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How does temperature affect the rate of a chemical reaction?

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Introduction

How does temperature affect the rate of a chemical reaction? Introduction This year in chemistry we have been studying different types of reactions and what affects their rate. To help with this work, we have been given an experiment to investigate and analyse the factors influencing the rate. The Aim of this experiment is to investigate the effect on the rate of reaction caused by changes in temperature. I will be using the "Iodine Clock" experiment to investigate how temperature affects the rate of a chemical reaction Background Knowledge * Reactants - chemicals you start with * Products - chemicals you produce * Activation energy - the amount of energy which colliding particles must have in order to start a chemical reaction and change reactant particles into products. This energy is used in the breaking of chemical bonds. What is the rate of a reaction? The rate of a reaction is the speed of a chemical reaction, calculated by measuring how quickly reactants (chemicals you start with) change into products (chemicals you produce). The rate of a particular chemical reaction is affected by various factors like the temperature, pressure, concentration and surface area of the reactants, or the presence of a catalyst. (The Oxford Science Study Dictionary) In a chemical reaction, the starting materials are called the reactants, and the finishing materials are called the products. It takes time for a chemical reaction to happen. If the reactant takes only a short time to change in to the product, that reaction is a fast reaction. The speed of or rate of that reaction is high. If a reaction takes a long time to change the reactant into the product, it is a slow reaction. The speed or rate of that reaction is low. The rate of a reaction is proportional to 1 Time taken for the change The factors which affect the rate of reaction are:- 1. ...read more.

Middle

I will also wash my hands after each practical lesson so that any spills of the chemicals will be washed off. Fair Test In order for my findings to be valid the experiment must be a fair one. I will make sure that the measuring cylinders for the potassium iodate and sodium disulphate will not be mixed up. I will also keep the concentration of the solution the same each time: * The amount of potassium iodate used will be 5cm� each time * The amount of sodium disulphate used will be 5cm� each time * The amount of distilled water used will be 30cm� each time I chose these volumes because in a previous experiment I carried out to find out the effect of concentration on the rate of reaction I used the same solutions and found that at room temperature (approx 21�c) the concentrations above took (on average) 117 seconds to turn a blue/black colour. This is almost two minutes, it is important that the timing is not too short because then human error would play a bigger part. I felt that this concentration would give me sensible values for the rate of reaction at each temperature without getting too small too quickly. 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 to maintain continuity. All of these precautions will make my final results more reliable and keep anomalies at a minimum and thus make the entire investigation more successful. Pilot Test I will carry out a pilot test to ensure that the way I have planned my experiment will actually work in practice and give me the range of results I require. I will do this by carrying out one test run for each extreme of temperature i.e. 10�C and 80�C and checking the time taken for the solution to turn a blue/black colour. ...read more.

Conclusion

My main limitation was time. To improve the reliability of the results more tests could have been done but there was limited time so this became a problem. I would also try to make my experiment even more accurate. I would do this by monitoring all the factors much more closely such as trying to make sure that the temperature of the solution remained the same throughout the time it took to react. I think it would be interesting to use a temperature probe connected to a data logger so that I could see (as a graph) if the temperature fluctuated at all during the time when the chemicals were reacting. Overall, I would state the experiment as a success since my predictions were supported by my results. This is important in reflecting success only if my prediction was sensible and logical. Just as important is where the experiment was not a success and why. I think that even though we didn't have any equipment to notice slight changes in temperature, that overall our experiments were accurate enough to make an certain conclusion, as all our experiments gave very similar results as you can see in the results table and there weren't any glaringly obvious errors or differences between them. I think that with the equipment we had we managed to carry out a very accurate experiment and produce an accurate conclusion and evaluation. We could do more work to take the investigation further, such as increasing the range of temperatures investigated by going below 20�c the intervals between recordings could also be altered, such as taking results every 5�c instead of every 10�c. This, as well as adding "extra-sensitive equipment" would all add to making the results more accurate and we would be able to give a definite, firm conclusion due to the sheer volume of results we would have and how accurate all these would be. March 2003 Lucy Blackbourn 1 ...read more.

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