So we have:
These results prove that copper carbonate thermally decomposes into Copper Oxide and Carbon Dioxide. Another way of confirming this is to compare the atomic numbers.
Copper Carbonate = CuCO3
copper carbon oxygen (x 3)
copper = 64
carbon = 12
oxygen = 16 (x 3) = 48
64 + 12 + 48 = 124
Copper Carbonate’s atomic mass = 124. The two substances that make up copper carbonate have the following atomic masses:
Copper Oxide = CuO Carbon Dioxide = CO2
copper + oxygen carbon + oxygen(x 2)
64 + 16 12 + 16(x 2)
80 44
80 + 44 = 124
The atomic numbers of copper oxide and carbon dioxide add up to the same atomic number as copper carbonate, which also proves that copper oxide and carbon dioxide is what it thermally decomposes into.
This information is what allows me to reach the following conclusion:
If I start with 124g of copper carbonate (CuCO3) I would have 80g of copper oxide (CuO) and 44g of carbon dioxide (CO2). This means when it is thermally decomposed, we lose 44/124 of carbon dioxide or 44/124 x 100 = 35.5% of carbon dioxide. My main experiment is to prove this theory.
Plan: I predict that when thermally decomposed copper carbonate loses 35.5% of carbon dioxide. In my experiment if I can find the mass of copper oxide left over I can subtract that from the mass of copper carbonate + crucible + lid and that will give me the mass of carbon dioxide lost. If I change that into a percentage, I will have my result. That result should be around 35.5% and I predict a range of 30% to 41%. That gives a margin of 5.5% on either side.
I will need:
- Bunsen burner It will be laid out like this:
- Crucible and lid
- Tripod
- Tongs
- Chalk stand
- Copper carbonate
- Scales
- Cooling mat
- Safety glasses
The cooling mat, tongs and safety glasses are all safety precautions. The cooling mat is too protect surfaces, the tongs to protect my hands and the safety glasses are to protect my eyes from any burning debris. I will be dealing with scorching hot materials and want to reduce the risk of being burnt as much as possible. I will have to remain diligent throughout the experiment.
In this experiment, my input variable will be the mass of copper carbonate being heated. This will affect the dependent variable – the mass of carbon dioxide lost – and is the factor I will be recording in this experiment. All weights recorded will be in grams and the only other unit of measure will be percent. For each different mass of copper carbonate I burn, I will repeat it three times. As I plan to do four different masses, this will give me a total of twelve results. These are enough results to draw up a graph and spot any patterns, and plenty enough to come to a clear conclusion. They will all be reliable because of the repetition and because the scales are accurate. They will all be recorded in grams, except the final set which will be in percent.
Results:
1.
2.
3.
Conclusion:
To make an accurate conclusion I have made an average table so that I am able to draw up my results into one graph instead of having to draw three.
Average Table
All the percentages in the average column fit my prediction perfectly. To double check them, I compared them with the average percentages from “person x’s” experiment:
These results correspond very well, if anything my results are more accurate simply because they are closer to 35%.
As my results came out successfully I drew up an average graph of the ‘mass/grams’ and the ‘mass of CuO/grams’ to spot any patterns.
(See graph paper)
This graph shows that although the percentage stays around the same point (35.5%), the ‘mass of copper oxide (CuO)’ rises as the ‘mass/grams’ rises. The ‘percentage of carbon dioxide (CO2) lost’ does the same. This is because the more copper carbonate that reacts, the more copper oxide and carbon dioxide is produced. However, the way the ‘mass of copper oxide (CuO)’ and the ‘percentage of carbon dioxide (CO2) lost’ rises follows no real pattern, it doesn’t go up exactly in twos or double exactly, but it doesn’t jump from one extreme to the other either. It just rises at the same steady rate as the ‘mass/grams’.
Evaluation: My experiment was successful because I was able to prove my prediction correct and come to a sensible conclusion. I did have a few anomalous results, but they did not prevent me from getting a clear answer. If anything, they acted as a useful comparison to the results that were clearly correct. The results that were anomalous were all to be found in the ‘percentage of carbon dioxide (CO2) lost’ column in the third table. They are highlighted in pink below:
As you can see, these results exceed the range that I have predicted by 2.5% and 2%. The reason for this could be due to two things; 1. A simple miscalculation or mistake when recording numbers or 2. The copper carbonate was not left to heat for as long as on other occasions and did not react completely. They are mistakes, but useful mistakes as I can compare them to other correct results and also ensure that similar slip ups do not reoccur in future experiments.
My experiment can be considered fair because I used the same scales, bunsen burner and other pieces of equipment each time I repeated the experiment. I did change the crucible and lid each time, but as they were weighed and the copper oxide was subtracted from their weight correctly each time, that doesn’t interfere. The results I obtained support my experiment (apart from the two anomalous results) so, assuming my experiment can be classified as fair, I can claim that my results support my prediction and follow my theory: that the results should be around 35.5% and I predict a range of 30% to 41% (5.5% either side of 35.5%). I do have enough results to come to a clear conclusion but if I were to repeat the experiment I would like to take the ‘mass/grams’ up to 2.0. That would provide a clearer conclusion and also allow a higher chance for a pattern to be spotted.
The main difficulty when carrying out the experiment itself was working out how long to heat the copper carbonate for. If I was to repeat the experiment, I would time how long each crucible was over the flame for. This would make the experiment fairer and more valid. I would also like to compare my results with more than one other person’s results, and to compare the basic results, not just the average results. This would give a better idea of the results other people are getting, what conclusions they are reaching and how they got there. But I would only try the above ideas if I were to repeat the experiment. As it is, results are all adequate and have allowed me to come to a valid conclusion that supports my prediction.
