Conduction, convection and radiation

• Conduction primarily takes place in:

  Solids
• How conduction works:

  When part of a solid absorbs heat energy, the atoms vibrate faster causing them to collide with their neighbours more frequently.

  These collisions transfer kinetic energy, their neighbours also vibrate and collide faster. Repeats so energy is transferred onto each particle.
• Thermal conductivity is a measure of how well a material conducts energy when it is heated.

  Which type of materials have a higher thermal conductivity?

  Metals
• What does ‘fluid’ mean and which states of matter are considered fluids?

  Particles free to move

  Liquids

  Gases
• Convection can take place in:

  Liquids

  Gases
• How convection works:

  As a fluid is heated the particles gain kinetic energy and spread further apart.

  This causes fluid to become less dense and so will rise above any cooler fluid that hasn’t been heated.

  As fluid cools down itl become more dense again, and will sink back down.
• Ways to help reduce heat loss via convection?

  Closing windows

  Covering self with blanket at night
• When we say heat energy is transferred by ‘radiation’, we’re referring to:

  Infrared radiation.
• Infrared radiation..

  Can travel through a vaccum

  A form of electromagnetic radiation
• Do hotter or cooler objects emit more infrared radiation?

  Hotter

  (Have more energy, so emit more energy)
• Warm fluids rise because they are less dense than cooler fluids.