1.1.7 Thermal Energy

• Thermal energy

  Total kinetic energy of all the particles in a substance due to their random motion
• Temperature

  Measures the average kinetic energy of particles in a substance
• Temperature is measured in degrees Celsius (°C) or Kelvin (K)
• An object with a higher temperature has more thermal energy
• The amount of thermal energy also depends on the mass and type of the substance
• Heat

  The transfer of thermal energy from one object to another
• Heat always flows from a hotter object to a cooler one until thermal equilibrium is reached
• Thermal energy and heat are measured in joules (J)
• Specific heat capacity (ccc)


  The amount of energy required to raise the temperature of 1 kg of the substance by 1°C
• Thermal Energy Change Formula

  Q=mcΔT
• Variables in the Thermal Energy Change Formula


  • Q (thermal energy transferred)
  • m (mass of the substance)
  • c (specific heat capacity)
  • ΔT (change in temperature)
• Heating Water

  • Thermal energy is transferred from the stove to the water
• Cooling Down a Drink

  • Thermal energy is transferred from the drink to the ice
• Metal Rod in a Flame

  • Thermal energy is transferred to the rod, causing it to heat up
• Conduction

  • Heat is transferred through direct contact between particles in a solid
• Conduction Example

  • A metal spoon heats up when placed in a hot soup
• Convection

  • Heat is transferred through the movement of fluids
• Convection Example

  • Water boiling in a pot
• Radiation

  • Heat is transferred through electromagnetic waves
• Radiation Example

  • The Sun warming the Earth through radiation
• Thermal energy is involved when a substance changes state
• Melting


  Requires energy to break the bonds between particles
• Evaporation/Boiling


  Requires energy to overcome the attraction between particles
• Condensation and Freezing

  Release thermal energy as bonds form between particles
• 84,000 joules of thermal energy are required to raise the temperature of 2 kg of water by 10°C