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Osmosis Coursework

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Introduction

Osmosis Planning: Aim: To find out the effect that osmosis has on the lengths and mass of the potato chip in different sugar solutions; distilled water, weak sugar solution and concentred sugar solution. Background Knowledge: Osmosis is a special type of diffusion; diffusion is the movement of particles from a high to low concentration until equilibrium is reached. It is the diffusion of water across a partially permeable membrane from regions of high water concentration (or low sugar concentration) to regions of low water concentration (or high sugar concentration). Osmosis will continue to occur until both sides have an equal concentration. Several things affect the speed of osmosis. These include heat, solution concentration and surface area (as the membrane will be bigger, allowing for more water transfer). "The cell surface membrane separates the cell contents from the surrounding environment. As you can see below, the membrane allows some molecules to pass through but not others."* Water Potential "A 'weak' solution will have a high concentration of water molecules. These 'free' water molecules will have a tendency to move about."* This is called high water potential. In a potato chip the cells have a cell wall which is freely permeable allowing all molecules to pass in and out. Under the cell wall is the cell surface membrane which is known as the semi-permeable membrane. And inside the cell is another membrane is the Tonoplast. This separates the vacuole from the cytoplasm.* Solute Potential The concentration of dissolved substances inside the cell is called the solute potential.* The solute potential is always in the negative, pure water is 0. ...read more.

Middle

* 1 weighing scales: to weigh the chips before and after the experiment. An electrical one should be used, to increase the accuracy of the readings. * Sugar (50 grams): to produce the Weak and Strong sugar solutions. * Water (100ml): to dissolve the sugar so as to create the weak and strong sugar solutions. Also to produce the distilled water solution. Independent variables: * The amount of sugar concentration, Dependant variable: * The length of the chip * The mass of the potato chip Control variable: * The size of the chip. If the potato chips were to be of different sizes, they amount of particles that pass through the semi-permeable membrane would be affected. The mass and length of the potato chip will also change. * The size and diameter of the test tube. This will affect the amount of solution held in the beaker. This would in turn affect how much osmosis take place. I will record the results from my dependant variables on a table, comparing the mass and size of the potato chips before and after the experiment. I will do this once. I understand that repeating the experiment provides more reliable results but due to time constraints, I am forced to carry out the experiment once. Fair Test: To make sure that the results of the experiment are reliable, I need to make sure that certain variables are kept constant in order for a fair test. These are: * The length of all the potato chips must be the same * The potato chips should be surrounded by the same amount ...read more.

Conclusion

It was easy to carry out and I encountered no problems that impaired the ability to carry out the experiment. The method worked properly. I received reliable results from my experiment. I know they are reliable because I can see they reflect the information in my Background Knowledge. I do not know if my experiment and results are consistent because I only carried out the experiment once. However looking at previous experiments into this topic I can say that my results are similar to previous experiments. In my experiment I was measuring how osmosis affects the lengths and masses of potato chips in different sugar solutions. The results show the difference of lengths and mass in the potato chip. This shows that my results are valid. I am confident with my findings because they match my conclusions. The results show the more concentrated a sugar solution is, the more length and mass the chip loses. The weakness of my experiment was the mass of the different potato chips before the experiment took place. They were not all the same. The strengths of my experiment are the uniform length of the potato chip prior to the experiment as well as the fact that it was carried out on controlled variables; i.e. the size and diameter of the test tube and the size of the chip. To make my experiment more accurate, I could have kept the chips at a constant room temperature. I should have put all the chips in at the same time, because others could have been in the beaker for a different amount time. I would have repeated the experiment a few more times to obtain reliable results. ...read more.

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