Raising the temperature makes particles collide more often in a certain time and makes it more likely that collisions will result in a reaction. (Information gathered from ‘Chemistry for You’ P193 by Lawrie Ryan and ‘Thinking Chemistry’ P255 by Michael Lewis and Guy Walker.)
When the particles collide they sever bonds and create new bonds, which is a chemical reaction. New substances are formed and energy is used during the reaction.
Method:
In order to carry out the experiment I first have to set up the apparatus. Once I have done this, I will check whether the apparatus is airtight by pulling the end of the syringe and seeing if it goes back into place. I will then add the chemicals into the Buckner Flask.
Equation for the reaction:
Calcium
Carbonate
After pouring 25ml of Hydrochloric acid and 2 grams of Calcium Carbonate into the Buckner flask, it is essential to seal the apparatus and start the stopwatch as quickly as possible. I then recorded the amount gas produced every 20 seconds until the measuring syringe had filled up (at 100cm3).
I then repeated the experiment three times for each of the 5 different temperatures of acids used and every time tried to make the conditions as similar as possible. This included measuring the starting temperature and volume of the acid every time and trying to get exactly the same weight of marble chips for each experiment. I would hope that this would mean that I had carried out a fair test.
The main safety precaution I took was to wear eye-goggles throughout the experiment. This was because the hot acid, which is an irritant, was dangerous and could have easily splashed into my face. The teacher also took the precaution of heating the beakers of acid because the lab was too small and having a Bunsen burner for each group could have been dangerous. Other safety precautions I could have taken would be to wear a lab coat – to stop acid from damaging my clothes and to wear gloves to protect my hands.
Conclusion:
The graph shows that in accordance with my prediction, increasing the temperature also increased the rate of reaction. It agrees with the prediction and the research about Collision Theories backs up the results. It is obvious to see that the rate of reaction has been affected by the changes in temperature. The only problem was the set of results found when I used 60°C acid, as they seem to be too low. This could be because the acid cooled too quickly and was not exactly 60°C when the experiment was started, or that the size of the marble chips was different. There are many contributing factors which may have made these results not exactly as I had expected.
Evaluation:
Overall, I think the experiment was carried out, and went well. The results seem fairly accurate and show strong correlation to my prediction. The experiment was carried out fairly and safely, making sure that measurements were as close to being exact as possible.
The only major flaw in my results was the three experiments carried out using 60°C Hydrochloric Acid. They seemed to be too low compared to the rest of my results and when I worked out the average and plotted them on the graph next to the others, the reaction seemed to be going at a much slower rate.
In my experiment, there didn’t seem to be any single anomalous results.
Generally, the evidence seemed to be of high quality and as accurate as could be expected from the apparatus used and the conditions in the laboratory. The trends are that: - The rate of reaction is increased by a raised temperature – as I had predicted.
To improve the experiment I could have used apparatus which gave much more precise results. The two sets of electric scales I used only gave measurements to 2 decimal places and may not have been exact because the petri-dish used to carry the marble chips would have affected the weight.
The test should have been carried out in strictly controlled conditions; this means that fluctuations in temperature and pressure could not have affected the rate the reaction.
Although three sets of results are acceptable, to make the conclusion of a better quality, I could have carried out the experiment again, which could give more comparison and would make a more accurate average.
I could have also tried the experiment using a greater range of acid temperatures. This would have shown more precise lines on my graph.
I feel that the evidence collected backs up my theory well. There is a strong correlation between the prediction and the results achieved. The results back up the conclusion made and show that my initial research, carried out in class time using ‘Chemistry for you’ and ‘Thinking Chemistry’ was also correct.
Another route, in which I could have investigated changes to the rate of reaction further would be to change the variable in the experiment to either surface area of the marble chips, or the pressure in which the experiment takes place.
