal significant errors that may have occurred throughout the experiment.

However some the errors that perhaps occurred due to some of the pieces were penetrated by the rod in removing them from the corer, this may have caused some significant error and decreases the reliability of the experiment. Due to the use of the same size potato it can be assumed that the reliability of this investigation is dependable as there is little differentiation in size. Also, all the potato pieces were from the same potato meaning they were also from the source limiting any uncontrolled variables to occur and increase the reliability of this investigation.

The uncertainties of this experiment were quite minimal however perhaps may have occurred during the process of weighing the mass of the potato pieces due to not pressing ‘tare’ before measuring the mass of each piece therefore altering the masses slightly and increasing the uncertainties. LIMITATIONS/WEAKNESSES/ERROR IN LABORATORY INVESTIGATIONS Table 9: Possible limitations with the investigation and improvement to these errors Limitations/weaknesses/error in the laboratory| Improvement| Inaccuracy in the measurements when cutting the potato pieces in to 2cm length. Due to the minimal cooking skill of the researcher the potato pieces were not precisely 2. 0cm but perhaps to varied 2. 1 cm. Significance of this would affect the data as is contradicts its purpose as a controlled variable. To improve on this matter perhaps cutting the potato into a cube or rectangle shape to a 4cm height then using a corer to remove pieces of potato. After, line the all the potato pieces and cut all of them simultaneously in half. This would reduce the variance of the sizes. | Penetration of the potato pieces by the rod of the corer. The rod used to push the potato pieces out of the corer was bent and proved difficult to utilise as it failed to push the potatoes out and penetrated them. Penetration to the potato pieces will increase the surface area and increase the occurrence of osmosis leading onto questioning the reliability of the investigation. Perhaps in a replication of this experiment to use a larger corer size and a straight rod to prevent unnecessary penetrations to the potato pieces. | Time limit in conducting the experiment. Because of the time limit in the beginning of the experiment many errors occurred due to the experimenter rushing. These errors that may be able to be prevented if the time for the experiment was to be increased. | Excess Sodium Chloride when measuring the final mass of the potato pieces. | When measuring the mass of the final potato pieces, only two ply of paper towel were used to dry of the excess solutions. However after the 3rd trial the paper was far too damp to dry off anymore excess which could altered the results. This could be simple resolved by using more plies of paper towel. 3. 3 Improving the Investigation MODIFICATION TO THE EXPERIMENT To decrease the uncertainties a different method could be used to cut the potato pieces simultaneously therefore limiting the slightly varied sized pieces. This new method could be lining all 30 potato pieces in a straight line then measuring 2cm and cutting all the pieces in one cut. This mew method will likely to decrease the uncertainty when cutting the potato pieces. Creating a longer time limit to the investigation would provide time to increase the reliability of this investigation.

By creating a different method to create the potato pieces so that there is no penetration of the use of the rod from the corer. In this investigation a small corer was utilised along with a bent rod was used to remove the pieces which caused penetrations in the potato pieces. If this investigation was to be replicated perhaps using a larger corer will be less difficult to remove the potato pieces and decreasing the chances of penetrating the pieces. Another method that could be considered is to not use the corer and cut the pieces manually from the potato, firstly into a rectangular prism or cube.

This method will completely eliminate the chances of penetration of the potato pieces thus, increasing the reliability of the data produced and of the investigation. Modifications to the experiment perhaps include an extension to explore different variables that would affect osmosis. These extensions could be exploring the effect of surface -area, temperature and perhaps comparison on the use of sucrose solution against the salinity. An interesting extension would be to include a vice-versa investigation to test the effect of the potato pieces to return to its original mass if placed in distilled water.

Bibliography Websites | Nigel D Purchon. 2012. Osmosis | Gondar Design Biology. [ONLINE] Available at: http://purchon. com/wordpress/biology/? page_id=173. [Accessed 01 October 12]. | BBC. 2012. BBC – GCSE Bitesize: Osmosis in cells. [ONLINE] Available at:http://www. bbc. co. uk/schools/gcsebitesize/science/add_gateway_pre_2011/greenworld/waterrev2. shtml. [Accessed 01 October 12]. | Bowen. 2002. Osmosis. [ONLINE] Available at:http://arbl. cvmbs. colostate. edu/hbooks/cmb/cells/pmemb/osmosis. html. [Accessed 08 October 12]. | Videos | Bozeman Biology. (2012). AP Biology Lab 1: Diffusion and Osmosis. Online Video]. 14 March. Available from: http://www. youtube. com/watch? v=LeS2-6zHn6M. [Accessed: 01 October 2012]. | Online Documents | Roberts, M. , Kolbenschlag, J. , Brady, J. & Rice, T. , 2009. Effect of Concetration on Osmosis. [Online] Available at: https://docs. google. com/viewer? a=v&q=cache:ioq9fMDSyNgJ:www. bvsd. org/schools/MonarchHigh/teachers/kdonley/Vodcasts%2520and%2520Podcasts/Student%2520Projects/Osmosis%2520Labs%252009-10/Effect%2520of%2520Concentration%2520on%2520Osmosis. pptx+&hl=en&pid=bl&s [Accessed 11 November 2012]. | Word Documents |

Holler, B. , 2012. The Effect of Salinity on Osmosis in Solanum tuberosum (potatoes). Gold Coast: Bianca Holler. | Appendixes Appendix A – Risk Assessment Appendix B – Turnitin Receipt “Osmosis Potato IA Term 4” to the assignment “Osmosis prac. ” in the class “A. Lal 2012 Year 10 Term 4 Osmosis” on 12-Nov-2012 09:28PM. Your paper id is 283825801. Appendix C – Journal Date| Task| Time | 1st of October | Constructed design and completed background information/theory | 120 minutes | 2nd of October | Constructed method and experimental materials | 60 minutes | 8th of October | Completed

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