GCSE BIOLOGY ASSESSMENT - OSMOSIS
Planning of Experimental Procedures
Background Knowledge:
Osmosis is the diffusion of water over a membrane; it takes place due to differences in the concentration of water surrounding an object such as a plant or animal cell whose surface is comprised of a membrane, to the concentration inside the object. The rate at which osmosis takes place, which is what the assessment is investigating, is affected by a number of factors, of which one must be investigated and the others controlled in order to make the experiment a fair test.
The following factors affect the rate of osmosis; one of these factors must be chosen for investigation in the experiment:
: The temperature of the water in which the experiment is conducted.
2: The size of the water concentration gradient; i.e. the difference in the concentration of water between the solution surrounding the object and inside the object itself.
3: The size of the pores in the membrane; i.e. the type and properties of the plant or animal cell used in the investigation, in this case the type of potato used.
4: The surface area of the membrane; i.e. the number of pores there are for water to diffuse through.
The experiment is to be conducted using potato chips as the cellular object, the potato chip could be weighed before and after placing in sucrose solutions in different conditions to find the rate of osmosis. The factors above could be investigated in a number of different ways; the first factor could be investigated by placing a number of standard sized chips of the potato used in a boiling tube of similar sucrose solutions in water baths at different temperatures, the potato chips would be weighed before and after the experiment and the rate of osmosis found. The second factor could be investigated by placing potato chips of the same size in sucrose solutions of different concentrations, the potato chips would be weighed before and after and the rate of osmosis found in each, a graph could then be drawn and the change in the rate of osmosis over the different concentrations seen. The third factor could be investigated by using potato chips of the same size but of different varieties, the size of the pores of the different varieties could be researched beforehand and the rate of osmosis in plant cells with different sized pores found. The fourth factor could be investigated by using a number of the same sized potato chips and cutting each up into different numbers of pieces; the pieces would then be placed into sucrose solutions and left for a certain time, the pieces would then be weighed and the rate of osmosis found.
Planning of Experimental Procedures
Background Knowledge:
Osmosis is the diffusion of water over a membrane; it takes place due to differences in the concentration of water surrounding an object such as a plant or animal cell whose surface is comprised of a membrane, to the concentration inside the object. The rate at which osmosis takes place, which is what the assessment is investigating, is affected by a number of factors, of which one must be investigated and the others controlled in order to make the experiment a fair test.
The following factors affect the rate of osmosis; one of these factors must be chosen for investigation in the experiment:
: The temperature of the water in which the experiment is conducted.
2: The size of the water concentration gradient; i.e. the difference in the concentration of water between the solution surrounding the object and inside the object itself.
3: The size of the pores in the membrane; i.e. the type and properties of the plant or animal cell used in the investigation, in this case the type of potato used.
4: The surface area of the membrane; i.e. the number of pores there are for water to diffuse through.
The experiment is to be conducted using potato chips as the cellular object, the potato chip could be weighed before and after placing in sucrose solutions in different conditions to find the rate of osmosis. The factors above could be investigated in a number of different ways; the first factor could be investigated by placing a number of standard sized chips of the potato used in a boiling tube of similar sucrose solutions in water baths at different temperatures, the potato chips would be weighed before and after the experiment and the rate of osmosis found. The second factor could be investigated by placing potato chips of the same size in sucrose solutions of different concentrations, the potato chips would be weighed before and after and the rate of osmosis found in each, a graph could then be drawn and the change in the rate of osmosis over the different concentrations seen. The third factor could be investigated by using potato chips of the same size but of different varieties, the size of the pores of the different varieties could be researched beforehand and the rate of osmosis in plant cells with different sized pores found. The fourth factor could be investigated by using a number of the same sized potato chips and cutting each up into different numbers of pieces; the pieces would then be placed into sucrose solutions and left for a certain time, the pieces would then be weighed and the rate of osmosis found.
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Teacher Reviews
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*** Although the author has a good understanding of osmosis there is quite a lot of poorly used scientific terminology and a lack of attention to detail.
