energy transfers Flashcards
what are the 4 ways energy can be transferred by-
evaporation
radiation
conduction
convection
radiation-
also known as infrared radiation
all things give out and emit ir
hotter=more ir emitted
transfers energy by waves
moves from one source toa nother through waves at the speed of light-electromagnetic waves
conduction-
energy transfers through particles
making them vibrate=increase in heat vibration makes them rise to the top
alluminium, zinz, sand -metals are good thermal conductors e.g like a hot spoon in a salon cooking
only solids conduct heat liquids and gases are poor conductors as the aprticles arent fixed so energy cant pass properly
thermal conductor=
materials easily allow energy to transfer through it
thermal insulator-
a material which doesnt allow energy to transfer through it
examples of insulators-
wood
plastic
rubber
water
neon
sand
vaccum
coat
a practical to show how thermal energy transfers thru e.g convection
you have a rod and you ahve pins hanging from it and you put a fire near it and each pins drops by turn by turn
convection?
process by which heat is transferred by movement of a heated fluid such as air or water
what does convection happen best in?
fluids-liquids and gases
vaccum-
no particles present
why cant heat travel by conduction or convection in space:
because the space between the sun and earth is a vaccum
an example of infrared radiation
heat energy from the sun
just like light it can be absorbed, emitted or reflected
dull dark colours are good or bad absorbers
good absorbers keepis in heat
light shiny colours are good or bad absorbers
reflects radiation-makes it cooler as they take in less energy and heat
convection-
only atkes place in fluids when part of a fluid is heated it exapnds and becomes less dense so it rises up cooler air moves in to take its place as it egts colder it sinks a nd the cycle repeatse
hot air and cold air rise or sink?
hot air rises
cold air sinks
dense-
closely compacted ins ubstances
warm air -density
less dense
cold air-density
more dense
example of convection
tea the steam rising when drinking it
example of radiation-
the sun x rays and microwaves
example of conduction-
the stove being hot when on the cooker
differences between conv,cond and radiation
cond-transfers thru solid e.g metals as poarticles are fixed so can get thru
conv-works for fluids as they ahve to rise and fall for the room to be hetaed or cooler so hota ir can rise and cold air can sink
radiation-doesnt need any particles to occur it tarvels everywhere giving out ehat and light
why cold air is more dense than hot air
cold air is more dense as moves slowly so particles collect together more -higher density but warm air is less dense bc tehy move faster creatinga n exapnsion-go far away so the compaction -closeness- bewteen them goes descrease so are less dense
