After 3 days, we take out the different materials from the test tubes, and put them in an oven to get the totally dry, so we can get the most accurate weight. After the marble and concrete are dry, we weigh them. Then we put them back into the test tubes and weigh those as well, to make sure that the weight difference is accurate, and see if maybe some of the acid is lost.
After 1 week, we repeat the procedure we used after 3 days, so that we are able to compare how the different pH-values and materials affected the results.
Data Collection
Initial Measurements
Measurements after 3 days
Measurements after 1 week
Record of the differences of the weight of the building materials
Record of the differences of the pH-values of the sulphuric acid
(H2S04)
Data Processing
It is quite difficult to interpret what role the pH-level played in this experiment. If one, for example, looks at marble 2 and marble 4, one can see that both had an initial pH-level of 5,0. However, marble 2 shows the least weight lost during 1 week, whilst marble 4 displays the biggest loss of weight.
This pretty much automatically leads to looking at their initial weight. As we compare them, we can see that there is “only” a difference of 0,063g between the pieces of marble and almost no difference at all between the initial weights of the test tubes containing the marble pieces and the sulphuric acid. The difference of the increase of the pH-level - 0,1 - is not “too high” either.
Concrete showed an enormous change in pH-value. Starting of with an initial pH-value of 5,0 it ended with a terminal pH-value of 11,89. That gives a difference of 6,89. However, the total weight loss (0,042g) only ranks in the middle, if one compares it to the other weight losses of marble.
If one compares the data collected throughout the experiment, it is hard to tell how the pH-Value or the different materials affected the results/outcomes.
One thing, however, is quite obvious: All the pH-values showed a pretty big increase in pH-level, which indicates that the different materials reacted as bases.
In the case of marble, which is nothing else than calcium carbonate - CaCO3, following reaction occurs:
Conclusion
Drawing a conclusion for this experiment is not very easy due to the fact that a generalization is quite impossible.
The statements in my hypothesis are mainly incorrect. As one could see, the pH did not affect the building the way it was expected. This is proven by the fact that a pH of 5 caused the biggest as well as the smallest loss of weight, even though, it was reacting with the same material. For that case, I predicted that the initial mass of the material would play role, and indeed, in this case it is true that the bigger the piece of marble was the more weight it lost throughout the whole experiment.
However, this is not too evidentiary due to the fact that Marble 3 did weigh the most in the beginning of the experiment, but the total weight loss is rather insignificant. In addition to that, Marble 3 had the lowest pH used, so that the small weight loss is actually inexplicable.
The only “correct” assumption stated in the hypothesis is that both marble and concrete reacted as bases. This is shown by the increase of the pH-value in every single case.
In conclusion one can say that this experiment was not very helpful on investigating the effect of acid rain on different buildings, since no general conclusion can be drawn.
Even though, we used pH-levels of 5 or less, which is defined as acid rain, it is impossible to compare our experiment with the effect acid rain has on actual buildings, since those are usually not exposed to rain all the time, but over a way longer period than just one week.
Evaluation
Several variables had an influence on our results, such as the value of the pH and how much the piece of a building material weighed in the beginning of the experiment. However, it did not really make sense how each variable affected the outcome, because they might influenced the result in one case totally differently in compared to another.
I assume that doing this experiment once more might have a totally different result, and probably more of the statements in hypothesis would be true, because they seem to make sense.
Even though, the result seems like a failure, due to inaccuracies like the concrete weighing more after 3 days than to beginning of the experiment, or the fact that a general result is lacking, there might be a improvement if one would watch the results over a longer period of time.
Nevertheless, this experiment and its outcomes are rather disappointing. Only the fact that we can say, with a very high certainty, that all the materials used, reacted as a base is a little ray of hope.
Suggestions of improvement:
- investigate the effect of acid rain on building materials over a longer period of time
- use more materials, and equal tests on each kind of material (that includes using several pH-values, and different initial weights)
- record the shape/surface of the used material in the beginning and the end of the experiment
- choose more parameters which might have an impact on the material
- measure the amount of acid used
http://en.wikipedia.org/wiki/Acid_rain
