Required Practical: Investigating Energy Changes

• ENERGY TRANSFER in chemical reactions can be measured by monitoring TEMPERATURE CHANGES.
• The LARGER the temperature change, the LARGER the energy transferred.
• You can use this to investigate how the amount of reactants in a reaction affects the amount of energy transferred.
• Variables like REACTANT MASS and CONCENTRATION can be investigated.
• You can apply the method to measure the energy change in NEUTRALISATION REACTIONS, reactions of METALS with ACIDS, DISPLACEMENT reactions, and reactions between CARBONATES and ACIDS. 

Set Up:

• Insulation: Use a POLYSTYRENE CUP with a lid for insulation to minimise energy loss to the surroundings.

Method for a Neutralisation Reaction:

• Prepare separate solutions of Hydrochloric acid (HCl) and Sodium Hydroxide (NaOH) with known concentrations.
• Measure the INITIAL TEMPERATURE of the solutions.
• Mix the reactants in the insulated cup and immediately cover with a lid to prevent heat loss.
• Stir the solution.
• Measure the temperature at regular intervals (e.g. every 30 seconds) and record the HIGHEST temperature reached.
• Calculate the temperature difference between the INITIAL and HIGHEST temperature readings.
• Repeat this process for DIFFERENT CONCENTRATIONS of acid.

Method for a Reaction between an Acid and a Metal:

• Add a solution of Hydrochloric acid (HCl) to the insulated cup.
• Measure the INITIAL TEMPERATURE of the solutions.
• Add a KNOWN MASS of Magnesium and immediately cover with a lid to prevent heat loss.
• Stir the solution.
• Measure the temperature at regular intervals (e.g. every 30 seconds) and record the HIGHEST temperature reached.
• Calculate the temperature difference between the INITIAL and HIGHEST temperature readings.
• Repeat this process for DIFFERENT MASSES of Magnesium.