Calorimetry and Thermochemical Experiments

Basic Calorimetry Setup

• Objective: Measure thermochemical data using a simple calorimeter.
• Example Experiment:
  • Measure the heat capacity of an unknown object (e.g., a piece of metal).
  • Process:
    • Heat the metal to a known temperature (e.g., in boiling water).
    • Transfer it to a known volume of room temperature water in a calorimeter.

Key Concepts

• Heat Transfer Measurement:
  • Measure temperature change of water as metal transfers heat to it.
  • Use mass of water and its specific heat to calculate the heat transferred (Q).

Conservation of Energy

• Equation: Q_water (heat absorbed by water) + Q_metal (heat released by metal) = 0.
  • Rearranged to: Q_water = -Q_metal.
  • Assumes negligible heat loss to the environment.

Calculating Specific Heat

• Specific Heat Calculation:
  • Calculate heat absorbed by water (Q_water) using known values:
    • Mass of water (derived from its volume).
    • Specific heat of water.
    • Temperature change of water.
  • Q_water = 1,632 joules (in the example given).
  • Q_metal = -1,632 joules (since heat absorbed by water = heat released by metal).
• Using Metal Data:
  • Plug in values for the metal:
    • Mass of the metal.
    • Temperature change of the metal.
  • Solve for the specific heat of the metal.

Example Calculation

• Given Data:
  • Metal mass: 59.7 g.
  • Water volume: 60 mL (mass = 60 g, since 1 g/mL).
  • Water initial temperature: 22°C.
  • Water final temperature: 28.5°C.
• Steps:
  1. Calculate Q_water = 1,632 J.
  2. Q_metal = -1,632 J.
  3. Solve for specific heat of metal:
     • Result: 0.382 J/g°C.

Conclusion

• Identification:
  • Specific heat calculated is close to that of copper.
  • Likely that the metal is copper based on comparison with tabulated values.