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Science Osmosis

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Osmosis Osmosis is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration. Similar to diffusion, osmosis is used in parts of the human body and in plant cells. In plants osmosis causes the cells to swell up if they're surrounded by weak solution and they become turgid. This is useful for giving the plants support so that it can stand, unsupported. This is how the partially permeable membrane works; Background I already know that there will be a change in weight when there are two different concentrations in the same liquid because of a theory I found by D.G. Mackean: "If a dilute solution (water) is separated from a concentrated solution (sucrose, sugar) by a partially permeable membrane (potato chip cell membrane or visking tube), then water diffuses across the membrane from the dilute to concentrated solution. This process is called osmosis". And because no molecules are reacted or evaporate in this process all the excess water molecules gained or lost will affect the weight accordingly. Planning My experiment is going to test the changes made to potato chips after they have been soaked in six different sucrose solutions: 0.0M (distilled water), 0.2M, 0.4M, 0.6M, 0.8M, and 1.0M. In this investigation I am trying to find out the weight change caused by the movement of water molecules in Osmosis and draw a conclusion from that. For this experiment to be fair all the chips will be kept the same size in each set of the three repeats I have decided to do. The potato chips will be: 1.5cm, 2.0cm and 2.5cm. The changes made to each potato chip with the solution in a galley pot will be observed and made into a graph for clear visual help to see the weight change. The recorded changes will include softness, weight and colour of the chips. ...read more.


I am also wiser on how to carry out the experiment because of my experience with the preliminary experiment. I will also know what trend of results I am expecting. Prediction From what I found in my preliminary experiment I predict that potato chips in the lower concentrated molar solutions will get bigger and therefore gain weight. Like the 0.0M visking tube in 0.5M solution, the potato chips in the 0.0M sucrose solution will gain weight because there is an unbalance in the concentration, water through osmosis will enter the partially permeable membrane call of the potato chip causing the cells to become Turgid and gain weight (from the extra water molecules). The potato chips will probably feel firmer because of the turgor pressure. In the mid range 0.4M to 0.6M solution I predict that there will be not much change in the weight of the potato chip because the level of concentration would be around the same so there would be no need for water particles to move around as much. In the higher concentrations I predict the potato chips will lose weight, as did the 1M Visking tube. because there will be an unbalanced molar gradient causing the water molecules from the potato to move to the beaker leaving the potato chips and therefore loosing weight, they should also feel soggy as they become more flaccid. The changes in weight are caused by the natural process called osmosis where water molecules move from a partially permeable membrane from a region of high water concentration to an area of low water concentration resulting in less water molecules (lower weight). Obtaining Evidence I used all the equipment safely to carry out the experiment, everything went well after I discovered one mistake I made which resulted in an anomalies result but I changed that and got all the results I was expecting. Sucrose solution Potato chip 1cm Change in weight Potato chip 2cm Change in weight potato chip 3cm Change in weight Average change in weight Texture 0.0M (Distilled water) ...read more.


first set and so after I realised this I dried them and weighed them with slightly altered results but the small difference is enough to change the average because I only got an average of 3 results, this makes me realise that if I want a more accurate and reliable set of results I will need to repeat it many more times. Also the graph showed me that the biggest difference in weight (steepest point on graph) was between 0.2M-0.4M hence the isotonic point was here therefore next time I will concentrate more on the section maybe experiment with 0.2M, 0.22M, 0.24M, 0.26m, 0.28M, and 0.30M so I can get the isotonic point even more exact but if I do this I will need to make the surface area of the potato chips precise to the millimetre which would be hard with class room facilities. Problems other than the anomalies and not drying the first set of results I had were to try in five minutes from when I dried and weighed the first one until I weighed the last one which proved to be difficult however I can overcome this problem if next time I work in a group, this was not possible this time. Another improvement I can make is there were three different sized potato chips in each pot; ideally there would be a Galley pot for each potato chip, this may have caused problems like two potato chips on top of each other may mean there is less surface are for osmosis to happen and the molecules in the solution would have more volume to try and make balanced maybe this would slow the process. Next time I could try to have a larger range of potato chip sizes and solutions for a more detailed experiment. Next time I could change other factors like volume of solution, temperature, light and other materials like plant cells to see if they would make a difference in weight. ?? ?? ?? ?? 1 ...read more.

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