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What variables effect omosis in potatoes

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GCSE Coursework

What variables effect omosis in potatoes.

Information about osmosis.

Osmosis is the movement of water molecules from a region where there is high concentration to where there is low concentration, this often occurs across a selectively permeable membrane. This is an area of selectively permeable cells that only allow certain substances to cross and prohibit others. The reduction in size of the chip may be due to this process.

In a plant cell – if it is put into pure H2O, it will not rupture because the cell wall is fully permeable to water so therefore osmosis can not occur.

Osmosis in a cell membrane – cell membranes are selectively permeable and if put into pure water it would swell because the cell wall is strong. They also do not burst but becomes turgid.

If a plant cell is put into a salt solution, water moves out of the cell and so the cell shrinks and becomes flaccid. This process is called Plasmolysis, the plant cell shrinks because the cell membrane tears away form the cell wall.


To find out what difference the concentration of a salt solution makes to the size of a raw potato chip.

I predict that that there is a proportional relationship between the current flowing through the wire and the strength of an electromagnet. Therefore this means that as one is increased then the other will increase. I think this due to the domain theory.

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10. Remove all of the iron filings collected in the container and weigh on the digital scales.

11. Record the results in a pre-made chart.

12. Remove the core from the wire coil and bang on a hard surface to remove any retained magnetism then repeat the experiment for each level of ampere (Starting at 1amps and increasing the amperes by 0.2amps each time until 2.6amps is reached).

This is a blue print of the circuit that should be constructed in order to carry out the experiment:  



Below is a list of all of the equipment that is essential requirements to carry out the experiment:

1x        Iron nail (10cm in length)

Insulated copper wires (50 coils around the shaft of the nail)

1x        Power pack

8x        Connecting wires and crocodile clips (

1x        Voltmeter

1x        Ammeter

1x        Variable resistor

1x        Iron filings (150grams, enough to repeat the whole experiment three times)

1x        Digital scales (Measurement of 2 decimal place accuracy)

Fair Test

To ensure that my test is as fair and non-biased as possible, I am going to keep all of the variables the same, except for current, which of course needs to change as this is the factor that is being investigated.

Also, to ensure accurate results, when measuring the iron filings I am going to use digital scales that supply information to 2 decimal places which I feel is an appropriate accuracy for the results that need to be obtained.

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Overall, I feel that the methods that I used to gain the results were very accurate and fair, although if I wanted to improve the quality and the validity of the results I would possible conduct the experiment in a different way. I would allow myself an appropriate amount of time in which I would repeat the experiment to confirm any possible trends that may be found. By doing this any possible anomalous results would be eliminated and a more sound picture of the results could have been given. Although despite this I believe my investigation has been very successful. My original prediction was proven to be correct and I feel satisfied that the experiment enabled me to gather suitable data that allowed me to make a valid conclusion. I have studied the graph and it was possible for me to identify some anomalous results. The most obvious one was in the first experiment at 1.8amps on the graph rises sharply and does not fit the line of best fit. I feel that this suggests this result is inaccurate. The result for 1.8amps from the second experiment confirms that the result was anomalous. The line of best fit for the average results (obtained from the mean average of the two experiments) represents an expected trend. The line is almost flat. I think that the graph would have been a perfectly straight line if the experiment were conducted in absolutely, perfectly controlled conditions.  If I were to repeat my experiment I would increase the current until the saturation point of the core.

By Ross Smith 11G

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