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My Aim is to see how concentration of acid will affect the time it takes for Sodium Thiosulphate to become cloudy and make a cross below it to disappear.

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Disappearing Cross Experiment Aim: My Aim is to see how concentration of acid will affect the time it takes for Sodium Thiosulphate to become cloudy and make a cross below it to disappear. Method: Apparatus Hydrochloric Acid Sodium Thiosulphate Distilled Water 250cm � Beaker- I need a beaker big enough to see the cross and although the 100cm� would be perfect volume wise I would prefer to use a bigger one so I can fit the cross under it and also be able to pour the reactants into it without any spillage 100cm � Measuring Cylinder- I have decided to use this cylinder for the Sodium Thiosulphate. I am only using 50cm � each time but I would prefer to use one in which I only have to measure to half way as opposed to using a 50cm � Measuring Cylinder and having to measure it right to the top. It will be easier to measure 10cm � Measuring Cylinder- This is the smallest Measuring Cylinder available. I will use this to measure out the Hydrochloric acid and Distilled water because there volume together will equal 10cm�. If I use a 50cm� Measuring cylinder, I won't be able to get a good enough accuracy. Stopwatch- For timing the experiment Pipette for measuring out accurately and piping back excess Hydrochloric acid Piece of paper with a black cross on it like this: To find out when the experiment has ended. It is dark and thick because I want to clearly see when the experiment has finished Paper towels: For washing beakers and measuring cylinders out. 1. ...read more.


Graphs Speed of reaction ? for time for reaction to finish This means the speed of reaction is inversely proportional to the time for the reaction to finish. This means as the speed of the reaction increases the time for the reaction to finish goes down. This is called Inversely Proportional Speed of reaction ? 1/Time This is proportional because as one goes up so does the other one. It will be much easier to plot a graph like this. It will be more accurate to show the rate of reaction over just speed. Results Table I have set my results out in three tables. This makes it easy to refer to my results. On each table I have written the Volume of acid in cm� , Volume of water in cm�, Time taken in seconds. Rate of Reaction (1/Time) rounded to 3 decimal places and percentage decrease from result before which is rounded to 1 decimal place. Regardless to say each result is the reaction between the concentration of Hydrochloric acid and 50cm� of Sodium Thiosulphate. The Red result indicates were I restarted the experiment because I did it over 2 lessons. Results Table 1 Volume of Hydrochloric acid (cm�) Volume of Distilled Water (cm�) Time taken for cross to disappear (seconds) Rate of Reaction rounded to 3 decimal places Percentage decrease rate from last result rounded to 1 decimal place 10cm� - 28.74 0.035 - 8cm� 2cm� 29.94 0.032 5.7% 6cm� 4cm� 33.54 0.030 9.1% 4cm� 6cm� 36.75 0.027 10% 2cm� 8cm� 47.19 0.021 23.3% Results Table 2 Volume of Hydrochloric acid (cm�) Volume of Distilled Water (cm�) ...read more.


It may have been because it was harder to measure out smaller amounts of acid but from that point the results seemed alright. Maybe it is the first two results which are wrong, I don't know and because I don't know that means that I can't say any of my conclusion is correct, so therefore I would have to do my experiments again. These are the ideals I would have 1. Sterilized beakers (by heating)- So the beakers are equally clean each time. The reason I couldn't sterilize them within the classroom is because the option wasn't available to me. This would means that I wasn't left with a little bit of the product each time. OR 2. Different beakers for each experiment- I would prefer to use the above method because you are going to get the same level of cleanliness each time with this you couldn't guarantee that 3. Each experiment done 5 times instead of three- So the averages would be fairer and the graph would most probably be more accurate 7. All the experiment done within the space of one lesson- So that I can work at the same level. I maybe more tired another lesson etc. There maybe other reasons why but I think I would prefer it like this As I have said my conclusion states -my results don't fully support my prediction therefore it is not right to draw up a conclusion and because the results in the three tables vary so much , that I would have to do the results at least another 2 or 3 times or ideally 5 times so that I can have fully accurate results, averages and graphs so I would then be able to draw a fully accurate conclusion up. GCSE Coursework Philip Stirups ...read more.

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