We are going to investigate the concentration of the Copper Sulphate Solution.
Prediction
I predict that as the concentration decreases, the reading on the ammeter will decrease too. I think the relationship is directly proportional between the concentration and the reading on the ammeter. So I predict that if I half the concentration the reading on the ammeter will half too. I think this because there will be half as many ions to carry the current.
The copper sulphate releases copper ions, which will flow through the solution toward the negative electrode, where the copper ions combine with the electrons to deposit copper on the electrode.
Preliminary work
For my preliminary work I have decided to try all different voltages with 100ml of copper sulphate to find which one I will set my power pack at during the experiment.
I have decided to try 6 volts because I believe this will give a good range of results.
I will now do more preliminary work to test if changing the concentration will produce a good range of results.
The results are not too close together or too far apart. We will keep the power pack set at six volts.
Method
Apparatus list
Beaker
Ammeter
Wires
Copper sulphate Solution
Water
Measuring Cylinder
Power Pack
Electrodes
Method
- First I will collect all my apparatus
- Then I will set up my equipment as follows
- Then I will collect 100ml of copper sulphate and put it in the circuit
- Then I will read the ammeter and write it in my table of results
- After that I will replace 10ml of the copper sulphate with 10ml of water
- I will do this six different times and replace 10ml of copper sulphate with 10ml of water each time
Results
Fair Test
To make it reliable I will repeat my experiment six times. I will also try and do all of my experiment on the same day and use the same equipment. I will also try to use the same batch of copper sulphate. I will also keep the total volume the same and the voltage setting, the distance between the electrodes. I will also keep the current and the depth of the electrode in the solution the same.
Safety
To make my experiment safe I will not put the power pack on too high and by washing my hands when I have poured out the copper sulphate solution as well as by wearing goggles so it cannot go in my eyes.
Conclusion
From my results I learned that my prediction was correct as the concentration went down so did the current. I was also correct in that they are directionally proportional:
It is roughly half of 13. My graph shows me that it is mostly a smooth curve accept for one anomalous result. I found that as the concentration goes down so does the current because there are fewer ions to carry the current to the negative electrode and to carry out the electrolysis. If there were 2 copper ions (50%), then there would be fewer to carry the current than if there were 4 copper ions (100%).
100% 50%
Evaluation
My Method could have been better I could have been better I could have measured the copper sulphate and water more accurately. My results are not very accurate because they do not form a smooth curve and do not fit in totally with my scientific knowledge.
Sometimes they went down quite evenly and others they drop quite dramatically. I could make our results more accurate by measuring the current more precisely and repeating the experiment a few more times. I got one anomalous result, which I am not going to concentrate on because it is only one out of six and because our experiment could be greatly improved.
I could avoid them next time by making our experiment more accurate and reliable. I could improve the experiment:
- By measuring the water and copper sulphate more accurately
- By using the same batch of copper sulphate, as the lab technician had to make another batch
- By doing it all on the same day
- Using the same equipment
My conclusion is valid because of my results and my graph, which backs it up and my scientific evidence. They are valid over the range of 100% to 50%. I could extend our investigation of the same variable by using a different method to collect relevant information. I could investigate the change in mass, by weighing the electrode. As the copper and the sulphate separate the mass of the beaker and its contents should change as the copper and sulphate would be on the electrodes.
