Conduction,Convection and Radiation

• What happens to energy when an object is heated?

  Energy is transferred to its thermal energy store
• What are the three ways heat can be transferred depending on the medium?

  Conduction, convection, and radiation
• How is heat transferred in solids?

  By conduction
• How is heat transferred in fluids?

  By convection
• How is heat transferred through empty space?

  In the form of radiation
• What is the key idea behind conduction?

  • Vibrating particles transfer energy to neighboring particles
  • Energy is transferred to the kinetic energy store of particles
  • Collisions between particles pass on energy
• What happens when one end of a piece of metal is heated with a Bunsen burner?

  Energy is transferred to the kinetic energy store of the particles at that end
• Why does conduction occur mainly in solids?

  Because particles in solids are held closely together
• What is thermal conductivity?

  How well objects transfer energy by conduction
• Which materials have high thermal conductivity?

  Metals
• Which materials have low thermal conductivity?

  Plastics and fluids
• How does convection occur in fluids?

  • Particles gain kinetic energy and move faster
  • Energetic particles move from warmer to cooler regions
  • Warmer fluid expands and becomes less dense
  • Cooler particles sink to take their place
• What happens to particles in a fluid when heated?

  They gain kinetic energy and spread out
• What is a convection current?

  A cycle of rising warm particles and sinking cool particles in a fluid
• How do blankets reduce convection?

  By stopping the free flow of warm air
• What do conduction and convection have in common?

  • Both involve particles gaining kinetic energy
  • Both are methods of heat transfer
  • Both require a medium for energy transfer
• How can heat energy be transferred without particles?

  Through radiation
• What type of waves carry energy during radiation?

  Infrared waves
• What happens to radiation emitted by hotter objects?

  They emit more radiation
• Why does it feel hot to put your hand over a barbecue?

  Because the hot metal emits infrared radiation
• What is the electromagnetic spectrum?

  • A range of all types of electromagnetic radiation
  • Includes infrared radiation
  • Important for understanding heat transfer