I predict that the further apart the electrodes are, the higher the resistance will be. This would mean I would get a graph which looked something like this:
I think the electrolyte will behave in much the same way as a wire would. The amount of resistance depends on the amount on energy that is lost pushing electrons (or ions) through a substance. In a wire the electrons move through a metal lattice, in response to an electric field caused by a source of voltage. I would expect the electrolyte to behave like the metal lattice; if the electrodes are further apart the ions will use more energy when passing between the electrodes.
Changing the distance between the electrodes by moving them further apart, I came up with the following preliminary results:
From these results I decided to make some changes. I decided to add a variable resistor to my circuit:
With the variable resistor added, I could then control the current to prevent anomalies caused by temperature change in the wires- therefore making the test fairer. I also changed the container with the CuSO4 in to a 1000ml beaker, as I felt the Tupperware container was too shallow. I then took some more results, using the same method, but keeping the current constant.
From my results I can see that there is a relationship between the distance between the electrodes and the resistance. The further apart the electrodes are the higher the resistance will be. My graph confirms this. I can see that for every 1cm decrease in the distance between the electrodes the resistances decreases by an average of 0.9 ohms. Therefore my prediction was partially correct as the resistance did change in relation to the distance between the electrodes. The electrostatic force acting on the copper ions did not affect the resistance; if they had my graph would have been a curve.
After taking the above results I calculated the error sizes:
Although from the error sizes it appears that some results could be anomalous, if I look at my graph, the averages appear to fit the trend. In fact, the 5.5cm result appears anomalous on the graph, despite having one of the smaller error sizes. This is probably because of the apparatus; the clamp stands could not go much closer together than 5.5cm, this would have affected our results as the distance might not be accurate.
If I were to do the experiment again I would use different clamp stands or some other equipment to hold the electrodes in place to prevent the problem described above.
An alternative way to measure this variable is by measuring the amount of copper deposited on the negative electrode and explore the difference in mass when the electrodes are further apart. You could also experiment with different electrolytes to see if this affected the resistance. I would do this using the following circuit:
You would be able to see what voltage you were using from the power pack, and to work out the resistance you would divide the voltage by the mass of copper which collected on the negative electrode. The figure for the resistance would not be in ohms. The relationship between distance between electrodes and resistance would still be clear.
