Thermal Energy (AQA GCSE Physics)

• Energy in the thermal store of an object is responsible for its temperature
  • Energy can be transferred to or transferred from an object or system

• The amount of energy needed to raise the temperature of a given mass of a substance by a given amount can be calculated using the equation:

ΔE = mcΔθ

• Where:
  • ΔE = change in energy, in joules (J)
  • m = mass, in kilograms (kg)
  • c = specific heat capacity, in joules per kilogram per degree Celsius (J/kg °C)
  • Δθ = change in temperature, in degrees Celsius (°C)

• The specific heat capacity of a substance is defined as:

The amount of energy required to raise the temperature of 1 kg of a substance by 1 °C 

• Different substances have different specific heat capacities
  
  • If a substance has a low specific heat capacity, it heats up and cools down quickly
    
    • It takes less energy to change its temperature
  • If a substance has a high specific heat capacity, it heats up and cools down slowly
    
    • It takes more energy to change its temperature

Low v high specific heat capacity

• Specific heat capacity is mainly used for liquids and solids
• The specific heat capacity of different substances determines how useful they would be for a specific purpose eg. choosing the best material for kitchen appliances
  • Good electrical conductors, such as copper and lead, are excellent thermal conductors due to their low specific heat capacity
  • On the other hand, water has a very high specific heat capacity, making it ideal for heating homes as the water remains hot in a radiator for a long time