Transferring energy

• Evaporation

  When part of a liquid evaporates, it is the fastest-moving particles that escape to form a gas. The particles that are left are storing less energy as movement and so the temperature of the remaining liquid is lower.
• Conduction


  • Takes place in solids and can also happen in liquids (although not very well)
  • The particles in a solid are held together tightly. When they gain energy they vibrate faster and further, and the vibrations are passed on.
  • Metals are the best conductors. Most other solids are poor conductors.
• Liquids


  • Particles are not as close, so conduction is not very good.
• Gases


  • Particles are a long way apart, so gases hardly conduct heat at all.
• Thermal insulator


  Something that does not conduct heat very well.
• Convection


  • Takes place in fluids (liquids and gases)
  • When part of a fluid is heated, the particles spread further apart and the fluid becomes less dense. This makes it rise. As it rises it meets cooler fluid and passes the energy on. More cool fluid moves in to replace the rising fluid, setting up a convection current.
• Infrared radiation


  Can transfer energy through empty space and also through transparent materials. Radiation does not require the movement of particles.
• Any hot or warm object gives off or emits radiation.
• Absorb radiation


  When something takes in energy from radiation.
• Infrared radiation


  • Similar to light. It can be absorbed or reflected, and it can also be focused.
• Dark, dull surfaces


  • Good emitters and absorbers of radiation.
• Light, shiny surfaces


  • Good at reflecting radiation. Poor absorbers and emitters of radiation.
• Convection


  The flow of heat energy from a region of high temperature to a region of low temperature by movement of a fluid.
• Fluids


  Liquids and gases. They can be made to flow from one place to another. Convection occurs when particles with a lot of heat energy in the fluid move and take the place of particles with less heat energy.
• Radiation


  The transfer of heat energy from a region of high temperature to a region of low temperature by infrared radiation. It takes place without the need of any particles.
• Conduction


  • The flow of heat energy from a region of high temperature to a region of low temperature without overall movement of the material itself.
  • Metals are good conductors of heat energy. Non-metals and gases are usually poor conductors.
  • Poor conductors of heat are called insulators.