The more ions in the solution, the more that will be pulled towards the electrodes and the more that will be exchanging electrons, and so the larger the current. The larger the voltage, the larger the force pulling the ions apart (more powerful positive and negative charges from the electrodes on the ions). This means that there will be more copper sulphate molecules breaking appart and so more ions reaching the electrodes, more electrons being transferred and so more current flowing.
Fair Test
I will not change these variables that may have an effect on the experiment (to the best of my abilities):
Distance between plates-Less time need to get to plates
Area of plates- I will keep this element the same so that there is the same amount of plate that can be reached by the ions in every section of the experiment.
Temperature- Increasing or decreasing the temperature would increase the speed of the ions and so current could be transferred faster.
Equipment
Circuit
Method
- Set up equipment as shown.
- Measure out 150ml of deionised water (deionised so that any ions already in the water will not interfere).
- Weigh out 1g of copper sulphate crystals on the weighing scale (1g gram is suitable since in the pre-trial we found that the 150ml of water would dissolve at least 5 g of copper sulphate which is the limit of out experiment).
- Turn the transformer to 2V and then switch on the current making sure the circuit is set up as shown.
- Take down the Amps and Volts from the equipment, into a results table like that below.
- Turn off the current and then repeat again with the current set to 4V and so on until you reach the maximum of 12V. You should have 5 results for this concentration.
- Repeat this experiment again with the same equipment etc to get something to compare to and to get an average from.
- Put another 1g of copper sulphate into the solution, to make 2g and then repeat the previous steps, getting five results and then repeating the experiment to get another five results that should be similar.
- Do the same with another 1g making it 3g of copper sulphate.
- Continue with this pattern until 5g of copper sulphate has been added in total and has been tested and retested with a total of 10 results.
Results
Analysis
Having drawn a graph from the results I obtained from the experiment, I can see that I have proven my prediction by the fact that as the concentration increases (when I add 1g of copper sulphate to the solution) the current goes up(this can be seen by the lines gradually sloping more and more towards the current axis(they slope in this particular fashion because of the fact that as the ampage increased the voltage dropped(The voltage dropped because resistance is shared in a ratio and as the resistance of the solution grew less, the resistance from the resistor(for safety purposes) stayed the same meaning the voltage was shared continually in a different proportions, the resistor always having the same resistance meaning as the current went up it needed more voltage to maintain its resistance, since the copper sulphates resistance is not constant, more voltage is given to the resistor and therefore the copper sulphate gets less))).
I can also that since the lines on the graph are straight lines(they are not unless drawn as a scatter graph but most if not all of the measurement are extremely close to the line of best fit and so we have left that and called it inaccuracy), the voltage and current are proportional (this is true for all straight line graphs), this means that the copper sulphate solution obeys Ohms Law and therefore has a resistance that can be measured. It is obeys Ohms law since the voltage is proportional to the current and that is the basis of Ohms law.
I can also see by measuring the distance between the lines that they are already relatively evenly spaced appart. This shows that for each gram of copper sulphate I add the current that the solution will conduct is increasing by the same increment each time.
To prove that the current is going up as the concentration goes up I have picked a voltage and I have measured the ampage of all the concentrations using that voltage:
As can be seen the graph is going up in a roughly straight fashion and so this means that there is a postive correlation between the concentration of copper solphate in the solution and also that the amount you add into the solution is proportional to the rise in current gained from adding that copper sulphate.
Also from the graph we can see that the higher the concentration, the lower the resistance. This can be seen by the gradients slowly getting less sleep and the resistance of a conducter can be found by measuring the gradient of a line(Y/X)
The resistance gets lower as you add more copper sulphate because you have more ions carrying more charge, therefore less resistance to the flow of electrons.
Rules- According to my graph
These results obtained from my scatter graph, seem to suggest that on average at 5V for every 1 g of copper sulphate added, the current increases by approximately 0.05 amps. This is obviously not going to be the same for every voltage, however it will follw a similar pattern , i.e there will be a constant interval between each concentration(the 0.05 in this example for example). This is for the same reason that has been explained earlier in this experiment involving a set amount of copper sulphate ions being added meaning that , therefore a set amount of electrons that can be tranferred and so a set amount of extra current that can be allowed to flow throught the circuit.
Lastly the very positive gradient of the graph shows that the more voltage you apply the more current (as voltage goes up so does the current). This is because when the voltage is increased the force exerted on the ions by the plates is increased and so more ions are breaking off and moving to the electrons and more electrons are being transferred and so there is more charge being transferred.
Evaluation
Our experiment has proven our prediction and given a lot more information etc to work with and formulate further hypotheses to be proven.
In the beginning of our experiment we set out to keep our experiment a fair test. I believe we did this to the best of our ability but some things were obviously out of our control, such as the temperature of the room. Otherwise things were kept within a certain range of accuracy and so I personally think that we conducted the experiment fairly.
I think that our results are fairly accurate since they are relatively close to the line of best fit meaning that they are all relatively accurate and do not stray far from the pattern they suggest.
There were obviously things that were ever so slightly off in our experiment, these things could have occurred for a number of reasons:
Equipment
∙ The scaling of the equipment (we took our measurements to 2 decimal places) meant that the measurement could have been 0.005 either way of what was written. This could lead to 2 readings of 0.04 when there should have been 0.35 and 0.44.
Human Error
∙Measurement of Copper Sulphate- This could obviously effect the experiment but I believe we measured our copper sulphate with a good degree of accuracy.
∙Solution- The copper sulphate could not have fully dissolved(we may have not stirred it enough). This could mean that the amount of copper sulphate effecting the experiment was reduced and so the results could be made inaccurate.
These are the only mistakes or inaccuracies really that could have had an effect on OUR experiment, due to the fact that other factors were closely watched and did and could not have happened.
Future Experiments
A follow on experiment to do after this experiment could be to try a different ionic compound and see if it works in the same way. Perhaps the solution would only work with an electrode made from one of the compounds elements, or maybe it would not matter and the solution would change. I believe this experiment would be very interesting.
