Section 4b: thermal energy
convection
radiation
conduction
sankey diagrams
heat in the home
how heat is lost
solutions
through conduction
-walls, windows & doors
through convection
-current in between two walls
windows
-thin glass is a poor thermal conductor
loft insulation = thick layer of fibre glass wool on loft floor - reduces conduction & radiation
drought proofing = strips of foam & plastic around doors & windows - reduces convection
cavity wall insulation = foam squirted in gaps between bricks - reduces convection, conduction & radiation
thick curtains = reduces conduction & radiation
hot water jacket = fibre glass wall - reduces conduction & radiation
double glazing = two layers of glass - reduces conduction & convection
definition = the transfer of energy through fluids but the upward movement of warmer, less dense regions of fluid
convection current 
examples - immersion heater, kettles, radiators, hot water tanks
- heated less dense air rises
- warmer air replaces cooler air
- cool, denser air falls
- cool air rises to fill the gap left by rising heated air
definition = the transfer of energy by infra-red waves
the heat energy travels in straight lines
infra-red waves can travel through a vacuum
can be reflected/absorbed by different materials
-shiny surfaces + white surfaces = good reflectors of thermal radiation
-matt black & dark surfaces = poor reflectors / good absorbers of heat radiation
Energy inputted useful energy output
waster energy output
the thickness of the arrow represents the amount of energy
thermal conduction = transfer of thermal energy through a substance without the substance moving
metals - good thermal conductors
wood - good thermal insulator
Process
- in the hot part of a substance, particles have lots of kinetic energy
- they transfer some of them to particles near them
- this process repeats/continues throughout the substance
metals process is more rapid, they have free electrons which move easily through the substance
efficiency = useful energy output / total energy input