Topic 1: Energy Flashcards
what are the four ways of heat energy transfer
conduction
convection
radiation
evaporation
why can conduction only occur in solids
solid particles need to be close together
what happens in conduction
-particles gain more kinetic energy when heated
-particles vibrate faster
-vibrations are passed onto neighbouring particles
why are metals best conductors?
they have delocalised electrons which carry vibrations faster
where does convection occur
(liquids/gases) fluids
what happens in convection
- particles gain kinetic energy
- particles move apart and become less dense
- causes the less dense particles to rise
- more dense particles falls
- this creates a convection current
where does radiation occur?
anywhere (including a vacuum - space)
what happens in radiation
- hotter objects emit more IR
- hotter objects (red and white)
- cooler objects (blue and black)
in terms of radiation, which material is the best emitter and best absorber?
black/ matt
in terms of radiation, which material is the worst emitter and worst absorber?
shiny/ white
how does heat travel?
heat travels from somewhere hot to somewhere cold
- the bigger the temperature difference, the faster the heat transfer
what happens when food gets to the same temperature as the fridge/ freezer?
maintains the same temperature
- fridge/ freezer is a closed system
what happens in evaporation?
- high energy particles leave the surface of the liquid
- reduces the average kinetic energy of the remaining particles
name different forms of home insulation
double glazing - vacuum between the glass panes
cavity wall insulation
loft insulation
draft excluders
carpets
curtains
jumpers (not part of home insulation but it does the same thing)
why are home insulators soft and squishy?
- pockets of air (small)
- poor conductor - particles are spread apart
- stops conduction
- convection can’t happen because pockets of air are too small for a convection current to be set up
