Disappearing X Experiment

Fair Testing
To ensure a fair test, I will make sure I keep the volume of the sodium thiosulphate the same, 25cm3. I will also make sure that I use the same cross on paper every time and not switch between a lightly drawn pencil cross and a heavy cross drawn in black marker, as this would affect the time taken for it to disappear. Also to ensure a fair test I will use the same beakers and measuring cylinders each time for holding the thio and the acid. This is because if I put the thio into a beaker that had previously held acid then it could start off a reaction and affect the overall reaction rate. Also, we need to wash the beakers and cylinders before using them as there could be another chemical left in the bottom. This could start off unwanted reactions and affect the reaction rate. Finally, we will make sure that the same person judges when the cross is no longer visible or the reaction times result could not be accurate, as 2 people could have different eyesight and therefore different opinions on when the x has disappeared.
…