Heat

Heat

1. Heat transfer

   • Conduction (contact)
     • Definition
       • Flow of heat
       • High to low temperature
       • Without movement of matter as awhole
     • Medium
       • Solids : Best conductors
         • Good conductors
           • E.g. Metals
         • Poor conductors (Insulators)
           • Air
           • Materials that trap air
             • E.g. foam, feathers
       • Gases : Worst conductors
   • Convection
     • Definition
       • From high to low level
       • Flow of heat
       • Movement of liquids of gases as a whole
     • Medium
       • Occurs in liquids and gases
     • Convection current (flow)
       • Hot air rises
         • Expands so the air is less dense
       • Cold air sinks
         • Contacts so the air is less dense
   • Radiation
     • Definition
       • Flow of heat
       • From high to low temperature
       • By electromagnetic waves
     • Medium
       • Solids, liquids and gases
       • Can pass through a vacuum
     • Colours
       • Matte black
         • Best absorber and emitter
       • Shiny silver
         • Worst absorber and emitter
         • Very good refector

2. Heat and its effects

   • Expansion and contraction
     • Expansion
       • Object expand and increase in volume
     • Contraction
       • Objects contract and decrease in volume