Conduction , convection, infrared radiation and vacuum flask

• Convection is the transfer of heat by the movement of fluids.
• The three main methods of heat transfer are conduction, convection, and infrared radiation.
• Heat is a form of energy it’s measured in Joules (J)
• Temperature is the of how hot or cold an object is. It is measured in degrees Celsius
• Hear energy will flow from the most positive(hotter) to the most negative electrode(colder)
• A cold object placed somewhere warm will absorb the heat from the surroundings.
• Conductors are materials that allow electricity to flow through them easily. They have free electrons which vibrate when heated passing along heat energy
• Insulators are materials that do not allow the flow of heat to pass through them easily. They don’t have free electrons hence why heat energy passes slowly through them.
• Metals are good conductors because they contain lots of free electrons
• When two objects at different temperatures are put together, the one with the higher temperature will lose heat until both reach equilibrium (the same temperature)
• Experiment: Which material is the best conductor?


  1. Prediction: think steel would be the best conductor

  2. Set up apparatus as shown above

  3. Heat the metal strips at the centre where they all meet

  4. Start the timer

  5. Record time taken / when the wax melts and the thumb toc falls
• Independent variable


  • Type of metal
• Dependent variable


  • Time taken for wax to melt
• Controlled variables


  • Same amount
  • Same size of thickness of metal strip
• Materials tested


  • copper
  • steel
  • aluminum
  • brass
  • wood
  • iron
• Water/Air is heated becomes less dense and rises. Cooler air is drawn in to replace it setting up a convection current
• Everyday examples of convection

  • Boiling water
  • Convection current
  • Hot air balloon
• Convection current

  Hot less dense air rises, cooler denser air sinks to replace it
• Setting up a convection current

  1. Water in pot is heated, becomes less dense and rises

  2. Cooler water is drawn in from the top to replace it
• Setting up a convection current

  1. Air in front of radiator is heated, becomes less dense and rises

  2. Cooler air is drawn from surrounding to replace it
• Setting up a convection current

  1. Hot air in balloon is heated, becomes less dense causing it to rise

  2. Cooler air is drawn in from surrounding to replace it
• Infrared radiation is heat emitted from warm objects ,which can travel through a vacuum
• Objects which emit infrared radiation

  • Light bulb
  • Toaster
  • Sun
• Recording infrared radiation emitted by an object

  1. Use an infrared sensor connected to a data logger

  2. Gives a numerical value
• Demonstration: Reflection of Heat
• Independent variable

  type of surface
• Dependent variable

  Time for cork to fall
• Controlled variables

  • Distance of metal plate from heater
  • Amount of wax
  • Thickness of metal plates
• Method

  1. Place the two metal plates at an equal distance from the heater

  2. Switch the heater on and start the stopwatch

  3. Stop the stopwatch and record time taken for each cork to fall
• Everyday situations where good absorbers, emitters and reflectors of infrared radiation are used

  • Absobers: Bottom of pots & pans
  • emitters:Top of pots & pans,, Radiators in car: Reflectors : Room heaters , light coloured clothing
• Areas of the home where heat could be lost

  • Walls
  • Roof
  • Doors
  • Windows
  • Floor
• How heat loss could be minimised

  • Cavity walls and mounting insulation
  • Double glazed/skinned windows
  • Insulation