Thermal Conduction (Cambridge (CIE) IGCSE Physics)

Thermal conduction in solids

Extended tier only

• Conduction is the transfer of heat from one region to another through particle vibrations and the movement of free electrons

• Conduction is the main method of thermal energy transfer in solids

• Metals are the best thermal conductors

  • This is because they have a high number of free electrons

Conduction: the atoms in a solid vibrate and collide, transferring energy

• Conduction can occur through two mechanisms:

  • Atomic vibrations

  • Free electron collisions

• When a substance is heated, the atoms, or ions, start to move around (vibrate) more

  • The atoms at the hotter end of the solid will vibrate more than the atoms at the cooler end

  • As they do so they bump into each other, transferring energy from atom to atom

  • These collisions transfer internal energy until thermal equilibrium is achieved throughout the substance

  • This occurs in all solids, metals and non-metals alike

• Additionally, if a solid contains free electrons, these can travel through the material freely and transfer thermal energy through collisions

Thermal conduction in liquids & gases

Extended tier only

• For thermal conduction to occur the particles need to be close together so that when they vibrate the vibrations are passed along

• This does not happen easily in fluids 

  • In liquids particles are close, but slide past each other

  • In gases particles are widely spread apart and will not 'nudge' each other when they vibrate

• Both types of fluid, liquids and gases, are poor conductors of heat

Relative thermal conductivity

Extended tier only

• Conductors tend to be metals

  • Better thermal conductors are those with delocalised electrons which can easily transfer energy

  • This means that there is a wide range of thermal conductivity 

Different materials have different levels of conductivity