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The effect of osmosis on weighed potato chips

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Osmosis Coursework Introduction In this piece of coursework, I will be looking at the effect of osmosis on weighed potato chips. I will be using different concentrations of a salt solution to show this. Scientific Knowledge Osmosis is the movement of water particles through a semi-permeable membrane from a high water concentration to a lower water concentration (so basically it is a special type of diffusion involving water molecules). A semi-permeable membrane is a membrane with microscopic holes in it. These holes are very small which only allow small molecules, such as H2O, through. A good example of a semi-permeable membrane is visking tubing. The water molecules actually pass through both sides of the membrane in a two way flow motion but as there is a higher concentration on one side and a lower on the other, you will find that there will be a steady net flow from the higher concentration of water to the lower. This will take sometime to show a significant effect. This then causes the higher concentration of solutes region to fill with water particles. The water particles act as if they are trying to dilute it so as to even up the dispersion of solute. This process of osmosis makes some cells swell up and become turgid. With plant cells this is a great property as this helps the support of the green plant tissue. There are two different cells, which are animal cells and plant cells. An animal cell looks like this: As you can see, the water molecules would have to pass through the cell membrane to get into the cell and this diagram gives a fully labelled picture of the plant cell. ...read more.


correct as when the potato was left for longer; it gave the water molecules more time to pass through the cell membrane and so therefore more osmosis was present and so my prediction was correct. Equipment For this experiment, I will be using: * Potatoes * Potato corer (no.4) * Boling tubes * Boling tube rack * Scalpel * Ruler * Tweezers * Scales * Stop watch * Cutting mat * Measuring cylinder * Salt solution * Distilled water Diagram Method I will cut pieces of potato to a length of 2cm and I will then weigh them. I will make sure that every piece is within 0.02g of a chosen centre point. If a potato is not within this boundary, I will discard it, as it will not give a fair result and not very accurate results. Once I have 25 potato pieces, in total, within this boundary I will record their weight onto a table of results. I will collect 5 Boling Tube racks and place 5 Boiling tubes in each rack which will contain one piece of potato and 10cm� of salt solution and each rack of boiling tubes will have a different salt solution per rack (15 in one rack and 2% in another...). Once the boiling tubes have stood for 30 minuets containing the potatoes, I will remove the potato and weigh it. This will then allow me to find out how much difference there is in weight between them and therefore be able to see the change through osmosis. Fair Test To make this experiment a fair one, I will have to: * Make sure that the diameter is fixed ...read more.


was reduced. I only had a few anomalies so therefore my results can be seen as reliable. The quality of my results are very good as I have lots of results and they all follow the same pattern and all fit to my predictions and so therefore my results are very reliable and are good quality results. The procedure was also very suitable, as another method wouldn't have got such accurate results. For example, if I had of used an animal cell instead of a plant cell then the cell would have burst with too much pressure from the small water molecules. I couldn't have changed any of the apparatus or the method to make the experiment any better as this experiment had very reliable results and so therefore there would be no need to change the method or apparatus. I could have further improved this experiment, however, by perhaps using an even more accurate form of timing as the experiment was judged on a stopwatch. From the moment the potato made contact with the solution and the moment that the stopwatch started could have had a difference between them and although this couldn't alter the final result, as it is only a few seconds difference so this wouldn't make much difference to the results that I have gained now but would make the experiment fairer. To provide more evidence, I could do each experiment that I have done in this investigation three times so that I could get an average from the three sets of results that I would obtain from this to get a further accurate result. Overall I am very pleased with my experiment and the results obtained. By Oliver Jarvis ...read more.

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