The effect of temperature on the rate of reaction

the second one for the time taken against the rate of reaction. Then I will analyze my evidences, draw a conclusion and evaluate my evidences.Note: A black cross should be used, because the black cross is easier to be seen through the cloudy mixture than the other colours.Variables that could be tested • The rate of production of Sulphur precipitates which will be noticed as increasing cloudiness. • Weight of the whole beaker where the reaction will take place will fall as SO2 gases given off (change will be minute).• The volume of SO2 can be measured using a syringe (very minute volume). • Volume of hydrochloric acid.• Concentration of hydrochloric acid solution.• Volume of sodium thiosulphate.• Concentration of sodium thiosulphate solution.• The cross.• The time taken for the cross to disappear.• The temperature of the mixture (sodium thiosulphate and hydrochloric acid).I will be testing the time taken for the cross to disappear. Therefore the temperature is the only variable that is going to be changedWhat will I measure? I will measure the time taken for the cross to disappear.How + water + Sulphur + Na2S2O3 + 2HCl 2NaCl + H2O + S + SO2Both reactants are clear chemical solutions and when they react together they form yellow precipitate of sulphur.This reaction is exothermic as the energy of reactants is greater than the energy of the products, and this is because the energy was given off to the surroundings.PlanI am going to monitor how the temperature affect the rate of reaction by putting the conical flask over a black cross, then heat the sodium thiosulphate solution, by putting them in the water path, before pouring it onto the dilute hydrochloric acid in the conical flask. As I pour them in the conical flask I will start timing till the sulphur makes precipitate causing the cross to obscure and disappear.I will experiment the time taken for the cross to disappear using variety of temperatures; 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C. And I will repeat the experiment five times for each set of temperature, before working out the average for each set of temperature, in order to get more reliable and precise results.After that I will work out the proportional rate of reaction using the following formula: Rate of reaction = 1 / time taken.Then I will plot the results in a table and draw two line graphs, one for time taken against the temperature and the second one for the time taken against the rate of reaction. Then I will analyze my evidences, draw a conclusion and evaluate my evidences.Note: A black cross should be used, because the black cross is easier to be seen through the cloudy mixture than the other colours.Variables that could be tested • The rate of production of Sulphur precipitates which will be noticed as increasing cloudiness. • Weight of the whole beaker where the reaction will take place will fall as SO2 gases given off (change will be minute).• The volume of SO2 can be measured using a syringe (very minute volume). • Volume of hydrochloric acid.• Concentration of hydrochloric acid solution.• Volume of sodium thiosulphate.• Concentration of sodium thiosulphate solution.• The cross.• The time taken for the cross to disappear.• The temperature of the mixture (sodium thiosulphate and hydrochloric acid).I will be testing the time taken for the cross to disappear. Therefore the temperature is the only variable that is going to be changedWhat will I measure? I will measure the time taken for the cross to disappear.How the temperature of water in the water bath.• Salt to decrease the melting point of water in the water bath.MethodAfter setting my equipment up, as shown in the diagram below, the first thing I will do is to draw a black cross on a piece of paper and place it under the 350ml conical flask, so I can see the cross by looking through the top of the conical flask. After that I will measure 50 cm3 of sodium thiosulphate (Na2S2O3) in the first measuring cylinder before pouring it into the conical flask where it is going to be heated by putting the conical flask inside the water bath. Using the thermometer I will be able to detect the temperature of it, and when it reaches the wanted temperature I will take it off. During the time while the sodium thiosulphate solution is being heated, I will measure 5 cm3 of hydrochloric acid (HCl) in the second measuring cylinder. So when the sodium thiosulphate solution is taken off the water bath and put on the black cross, I can add 5 cm3 of the HCl to the conical flask. As I mix them together I will start timing. (After mixing the two chemicals I will notice that the mixture is becoming cloudy.) When the cross is not being seen any longer I will stop the stop watch and record the time taken for the cross to disappear in my results table.I will repeat this experiment five times for each set of temperature below:0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C. Then I will work out the averages, in order to get more reliable and precise results to make the investigation more successful, and then work out the proportional rate of reaction using the following formula: Rate of reaction = 1 / time taken. When doing the experiment with temperatures