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Unit 11.1 How is heat (thermal energy) transferred and what factors
affect the rate at which heat is transferred?
Thermal (infra-red) radiation is the transfer of energy by electromagnetic
All bodies emit and absorb thermal radiation.
The hotter the body the more energy is radiates.
Dark, matt surfaces are good absorbers and good emitters of radiation.
Light, shiny surfaces are poor absorbers and poor emitters of radiation.
The transfer of energy by conduction and convection involves particles.
Under similar conditions, different materials transfer heat at different
Conduction is the transfer of energy through a substance without the substance
The structure of metals make them good conductors of heat:
1. As the metal becomes hotter, its tightly packed particles gain more kinetic
energy and vibrate.
2. This energy is transferred to cooler parts of the metal by delocalised
electrons, which move freely through the metal, colliding with particles and
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Convection is the transfer of heat energy through
movement of particles. It is the transfer of heat energy
through fluids by the upward movement of warmer, less
dense, regions in the fluid.
Convection occurs in liquids and gases and created
1. The particles in the liquid or gas which are nearest
the heat source move faster causing the substance to
expand and become less dense than in the colder parts.
2. The warm liquid or gas will rise up.…read more