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What factors affect osmosis?

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Introduction

What factors affect osmosis? In my investigation I am going to attempt to discover if osmosis is affected by a certain factor. Osmosis is the movement of water from an area of high water concentration through a semi-permeable membrane to an area of low water concentration. Osmosis is affected by water potential which is the term used to describe the movement of a concentration of water, and as a general rule water always falls from an area of high water concentration to an area of low water concentration in a similar way to gravitation or electrical potential. In simple terms, it is sometimes referred to as the diffusion of water. I am going to find out how the concentration of a solution affects osmosis in an investigation using potatoes and sucrose solution. Osmosis depends upon a semi-permeable membrane because this allows water to pass both ways through the membrane but not other solutions with larger molecules, for example sucrose solution (see diagram to the right). A number of factors could affect osmosis such as; type of plant material, temperature, type of solution or concentration of solution. I could have chosen to investigate any of these factors effect on osmosis but instead I chose to investigate the concentration of solution, as I believe it will have the greatest effect on osmosis and will allow ...read more.

Middle

I will take six readings, one from each different solution and then repeat all six, three times to ensue that a fair test is carried out which I believe is important to ensure the accuracy of my work and allow me to draw the correct conclusions. This will mean that I end up with a total of 18 results, which I hope will be enough to give me a complete and accurate picture. My method for this investigation is; 1. Produce my solutions of six different concentrations (as detailed in the table above) and measure using a measuring cylinder. They will then be poured into the different beakers. 2. Next, I will take six samples of potato from the one (or two, if I am unable to get a sufficient amount of samples from the first) using a borer and then measure the mass to ensure they are all the same. Then, simultaneously place the potato cylinders into each different beakers. 3. After a set period of time I will then remove the potato cylinders from their solutions but will be careful not to mix them up. 4. I will dry the cylinders and measure their mass using an electronic balance. I will then record the results in a similar table to the one below; Concentration (M) ...read more.

Conclusion

There are 3 of these in test number 3 and this could be due to a number of reasons such as inaccurate weighing equipment or accidental inaccurate measuring of the solution/water ratio. However the results are pretty much exactly as I expected expect for the 0.2M and 1.0M concentrations across all three tests, which were higher and lower respectively than I would have expected. I could have improved my investigation by numerous means. For example I could have used a biuret to more accurately measure my solutions or I could have chose to completely re-do any tests that contain an outlier, in my case this would be test number three. It could have also been beneficial if I had ensured that I was using the electronic balance more carefully that I was. I could also expand my work by changing other factors to see what effect that has on osmosis, such as changing the type of solution or type or plant material. However I do believe that my results gave enough information to answer my initial question, "What factors affect osmosis" and I can safely say that the type of solution does affect osmosis. Overall I believe that my first set of results were the most accurate and If I were to put my trust in any of the data set's it would be the first one. Page 1 of 6 ...read more.

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Here's what a teacher thought of this essay

4 star(s)

This account of an investigation into the effect of varying sucrose solution concentration on the passage of water into and out of potato tissue by osmosis is generally well written and covers most of the required sections in an experimental report. The writer makes a determined effort to fully explain the process of osmosis, although a number of out-dated terms are used. A detailed method is followed by some 'interesting' data which the writer makes a good effort to analyse.

To gain the higher grades at GCSE, the following issues need to be addressed:

[1] A clearly expressed hypothesis is needed from the outset, one which links the IV and DV, together with detailed biological evidence to support it. This evidence should be obtained, at least in part, from the work of other scientists who have carried out similar investigations.

[2] The language of osmosis should be updated.

[3] Control variables should be listed in table form and their potential effect on the DV discussed.

[4] The reliability of the results needs careful examination by comparing them with data from other scientists.

Despite these shortcomings, this is a good attempt at a difficult topic.

4 stars

Marked by teacher Ross Robertson 10/05/2013

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