below 20°C, I will use ice to cool down the water in the water bath, and I can use salt to reduce the melting point of the water in the bath.After finishing my whole experiment I will draw two graphs to help me analyzing the results.PredictionI predict that as the temperature increases, so will the rate of reaction and that is because at high temperatures the particles acquire more energy and start moving around faster which will allow more collisions per second, and most of these collisions are more likely to lead to successful collisions, as particles with more energy are more likely to overcome the activation energy, which is the minimum energy needed for particles to overcome the energy barrier. Also at low temperatures the particles move slowly with a little energy, therefore making successful collisions is less likely to happen as they might not overcome the barrier energy. And this supports the scientific fact which says that the rate of reaction will double as the temperature rise 10 degrees.I also predict that as the temperature increase the time taken for the cross to disappear is will decrease, while the rate of reaction will increase, so I can predict that I am going to have a positive correlation graph for temperature against rate of reaction, while the temperature against the time taken will lead to a negative correlation. As shown in the diagrams below.This graph shows positive correlation This graph shows negative correlation I also predict that the graph is going to be curved, because the rate of reaction will not increase at the same ratio as the temperature increase.Preliminary work Before I do the real experiment I have used computer software “Focus Educational Software – Science Investigations 2” as a part of my preliminary work, and these were my results:Method 1: 0.1M – 50cm3 of Na2S2SO2 and 2M – 5cm3 of HClTemperature (°C) Time taken (s)0 32630 3650 1770 6100 3Method 2: 0.1M – 50cm3 of Na2S2SO2 and 2M – 20cm3 of HClTemperature (°C) Time taken (s)0 9830 1350 570 2100 1Method 3: 0.1M – 50cm3 of Na2S2SO2 and 2M – 5cm3 of HClTemperature (°C) Time taken (s)0 40330 4450 1470 7100 2I have noticed that by using the first method will go quite quickly (high rate of reaction), while by using the second method the reaction will occur very fast (very high rate of reaction), and I would not be able to record the time taken accurately. I have also noticed that by using the third method the reaction will occur too slowly (low rate of reaction). So by considering my time limit for this experiment, I found that the best method I can use to manage my time is the first method. As think it will be fast, and I can record my results very accurately. The preliminary work was useful for me as I have became familiar with what I am going to do in the experiment beside checking my plan and method, which I think are correct and very good. So I will leave them as they are now without changing anythingResults TableTemperature(°C) Time taken for the cross to disappear (s) Average (s) Rate of reactionExp.1 Exp.2 Exp.3 Exp.4 Exp.5 0 148.65 147.86 147.51 145.86 146.41 147.26 0.00710 85.26 85.39 83.69 84.45 81.53 84.06 0.01220 50.71 48.42 48.93 49.17 48.38 49.12 0.0230 25.59 26.85 25.28 23.38 27.16 25.65 0.03940 18.14 17.26 17.94 19.37 17.96 18.13 0.05550 13.27 13.35 12.84 13.67 12.47 13.12 0.07660 6.25 7.47 6.75 5.27 6.25 6.41 0.15670 4.83 3.63 4.33 3.16 3.74 3.94 0.25480 2.39 1.63 3.26 3.45 2.86 2.72 0.368* The average = the mean of the time taken* The rate of reaction = 1 / time taken * The green records are repeated due to the different in pattern between them and the other records, the old record are shown below.New record Old record6.25 15.861.63 5.213.26 4.96New record Old record145.86 137.75147.86 139.2785.26 79.4648.42 53.3648.38 44.7525.59 22.0513.27 17.8513.35 15.215.27 18.87ConclusionAfter looking at the results table and the graphs I have noticed that as the rate of reaction is directly proportional to the temperature, which means that the as temperature increases the rate of reaction increases, showing a positive correlation between them exactly as I have predicted. And this is because when the sodium thiosulphate is heated up its particles acquire energy and start moving around faster, which allow more collisions between the particles of the sodium thiosulphate and the hydrochloric acid particles. And most of these collisions are likely to lead to a successful collision as the particles have enough energy to overcome the activation energy barrier. In other word there are more frequent collisions per second and as we know the chemical reaction takes place when the reactant particles collide, so when there are more collisions the reaction will be quicker, in our case the sulphur precipitate will form more rapidly obscuring the cross under the conical flask.Also as I have predicted this reaction is exothermic because the energy of the reactants is greater than the energy of the products.In my experiment the energy transferred to the surroundings is in form of heat and this is detected by the rise of the temperature.Also the results show that as the temperature increases the time taken for the cross to disappear decreases, and this means that that they are inversely