The temperature profile of this exothermic reaction can be used to identify the end point

In this video from Malmesbury Education Mr Mitchell shows you how to measure the temperature change of an exothermic reaction.

The video explains that at the end of the reaction you should start to see the temperature level off or decrease. Below are some typical results for this practical from the AQA Required Practical Handbook. Students should be able to calculate the mean maximum temperature to complete the table.

 Total volume of Sodium Hydroxide added in cm3                 Maximum temperature in °C                    
         First trial            Second trial        Mean    
                                         0           20.0           21.0  
                                         5            24.0           24.6  
                                        10            26.8           27.6  
                                        15            28.6           29.6  
                                        20            30.8           31.3  
                                        25            31.8           32.8  
                                        30            32.0           32.6  
                                        35            31.6           31.8  
                                        40            30.6           31.0  

These results can be used to identify the volume of sodium hydroxide that was needed to neutralise the hydrochloric acid. Students should be guided towards drawing two lines of best fit which intersect to give the end point of the reaction and can be used to find the volume of sodium hydroxide.

Temperature change of neutralisation

Sketch graph to show shape of results. For this practical the value on x-axis would be ‘volume of sodium hydroxide added in cm3

Also check out

  • Monitoring reactions – this article provides an overview of related key concepts in the curriculum, with ideas, questions and links to more resources.
  • Acids and bases: creating solutions – an article addressing common misconceptions and students’ difficulties surrounding this topic.
  • A hot dinner from a can – challenge students to produce a design and create a proto-type of a self-heating can of food.