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# Science CW

Extracts from this document...

Introduction

Science Coursework: Sodium Thiosulphate Experiment Introduction The aim of this experiment is to examine how a different amount of concentration effects the rate of reaction. First I will use my preliminary results to find a suitable time to use for the rest of my experiments. I will then determine how different amounts of concentration effect the rate of reaction. Na2 S2 O3 (l) + HCL (l) NaCL (aq) + SO2 (g) + S (s) Preliminary Plan In this part of the experiment I will be using 0.2 and 0.04 to determine a suitable rate of reaction to use for the main experiment. I will be using different volumes of each of the chemicals. I will be looking for a relatively short time so I will not be taking too long on the main experiment. I will place the chemicals into the beaker and then using a timer I will be seeing how long it takes for the X to disappear underneath the beaker, the X disappears because the reaction forms a yellow cloudy precipitate of sulphur, which obscures the view through the beaker. I will be using the same person to look for when the X disappears and also the same beaker and measuring cylinders for each of the chemicals. Preliminary Prediction I think that the 0.2 solution will react faster then the 0.04 solution. ...read more.

Middle

High Concentration Low Concentration These two diagrams show that if something is highly concentrated then the particles have more chance of colliding with other different particles. This is the theory I am basing my experiment on. Variables Surface Area: This can effect a reaction because if you are conducting the experiment on a small surface area the particles have more chance of colliding and reacting, compared to a large surface area. Volume: This can effect a reaction because you can experiment on different type of volumes and they will most likely not give the same times or rate of a reaction. Catalyst: This can effect a reaction because a catalyst is used to speed up or slow down a reaction. Shaken or Stirred: This can effect a reaction because if something is shaken or stirred then the chemicals become mixed up and increase the chances of a faster reaction. Light: The light can effect a reaction because light also generates heat, which speeds up the movement of particles and, therefore, increases the chances of a reaction. Heat: This can effect a reaction because when you heat something it will often speed up the particles and increase the chance of a reaction, you can use a Bunsen burner for these types of experiments. Pressure: This can effect a reaction because if something is pressured into a particular area then it often means that there is less room for the particles to move and increases the chance of reaction because they are travelling in such a small area. ...read more.

Conclusion

I also predicted that as you double the concentration the rate would also double; my prediction was very close as the actual results showed that if you double the concentration you will approximately get triple the rate. Evaluation In this experiment I have learned that the rates of reaction increase as the concentration does. I had one slight anomaly on my Rate of Reaction Graph; which shows that I must have made an error somewhere, this may have been due to contamination, or lack of concentration. My results showed me that I have done the experiment very well and not much went wrong although I did have one slight anomaly on my Rate of Reaction graph; the rest of the results differed by very little. To improve my experiment I feel I could have tested each concentration more times to make sure I was getting the right results, I may have been able to result in no anomalies if I re-tested the concentrations more times, this would have made my experiment more accurate. I also feel that I could have used a smaller X which I drew on the paper as mine was very large and, therefore, exaggerated my results; this would have affected the rate of reaction if the X had been smaller and, therefore, also shortening the time of the experiment. To conclude, my experiment seemed very reliable but could have been even more so if the possible changes would have been put into effect. ...read more.

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