Limesone and Acid Decomposition

This topic submitted by Dave Clark, Andy Jameson, Kyle Kennedy, Dan Frank ( ) on 12/10/98 .

Dave Clark Andy Jameson Natural Systems
Dan Frank Kyle Kennedy 10/21/98

Final Lab Report

I) Introduction
a) Our group attempted to answer several questions pertaining to acid rain as well as limestone and calcite decomposition. The main problem which we attempted to tackle was what effects acid rain had on limestone structures. We determined the rate at which limestone decomposed by performing a comprehensive laboratory experiment. This experiment tested the rate of disintegration of both limestone and calcite when placed within varying pH levels of acid. The purpose of this experiment was to determine how much damage acid rain is doing to the limestone buildings within the Oxford community. We had several predictions as to what will occur during our experiment. Briefly, our first hypothesis deals with our laboratory findings. We felt that limestone and calcite will undergo a greater change when placed in a solution of a lower pH level. Likewise, a higher pH level will yield less of a change on the rocks. Judging by our findings in the lab, we will eventually be able to determine the rate at which limestone will decompose due to acid rain. Our group did this by comparing the actual pH level of the rain to our findings in the laboratory. We also felt that the limestone will attempt to neutralize the acid solutions, thus, our experiment must be closely monitored.
b) We decided upon this question because it is such a broad subject to study. Acid rain has an enormous impact upon our earth and is constantly affecting our ecosystems. Since man began polluting the earth with factories and automobiles, acid rain has been a serious environmental issue. Our group felt that an acid experiment would offer us a solid experiment which would yield varying results. We noticed that many of Miami's buildings are made of limestone. We learned in previous classes that acid has the ability to break down limestone. Thus, we naturally were curious to determine if the acid rain in Ohio will have an affect upon the local limestone structures.
c) Our group was hoping to determine exactly how much of an impact acid rain had upon Miami's limestone buildings. Obviously, we knew the rain would not have a large affect, in fact, it was surprising to see any effects at all. However, we knew if we could note some change; if we could determine whether or not limestone is affected by rainwater in Miami; then we would be able to determine how much longer the buildings will last before they need to be treated or renovated. Let us say now, that it will most likely be a very, very, very long time. However, we feel this experiment is very interesting and holds a great deal of scientific value.
d) There is an enormous amount of importance relative to our experiment. As stated before, acid rain plays an enormous role in nature, throughout the world today. Factories and automobiles release toxins into the air each day. These toxins are absorbed by moisture within clouds, and later, deposited back upon the earth. We felt that studying acid rain would be both educational and beneficial to what we know about acid rain. Our environment and natural ecosystems are slowly being weakened by acid rain. Hopefully, we can identify an acid rain problem in a our area so solutions can be reached before its too late. We feel that this research is interesting because it can be easily tested and has a great deal of relevance as far as our every day lives.

II) Relevance
a) Obviously others have done more extensive and comprehensive work concerning the effects of acid rain upon ecosystems. Likewise, data has been collected pertaining to acid rain's affect upon manmade limestone and metal structures. As documented in such works as Acid Rain; The Devastating Impact On North America, our earth has a clear problem with acid rain. Lakes and rivers have been affected by acid rain in numerous ways. In numerous instances, aquatic organisms such as plants and fish have died due to the high levels of acidity in that particular body of water. This acidity is caused by acid rain. We have all seen pictures of buildings and sculptures, streaked with rainwater marks. Hundreds of books and articles have been written by such editorials as The Washington Times and the Chicago Tribune. These institutions are aware of the problems facing us. The marks on buildings can be attributed to acid rain. The rainwater eats away at the material, such as limestone, and causes it to corrode. Buildings such as the Notre Dame Cathedral face these problems. This type of deterioration is predominately found to the east of industrialized cities or areas which hold large populations. This is due to the number of toxins and pollutants which have been released into the air. These pollutants travel westward through the earth's jet stream and are eventually deposited upon town, lakes, and forests in the form of acid rain.
b) We feel our experiment is more localized to the region of southwestern Ohio. Our experiment will probably not influence the way all humans look at acid rain. This is because we are not necessarily attempting to prove an hypothesis correct. We know that acid rain has a negative affect upon manmade structures made of various types of metal or rock. Instead, we are attempting to determine what effect acid rain has on buildings here in southern Ohio. We are hoping to contribute to the knowledge about acid rain within our area. Our group feels that it is important to know how much damage the rain is doing to our buildings here at Miami.

