• Place a boiling tube into the narrow neck conical flask, and ensure it fits snugly

• Place the conical flask on top of the white card containing the cross

• Measure 10ml of 0.05M Sodium Thiosulfate to the boiling tube

• Carefully place a thermometer into the tube and record the temperature

• Add 1ml of the Hydrochloric Acid and start the stopclock

• Look down the tube from above and record the time for the cross to disappear

• Record the final temperature of the reaction mixture. Pour the contents of the boiling tube into the stop bath

• Add warm water to the conical flask around 25⁰ C, and place the boiling tube snuggly in the conical flask

• Add 10ml of 0.05M Sodium Thiosulfate to the boiling tube and carefully place a thermometer into the tube and record the temperature after 3 minutes

• Add 1ml of Hydrochloric Acid and start the stopclock

• Observe until the black cross disappears from view and record the time taken for the cross to disappear

• Record the final temperature of the reaction mixture

• Pour the contents of the boiling tube into the stop bath

• Repeat these steps at 3 other temperature 35⁰ C, 45⁰ C and 55⁰ C

The experiments use the same amount and the same concentrations of reactants. The only variable is the temperature

For each of the 5 temperatures calculate to 3 significant figures, where t is the time taken for the cross to become fully obscured

Plot a graph of on the y axis against the temperature

The rate constant (K) is a number that connects the concentration of reactants to the rate of that reaction

The rate constant is different for every reaction, and can change due to different variables such as temperature, pressure or the presence of a catalyst

Increasing the temperature of reaction generally increases the reaction rate. This is because as the temperature increases, the molecules included in reaction gain energy and therefore move faster, which increases the number of successful collisions