GCSE Required Practical: Measuring Specific Heat Capacity

Introduction

• Practical demonstration by Mr. Rees from Mansbury School Science.
• Aim: Measure the specific heat capacity (SHC) of materials: Brass, Copper, and Aluminium.
• Setup: Aluminium block with a heater and thermometer.

Preparation

• Heater & Thermometer Setup:
  • Heater inserted into block.
  • Thermometer inserted with a few drops of water to avoid air gaps.
• Power Supply:
  • Use DC power, aim for ~10 volts.

Procedure

1. Initial Temperature:
   • Record at eye level; initial reading: 24°C.
2. Start Experiment:
   • Begin timer when power supply is turned on.
3. Data Collection:
   • Record temperature every minute for 10 minutes.

Specific Heat Capacity Calculation

• Equation:
  • SHC = Energy / (Mass x Temperature Change)
  • Energy (in Joules) needed to raise 1 kg of material by 1°C.
• Units:
  • Joules per kilogram per degree Celsius.

Mass & Energy Calculation

• Mass:
  • Blocks are 1 kg.
• Energy via Power Measurement:
  • Two methods:
    1. Easy but Less Accurate:
       • Use a joule meter; e.g., 19 flashes = 1900 joules in 30 seconds.
       • Power = 1900 J / 30 s = 63 watts.
    2. More Accurate:
       • Use a voltmeter and ammeter.
       • Power = Current x Voltage; e.g., 3.47 A x 10 V = 34.7 watts.

Results & Graphing

• Graph:
  • Temperature vs. Time (or Energy).
  • Linear portion of graph used for calculations.
• SHC Calculation:
  • SHC = (Power x Time) / (Mass x Temperature Change)
  • Use line of best fit and right-angle triangle method for time/temp.

Observations & Conclusion

• Experimental SHC for Aluminium: 1050 J/kg°C.
• Actual SHC for Aluminium: 900 J/kg°C.
• Discrepancy Explanation:
  • Energy loss due to lack of insulation.
  • Suggestion: Insulate block with foam.
• Further Experiments:
  • Repeat with Copper and Brass for comparison.

Tips

• Consider insulation to reduce energy loss.
• Measure voltages and currents accurately for better results.
• Take mean of fluctuating measurements if necessary.