Measurements and Trials
In this experiment, we will take five measurements. These will be when the 100 millilitres of liquid will be 20% acid and 80% water, when 40% is acid and 60% is water, when 60% is acid and 40% is water, when 80% is acid and 20% is water and finally when it is 100% acid.
We will do four trials, using the same quantities of water and acid and then in our table we will calculate an average. We will do this because an average is easier to analyse and draw a conclusion from than four separate results. It is also more helpful when constructing a graph.
Prediction
I predict that in our results we will find that the less concentrated the acid is the slower the rate of reaction.
I think this because in diluted acid there are less acid particles and therefore less chance of a collision between acid and limestone atoms. Therefore, if the acid is more concentrated there are more acid particles and more chance of a collision. In pure acid, there are only acid and limestone particles. This means that there are more collisions and gas is emitted faster. The more collisions that happen, the faster the reaction.
I also think that the liquid which is 100% acid should have a rate five times faster that the solution containing 20% acid. This is because there are five times more acid particles and therefore five times more collisions should occur. However the speed will get gradually slower, especially for the more diluted solutions, as the collisions take place. This is because after a reaction the particle is used up and there are less collisions taking place. When the solutions have lost the same number of particles that would have more impact on the 20% acid substance as it had less to begin with. This could mean that the reaction is more than five times slower than the pure acid. As there are less reactions taking place the rate will slow down.
Apparatus
In this experiment we will use:
A balance and a spatula to weigh out the limestone,
Two measuring cylinders to measure out the acid and water and to collect the gas in,
A conical flask to contain the reaction,
A delivery tube with a bung for the gas to flow through and
A water trough
Displaying Results
This is how I will display my results after completion of the experiment. I will then draw a graph from the results.
Precision
In this experiment I think my results will be fairly precise. This is partly because we have chosen to use seconds instead of minutes, this has an effect because if we have to round up our numbers when plotting the graph it will be much more accurate rounded to a whole second rather than a whole minute. It is also because we have decided to use 100 millilitres of solution instead of just 20. This has an effect because in just 20 millilitres of solution, to get five measurements we would have to use 4 ml of acid, then 8 ml of acid and these small numbers are very hard to measure out.
We have also decided to measure the limestone to within one tenth of a gram and even though we cannot measure the acid and water exactly we will use our eyes to judge as best we can.
Secondary Research
I did some further research into the effects of acid rain and my full research is attached to the back of this report. However, I found ten important references in my research.
Reference 1 states that acid rain has eroded the stonework of Lincoln Castle in Lincolnshire. It has left a statue barely recognisable (see the diagram). It also states that emissions, from industrial areas, of nitrogen and sulphur are thought to be the cause of acid rain but it is not understood exactly how it forms.
This reference was written by Jim Winkley.
Reference 2 states that acid rain is often carried a long distance from its source. This means that places where acid rain is frequent may not be to blame for it. This also explains how forests and lakes become contaminated. It also states that acid rain is not always in the form of rain, but it can also be snow or fog. This means that the correct term is actually ‘acid deposition.’
This reference was from Microsoft Encarta encyclopaedia 2001 and can be found under ‘’Acid Rain Damage.’’
Reference 3 is regarding the attempts to clean up acid rain. A ventri air scrubber removes polluting particles from gas emissions. If this is used to treat fossil fuel smoke then it could considerably reduce acid rain.
This reference was found on Microsoft Encarta encyclopaedia 2001 and can be found under the section ‘’Anatomy of an Air Scrubber.’’
Reference 4 says that acid rain is caused by industrial emissions mixing with atmospheric moisture. It also says that only recently has the problem become severe and widespread enough to spark international concern.
This source was from the ‘’Air Pollution and Acid Rain’’ section of Microsoft Encarta encyclopaedia 2001.
Reference 5 is a diagram of the formation of acid rain and its effects. It shows that acid rain begins in factories, which are quite often burning fossil fuels. It then forms and artificial cloud as the pollutant particles mix with moisture. The rain falls and damages forests making the plants unable to photosynthesise efficiently. It falls in lakes and upsets the food cycle by destroying all of the fish. Finally, it causes artificial soil by damaging root systems.
This source was found in the same place as reference 4.
