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Thermal physics (Shi Yu) (Kinetic molecular model of matter (Evaporation…
Thermal physics (Shi Yu)
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Thermal processes
Conduction
What is conduction?
Conduction is the movement of heat from one side to another side that has a lower temperature when they are touching each other.
How heat is transferred by conduction?
For non-metal solids :
1.Energy is transferred because the vibrating atoms jostle (or push) one another
2.This shares energy between neighboring atoms
3.The result is a flow of energy from the hot end to the cold end
Additional point for metals :
Free electrons in a metal also carry energy when heat is transferred through a metal
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Summary :
1.Gases are very poor conductors of heat energy.
2.Liquids and non-metal solids are usually poor conductors of heat energy.
3.Metals are good conductors of heat energy.
Convection
What is convection?
1.Convection is the heat transfer due to the bulk movement of molecules within fluids such as gases and liquids.
2.This movement of water is called a convection current.
Convection vs Conduction :
Convection – movement of hot material particles itself
Conduction - heat transferred without moving the material itself
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Radiation
What is Radiation?
1.All hot objects emit thermal radiation, part of the Electromagnetic spectrum of waves.
- Like all electromagnetic waves, infrared radiation can travel across a vacuum space, which is why we are able to feel the heat of the Sun across the vacuum space
What is the best emitter of thermal radiation?
silver surfaces are the best emitters of thermal radiation
Matt black surfaces are the worst emitters of thermal radiation
What is the best absorber of thermal radiation?
Matt black surfaces are the best absorbers of thermal radiation.
silver surfaces are the best absorbers of thermal radiation.
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