Energy transfer by heating

• Metals are the best conductors of energy.
• Non-metal materials such as wool and fibreglass are the best insulators.
• The higher the thermal conductivity of a material, the higher the rate of energy transfer through it.
• The thicker a layer of insulating material, the lower the rate of energy transfer through it.
• The specific heat capacity of a substance is the amount of energy needed to change the temperature of 1kg of the substance by 1C.
• Use the equation ΔE = m c Δθ to calculate the energy needed to change the temperature of mass m by Δθ.
• The greater the mass of an object, the more slowly its temperature increases when it is heated.
• To find the specific heat capacity c of a substance, use a joulemeter and a thermometer to measure ΔE and Δθ for a measured mass m, then use c = ΔE / m Δθ.
• Electric and/or gas heaters and gas or oil-fired central heating or solid-fuel stoves are used to heat houses.
• The rate of energy transfer from houses can be reduced by using:

  • loft insulation
  • cavity wall insulation
  • double-glazed windows
  • aluminium foil behind radiators
  • externl walls with thicker bricks and lower thermal conductivity
• Cavity wall insulation is insulation material that is used to fill the cavity between the two brick layers of an external house wall.