Thermal Conduction (CIE IGCSE Physics)

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

Two solids of different temperatures come in contact with one another, thermal energy is transferred from the hotter object to the cooler object

• 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 bump into each other

• 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

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

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• 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 rates of conductivity