measuring temperature changes

• What is the purpose of measuring temperature changes in reactions?

  To know how much energy is absorbed or released
• How can temperature changes be measured during a reaction?

  By following the change in temperature of a reaction mixture
• What is the procedure for measuring temperature changes in a reaction?

  1. Place a polystyrene cup in a beaker of cotton wool.
  2. Add a known volume of the first reagent.
  3. Measure the initial temperature.
  4. Add a measured mass/volume of the second reagent and stir.
  5. Cover the cup to reduce evaporation.
  6. Record the maximum or minimum temperature reached.
  7. Calculate the temperature change.
• Why is cotton wool used in the experiment?

  Cotton wool provides insulation to limit energy transfer
• What happens to the temperature when ammonium chloride dissolves in water?

  The temperature decreases; it's endothermic
• What happens to the temperature when calcium chloride dissolves in water?

  The temperature increases; it's exothermic
• What occurs during a neutralisation reaction?

  • An acid and a base react.
  • They form a salt and water.
  • Most neutralisation reactions are exothermic.
  • Example: HCl + NaOH → NaCl + H₂O
• What is unique about the neutralisation reaction between ethanoic acid and sodium carbonate?

  It is endothermic
• What characterizes displacement reactions?

  • A more reactive element displaces a less reactive one.
  • These reactions release energy; they are exothermic.
  • Example: Zinc powder and copper sulfate react.
• What is formed when zinc powder reacts with copper sulfate?

  Zinc sulfate and copper
• What are precipitation reactions?

  • Insoluble solids formed when two solutions mix.
  • They are exothermic.
  • Example: Lead nitrate and potassium iodide form lead iodide precipitate.
• What happens to the temperature during a precipitation reaction?

  The temperature of the surroundings increases
• Why is it important to keep a lid on the polystyrene cup during the experiment?

  To reduce energy lost by evaporation
• What is the significance of using fluffy cotton wool in temperature change experiments?

  • Provides insulation to limit energy transfer.
  • Ensures accurate temperature measurements.
  • Prevents external temperature fluctuations.