Edexcel iGCSE Chemistry -3.2 Calorimetry Experiments- Study Notes- New Syllabus

3.2 Simple Calorimetry Experiments

Definition:

Calorimetry is the measurement of heat energy changes during chemical reactions.

In GCSE experiments, heat changes are usually measured using a thermometer and an insulated container.

Basic Principle

The heat energy change of the reaction is calculated using:

• \( m \) = mass of solution (g)
• \( c \) = specific heat capacity (usually \( 4.2 \, \mathrm{J\,g^{-1}\,°C^{-1}} \))
• \( \Delta T \) = temperature change (°C)

General Apparatus

• Polystyrene cup (insulation)
• Beaker
• Thermometer
• Measuring cylinder
• Stirrer
• Balance (if required)

1. Neutralisation Reaction   

Example:

\( \mathrm{HCl(aq) + NaOH(aq) \rightarrow NaCl(aq) + H_2O(l)} \)

Method:

• Measure a known volume of acid into the cup.
• Record initial temperature.
• Add measured alkali quickly.
• Stir and record maximum temperature.
• Calculate \( \Delta T \).

Temperature increases → exothermic.

2. Displacement Reaction

Example:

\( \mathrm{Zn(s) + CuSO_4(aq) \rightarrow ZnSO_4(aq) + Cu(s)} \)

Method:

• Place copper sulfate solution in cup.
• Record initial temperature.
• Add zinc powder.
• Stir and record highest temperature reached.

Temperature rises → exothermic.

3. Dissolving (Enthalpy of Solution)

Example: dissolving ammonium nitrate.

• Measure water into cup.
• Record temperature.
• Add solid and stir.
• Record lowest temperature.

Temperature falls → endothermic.

4. Combustion Experiment

Example: burning ethanol.

• Measure known volume of water.
• Record initial temperature.
• Burn fuel beneath container.
• Record final temperature.
• Measure mass of fuel burned.

This is less accurate due to heat loss.