proportional so shows negative correlation, as I have predicted.The first graph shows the relation between the temperature and the rate of reaction, of the sodium sulphate and the hydrochloric acid, and its best fit line shows positive correlation, as I have predicted. Looking at the second graph, we see totally opposite relation as the curve of best of fit goes down showing a negative correlation between the sodium thiosulphate and the hydrochloric acid, as I have predicted. Therefore my prediction is right because the graphs have the same descriptions as I predicted, also as I predicted the temperature increases the rate of reaction increases and as the temperature increases the time taken for the cross to disappear decreases. Also I have noticed in the second graph that below 60°C the rate of reaction was increasing in a low rate and once the temperature rose above 60°C the rate of reaction started to quick up faster. I think this is because as the reaction overcame the activation energy it started fasting up. And by using the same idea we can explain why in graph 1 the curve was decreasing in a high rate when the temperature was under 40°C and why did it start to slow down when the temperature went above 40°C.I can see that in both graphs some of the points do not fit with the curve. For example at 40°C in graph 1, 40°C in graph 2, 60°C in graph1 and in 60°C in graph2 the points are upper or under the trend line, and I think that might be because of the misreading of the stopwatch or because of leaving some water in the conical flask while washing it, as water reduce the concentration and slow down the rate of reaction so it would get more time for the cross to disappear.Also by looking on my results table and the two graphs I have noticed that as the temperature raise by 10°C the rate of reaction nearly doubles, as I have predicted.Evaluation The experiment process went well and there were no problems during it at all. The method covered all the needs, as well as being a fair test; however I think I could improve it using many ways. The results obtained were precise and reliable, and I have tried my best to repeat it five times using a fair test method. And the collisions theory has improved its reliability and accuracy, as it supported my results. But even though there were some anomalies, which I have repeated again, and they are coloured in green in the table of results. I have tried to investigate the reason behind getting them out of the pattern and I think that this might be done by leaving some water in the conical flask while washing it, as water reduce the concentration and slow down the rate of reaction so it would get more time for the cross to disappear. Also the reason might be a mistake in taking measurements or a delay in starting the stop watch. Another possible reason could be that sodium thiosulphate has lost some heat while pouring it in the conical flask and mixing it with HCl. According to my evidences my conclusion, which is that as the temperature increases the rate of reaction increases and as the temperature increases the time taken for the cross to disappear decreases to the more frequent collisions per second, is right and that is because I have repeated the experiment five times; also I have repeated the anomalies which do not fit in pattern with the rest of results in order to get the reliable and precise results.Also As I said above the reaction between sodium thiosulphate and the HCl is exothermic as the mixture’s temperature rise up and so the inaccuracy between the mixtures temperatures when repeating or when doing it for other temperature range is possible and unfortunately I do not think we can do anything towards this problem. I still think that I could get even more precise results if I used the light transmitter instead of relying on the human eye detecting when the cross will disappear, as the light transmitter can measure the amount of light that coming through the mixture by a bulb or a light source placed on the other side of the conical flask. The light transmitter can tell when there is no light coming through the mixture which means that the solution has become too precipitate and this will give the exact amount of time taken for the precipitate to obscure the sight. Below there is a table of results taken by the software “Science Investigations 2” which compare the results taken by using the cross, and the results that I would take if I used the light transmitter. Temperature (°C) Time taken by cross method(s) Time taken by using light transmitter (s)0 326 48530 36 6050 17 2370 6 9100 3 3Also I wished to extend it more and to see how changing the concentration of the hydrochloric acid can change the rate of reaction between sodium thiosulphate and hydrochloric acid, and I wanted to compare how the temperature of different HCl concentrations can affects the rate of reaction, but unfortunately I did not have enough time.Bibliography• GCSE Science Class Book – By David Baylis, Graham Booth and Bob McDuell• AQA GCSE Chemistry second edition – by Terry Mansfield, Ian Brandon and Rafael Fernandez.• OCR Double Award Science Staged Assessment Year 10, GCP.• Focus Educational Software, Science investigations2.• http://www.sci-journal.org