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What factors affect osmosis in potato cylinders?

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Introduction

What factors affect osmosis in potato cylinders? My aim is to investigate the different factors that effect osmosis in potato cylinders. Osmosis is the diffusion of water molecules from an area where they are in concentration to an area of a lower concentration through a partially permeable membrane and osmosis will not usually occur when something is fully permeable. The diagram below is an example of when osmosis takes place: The possible variables that could effect this investigation are: * Temperature- In warm solutions the particles have a higher amount of kinetic energy and therefore move more quickly. This could increase the rate that water molecules diffuse through the partially permeable membrane so the temperature must remain the same. * Strength of sugar solution- the more concentrated a solution is the stronger it is which means less water molecules which effects how osmosis occurs. * Surface area of potato cylinder- more surface area means that a higher amount of water can be absorbed and more osmosis can take place, the surface area for each potato cylinder must also be the same. * Amount of sugar solution- changing the volume of sugar solution could mean that some potato cells would not be in contact with the solution and therefore would decrease the amount of osmosis. ...read more.

Middle

The following apparatus will be used in this experiment: * Cork borer- size 6 * Cutting tile * Beakers * Boiling tubes * Knife * Electronic top-pan balance * Tube Rack The following method was used during the experiment: 1. Using a Cork Borer, of size 6, dig firmly into the potato to get equal 5 potato cylinders of the same diameter. 2. Then, using a knife and a steel rule cut each cylinder to a length of 5cm, on a cutting tile, also making sure there is no potato skin. 3. Next, dry the potato cylinders with tissue paper and then weight of each of the five potato cylinders were measured individually using an electronic top-pan balance. 4. Into the five different boiling tubes, one potato cylinder was placed. 5. Then, some of each sugar solution, of strengths 0.0M, 0.25M, 0.50M, 0.75M and 1M, was poured into each boiling tube so that the solution covered the entire cylinder. 6. Each boiling tube was then labeled according to what sugar solution was poured into it. 7. All five boiling tubes were then left in a tube rack for 24 hours. 8. After this period the weight of each potato cylinder was measured again using an electronic balance and recorded to two decimal places. ...read more.

Conclusion

This means there was possibly the least amount of experimental errors during my experiment. Yet, some of the possible experimental errors could have been accounted for or caused by using an unequal amount of solution in each boiling tube and the strength of the solutions may not have been composed exactly correct. To further my investigation and to provide me with additional relevant evidence and data I could have investigated osmosis in a narrower range of sugar solutions: As the line of best fit goes into 0.25M on my graph, meaning the weight change for 0.25M was 0g and no osmosis took place, I could have investigated osmosis in smaller graduations, between 0.0M and 0.25M (e.g. 0.05M, 0.10M, 0.15M, 0.20M).This would have helped me to find out which sugar solution had the same molarity as the potato cylinder, according to my graph and procedure. On the next page (6a), there is an extract from a textbook which describes the process of osmosis and what generally usually happens during osmosis. Comparing my results to this information the results I have found during my investigation do seem to be along the right lines and show that I have found enough evidence from this experiment to support a firm conclusion and also show they are reliable. From the textbook 'Heinemann Advanced Science' by Ann Fullick (page 53, chapter 1.4 - Cellular processes). 1 ...read more.

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4 star(s)

****
A generally good account of the investigation with a sound understanding of osmosis evident. However, there is too much imprecise use of scientific language.

Marked by teacher Adam Roberts 01/05/2013

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