III) Materials and Methods
a) Our experiment has become quite extensive and it involves numerous aspects of acid, limestone, and calcite. First, we must explain how we designed our experiment. The experiment is designed so that in all, we had 65 samples of acid. Twenty-five samples were designated for calcite study. Forty samples were for the study of limestone. We have such a large number of samples to ensure that we have a larger array of results. Our margin of error will decrease with the more samples we have for the experiment, leaving us with unbiased results. The first part of our experiment deals with acid and limestone. We have designed our experiment so that we tested eight different pH levels, each with five samples. This gave us 40 total acid/limestone samples. The acid was created by adding hydrochloric acid to water; (HCL + H2O) We measured the change in the limestone (CaCo3) during the experiment. Our group did this by measuring each rock's size and weight both before and after the experiment. We also measured the rocks each week to chart the process of deterioration. We used acid solutions with pH levels of 2, 3, 4, 5, 6, 7, and 8. The change in size, shape, and weight told us what affect the acid has upon the limestone rock. The second part of our experiment dealt with acid and calcite. We using calcite because this rock exhibits many of the same properties as limestone. Essentially, calcite is limestone in its pure form. Once again, broadened our search for the correct data. The calcite part of the experiment had five pH levels, each with five samples. Thus, had twenty-five total calcite samples. The calcite was measured in much the same way as the limestone was. We measured the size and weight of the calcite both before, during, and after the experiment. Any changes were noted in our final analysis. We created acid samples with pH levels of 2, 4, 6, and 8. Our calcite data was compared with the limestone data, mirroring eachother in ways such as decomposition. The third and final part of our experiment dealt with local rain water and limestone and calcite. The pH level of Oxford's rain can be obtained via the internet through the National Weather Service. We were also going to test actual rain samples, but for some odd, frustrating reason, measurable rain only fell at 4 A.M. during our experiment. Our eventual goal, was to compare our man-made acid solutions to the rain-made solutions. For example, if the acid rain has a pH level of 8, then we would analyze the data for the lab portion of our experiment with a level of 8. By studying how the acid affects the limestone and calcite, we are able to make an estimation as to how log Oxford's building's will last. (Again, this number will be very high.)
b) Like any experiment, ours is not perfect. Our major problem revolves around the acid solutions. Creating them was difficult because we have never dealt with acid on such a large scale. However, we have spoken with Dr. Bill Green and he has given us valuable advice. He has also offered his advice and support to us throughout our experiment. Dr. Green told us it is difficult to make exact pH levels. He told us to simply use a trial-and-error method in creating the pH levels. Going on his advice, we simply added drops of acid to the water and then measured the solution. Creating the solutions was not as hard as it initially seemed. The lower levels simply required more acid while buffer solutions of 4, 7 and 10, aided us in raising the pH levels. Though it seemed impossible at first, we quickly mastered the art of acid mixing. The second acid problem we faced was that limestone is a base. Thus, the limestone attempted to neutralize the acid solution. In order to keep the acid levels at the same level, we adjusted the solutions every day. EVERY...SINGLE...DAY. It was necessary to tend to the solutions as we quickly found the solutions would rise daily. By adding both acid or buffer as needed, we were able to create the desired pH levels, and maintain their levels.
c) We involved the class in our experiment by allowing them to create solutions of their own. We divided the class into four different teams, with each team being assigned to a different pH level. Each team was taught how to create a pH level and then perform a test upon both calcite and limestone. The class experiment lasted a week and a half with each group testing three limestone and three calcite samples. We assisted each group in the creation of the acid to ensure that they were accurate. Our group adjusted the teams' samples in case the acid levels rose. By supervising the creation of the acid solutions and maintain them during the week, we were able to ensure that the groups had accurate data. Much to our dismay, time constraints did not allow us to perform follow-up research on these samples. We were hoping to let the students check their acid the following Monday, but another group was presenting. However, we still monitored the solutions for a short time. Hopefully, the class found it interesting to create acid samples and experiment with rocks.
d) I have already stated our materials, yet I will quickly restate them. We have constructed 65 "beakers" out of various soda cans. These cans held each of our solutions. This, let me remind you, is alot of cans. We have also gathered limestone from the local creek and calcite from the good people at Ward's Natural Science Establishment. Hydrochloric acid was provided by Miami University as well as tap water. Of course, the rain would have been provided by mother nature, yet she didn't want to cooperate.
e) I've already described the manner in which the class will be involved, Each group had a different pH level. They were to explain what effects they saw, and if they saw effects, why.
f) See Timeline

