Heat Transfer

Conduction Convection Radiation

Transfer of heat energy through particles of a solid In metals, atoms arranged very close together in regular pattern. Heat energy can pass rapidly across most metals

A material that doesn’t transfer heat energy easily

They transfer heat by process of conduction

Transfer of heat energy in liquid or gas. If we heat beaker of water, water at bottom heats up & rises. This is seen by adding dye to bottom of beaker of water

Pattern of liquid or gas rising & falling

When liquid absorbs heat energy, particles gain energy & move further apart as they have more kinetic energy As particles are more widely spaced, they have lower density than those in cooler liquid This lower density in warmer liquid causes it to rise & is replaced by older liquid of higher density

They have free electrons that can move & transfer heat energy as well as atoms in conductor vibrating faster. Heat transferred inform of kinetic energy

Transfer of heat energy by waves passing out from a hot surface

Earth receiving heat energy from sun, through vacuum of space. Heat energy transferred in infrared waves Heat off fire Heat radiating out from any object

Best emitters & best absorbers

Worst emitters & worst absorbers

Matt surfaces better emitters & absorbers than most gloss surfaces

Atoms in metal arranged in regular structure & very close together In metal atoms, outer electrons not tightly attached; they’re free/delocalised This means these electrons can move easily throughout whole metallic structure As electrons move, they carry heat energy from one part of metal to another

Outer electrons aren’t free , so they can’t pass throughout structure Only way heat energy can transfer s by passing fro atom to atom - much slower process

Cavity wall insulation Loft insulation Double glazing Carpets