Measuring Energy changes

• Endothermic


  A reaction where the temperature of the solution decreases
• Exothermic


  A reaction where the temperature of the solution increases
• Measuring energy changes


  1. Use an experiment to investigate the temperature change of a chemical reaction

  2. Take the temperature of the reactants and mix them in a polystyrene cup

  3. Record the highest or lowest temperature reached

  4. Calculate the temperature change by subtracting the initial temperature

  5. If temperature increases, reaction is exothermic. If temperature decreases, reaction is endothermic

  6. Reduce energy loss to surroundings by using a lid and insulation

  7. This method works for various reactions like neutralisation, metal-acid, acid-carbonate, displacement
• The biggest problem with temperature measurements is the amount of energy lost to the surroundings
• You can reduce energy loss by putting a lid on the polystyrene cup and putting the cup into a beaker of cotton wool
• Apparatus


  • Thermometer
  • Large beaker
  • Polystyrene cup
  • Reaction mixture
  • Cotton wool
• Investigating effect of variables on temperature change


  1. Use the same method to test the effect of different variables like mass or concentration of reactants

  2. Example: Test effect of acid concentration on temperature change of neutralisation reaction between HCl and NaOH

  3. Use 25 cm3 each of 10 g/dm3, 20 g/dm3 and 30 g/dm3 HCl and NaOH

  4. Record highest temperature reached and calculate temperature change

  5. Compare results to see how acid concentration affects temperature change