Internal Energy and Energy Transfers

• Internal energy of a substance

  The energy stored by the particles

  The sum of the total kinetic and potential energies that make up the system
• Heating a substance


  Transfers energy to the substance

  Increases the energy of the particles that make up the substance
• What heating a substance can do

  • Raise its temperature

  Change the state of the substance
• Factors that determine temperature change of a system

  • Mass of substance being heated

  Type of material (Specific heat capacity)

  Energy inputted into the system
• Equation to calculate temperature change when a substance is heated


  ΔE = m c Δ𝛉

  Energy (J), Mass (kg), Specific Heat Capacity (J/kg/°C), Temperature (°C)
• Specific heat capacity


  The amount of energy needed to increase the temperature of 1kg of a substance by 1°C
• Changes of state


  The internal energy of the substance will be increased or decreased

  The temperature of the substance will remain constant
• Specific latent heat


  The amount of energy needed to change the state of 1kg of a substance with no change in temperature
• Equation for energy required to change state

  Energy to change state = mass x specific latent heat

  Energy (J), Mass (kg), Specific latent heat (J/kg)
• Specific latent heat of fusion

  The energy required to change 1kg of a substance from solid state to liquid state without a change in temperature
• Specific latent heat of vaporisation

  The energy required to change 1kg of a substance from liquid state to gas state (vapour) without a change in temperature