Biology Coursework: Osmosis Investigation - page 1
Keywords: biology coursework osmosis potato potatoes sucrose molar mass change
By ruth on 08/11/2006 17:19:48
Level: GCSE Key Stage 4 (Years 10-11)
Page Number: 1 of 7 pages: 1 2 3 4 5 6 7Biology Coursework: Osmosis Investigation
Aim:
The aim of this experiment is to find out the concentration of a potato, by testing pieces of potato in boiling tubes with various sucrose solutions to observe the rate of osmosis, and finding the concentration at where there was no mass change.
Variables:
The independent variable I will be investigating is the concentration of sucrose solution and the dependant, the potato. I am investigating how the varied concentrations of sucrose solution affect the mass of a potato, in order to find the concentration of the potato, where the mass will stay the same.
To carry out a fair test I will firstly make sure I use the same potato- as perhaps different types may be genetically modified and have different rate of osmosis. I will also put cling film over the boiling tubes which will stop any evaporation of the sucrose solutions, therefore affecting the results. I will do three repeats of the experiment, by putting three pieces of potato in the same test tube and from this create an average (but I will ignore any obvious anomalous results). I will calculate the percentage change in mass rather than use the same sized pieces of potato and measure the mass change, as this could not be guaranteed to be accurate. I will finally keep the temperature of the boiling tubes the same by putting them in the same place, as osmosis is affected by temperatures varying.
Prediction and theory:
I predict that the concentration of the potato will be at around 0.5 molar. This is as in my preliminary this is where the line crosses the 0% change in mass line. I think that the potato pieces in the higher concentrations will have smaller final masses. This is as in osmosis the water moves from a region of higher water potential to lower water potential, and so the water will diffuse out into the highly sucrose concentrated solutions therefore losing mass. So this also means that the potato in low concentrations will gain weight as there is a lot of water in their solutions which will diffuse through the partially permeable membrane to the region of lower water potential. So finally, I predict that the point of equilibrium where there is no movement of water molecules, due to the same concentration in the solution
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