To see how the concentration of a reactant affects the rate of reaction, in this case sodium thiosulphate and acid.
For a reaction to occur, the particles of the reactants must be colliding with each other with enough energy, the amount of energy needed for the reaction is called activation energy. Activation energy is altered by temperature, concentration, surface area of and the pressure on the reactants. Stirring the reactants also increases the rate of reaction because the particles are travelling at a higher speed therefore less time will be taken for a sodium thiosulphate molecule to collide with an acid molecule.
As the concentration of sodium thiosulphate increases, the time it takes for the reaction to complete will decrease, less with each higher concentration.
Because this experiment is only conducted to see how the concentration of a reactant affects the rate of reaction, other variables must be kept the same for it to be a fair test: the same person is going to watch the reaction; a thermometer can record the room temperature to make sure that it’s consistent throughout the experiment; the other variables will stay consistent without interferences; none of the reacting solutions will be stirred.
3.2 small beakers
4.Large measuring cylinder (25ml)
5.Small measuring cylinder
9.Write ‘water’, ‘sodium thiosulphate’ and ‘acid’ across a piece of paper then draw a shape.
10.Fill up the large beaker with sodium thiosulphate and place it over the word on the paper.
11.Fill up one of the small beakers with acid and the other with water then place each over its word on the paper.
12.Fill up the large measuring cylinder with 25ml of sodium thiosulphate, use the dropper for corrections.
13.Use the dropper to fill up the small measuring cylinder with 2ml of acid.
14.Pour sodium thiosulphate