I also predict that the relationship will be directly proportional between the time the voltage and the mass of Copper deposited on the Cathode (negative electrode). I can therefore predict that if I double the time of the experiment, I will therefore be doubling the charge. This is because the mass of any element deposited during electrolysis is directly proportional to the number of coulombs of electricity passed.
Equipment
- Copper sulphate solution
- Beaker
- Power pack
- Copper strips
- Stopwatch
- Wires
- Cardboard
- Weighing scales
- Hair dryer
Preliminary work and investigation
As I wanted to make sure my results in my test would be appropriate I believed it would be a good idea to conduct a preliminary test to determine how long I should keep the anode and cathode in the copper sulphate solution. As I feared if I didn’t leave the anode and cathode in long enough there would be a very little difference within the difference of the weight. Although if kept in too long it may wear the anode away completely and be very time consuming.
Therefore I set up the power pack to 6 volts as this was the middle voltage we would be testing and started up the electrolysis experiment for a duration of 2 minutes, then again for 3 minutes and finally once again for 4 minutes. During the space of 2 minutes the weight difference was so small we were unable to detect it on our scales. 3 minutes gave us a reading and 4 minutes was a big difference therefore we believed it would be most suitable for us to undergo the experiment for a period of 3 and half minutes for each voltage.
Fair testing
To ensure I conduct the experiment fairly I needed to make sure I used the same solution throughout the whole test therefore there would be no disputes into whether the concentration of the solution affected the experiment.
Once the anode and cathode were out of the water they had a lot of water on them which would have affected the weight when we weighed them, therefore we used a hairdryer to dry out the copper sticks although we had to be careful not to drop any of the copper or it would ruin the test.
The distance between the anode and cathode were kept the same by holding them secure by the use of cardboard. Also each test had exactly 3 and half minutes each.
Safety
As this experiment is mainly based around electricity the main hazard is from electrocution especially as there is a liquid near by therefore we need to particularly work slow and carefully and any electrical equipment.
Diagram of the experiment
Method
The equipment listed will be set up as followed in the diagram. The anode and cathode will be weighed accurately then recorded up on a piece of paper. The anode and cathode will be secured within the cardboard then placed over the beaker with the cardboard supporting it. The crocodiles will be clipped on to the appropriate ends (negative to cathode and positive to anode). The power will be then turned on at 2 volts for a period of 3 and half minutes. Once this is done the anode and cathode will be blown dry with a hair dryer carefully for as not to spill any of the copper. The anode and cathode will then be weighed. Once this is done the experiment will be done for 4volts, 6volts, 8volts, 10volts each voltage will be tested three times.
Results
Test 1
Before After Change
Test 2
Before After Change
Test 3
Before After Change
Analysis
By looking at my results I can see that I was correct in my prediction although there was very little difference in change between the anode and cathode after each test. I believe that there may be some fault in the accuracy in my test due to the results in test 2. This is because of the lack of difference in each of the voltage changes.
Therefore this leads me to believe that there must have been another factor preventing the electrolysis. I think this might have been the copper sulphate solution as I used the same one throughout the experiments this could have affected the speed as the liquid was getting very cloggy with copper chunks.
I believe that I should have used higher levels of voltages in my experiment and left it for a longer duration. This would have given a larger difference in my weight. The scientific reason for this is the fact that I know from previous work that the voltage is directly proportional to the amount of weight deposited along with the time; therefore this would give me the chance to draw up a definite conclusion from my results as there will be a bigger difference within my results.
I also believe that the temperature of the solution may have affected the results, as the atoms will be given more energy to move from the anode and cathode. Therefore it may have altered my results. The only time I can let temperature change in the solution is when the power is on then is inevitable that it will become warmer.
My results do follow my prediction by looking at results 1 and 3 on my graph, as there is a direct proportion between the increase in voltage and the weight.
Evaluation
I believe that the procedure was done very carelessly as the drying process before weighing needed to be done quickly as we were limited for time so it was done quickly and carelessly causing bits of copper to fall off the cathode sometimes.
Errors could have been caused by the fact that not all the ions "stick" to the cathode, and so end up at the bottom of the solution. This happens most at higher levels of voltage there by causing an incorrect measurement of the weight for the cathode. Test 2 showed all the anomalies as there was very little change in weight. I believe this to be because of carelessness while weighing the anode and cathode as copper shards fell off the cathode.
While trying to put the electrodes back into the cardboard we were unable to keep them the same distance apart due to the electrodes becoming more and more bent. The apparatus, such as the voltmeter, which is quite old and also may not be perfectly calibrated, could have caused other errors. Also the scales, which only show the mass to 2 decimal places, could have caused problems the rest of the digits in the weight are cut off with out rounding. Therefore this experiment could have been made more accurate by using lower current values, with the same size and separation of electrodes, controlling the voltage so that the temperature is constant, and using a more accurate voltmeter and a balance which rounds the other decimal places.
I could have conducted the experiment differently by letting the copper dry naturally this will have prevented accidentally dropping the copper, which will have caused an error in measuring the weight.
I could also look further in to this type of test by seeing if temperature of the solution could affect it. This may give me evidence that the temperature also affects the weight. I would keep the voltage at a fixed 8 volts then try heating the solution at 10-Celsius intervals. Then I could conduct the experiment the same as the one I have just done.
