P1- Specific heat capacity

• Specific Heat Capacity


  The amount of energy needed to raise the temperature of 1 kilogram of a substance by 1 degree Celsius
• Units for Specific Heat Capacity

  J/°C/kg (Joules/Degree Celsius/Kilogram)
• Equation to calculate temperature change when a substance is heated


  1. ΔE = m c Δ𝛉

  2. Energy (J), Mass (kg), Specific Heat Capacity (J/kg/°C), Temperature (°C)
• How to calculate power of heater if not given

  Connect in parallel with voltmeter, in series with ammeter, then apply P = I x V
• Metal blocks used in experiment

  • Have two holes - one for heater, one for thermometer
• Improving thermometer reading


  Add a few drops of water in the hole with the thermometer to improve thermal contact and ensure even heating
• Measurements recorded during experiment

  Temperature value every 10 minutes from when heater is inserted and switched on
• Graph plotted with data

  Temperature against work done by the heater
• Calculating work done by heater

  Using equation: Energy = Power of heater x Time
• Graph of temperature vs work done

  • Should be a linear relationship, producing a straight line
• Why graph may not be linear initially

  There will be thermal inertia whilst block and heater warm up
• What gradient of graph represents

  The inverse of the heat capacity for the metal block
• Obtaining specific heat capacity of metal

  Divide inverse of gradient by mass of metal block
• Difference between heat capacity and specific heat capacity

  Specific heat capacity is the heat capacity measured for a mass of 1 kg
• Reason for insulating metal block

  • To reduce heat loss to environment and ensure accurate temperature reading
• Safety precautions


  • Avoid touching metal
  • Use heatproof mat
  • Avoid spilling water near power supply when adding drops to thermometer hole
• Method


  1. Set up equipment, ensuring to wrap insulation around the base and sides of the block. The heater should fit snugly into one hole in the block.

  2. If the thermometer has an air gap surrounding it when placed in the second hole, drop water into the hole using a pipette to increase thermal contact.

  3. If the power of the heater is unknown, switch on the power supply and measure the current and potential. Calculate the power using the equation P = IV where I is the current (measured in Amps) and V is the potential difference (measured in volts).

  4. Keep the power supply on and start the timer. Measure the temperature of the block every 10 minutes.

  5. Plot a graph of temperature against work done by the heater. Calculate the gradient of the line.

  6. Specific heat capacity is the gradient divided by the mass of the block. Since the mass is 1kg, the inverse of the gradient = specific heat capacity of the block.