Using my preliminary experiments I decided on using the following apparatus:
- 2 thermometers
- 2 250ml beakers
- 2 measuring cylinders
- 1 conical flask
- 1 stopwatch
- paper with black X
- 1 pair of goggles
- 2 test tubes
Method
5 cm of HCl and 15 cm of sodium thiosulphate are poured out into two measuring cylinders. A beaker is half filled with hot water from a tap. Both the HCl and the Sodium Thiosulphate is poured into two separate test tubes and then placed in the beaker full of hot water, the two test tubes are then taken out and the contents of both are poured into a conical flask. The time it takes for the X to disappear is timed and recorded. The experiment is repeated using all the temperatures. The entire procedure is the repeated three times for each temperature.
Safety
A pair of goggles will be worn during the heating part of the experiment in order to protect the eyes. Hands will also be washed after contact with the chemicals.
Fair Test
In order for my findings to be valid the experiment must be a fair one. I will use the same standard each time for judging when the X has disappeared. I will make sure that the measuring cylinders for the HCl and thiosulphate will not be mixed up. The amount of HCl will be 5 cm3 each time, and the amount of thiosulphate will be fixed at 50 cm3. All of these precautions will make my final results more reliable and keep anomalies at a minimum, making the entire investigation more successful.
Prediction
I predict that as the temperature is increased the rate of reaction will increase. This means that the graph drawn in my analysis will have positive correlation, and will probably be curved as the increase in rate of reaction will not be exactly the same as the temperature is increased. I can state this because of what I know about the collision theory. When the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy making it easier for the particles to break their bonds and form new ones, therefore increasing the rate of reaction as the temperature increases. 0C
Obtaining Evidence
Analysis
In this experiment I have found that as the temperature is increased the time taken for the reaction to take place decreases. This means the rate of reaction increases as it takes less time for a reaction to take place, so more take place per second. This is also shown in my graphs of the average time against temperature and the rate of reaction against time. As it is visible from graph 2, as the temperature increases past 25oC the rate of reaction increases dramatically, this is due to the reaction working best at around this temperature, with the particles having a greater amount of energy to break their bonds more easily, and with a greater force as the particles collide.
Conclusion
The evidence which I obtained all fitted into the pattern of the higher the temperature then the faster the reaction would take place, I followed all of the safety rules and followed the correct procedure when obtaining the results, I made sure that the temperature did not exceed 40oc, I made sure of this by closely watching the temperature shown on the thermometer at all times. I also made sure that no chemicals spilt onto the table. I made sure that all of the results were correct by carefully measuring the chemicals into the beakers and when obtaining the results I kept a close eye on the cross and stopped the stop clock as soon as the cross was not visible to my eye. The accuracy of my results were fairly good, if I had any anomalous results from the other results I repeated the experiment to make sure I had not done anything wrong though administration etc, I know the results were accurate because they had a fairly strong, positive correlation, which means there was a good pattern in the results. However when anomalous data did occur, in the first test at 15oC the results showed 71.47, whereas at in the second test of the same temperature, the results showed 67.7. Although the difference of the data could change the overall accuracy of the results, we did not alter it due to not having enough time.
I could improve my results by using a larger variation in temperature – I have only used five different temperatures; I would certainly get more reliable results and a better correlation between my results by using more temperatures. Repeating the experiment more times – I would definitely get more reliable results if I repeated them more times, I would get a higher range of results. As for the anomalous results I would carry out more tests to decrease or increase the average and the compare this with my original average to see which is the most reliable.
Elliot Snape
