heat

conduction Conduction = the transfer of heat by the collision of particles in a solid Heat conductor = a substance that conducts heat well (metal > paper) Heat from flame = energy being added to the end of the metal rod Metal particles closest to the source of heat/energy have more energy… → move more quickly → have more collisions → have weaker attractive forces → have more space between them → that part of the rod expands Particles closest to heat source collide with neighbours and transfer their energy to them Process continues down the metal rod → rod expands and feels warmer

RADIAtion So far heat transfer has occurred by convection (fluids) and conduction (solids) where both depend on the motion of particles Radiation = the transfer of energy by means of waves (travelling across empty space) Energy transferred by radiation = radiant energy ex) light ex) sun’s heat Some objects absorb radiant energy better than others; some emit (give off) radiant energy better than others Which object will absorb radiant energy fastest? Which object will emit radiant energy fastest?

radiation Dark colours tend to absorb radiant energy best As the surface area increases, the energy absorbed also increases Dark colours tend to emit radiation best As the surface area increases, the energy emitted also increases A good absorber is also a good emitter Light and shiny colours are good reflectors of radiant energy