Reference 6 states that all rain is actually slightly acidic but acid rain is a term used to describe rain which has been mixed with pollutants and is far more acidic than it could ever normally become e.g. in some places in the world the rain is more acidic than vinegar. It also states that the Parthenon in Greece and the Taj Mahal in India are being slowly destroyed by acid rain. In addition, over 18, 000 lakes in Sweden have become too acidic for fish to survive in.
Reference 7 says that in North America many lakes are said to have a pH number of five or less. A pH number of seven is pure water, any more is alkaline and any less is acidic. It also says that action has not been taken by governments to reduce acid rain because it would hinder the growth of industry.
Both references 6 and 7 were found on the web site .
Reference 8 says that before the industrial revolution the pH of rain was between five and six so the term acid rain is now used to describe rain with a pH number off below 5. It also says that the winds coming into Britain arrive from the Atlantic so that not much acid rain is carried here. Other European countries are less fortunate especially the central ones, which have high quantities of acid rain.
Reference 9 is a diagram showing the percentages of damaged forests in Europe. It shows that the central and more developed countries such as Germany, France and Sweden are affected the worst.
Both sources 8 and 9 are from the web site .
Reference 10 simply states that the state of Ohio is home to 80, 000 sources of contamination and emits around two million tons of sulphur dioxide a year.
This reference was found at the web site
Method
In this experiment, we firstly made sure that all of the safety regulations were followed and that we knew exactly how to complete the experiment. We had already decided on our measurements and each of our specific jobs during the pre-trial run.
One person needed to fill the measuring cylinder with water each time, making sure there were no air bubbles. One person carefully measured out the acid and water solution while another person measured out five grams of limestone. The final person washed out the conical flask and wiped the table after each test. On the two separate days it took to obtain our results, we took the room temperature to see if it had any impact.
When it was all set up as in the diagram below, with the conical flask attached to a delivery tube which fed the gas into the measuring cylinder, we placed the limestone in the conical flask and poured in the acid. We started the stopwatch when the bung was in place. During the experiment someone had to be swirling the flask, someone was watching the gas fill the cylinder, another person was watching the stopwatch and the final person was already weighing out the limestone for the next trial.
After 25cm of gas was collected we recorded the time and prepared for the next test. We repeated this for five percentages of acid and we completed four trials.
Diagram
Results
- = Anomalous results which are not included in the average.
The temperature of the room on day one during which we carried out trials one and three was 21 C.
The temperature of the room on day two during which we carried out trials two and four was 19 C.
Accuracy
In this experiment we made our results as accurate as possible by conducting four trials. This increases the accuracy because after discounting anomalous results you are still left with three with which to calculate the average. Having four sets of data also helps when deciding which results are anomalous because if you only had two results, which were abnormal you wouldn’t know which one was anomalous since you only have one to compare it to.
I think that during this experiment we were quite accurate because we worked diligently and carefully. I think our results are about as accurate as we could make them because we measured the time in seconds to two decimal places and we weighed the limestone to within a tenth of a gram.
Graphs
Conclusion
In this experiment, we have discovered that when the concentration of acid is higher the reaction is faster.
This means that acid that is more dilute produces a slower reaction.
I found that my prediction was correct, I predicted the rate to be slower when the acid was more dilute. My results prove this because the average time for 100% acid was 14. 33 seconds and the average time for 20% was 83. 12 seconds. All of the other results fitted quite evenly in between these two.
I found this because when there were only acid particles (100%) reacting with limestone particles, many more collisions took place. This produced a much faster rate. When there were only 20% acid particles there were 20% less collisions.
I discovered that the rate of reaction for 100% acid was 5. 8 times faster than for 20%. In my prediction, I had said it would be five times faster but I had not taken into account the fact that it would slow towards the end of the trial.
I also found that the temperature had no visible effect because our results were varied on each day. For example one day one when trials one and three took place the results for 20% were 50. 97 and 105. 87. Then on day 2 when trials two and four took place the 20% results were 66. 70 and 108. 93. These results are very varied and prove that the temperature change was not enough to make any impact.
My experiment shows that the effect of acid on limestone is greater when there is more acid and therefore proves that is the amount of pollutants in the air were reduced then the effect of acid rain would be less.
