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The rate of a chemical reaction can also be changed by changing the temperature of the reactants and this is discussed on this page
Below is another example of an experiment that can be used to demonstrate the affect of changing the temperature on how long it takes for a reaction to complete. As with the experiment on changing the concentration the reaction being discussed is that between sodium thiosulfate and hydrochloric acid.
As the variable being investigated is the temperature the method must be changed to allow the temperature to be changed (it will be the independent variable) while keeping the other variable controlled and measuring the time (the dependent variable)
The following method was used to obtain the results shown further down the page:
A 100ml beaker was placed on top of a piece of paper with a cross on it.
10ml of hydrochloric acidwas added to the beaker.
The measuring cylinder was washed thoroughly and 10ml of sodium thiosulfate was measured.
The sodium thiosulphate was heated to the required temperature (approximately 20, 30, 40, 50 and 60ºC).
The sodium thiosulphate was then added to the beaker and timing started immediately.
The timing was stopped when the cross on the paper was no longer visible.
The method used to heat the sodium thiosulfate is shown in the diagram below. Why do you think it was the sodium thiosulfate was heated and not the acid?
Example results from the above experiment are shown in the table and graph below.
From the results of this experiment you can see that as the temperature of thiosulfate increases the time taken for the X to disappear decreases.
This means the reaction is finished sooner and therefore is proceeding at a faster rate. Increasing the temperature increases the rate of the reaction.
When a material is heated it contains more energy.
The particles will move more quickly and collide more often with other particles.
Therefore if reactants are heated the particles collide more often and the chemical change happens at a faster rate.
Increasing the temperature of reactants increases the rate of reaction.
Increasing the temperature of reactants increases the rate of reaction.
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