Energy changes in a displacement reaction Essay
Energy changes in a displacement reaction
To make this experiment a fair test, certain variables need to be kept the same. The same person needs to be kept the same, so that the reaction speed is kept the same. Also, 50cm3 of copper sulphate needs to kept the same all the way through also, so that the reaction with the zinc will be fair. The 50cm3 measuring cylinder will have to be used, as the same error margin will be the same. The mercury thermometer used is also important, as the error margin on it need to be kept the same. The same room pressure and temperature also need to be kept the same, as far as is possible. Results.
Amount of Zinc (g) Temperature before (i?? C) Temperature after (i?? C) Temperature change (i?? C) Average (i?? C) To work out how much energy is transferred for each temperature change during the experiment, I can use the equation:
Energy Change = 4. 2 x mass of solution x temperature rise In this equation, 4. 2 represents the density of water and the mass of the solution is 50. Therefore, using the heat increase for each mass of zinc, the total amount of energy change can be found. Energy Changes Amount of Zinc (g) Temperature change (i?? C) Energy Change (J) Average 0Analysis I can conclude from this experiment that temperature does increase with the addition of zinc. This can be seen in my results table e. g. for 0. 25g the temperature change is 3. 25i?? C and for 0. 5g the temperature change is 8i?? C. This also causes an increase in the energy given out by the reaction.
I also predicted that the temperature increase would be directly proportional to the mass of zinc added. This was also correct. This can be seen on my graph. However, the temperature continued to increase after the maximum value had been reached. I predicted that it would stop increasing at this mass. In my theory, I have talked about the energy changes in a displacement reaction. The equation I have used shows the energy change. This helped me predict what would happen in the results and so my prediction was correct. Also, knowing that the recording of heat can find the energy change allowed me to determine the energy increase.
Evaluation I can make a firm conclusion for this experiment that the energy change will increase with increasing mass of zinc added because my results are accurate and reliable. In my results, I have one anomalous result at 0. 75g, which was 0. 5i?? C off the line of best fit. Apart from this one point, my results were quite accurate as they follow the line of best fit. There are some explanations for this: Not all the zinc reacted with the copper Some heat might have escaped from the open cup There could have been errors in the reading.
The stirring could not have been thorough and consistent These can be improved by: Using a lid on the cup to keep the heat in Using electronic scales which weigh to more than one decimal place to make the weighing more accurate Using an electronic thermometer will increase the accuracy of the temperature measurement Using a pipette or burette instead of a measuring cylinder will increase the accuracy of the measuring of the copper sulphate The results I have found are reliable as the graphs match what was expected. The results have also been reproduced throughout the experiment. Conclusion.
My conclusion to this experiment is that it was fair and accurate method. It gave reliable results and the apparatus provided gave accurate results. However, these results can be improved further if: More repartitions of the experiment were done. This would provide more results and add to the evidence for the experiment and also increase accuracy The experiment was tried with different metals, ones that are at different levels in the reactivity series. This would be done to see how the use of different reactions change the temperature and energy changes and if the theory still works with different metals.
Also, using salts with a metal lower in the reactivity series than the base can show whether distance in the reactivity series affects the energy change. Different concentrations of the salt were used. This can also show the difference between the temperature and energy changes Data logging could be used so that there is now chance in human error in the experiment.
University/College: University of California
Type of paper: Thesis/Dissertation Chapter
Date: 13 October 2017