The results we obtained from the preliminary experiment were.
From the preliminary experiment I can conclude that the speed of the reaction becomes slower as less thiosulphate is added and more water is added. This happens because the solution becomes diluted making the amount of molecules colliding into each other smaller. Therefore it takes longer for the collisions to occur.
If the volume of thiosulphate is increased and the volume of water is decreased, the reactions would be quicker also. There would be more collisions, as the solution would be stronger.
Apparatus:
- Thermometer
- Beaker
- Measuring cylinders
- Conical flask
- Tripod
- Gauze
- Heatproof mat
- Stopwatch
- Bunsen burner
- Pair of tongs
- Pair of goggles
Diagram:
Prediction: I predict that as the temperature increases so will the speed of reaction. I think this because of the collision theory which says that for particles to react they need to collide with enough energy to cause a reaction. By increasing the temperature the energy of the particles will increase.
Method: The different temperatures I will use for this experiment are: room temperature (about 25c) 30c, 35c, 40c, 45c and 50c
Firstly set up equipment as show in diagram then put on safety goggles for protection. After you have done this Measure reactants pour Hydrochloric acid into Measuring Jug and put thermometer in, to get the solutions temperature at room temperature. Then add thiosulphate and immediately start stop clock, stop when the black cross underneath the beaker disappears completely, note the time of the reaction in results table. Wash measuring jug, light Bunsen burner on safe flame, pour in Hydrochloric acid. Put measuring jug onto the tripod and gauge and heat solution with the Bunsen on blue flame use thermometer to get the exact temperature you need. Once on correct temperature add thiosulphate and start stop clock immediately. Stop the watch when the black cross disappears. Now repeat the sequence for 35c, 40c, 45c and 50c. Once you have done this record results into a table and put into a graph.
Safety: A pair of goggles will be worn during the heating part of the experiment in order to protect the eyes. When handling hot beakers and measuring cylinders a pair of tongs will be used. A gauze and heatproof mat will be used while heating to avoid any damage to the equipment. Bags must be kept out the way to avoid people tripping and any long hair must be tied back.
Fair test: In order for my findings to be valid the experiment must be fair. 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 hydrochloric acid and thiosulphate will not be mixed up. The amount of hydrochloric acid will be the same each time, and the amount of thiosulphate will be fixed. During the heating stage of the experiment, a blue flame will be used throughout. Also the same Bunsen burner and gas tap will be used. All of these precautions will make my final results more reliable.
Results table:
Conclusion: From my results I can clearly see that the heat affects the reaction rate massively, the hotter the solution the quicker the reaction. My results show this, I know because of the curve in the graph. This is because as you heat up the particles they gain more energy. The results from this experiment prove that my prediction was right, in my prediction I said that as the temperature increased so would the speed of the reaction. I can tell I am right by looking at my table of results and also on the graph I can tall by the slight curve of the line of best fit.
Evaluation: I was pleased with the way the experiment went and thought I was successful in obtaining accurate results. The experiment was conducted fairly; we kept it a fair test by keeping all the variables the same apart from the temperature. I repeated my results three times; I was slightly disappointed that the repeats weren’t as similar as they could have been to the previous results. However I still succeeded in proving my prediction.
I could have improved my investigation by doing a number of different things; firstly I would of benefited by gaining some extra background information about the collision theory and factors, which affect the rate of reaction. The experiment could have been improved by investigating how the use of a catalyst would affect the rate of reaction. Lastly I could have improved it further by changing some of the other variables such as the surface area or pressure (of the gas). Overall I was pleased with hoe the experiment was carried out and the results obtained.