• All things are made up of molecules
  • When things get heated, they absorb heat energy
  • With more energy, molecules are able to move faster
  • When molecules move faster, the temperature rises

What is Thermal Energy???

  • Thermal Energy is energy resulting from the motion of particles
  • It is a form of kinetic energy and is transferred as heat
  • Thermal Energy Transfer can occur by three methods:
  • Conduction
  • Convection
  • Radiation


  • Conduction is the transfer of thermal energy through direct contact between particles of a substance, without moving the particles to a new location
  • Usually occurs in solids
  • When heat is supplied to one end, molecules at that end start to move more quickly
  • In the process, they bump into their neighbours, transferring the kinetic energy


  • Convection is the transfer of thermal energy through movement of particles from one location to another
  • Usually occur in fluids (liquids and gases)
  • Example with boiling water:
  • Water at bottom of pan is heated first
  • Heated water expands and density decreases
  • Heated water begins to rise
  • Cooler water with higher density from the sides of the pan rush down to take its place
  • The cooler water gets heated and the cycle repeats
  • We call these Convection Currents


  • Radiation is the emission of energy as waves or particles or rays
  • Radiation does not require a medium to transfer energy
  • Radiant energy is either reflected or absorbed by matter
  • Energy that is absorbed increases the kinetic energy of the object
  • This increases the temperature of the object
  • Example … frying pan on a stove top
  • Energy is radiated from the heat source and absorbed by the lower surface of the pan
  • Example … the sun
  • Sun radiates energy in form of solar radiation
  • When this energy reaches Earth, it is absorbed by matter (air, water, land)
  • Absorbed radiant energy increases kinetic energy of the matter, raising its temperature
  • The sun is an emitter
  • It gives out heat
  • The Earth is an absorber
  • It takes in the heat

Factors Affecting Radiation


  • Colour of the surface
  • Albedo is the percentage of the incoming solar radiation that it reflects
  • Albedo of Earth is about 30%
  • Light-coloured, shiny objects reflect more solar radiation and have a high albedo (ice, snow, sand)
  • Darker, dull objects absorb more solar radiation and have a low albedo (forests, soils)
  • Factors Affecting Radiation
  • Surface Temperature
  • The higher the surface temperature, the higher the rate of transfer

Surface Area

  • The larger the surface area, the higher the rate of transfer
  • Thermal Energy Transfer in the Atmopshere
  • Things to Know:
    • Atmospheric Pressure > the pressure exerted by the mass of air above any point on Earth’s surface
    • Warm air is less dense than cold air
    • Warmer regions generally have less atmospheric pressure than colder regions
    • Wind > the movement of air from areas of high pressure to areas of low pressure
    • The rising and sinking masses of air in convection currents cause changes in atmospheric pressure … causing wind

Wind Patterns and Coriolis Effect:

  • Moves from WEST to EAST
  • Closer to equator in colder monthes
  • Closer to Poles in warmer months
  • Thermal Energy Transfer in the Hydrosphere
  • Effect of water on transfer of heat is significant
  • Earth’s climate is effected by phase changes in the water cycle

Water Cycle

  • Water molecules undergo changes of state (e.g. solid to liquid)
  • When these changes occur, thermal energy is either released or absorbed
  • Released from liquid > solid
  • Absorbed from Liquid > gas
  • Temp. remains the same between phase changes
  • Through changes of state is how thermal energy is transferred through the biosphere

Ocean Currents

  • Main pathways to transfer thermal energy from warmer regions to cooler regions
  • Global winds push the water, driving the surface currents of the ocean
  • Pattern of ocean currents is modified by the Coriolis Effect
  • Currents in North veer to the right
  • Currents in South veer to the left
  • Thermal energy is also transferred vertically via convection currents
  • (same principles as with air)

10 thoughts on “Thermal Energy Transfer: Conduction, Convection, Radiation

  1. Halil

    thanks so much! I’ve got GCSE physics unit 1 exam tomorrow and this has helped loads!

  2. may

    this did not help at all!!!!! :(

  3. MacB

    Re: May.

    What are you having trouble with in this subject matter?

  4. grrrrr

    did not help at all

  5. kenjay

    You didn’t answer my question! :(

  6. @kenjay

    What is your question?

  7. this helps me so much

  8. Connor

    Very useful

  9. Peter P.

    This is good, it really helped. It is really informative. Wow!!!!!!!!!!!!!

  10. Emily O.

    This really helps!!!

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