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Investigating Osmosis.

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Investigating Osmosis Introduction Definitions - Osmosis is the movement of water molecules from where they are at a high concentration to where they are at a lower concentration through a selectively permeable membrane. A selectively permeable membrane is one which allows only molecules of a certain size through. This very basic diagram shows osmosis occurring between sugar solutions and water in visking tubing and beakers. The bag expands because the water moves from the beaker where it is at a higher concentration through into the tubing where it is at a lower concentration. Example of osmosis - Osmosis is the way in which plants absorb water (and get their minerals).The cell walls in the root hairs are semi-permeable. In the soil, the water is fairly pure and has no dissolved sugar in it so there are lots of water molecules and no big sugar molecules blocking their way. Many water molecules hit the cell walls and pass through to the inside. Inside the cell there is more dissolved sugar, so not many water molecules hit the cell wall from the inside. As a result, more water molecules go in than come out. Overall, the effect is that water molecules pass from the area of low sugar concentration (the soil) into the area of high sugar concentration (the cell) and any minerals dissolved in the water get carried into the cell as well. ...read more.


The results are as follows. Aim The aim of this experiment is to investigate the effect of varying concentration of salt solution on the amount of osmosis occurring between the solution and a potato chip of a given size. From the pilot work carried out and the results collected I can determine that the method used was accurate because there were no anomalous results, and therefore it should be able to be used in the experiment. The results also seem to follow my prediction that the lower the concentration of the salt solution in the test tube the larger the mass of the potato will be. Method * Take a potato and from it using a borer cut out 7 tubes onto a white tile. * Make sure all the tubes are 4.2cm long and 2.4g in weight. Remove potato skin from the edge of the tubes. * Fill 7 test tubes each with 4cm� of salt solution of different concentrations. * Place 1 potato chip in each test tube and leave for 1 hour for osmosis to occur. * After 1 hour remove the chips and remove excess water by rolling them on a paper towel. Excess water would increase the mass and affect the results. * Record the weight of each potato chip using an electronic balance. * Then repeat the method twice to give 3 sets of data for more accurate results. ...read more.


The errors we encountered would be like this in order of their impact on our work 1. Time 2. Lack of potatoes that could be used to provide consistently accurate results 3. Temperature control Reliability As you can see from my results tables and graphs my data seems to be very reliable and accurate to a high degree. There appear to be no anomalous results that could have been caused by errors in my work but there are still things that could be done to improve this experiment. Possible Improvements Things that could be done to improve the experiment that I carried out are to carry it out in a controlled environment where the temperature could be kept constant, to be provided with more potatoes that had not been used previously and that were of a reasonable size and to monitor the time more effectively by keeping an eye on the stop clock constantly instead of leaving it over break. Safety Safety equipment that we used were aprons to protect our clothes, goggles when producing salt solutions using a Bunsen burner, protecting our eyes. Caution should be exercised when using scalpels to cut the potatoes. Sources of information Introduction - Information on osmosis in roots taken from http://fp.thurstoncollege.plus.com/photosynthesis/osmosis.htm Information on osmosis in animal cells taken from http://www.revisioncentral.co.uk/Biology/diffusion.htm Diagrams of red blood cells http://biog-101-104.bio.cornell.edu/BioG101_104/tutorials/osmosis/rbc_fs.html Katie Reynolds Page 1 of 8 ...read more.

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