Temperature's Effect on the Rate of Reaction

Temperature's Effect on the Rate of Reaction
During this investigation I am going to experiment with temperature and how it changes the rate of reaction. However, I understand that other factors can change the rate of reaction such as the concentrations of the substances used, the catalysts used or the surface area of materials used. Hypothesis == I think that as I increase the temperature of the experiment, the rate will increase also. I think that if I double the temperature, the reaction rate will double as well. I think this because I have performed various experiments in the past that have proved this to be right. Experiments that show this include basic ones such as boiling water to change its molecular structure and become water vapour/steam. I believe that when the reactive substances are heated, the activation energy is lowered and the reaction will take less time to happen. I have also been taught the collision theory, when particles are heated they obtain more kinetic energy allowing them to hit each other at a faster pace causing them to merge and form a reaction. I can also see from everyday life that heat can cause reactions to take place at a faster rate such as food rotting or milk turning sour.
Method == In my investigation to test what effect temperature has on the rate of reaction, I am going to perform an experiment based on colour change. The experiment will involve mixing a 0.1M solution of Sodium Thiosulphate with a 1M solution of Hydrochloric Acid. This will produce a gradual change of colour from clear to murky yellow. Two methods of observation will be used to monitor the change in colour. Firstly, a beaker will be marked with a black cross on its base. Then, both substances will be added to the beaker (which will be sat on a white sheet of paper) to form the mixture. Through observation, I will use my naked eye to see when the black cross is no longer visible (due to the mixture increasing in opaqueness). I will also repeat the experiment, replacing the method of observation with a computer-controlled means of detection. The device used comprises of an ldr (light dependant resistor) to detect the amount of light passing through the mixture and a bulb placed above the mixture, shining through. The temperature of the substances used will be altered by placing them in a water bath until they reach the desired temperature. Each process, manual and computer-controlled, will be repeated several times to ensure an average that will rule out anomalous results. To enable accurate results to be obtained, I will need to carry out a few procedures to make it fair. I will make sure that the measuring cylinders used to measure out the HCl and Sodium Thiosulphate do not get mixed up, the standard for observing the cross disappearing will remain the same throughout, the computer-controlled equipment will be unchanged and the amounts of each of the substances will also stay the same. Each time the experiment is repeated, the conical flask will be cleaned out and dried to avoid cross-contamination. [image] [image] Equipment ===== ? Thermometer ? Beaker ? 2 measuring cylinders ? Bunsen Burner ? Tripod ? Gauze ? Heat-proof mat ? Conical flask ? Stopwatch Results === Here are the manual observation results:- -??????????????????? Temperature (?C) Time (seconds) Exp.1 Exp.2 Mean 10 178 169 174 25 58 70 64 35 45 37 41 45 29 27 28 55 16 18 17 See next page for the coinciding graph. -?????????????????? See the page after for the insight graph (computer sensed results). Analysis The experiments performed have proved my hypothesis to be partially correct. As I increased the temperature, the time taken for the reaction decreased, therefore showing a greater rate of reaction with a higher temperature. The lines of best fit on my graphs also prove this part of my hypothesis to be correct. The lines slope downwards from left to right, showing negative correlation. This shows that the time taken for the reaction to take place decreases as the temperature increases. When a graph of temperature against rate of reaction is plotted, positive correlation is evident and shows that the rate increases when the temperature does. The reaction take place at a faster rate because when the particles of a mixture are heated, they are given more energy and consequently move faster. This means they will collide more frequently and also with a great deal more energy. This increase of energy increases the likelihood of the particles breaking the threshold of activation; they overcome the activation energy barrier and as a result, react successfully. Evaluation The experiments performed were suitable for supporting my hypothesis. The results obtained were of a certain degree of accuracy but there were a few anomalies, such as the experiment starting at different light levels in the computer-sensed instance. This would have been because of people walking past the window and temporarily blocking the light. However, it is not so extreme as to degrade our results as the graph still shows a pattern similar to that seen in the manual observation graph, therefore the results were suitable to use. To further this investigation, I could experiment with the concentrations of the substances used whilst keeping everything (including the temperature) constant.

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