The 1m and 2m results on the graph appeared very similar. Although the 2m results finished more rapid than 0. 5m and 1m, the 1m was not far behind at all. On the graph the gradients of both lines were extremely steep compared to the 0. 5m line. (Taking in account my x axis had to go up to 6 minutes for the 0. 5m and 1m and 2m results both finished in under 1:10 minutes). In the 1m test the release of carbon dioxide was very stable. Apart from the first time recorded; which was 9 seconds, none of the other recorded times exceeded 5 seconds to give off 1cc of carbon dioxide at a time.
The 2.0m results were less steady than this and actually took longer for it to finish than 1m. It did start off faster than 1. 0m but then the rate reduced by the time it got to 4cc. On the particle size graph each results for this were very distinct. The powdered calcium carbonate reaction was too fast for us to record and by the time it had released all 10cc of carbon dioxide the was 1 second. The gradient on the graph for this one was tremendously steep and was nearly just a vertical line. The small marble chips line on the graph is also quite steep and was stable too.
The large marble chips line did not have a steep gradient. Like the 0.5m line the rate of reaction started of quite slow but then quickened its pace by the time it had released 3cc of carbon dioxide. This quickened rate was steady throughout the rest of the test. It took 2:16 minutes to release its 10cc of carbon dioxide. On the temperature graph each line of best fit for the results on the three tests were similar. All three intersect nearly in the same place. The gradients are moderately steep and they all show a slight curve. This means they all started off slowly then the rate of reaction sped up, but then slowed down. The all also managed to release 10cc of carbon dioxide in less than 47 seconds.
The test for temperature at 40i?? took the fastest time and the room temperature test was the slowest. The test at 40i?? started off fast taking only 8 seconds to release 1cc of carbon dioxide, then took 7 seconds to give off another 1cc. It then took 16 for it to release 5cc and the rate then stabilised. For every 1cc it released after that it took 3 seconds each time. To conclude, the longest experiment took 5:27 minutes and that was the test for concentration with 2. 0m and the fastest was the testing of particle size with the powered which was so fast, it only took 1 second.
In the tests of concentration more dilute the acid was, the slower the speed of reaction was. (Apart from the 2m results which took slower than the 1m results). In the temperature experiments the cooler the acid was, the slower the rate was and in the particle size experiment the more surface area the calcium carbonate had the faster the rate of reaction. I can support this conclusion, because of the careful experiments we carried out to obtain evidence and the graphs and tables of results from the experiments we performed. My conclusion relates to my hypothesis as I roughly predicted that these would be my end results.
Apart from the 2m test being slower than the 1m test, I predicted correctly. As I said that the changes of temperature would affect the rate of reaction the most (in time) the results for them were all under 47 seconds. In the particle size tests I predicted that the results would be very contrasting and evidence proves I predicted right. Evaluation The end results we obtained were fairly reliable; keeping in mind the resources we were given. There was a fair amount of evidence and results to come to a conclusion although I feel there could have been more experiments carried out to come to a more accurate conclusion.
There was one test that did not follow the pattern of the other experiments and that was the concentration test of 2 molar. It should have been quicker than the 1m test but instead it was surprising slow. There were not any other anomalies on the tests that I had come across apart from the 2 molar tests in concentration. This may have been because, the acid we used had been mixed up with the other acids or the one we used was not prepared properly. If I were to do these series of experiments again, then I would have given myself more time to do them so I could do more tries for each variable to attain more precise outcomes.
For example, instead of just doing three tries for 2m in concentration, I would have done 6 or 7 tries, and then taken an average. I would have made certain that the acid I was using was equally and accurate in every experiment to ensure fair testing. I would have carried a large range of experiments to study each variable better. For instance, for temperature I could use more than just room, 30i?? and 40i??. I could have done 25i?? , 35i?? , 50i?? even going cooler than room temperature, such as 10i?? and 15i??. I could have also used a variety of sizes of the calcium carbonate and more than just three concentrations of acid.
I also would have carried out another type of experiment to back up the evidence I already have that the changes in temperature and concentration effect the rate of reaction. I would use sodium thio sulphate which is a liquid with hydrochloric acid. As the sodium thio sulphate reacts with the hydrochloric acid it becomes cloudy. So instead of measuring the carbon dioxide to confirm the rate of a reaction 1 would time how long it took for the hydrochloric acid to go cloudy. To do this I would mark a paper with a cross and place it under a beaker.
I would pour hydrochloric acid into this beaker (Making sure I used the same amount of acid in each experiment). At this point I would still be able to see the cross through the clear acid. As I poured in the sodium thio sulphate (Also making sure I used the same measurement of this in each test) I would start the stop clock and time the reaction until I could not see the cross on the paper. I would repeat this with 0. 5m, 1m and 2m of hydrochloric acid and maybe heat it the acid like in the other tests to support my other evidence that shows what effects the rate of reaction.
I would have predicted the same things for these experiments too. All these changes and extra tests I have mentioned would have made my results more reliable, because there would be more accuracy involved. It would also give me a clearer idea on what affects the rate of reaction. Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.