IV) Results
a) Now for the fun stuff. The results which we got were quite conclusive and very astonishing. First, let me just say that acid and limestone react well with eachother. Let me also say that acid burns when sniffed or taken internally through cuts or scrapes. Before I get to our graphs from Statview, let me put the data in basic terms. For the pure calcite, the lower pH levels of 2, 3, and 4 showed the greatest change. Some decreased as much as .5 grams, which is a significant loss. Likewise, the lower limestone samples of 2 and 4 showed a loss of between .3 and .5 grams. In both cases, the higher pH levels such as 7, 9, and 10 showed little or no loss at all. From these results, we were able to conclude that a higher concentration of acid in water will have a greater affect upon both limestone and calcite. The higher the acidity level, the more loss of mass. Thankfully, our hypothesis was correct. However, during the experiment, we noticed a startling trend. The higher pH levels such as 8 or 10 actually gained weight during the experiment. You can imagine how surprised we were when we saw the rocks gaining weight. After thinking about this phenomena, we've concluded that the rocks were reacting with the buffer solutions and acid as well. In doing so, mineral deposits were being formed on the rocks. CO3 was being released during the reaction, causing a deposit to form on the rocks. Eventually, due to this releasing process, the water in each beaker completely evaporated. Clearly, we were not prepared for such a twist, however, it certainly made the experiment much more interesting. Overall, we can now definitely say that high pH levels have little or no effect on limestone. Likewise, low pH levels have a great impact upon these rocks.
b) Graph A1, A2, A3
In these graphs, we are comparing the total percent change of both calcite and limestone according to their pH levels. We took our data from the pH's of 2, 4, and 8 because both limestone and calcite had results in this range. As shown on the graphs. the lower pH's showed a much greater rate of percentage change. We could also see, in high pH levels such as 8, the weights actually increased. Since the limestone lost a greater percentage of weight at the lower levels, they gained less weight at the higher levels. For all of these graphs the p-value was greater than .05, so we accepted the null hypothesis. This means that we accepted the fact that there was no significant difference in the data for these graphs.
c) Graph B1 and B2
These histograms show the percentage change over two given dates at the beginning and end of the experiment. Again, these graphs display the contrast between limestone and calcite. We compared pH levels of 2 and 8 to measure both ends of the spectrum to obtain varying results. It is difficult to determine the exact meaning of these graphs. I will explain the calcite test to gain an understanding. On November first, all five calcite samples were measured in Ph 2. This graph shows 2 samples showed a percentage decrease of 0; 1 showed a change of 2; 1 showed a change of 3; and 1 showed a change of 10.5. Keeping in mind the experiment began on October 28th, these results are a week old. Now, for Nov. 30th, results are different. They are a month old. You can see on B2 for calcite in Ph 2, there is a greater range of percentage change. The other graphs explain the same data for limestone in 2 and 8 as well.
When we compared the two substances, calcite and limestone, looking for the percentage of change in the rocks, we found that the two were statistically different, sometimes. We separated the data by pH, and by date. We used bar graphs to visually show the percentage change in the rocks from date to date. In the pH 2 rocks, calcite ended up with a 7.7% total loss. We found that the different dates were statistically different from one another because the t-test gave us a p-value of .0001. While the limestone ended up with a 13.6% total loss and the dates weren't different because of the .6882 p-value. The calcite rocks emerged in the pH 4 solution ended up with a 2.9% overall loss. The dates were not different from each other because the p-value was .5447. The limestone in the pH 4 solution had a 5.4% total loss. The limestone rocks were statistically different from one another though. They had a p-value of .0001. The calcite and limestone that were in the pH 8 solutions did something a bit different. The rocks actually gained mass. The calcite had a maximum negative percent loss (a gain) on November 1st, at -.47%, then it began to lose mass. It ended up with a -.05% change. The dates were not different from one another because they had a p-value of .6137. The limestone on the other hand had a maximum negative percent loss on November 8 at -.2%. Then they began to lose mass. These rocks had a p-value of .9061, and therefore were significantly different.

