Pilot
Before this investigation I had conducted a previous experiment on electrolysis. The pilot test helped me decide what variable I wanted to investigate and how much the time should be increased for each experiment. I decided from looking at the results of the pilot test that the time should be increased by five minutes for each experiment.
In pilot test I encountered three problems, when the electrode needed to be taken out some copper fell off. I decided the solution to this was to put the electrode deeper in the copper sulphate, this would give the copper more surface area to form on. The second problem was that tiny little bits of copper were left floating in the copper sulphate solution after the electrodes were removed. To solve this problem I decided to the filter the copper sulphate solution in to another beaker leaving behind the tiny bits of copper; this let to another problem. The problem was the filtering took to long and we would not have enough time to finish the results for the investigation, so I decided to have three beakers one for filtering and the others to hold the copper sulphate solution.
After the pilot experiment I decided that it would be best to take around six results so it would be easier to show the effects of time on the cathode on a graph. Also it helped me to decide what results I would obtain, they were before mass, after mass, change in mass and current. I decided that it would be best to try and repeat the results, so I could get an average to make the results and graphs more accurate.
Pilot results
The time limit for the experiment was ten minutes.
Fair Test/Safety/Accuracy
To keep my experiment fair, firstly I will use the same pieces of copper for my electrodes, also to make the test fair I will label each electrode positive and negative and label them with my name so that we use the same electrodes for each experiment.
Another way I will keep my experiment fair is to keep the powerpack on the same voltage of ten volts, and at the end of each experiment I will takeoff the excess copper on the cathode. To be safe I will use goggles when pouring the copper sulphate solution.
To be accurate I will need to use a timer so each experiment can be stopped and started accurately. Another way to be accurate is to use a digital scale, accurate to 2 decimal places.
Plan
Before we start the experiment we have to set up a circuit that includes a powerpack, ammeter which will be connected in series, stop clock, beaker, filter and electrodes in copper sulphate. Once I have the circuit ready, I need to cut two 5cm long copper electrodes out from a copper sheet and weigh them, once I have weighed them I need to record the weights.
After the weighing I will complete the circuit with the copper electrodes and copper sulphate. Then when the circuit is complete I will turn on the powerpack and timer with the help of my partner.
Once the experiment is over I will let the electrodes dry off and weight them again and record the results. While I am doing this, my partner will be filtering the copper sulphate solution and getting the circuit ready for the next experiment. However, before using the electrodes again I will remove the excess copper on the anode by using sandpaper.
After I have collected all the results I will study them and put them into graphs. I will then use the graphs and results to see if my hypothesis was correct. The range of results I will collect will be, before and after mass of electrodes and the current. I will aim to conduct one repeat for each result to obtain an average.
Equipment
There are a few pieces of equipment I need to carry out the experiment successfully they are:
- Powerpack – this is used to supply the electricity we need to conduct the experiment and push the electrons around the circuit so copper atoms will form at the cathode.
- Stop Clock – this will be used to measure the amount of time for each experiment, so I can be accurate.
- Crocodile Clips – the crocodile clips are to hold the two copper electrodes in place.
- Ammeter – the ammeter will be used to measure the current flowing through the circuit.
- Filter – this will be used to get rid of the excess copper in the copper sulphate solution.
- Sandpaper - this is used to get rid of the copper additional copper atoms on the cathode.
- Hairdryer - this will be used to speed up the dying of the electrodes.
- Digital Scale – this piece of equipment will be used to weigh the two electrodes more accurately.
Diagram
Results
Conclusion
From my results, I have found out that when the time is increased that the mass on the cathode is increases. The table of results also shows me that my hypothesis was correct but if you double time the mass on the cathode does not double. My graph shows that my hypothesis was partly correct and incorrect. It shows that there is change on the cathode, when the time is increased but the mass does not double. My graph also shows that the copper from the anode left but did not reach the cathode.
Another thing I have discovered from the use of my graph is freak data, which makes these two, pieces of data void.
The two pieces of date are experiments number three and number six. Experiment 3 is void because the change in mass falls compared to the previous experiment. Experiment 6 is void because the change in mass for anode is –0.09 but the change is mass is +0.44.
The graph also allows me to see what has happened in each experiment for example, in experiment 2, I can see that 0.9 grams was lost by the anode but only 0.3 grams was gained by the cathode. This shows me that the rest of the mass was deposited in the bottom of the beaker.
Evaluation
From my results table and graph, I can see that there were many problems. Firstly time was a huge problem; we did not have enough time in lessons to conduct a 30 minutes experiment. Next time to overcome this I will not use such large time intervals I will use time intervals like 2 minutes. .
My second problem was during the experiment the anode simply eroded too fast for the cathode o pick up the copper ions. This made my results more unreliable. To solve this problem next time I will reduce the voltage. I think these two problems let to the results being unreliable, because there are two results that are anomalous.
I don’t think it was the procedure of the investigation that made the results unreliable, so I would not change the procedure, because I used a timer and digital scale to make the experiments accurate.
