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.
Prediction I predict that as I decrease the concentration of the hydrochloric acid, the reaction rate will get slower.
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.
I will then measure how long it takes for a chemical reaction to take place.
The time might vary depending on the concentration of Sodium thiosulphate.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.Explanation Of Prediction I think that 25cm3 acid and 25cm3 thio will react faster than any of the solutions with a lower concentration of acid because there are more acid particles in the solution, which means more particle collisions, resulting in a faster reaction.If the solution is diluted, there aren't as many acid particles to collide with the thio particles and so the reaction is much slower.Then we drew a cross onto a piece of paper and put an empty conical flask on top of the paper.Next, we poured the 25cm3 acid and 25cm3 thio into the conical flask and started the stop clock.Disappearing Cross Investigation Aim: To see how long it takes for sodium Thiosulphate and hydrochloric acid to react at different concentrations.My Hypothesis: Using the idea of the particle theory, the more dilute a solution is, the more time it will take for the particles to react.In a successful reaction particles need to collide with enough energy to form new bonds and this releases energy, this is known as exothermic because energy is being released into the surroundings. The rate of a reaction is affected by four factors.The four factors are: Catalysts, Concentration, Surface Area and Temperature · Temperature raises the amount of collisions between particles because it causes the particles to move around more rapidly , and if they’re moving around more quickly they will collide more often.