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Investigation into how the concentration of sugar solution affects osmosis in a potato.

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Introduction

Investigation into how the concentration of sugar solution affects osmosis in a potato Planning Introduction Osmosis is the passage of water molecules from a weaker solution into a stronger solution, through a partially permeable membrane. The potato I will be using will allow water molecules to advance into it by tiny holes in the membrane; the sugar will be too large to fit through. Osmosis is the movement of water molecules from a region of high concentration to a region of low concentration through a partially permeable membrane, this means that if the water concentration is high in the potato tissue then the water will pass out of the potato back into the solution. If the water concentration is low in the potato tissue then the water molecules will pass from the solution back into the potato resulting in accumulation of the mass. Therefore, If there is very little different in the two water concentrations, there shouldn't be a big change in mass. During osmosis the cell will change like this: Diagram 1. Diagram 2. Diagram 3. These could be potato cells. In diagram 3 which is filled with water (dots) is known as turgid. This cell can take in no more water. If these potato cells were placed in a solution with a low water concentration, like diagram 1 then the opposite would happen. Water would move out of the cell into the solution. In extreme cases the cell membrane breaks away from the cell wall and the cell is referred to as plasmolysed. The potato cells will have decreased in length, volume and mass. During our experiment the potato will need some kind of element to survive. ...read more.

Middle

Keep the potato samples at 1 gram before they go in to the solution. If any are above 1 gram then the surface area will be bigger causing osmosis to happen at a quicker rate and more cells to lose or gain water 2. Make sure I remove the skin of the potato. The skin if different from the tissue of the potato 3. Use the same potato. This is because many factors due to the potato may affect the experiment. For example, the age and sizes might of the potato might be different which means one potato might have more water in them then the another 4. Stop the evaporation from any of the solutions. If evaporation causes the potato tissue to be out of water then the potato wouldn't have as much surface area as any of the others. I will use a bung to stop evaporation 5. Temperature: The temperature may affect the reliability of the experiment. For example, at extreme temperatures the cells of the potato may die, at less extreme temperatures the experiment may be speeded up. To keep this from happening, all the test tubes will be kept in the same place and at the same time of the 15-minute experiment 6. An accurate amount of the solutions. More bathing solution could affect the rate of osmosis, I will use a measuring cylinder the measure the solutions 7. The beaker and measuring cylinder must be washed every time. If it is not washed it could cause the solution to become contaminated with different molarities 8. Averages will be taken out of the results to make the experiment as accurate as possible Obtaining Evidence When I am obtaining the evidence for my results I will take all these aspects into consideration: Safety aspects I will carry out the experiment safely and as accurately as possible. ...read more.

Conclusion

Also when the potato was dried to remove surface liquid it was not necessarily done the same on each potato, a more accurate and uniform way of drying would improve the accuracy further. The evidence I obtained is very reliable as you can see from my graph of average (page 8). I collected a big range of evidence therefore I can back up my conclusion with the evidence I obtained. As I have found only one anomalous point in my results I can confidently state that the evidence I have collected is sufficient to support the conclusions I have made. However the anomalous point that I encountered makes the results less reliable but as I did three attempts of each molar concentration and then took averages the anomalous point is not noticeable in my final averages (see graph page 8) the graph is systematic and in a stabile shape. This critical account of the evidence concludes in reliable data collected, giving me a reliable conclusion as the results, overall, support the conclusions that I have made. Further work that could have been extended onto this investigation to provide additional relevant evidence would be to test different molar solutions closer than the solution I tested. For example, - 0.20, 0.21, 0.22,0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30. This would produce much more accurate results. I would carry out the investigation in exactly the same uniform pattern that has been used in this experiment, but I would change the molar variables. Together with the information that I have achieved in this investigation would produce very precise results because there is more information that is collected. Other variables in the experiment could be changed for example instead of changing the mass of the potato the species of the potato could be changed. For example I could use a new potato and a really old potato. 11 1 ...read more.

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