energy transfers

Question 1

what are the 4 ways energy can be transferred by-

Answer 1

evaporation
radiation
conduction
convection

Question 2

radiation-

Answer 2

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

Question 3

conduction-

Answer 3

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

Question 4

thermal conductor=

Answer 4

materials easily allow energy to transfer through it

Question 5

thermal insulator-

Answer 5

a material which doesnt allow energy to transfer through it

Question 6

examples of insulators-

Answer 6

wood
plastic
rubber
water
neon
sand
vaccum
coat

Question 7

a practical to show how thermal energy transfers thru e.g convection

Answer 7

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

Question 8

convection?

Answer 8

process by which heat is transferred by movement of a heated fluid such as air or water

Question 9

what does convection happen best in?

Answer 9

fluids-liquids and gases

Question 10

vaccum-

Answer 10

no particles present

Question 11

why cant heat travel by conduction or convection in space:

Answer 11

because the space between the sun and earth is a vaccum

Question 12

an example of infrared radiation

Answer 12

heat energy from the sun
just like light it can be absorbed, emitted or reflected

Question 13

dull dark colours are good or bad absorbers

Answer 13

good absorbers keepis in heat

Question 14

light shiny colours are good or bad absorbers

Answer 14

reflects radiation-makes it cooler as they take in less energy and heat

Question 15

convection-

Answer 15

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

Question 16

hot air and cold air rise or sink?

Answer 16

hot air rises
cold air sinks

Question 17

dense-

Answer 17

closely compacted ins ubstances

Question 18

warm air -density

Answer 18

less dense

Question 19

cold air-density

Answer 19

more dense

Question 20

example of convection

Answer 20

tea the steam rising when drinking it

Question 21

example of radiation-

Answer 21

the sun x rays and microwaves

Question 22

example of conduction-

Answer 22

the stove being hot when on the cooker

Question 23

differences between conv,cond and radiation

Answer 23

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

Question 24

why cold air is more dense than hot air

Answer 24

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