Apparatus:
Copper sulphate -This what you need to do the experiment
2 electrodes anode and cathode -These are what are needed for the experiment
1 small beaker - This is where the copper sulphate solution will go
A power pack - This will be the power supply
Crocodile clips - These connect the electrodes to the wires
Wires - These help the current go around the circuit
Amp meter - This tells you how many volts are travelling through the circuit
Measuring cylinder - This measures out the copper sulphate accurately
Fair test:
Throughout the investigation a fair test had to be maintained, to avoid bias results. For this reason, it is important to keep the surface area of the electrodes the same because the greater the surface area the greater the loss in mass the same electrodes will be used each time.
It is also important to keep the temperature of the electrodes the same each time because when the electrode is hot, they will expand, once again increasing surface area and making my results inaccurate. To make sure that the time has no affect on the experiment, I will time each experiment for four minutes only. This way it will remain the same in each test and will not affect my results.
Finally, my experiment set up ensures that the electrodes will not touch at any point on the experiment. So the electrodes will not gain or lose mass because they will not come into contact with the copper ions in the solution. They will always be clipped at opposite parts of the beaker and if they do come into contact.
I will always use 500 ml of copper sulphate solution. The weights recorded for the cathode will be measured by an electronic scale, which is more accurate, and to the nearest milligram.
Safety
I will ensure a safe test by:
- Keeping the glass beakers away from the edge
- My hands will be dry at all times when coming into contact with the electricity
- The wires will be kept off the floor to avoid tripping up
- I will keep a clean area to work with which will minimize accidents and breakages as well
Method:
I would place 50 ml of copper sulphate in a small beaker. The strength of the copper sulphate would be 0.5M. I am also going to place 2 electrodes in the beaker held by crocodile clips, which would be connected to a power pack. First I will always weigh the electrodes. I will vary the amount of voltage passing through I will start off with 12 and go down to 6 then 3. I will always pass the volts through the solution for 1 minute. I will remove the electrodes and weight them again and record how much copper has bee deposited. Then do the same I will do this for 4 minutes. The negative charge is called the cathode and the positive one is called the anode. The cathode attracts the positive charge from the copper sulphate solution and the anode attracts negative charge.
Results:
These are the results that I obtained when following the procedure in my plan. I did the experiment 3 times for each result 4 times to give accuracy and make it easier to spot a general trend and the anomalous results.
1st experiment
2nd experiment
3rd experiment
Conclusion:
From my investigation I have found out that the greater the current, the greater the gain in mass at the cathode which I predicted. This is clearly visible from the graph I have drawn. The reason why I believe that this happened is because at the greater current, the anode was decomposing more and putting more copper ions into the water in a set time than at a smaller current. This means that the copper ions could get slowed down when moving towards the cathode. From the results table I have noticed the more volts going into the solution will give more copper deposited on the electrodes. My original prediction was correct. The higher the voltage the faster the particles will move which will produce more copper deposited on the electrodes.
The pattern of my results:
My results start at a low number and end at a high number. This means as the current of electricity is increased the more copper is given off. This is because the reaction is faster so this released more copper in larger doses, making the cathode gain in mass.
Evaluation:
The experiment I think went very well and I managed to get all the information I needed which I am very pleased about. The graph proved my predictions were correct. As my results very fairly accurate I came to a good conclusion. My method was also a good way to carry out the experiment as it was safe, so I got good results and proved my prediction was right. Although this was a successful experiment, there were some factors of the experiment, which could have been improved to make it even more successful. One of these factors could have been the electrodes, some were still quite dirty and clearly still had irremovable substances from previous experiments still attached to them. If this experiment were to be repeated for a second time, in need of greater accuracy, it would be very important to have a new pair of electrodes, which have never been used before. Another factor which may have affected the overall outcome of the investigation may have been the fact that the practical work of the investigation was carried over from lesson to lesson, meaning that variables such as the concentration or the amount of the copper sulphate solution could have changed between lessons. To overcome this problem, a supply solution of copper sulphate should have been made so as the concentration remained the same at all times. The same electrodes and equipment should have been used throughout. I found this investigation very interesting and if I were to do this investigation again I would change the variables in this experiment, which may or may not affect the mass of copper deposited onto the cathode, such as changing the concentration or temperature variable.
