Thermal Energy

Question 1

what does thermal energy tend toy do

Answer 1

flow away from a hotter object to its cooler surroundings

Question 2

heat energy can be transferred by …

Answer 2

radiation
conduction
convection

Question 3

thermal (infrared) radiation is the transfer of heat energy by…

Answer 3

electromagnetic waves

Question 4

conduction and convection involve what

Answer 4

the transfer of energy by particles

Question 5

what is the main form of heat transfer in solids

Answer 5

conduction

Question 6

what is the main form of heat transfer in liquids and gases as solid particles cannot move

Answer 6

convection

Question 7

emission of thermal radiation occurs in what

Answer 7

solids liquids and gases

Question 8

any object can both … and … heat radiation, even when conduction and convection are taking place

Answer 8

absorb

emit

Question 9

all objects are … emitting and absorbing heat radiation

Answer 9

continually

Question 10

an object that’s hotter than its surroundings emits … radiation than it absorbs (as it cools down)

Answer 10

more

Question 11

an object that’s cooler than its surroundings absorbs .. radiation than it emits (as it warms up)

Answer 11

more

Question 12

in a solid, the particles are held … together

Answer 12

tightly

Question 13

when one particle vibrates in a solid, it … with other particles nearby and the … quickly pass from particle to particle to spread throughout the whole object, hence increased heat radiating from the surface

Answer 13

collides

vibrations

Question 14

what out of the 3 heat transfer methods work in a vacuum

Answer 14

heat radiation (as doesn’t rely on particles)

Question 15

what is convection

Answer 15

it occurs when the more energetic particles move from the hotter region to the cooler region - and take their heat energy with them

Question 16

how do immersion heaters work

Answer 16

• where the heater coils are the water on top heats
• this hot water becomes less dense and rises
• at the top fast moving particles collide with slow moving particles (cold ones) and transfer heat)
• water then cools and becomes more dense
• denser water sinks again to where the heater coils are
• this works in a circular motion
• water stays cold below the heater because there is almost no conduction
• only get convection currents in the water above the heater as hot water rises

Question 17

convection is most efficient in what type of containers

Answer 17

round/squarish ones

Question 18

insulating your house … heat transfer

Answer 18

reduces

Question 19

explain what it does: loft insulation

Answer 19

a thick layer of fibreglass wool laid out across the loft floor and ceiling reduces heat loss from the house by conduction and convection

Question 20

explain what it does: draught proofing

Answer 20

strips of foam and plastic around doors and windows stop draughts of cold air blowing I’m, reduce convection

Question 21

explain what it does: cavity wall insulation

Answer 21

foam squirted into the gap between bricks stops convection currents and radiation across the gap, insulating foam traps air which acts as an insulator and reduces heat loss by conduction

Question 22

explain what it does: hot water tank jacket

Answer 22

lagging such as fibreglass wool reduces conduction and radiation

Question 23

explain what it does: double glazing

Answer 23

two layers of glass with a narrow air/vacuum gap between reduces conduction and convection

Question 24

explain what it does: thick curtains

Answer 24

big bits of cloth over the window to reduce heat loss by conduction and radiation

Question 25

how does human hairs on the skin insulate us

Answer 25

stand up to trap a thicker layer of insulating air around the body, limits the amount of heat loss by convection

Question 26

how do humans reduce heat loss by wearing layered clothes

Answer 26

the pockets of air trapped in the clothes and between layers mainly reduce heat transfer by conduction and convection (as air is an insulator)

Question 27

how do humans reduce heat loss by wearing just clothes

Answer 27

reduce heat loss by radiation from the body, as the material absorbs some heat radiated out by our bodies