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# The Iodine Clock

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Introduction

The Iodine Clock Aim: To investigate the factors affecting the time it takes for the chosen solution to react after the solutions have been mixed together. Theory: For this investigation I will be investigating how the concentration of a solution can change the time it takes for a solution to react. The only factor I will be changing is the concentration of Sodium Sulphate by mixing the amounts with water. Prediction 1: I predict that as the concentration of the substance increases, the rate at which the reaction takes place will also increase in speed, I believe that this will happen because through further research about collision theory and rates of reaction this is the way in which the pointer all lead to, (as shown in the preliminary work). Preliminary Work: Through other knowledge we already know that there are many factors that affect the speed at which a reaction takes place. The six key factors that can change a rate of reaction are as follows: * Temperature, * Concentration (of a solution) * Surface Area * Light * Using a catalyst * Pressure (of a gas) As we are investigating the affects of the concentration that is the one we will change and we will make sure to keep the others the same so not to affect the rate of reaction. ...read more.

Middle

Watch the experiment until the solution turns a different colour and then record the time that was taken. 4. Repeat the experiment changing the concentration of the Sodium thiosulphate each time, and then repeat the investigation again to make sure that there are no anomaly results, and find the average of all the results which can then be plotted onto the graph. Diagram 3: Safety: * Wear safety goggles to make sure you don't get any of the reactants into your eyes. * Be careful of spillages; be sure to mop up any spilt liquid as quickly as possible to avoid any accidents. * When any of the glass is broken be sure to clear it up as soon as possible to stop anyone cutting themselves. * Make sure that all bags and stools are away before starting the experiment to make sure that no one trips over. Results: Amount of Sodium thiosulphate (ml) 1st time (seconds) 2nd time (seconds) Average (seconds) 10 ml 572 s 608 s 590 s 8 ml 368 s 401 s 385 s 6 ml 317 s 355 s 336 s 4 ml 260 s 242 s 251 s 2 ml 130 s 147 s 139 s 0 ml 15 s 12 s 14 s There was no need to repeat any of the results a third ...read more.

Conclusion

Theory: I already know from further resources that when the temperature of a substance increases the particles in that substance get more energy and so move faster; causing more collisions and so the experiment speeds up; as shown in Diagram 4: Prediction: I would predict that as the temperature of the solution increased the time it took to change colour would decrease, as the particles would have more energy to bump into each other and so more reactions would take place. This would mean that the solution would turn a different colour faster. Method: 1. Set up apparatus as shown in diagram 5 for the water bath and then place into large container as shown in diagram 2. Heat each test tube of ammonium persulphate and water until it reaches the correct temperature by putting into a water bath, (only change the temperature of this as it will be too complicated and difficult to get everything at the right temperature.) and checking with thermometer. 2. Place all the reactants into the beaker and watch until the solution starts to change colour, as soon as this happens stop the experiment and record the results. Diagram 5: Although there are many changes I could have made to the experiment I think that the results that have been produced show reliable evidence to prove my prediction correct and to assume that the theories are in fact true. ...read more.

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