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Energy Change Associated With Neutralisation

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Introduction

Energy Change Associated With Neutralisation * Aim In this investigation I am trying to find out how energy is transferred from the reactants to the product and if any of it is released as heat energy. In the investigation my aim is to examine the change in temperature in a neutralisation reaction, specifically the change from the start temperature of the acid and the alkali to the finish temperature of the neutral solution. I would like to produce an unbiased and fair set of results. I would like to produce results which match my prediction and the scientific theory behind them. I would like there to be an obvious trend in the results and a pattern which can be easily be used to predict further results when changing the strength of the acid. Preferably there would be no anomalous figures. I aim to undertake a safe and well-planned investigation after which I will be able to arrive at a thorough and decisive conclusion. I aim to take the right amount of measurements for there to be an accurate result, not to take too many unnecessary ones. I aim to take the temperatures of all the solutions before the reaction and the temperature of the product afterwards so as to ensure that the temperature difference is measured correctly. My overall aim is to perform a safe, well-planned, precise and conclusive investigation into the temperature changes during neutralisation. * Prediction My prediction is that the temperature of the product will be higher than the initial average temperature of the two reactants. As the two reactants are mixed together the temperature of the solution will rise significantly. If my prediction is correct and the temperature rises then I will know that energy is released in a neutralisation reaction. If the strength of the acid reactant is reduced the temperature rise will be less significant. This is because there will be less acid which will mean less product, therefore there will be less thermal energy. ...read more.

Middle

The amount of alkali will always stay the same; 40ml. I will be changing the strength of the acid by diluting it with water. Therefore the amount of water is also a variable but the two are connected and I will say that the acid strength is the variable in my investigation. As I dilute the acid further with more water I predict that the temperature of the acid and water will decrease as the ratio between them gets smaller. This because the water will be coming out of a tap so it will be colder than the acid and the alkali which will have been standing at room temperature for a number of hours. I will not be able to control the temperature of the water. Consequently the average start temperature of the reactants will not stay the same and will decrease. This means the finish temperatures will not necessarily follow-on from each other and there may not be an obvious pattern. This is until I have calculated an average start temperature for the reactants, then they should match up with their finish temperature. I will have to hope the room temperature will stay the same as I cannot control it but if there is any change it will be very minimal. The temperature of the surfaces the reactants will be on will stay the same because I will not change them during the experiment. * Method Firstly I will fill my two 500ml beakers, one with hydrochloric acid and one with sodium hydroxide. I will then get my three 100ml beakers, my two 100ml measuring cylinders and my two 40ml measuring cylinders. I will put one 100ml beaker and one of each of the two measuring cylinders with the 500ml of acid and one beaker and one of each of the two measuring cylinders with the 500ml of alkali. Now I have two groups; the acid group and alkali group. ...read more.

Conclusion

From my results I can see that there is a change in temperature during a neutralisation reaction. The temperature rises depending on how strong the acid is but in my investigation it was between 9.8oC and 3oC after 1 minute. The stronger the acid the more the temperature increases. I think my results would be able to be used to predict further results when changing the strength of the acid. * Evaluation Overall I think my results are reliable. None of them are anomalous and they all follow a trend. They follow my prediction and scientific reasoning. If there were a number of anomalous results then would question their reliability but as there are not I know that they are reliable. They follow the line of best fit incredibly well, better than I had predicted. Because all of my three experiments, for each strength of acid, got about the same recordings this suggests to me that they are accurate and reliable and there will be no need to repeat any of them. I think the only way I could have improved my investigation would be to have used a more accurate measuring device. This would mean that the recordings would be more accurate. This option was not available to me and at the time I could only use thermometers that only measure in 1oC scales. As a related investigation I could investigate how the strength of an alkali effects neutralisation. I could see if the results of it are similar to the results I have for the strength of acid. I could also see how the quantity of the reactants affects the temperature during neutralisation, whether more of them would mean a higher temperature, or the opposite. Another option would be to investigate other chemicals and see if they have the same properties as hydrochloric acid and sodium hydroxide, i.e. if they gave off the same amount of thermal energy during a neutralisation reaction. All of these would certainly give me more information about the energy changes associated with neutralisation. ...read more.

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