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Science Coursework - Osmosis investigation

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Yazan Qabba'ah 10.8 Science Coursework Osmosis investigation Introduction: Osmosis is the process by which a liquid substance passes spontaneously through a semipermeable membrane, that is, a membrane that allows the liquid to pass through it but not some other dissolved substance. If the membrane is placed vertically between a pure solvent such as water and an aqueous solution, the water flows through the membrane into the solution. The volume of the solution is increased and its level raised. The flow of pure water into the solution can be prevented by applying a pressure upon the solution, called the osmotic pressure. Osmosis is a special case of diffusion, a process in which a substance always goes from a region of relatively high concentration to one of lower concentration. (Pure water passes into solutions where the water is less "concentrated.") MEMBRANE Pure water Sugar dissolved i.e. a 100% in water i.e. less concentration than a 100% of water. Concentration of water. * Water diffuses from where its in a high concentration to where its in a low concentration. * The only thing that can pass through the membrane is the water molecules. The solute molecules (e.g. sugar) can't pass through the membrane. water Pure water water Turgid water Sugar solution water water water Flaccid Aim The aim of this Coursework is to investigate and find about how the concentration of solutions affects the role of osmosis. For this I am going to carry out experiments using different concentrations of solutions. ...read more.


3.7?3.2=?0.5), and calculated the percentage of change in mass (e.g. -0.5?3.7?100). Results of experiment:. Concentration of sugar solution (%) Start mass (g) End Mass (g) Change in mass (g) % Change in mass 0 3.7 4.5 0.8 22 5 3.7 4.4 0.7 19 10 3.7 4.5 0.8 22 15 3.7 4 0.3 8 20 3.7 3.8 0.1 3 25 3.7 3.2 -0.5 -14 Concentration of sugar solution (%) Start mass (g) End Mass (g) Change in mass (g) % Change in mass 0 3.7 4.3 0.6 16 5 3.7 4.2 0.5 14 10 3.7 3.9 0.2 5 15 3.7 3.9 0.2 5 20 3.7 3.8 0.1 3 25 3.7 3 -0.7 -19 Concentration of sugar solution (%) Start mass (g) End Mass (g) Change in mass (g) % Change in mass 0 3.7 4.2 0.5 14 5 3.7 4.3 0.6 16 10 3.7 4 0.3 8 15 3.7 3.1 -0.6 16 20 3.7 3.3 -0.4 -10 25 3.7 3.2 -0.5 -14 Here are the formulae I used : Change in mass ? start mass ? end mass % change ? change in mass ?100 start mass I made another table and added the three % changes of each concentration and divided them by 3 to get the average % in change in mass of the potato. Average table Concentration (%) % Change in mass 0 17 5 16 10 12 15 10 20 ?5 25 ?16 Observation and analysis This graph has a negative correlation. ...read more.


We also repeated the experiment three times so we are sure to get accurate and fair results, and we succeeded in doing that. We got very reliable results which helped me to come op with a firm conclusion. In this example below, as the concentration gets higher, the change in mass decreases. There was not any anomalous results. Example:- Concentration (%) % Change in mass 5 16 10 12 There are few things I could have done to improve the reliability of this investigation. We could've been more accurate in obtaining evidence i.e. use cleaner equipment free of contamination, more time to carry out the experiments as this will give us more reliable results. To improve my certainty of the conclusion, we could've experimented with wider range of concentrations of solutions i.e. 30%, 35%, 40%, and we could have used different masses of potatoes, and used different solutions to be experimented with i.e. alkaline or acidic solution to observe how the process of osmosis is altered. We can also experiment with different temperature, for instance -2, 0, 4, 7, 15, 25, 35 or 50 centigrade; or maybe use another substance instead of potato, such as a human cell, porous rock or a small balloon filled with lactose solution. I think using any of these the effect on osmosis will be the same as when using a potato. This is because water always diffuses from where it's high to where it's low in concentration. I think that my results were good enough to make an analysis because you can see from this investigation that I came up with a firm good conclusion. Osmosis Coursework Yazan Qabba'ah 10.8 ...read more.

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