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Osmosis Investigation

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Background information: Here is some background information on related topics taken from "Science Explained": References: * Osmosis * Diffusion * Active transport Osmosis Osmosis is the movement of water molecules through a partially permeable membrane; it travels from a dilute solution to a concentrated solution. Water molecules are very small. Each one consists of an oxygen atom and two hydrogen atoms. A partially permeable membrane is a membrane, which only lets through some molecules but not others. Example: If you set up an experiment with visking tubing like this: (Visking tubing's holes are big enough to let water molecules through but not some e.g. sugar molecules). So the water molecules pass through the tubing in with the sugar molecules, so the water level rises. Diffusion Diffusion is the movement of gas particles, from a highly concentrated area to a low concentrated area. Example: Imagine you put some gone off milk in the corner of a room, then stand in the other corner. You will not be able to smell it until the particles have spread (Diffused) around the room. The particles eventually manage to spread themselves equally around the room leaving all areas the same concentration. Active transport Active transport is the movement of substances through cell membranes, using energy. This energy is in the form of adenosine triphosphate (found in all living cells, a high-energy compound, produced by respiration). ...read more.


Experimentation is necessary to determine which membranes permit selective flow or osmosis, because not all membranes act in this way. Many membranes allow all or none of the constituents of a solution to pass through (permeable or non-permeable membranes); only a few allow a selective flow. As the potato is a plant cell, it contains a vacuole and a cytoplasm. The cell membrane is also partially permeable i.e. it lets some substances in but not all substances. This means that water diffuses into cells by osmosis, if the cells are surrounded by a weak solution. (Osmosis is the movement of water molecules from a high area of water potential to an area of low water potential through a selectively permeable membrane.) If the cells are surrounded by a stronger solution, e.g. salt water, the cells may loose water by osmosis. Prediction graph: I have drawn a graph based on what I think will happen due to pre-tests and background information knowledge taken from "science explained" written by Colin. A. Roland. Results: (The temperature was 20 degrees centigrade) Test Tube Number Test A Weight before (g) Test A Weight after (g) % Change of the mass Test B Weight before (g) Test B Weight after (g) % Change of the mass 6: 1.0 1.53 0.93 -39.2 1.50 0.95 -36.6 5: 0.8 1.55 1.05 -32.2 1.55 0.99 -36.1 4: 0.6 1.62 1.01 -37.6 1.73 1.11 -35.8 3: 0.4 1.67 0.91 -45.5 1.57 1.13 -28.0 2: 0.2 1.73 1.52 -12.1 1.58 ...read more.


I could have also used a machine to cut the potato chips. My results did lie close to the curve, and therefore were fairly accurate, but if I was doing the experiment again I could make changes, some as mentioned above. I could also use a more accurate measure to measure out my solutions. This would ensure that I have an accurate amount of fluid in each test tube. I could also weigh each chip on a digital and more accurate scale, e.g. not to 0.00 but to 0.0000g. There was one main anomalous result. This may have been caused by human error, or one out of my six results could have been inaccurate, and changed the average drastically. Or perhaps the potato chip was not cut accurately, or that part of the potatoes, cells did not loose/gain mass well. My results did vary a lot for the same concentration. The fact that a certain part of the potato may not be the same as another was shown as the chips all of the same length were not the same weight, or even close. This is another reason to use cloned potatoes. My results were consistent, and there were no results that were ignored. I could extend my enquiry by testing the percentage change in mass with morality using a different substance. By this I mean using a different vegetable, perhaps celery or cucumber. Then I could find out whether osmosis occurs with the same patterns and trends with any vegetable. ...read more.

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