V) Discussion and Conclusions
This truly has been an exciting experiment for our group. In my opinion, our experiment was valid and interesting. There were many questions surrounding our experiment. To name a few; "What kind of acid?" "How many samples?" What kind of rocks?" "How often do we adjust the samples?" "Will this actually work?" "Why are we doing this?" Most commonly asked: "Do we have to check every day?" We enjoyed this experiment because it made science fun. Our group decided the outcome and path which the lab. took. Obtaining our results was the most exciting part of the experiment. Through careful observation and planning, we were given results which made sense. Our lab. was controlled well, and we didn't let it become too complicated. We obviously know that acid rain would take millions of years to dissolve acid rain. Our experiment wasn't perfect. Rain water doesn't immerse Oxford's building's like we did to the rocks. Instead, rain merely douses the buildings. Thus, actually buildings aren't subjected to constant immersion. However, buildings are affected by winds, driving rain, heat, and other forms of weathering. These factors were not taken into account during our experiment. Undoubtedly, these weathering effects with cause damage to any structure.
During this experiment, we learned the effects of acid on limestone rock. Once again, we found that strong acid has a significant effect on these rocks. Weak acid does not. We would have liked to study the rain's effects more closely, but time constraints and mother nature didn't cooperate. It would have been interesting to see how much weight loss occurs in one month using limestone and rainwater. Oxford's rainwater is around a pH of 4.5 now, yet it has been as low as 3. (Thank you Hayes) If it's been as low as 3, well then, that's pretty close to 2. Thus, there is the opportunity for definite change within Oxford. I'm sure that eventually, someone will feel crazy enough to try such an experiment again. (65 cans is alot) If they do, we'd tell them to include rainwater first, not last...especially with Ohio's crazy weather. (70 in December) It would also be interesting to see if any chemicals are used to treat Oxford's limestone structures. If so, then they could be added to the solutions to see if they counteract the acid's effects.
In conclusion, let me just say that this was truly a unique experience. Obtaining our own data was simply more fun than sifting through some old scientist's whom I've never heard of. Plus, we actually proved a hypothesis correct and got measurable data. Overall, our group worked well together, each sharing the large workload. Measuring the acid each day was a pain, but well worth it in the end. Again, acid burns when inhaled, so if anyone ever does this again, please be careful. I guess that about wraps up our final report. I must say I am extremely glad to say this. I thought we would never reach our final conclusion. But we still had fun.

VI) Bibliography

Bruice, Paula Y. Organic Chemistry. Santa Barbera: University of California Press, 1998.

Bell, R.P. Acids and Bases: Their Quantitative Behavior. New York: John Wiley & Sons, Inc., 1952.

Coates, Steve. "Chemists Find Ways to Save Monuments From Pollution." The New York Times 18 November. 1997, Late Edition.: F4.

Egan, D'arcy. "Limestone Correcting Acid Rain Damage." The Plain Dealer 6 June. 1997, Final Ed.: 10D.

Howard, Ross. Acids Rain: The Devastating Impact Upon North America. New York: McGraw Hill Book Company, 1980.

Livingston, Richard A. "The Elements From on High." The Washington Post 19 March. 1994, Saturday, Final Edition.: A19.

McWilliams, Brendan. "Rainwater as Sculptor." The Irish Times 25 September. 1993, City Edition.: Weather.

Mygatt, Matt. "Protective Coating: New Limestone Preservation Slows Wear and Tear on Monuments." Chicago Tribune 16 February. 1997, ChicagoLand Final Edition.: 5F.

Pettijohn, F.J. Sedimentary Rocks. Baltimore: John Hopkins University Press, 1949.

Record, Frank A. Acid Rain Information Book. Park Ridge, New Jersey: Noyes Data Corporation, 1982.

Tucker, Maurice. The Field Description of Sedimentary Rocks. New York: The Open University Press, 1982.

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