heat transfers (topic 1). Flashcards
the student concludes that iron is the best conductor of heat because it has the highest time for the pin to drop, is the student correct (3)
- no
- iron is the worst conductor of heat
- the best conductor will cause the pin to drop in the lowest time
- copper is the best conductor of heat
describe how heat travels along the metal rods to cause the pins to drop (3)
- heat is transferred along the rods via conduction
- as particles heat up they vibrate more
- as neighbouring particles collide, heat is transferred between particles
(6)
- cup slows down energy transfer to surroundings
conduction: - vacuum contains no particles
- reducing / stopping conduction through the walls
- plastic lid is a poor conductor of heat
convection: - air is trapped by lid
- preventing convection from the surface of the drink
radiation: - shiny inner surface is a poor absorber of heat
- outer shiny surface is a poor emitter of heat
- energy transfer by radiation reduced
describe how loft insulation reduces heat loss through the roof, you should refer to methods of heat transfer in your answer (4)
conduction:
- insulation is made of fibres which are poor conductors / good insulators of heat
- minimising heat loss by conduction
- air trapped between fibres is a poor conductor of heat
convection:
- air is trapped between fibres
- preventing convection currents forming
a factory chimney is used to expel hot gases from an industrial process, the base of the chimney is hotter than the top, describe how a convection current forms because of the temperature difference (6)
- the gas molecules are hot as they leave the industrial process
- causing them to expand / move apart
- the gas becomes less dense and rises
- cooler air takes the place of displaced gas
- gas at the top of the chimney cools
- becoming more dense and falls
- repeated process is known as a convection current
explain why the black rings are warmer to the touch than the white rings (3)
- black is a good absorber and emitter of heat
- white is a poor absorber and emitter of heat
- when sunlight is incident on the chimney, the black rings absorb the heat
- the black rings emit absorbed heat which results in them feeling warm to the touch
- the white rings absorb less heat from the sun and reflect more of it back to the surroundings
the students concludes that the shiny paper is the best at radiating heat because it keeps the water hotter for longer, is the student correct (2)
- no
- the shiny paper is the worst at radiating heat
- black is the best absorber and emitter of heat
- the temperature of the black test tube drops the most because it is the best at radiating heat
in sunny countries, buildings are often painted white, using the ideas of heat transfer, explain why the buildings are painted white (3)
- white is a poor absorber / emitter of heat
- painting the building white will reduce the heat absorbed
- keeping the internal temperature low
at the base of the lava lamp there is a heater which heats the contents of the lava lamp, describe how the arrangement and movement of the wax particles changes as it is heated (2)
- the particles lose their regular arrangement and become more randomly aligned
- when in solid form the particles vibrate about fixed positions
- as the wax melts, the particles vibrate more rapidly and are able to slide past one another
the wax moves up and down in the lava lamp, using ideas about heat transfer explain why the wax moves up and down in the column (4)
- as the wax is heated, the particles spread out
- becoming less dense
- and rise
- wax at the top begins to cool
- becoming more dense
- and falls
- the process repeats, forming a convection current
describe how the motion of the water particles changes as the lake warms up (2)
- the water gains kinetic energy
- and the average speed of the particles increases
using ideas of heat transfer, explain how the wetsuit keeps Julia warm (3)
- the wetsuit is made out of an insulating material
- preventing heat loss by conduction
- a thin layer of water is trapped between the body and the wet suit
- the thin layer of water is in contact with the warm body, causing it to heat up
radiators are used to heat air in cold rooms, using ideas about heat transfer, explain how radiators heat a room (4)
- the surface of a radiator is hot
- air near the radiator is heated / gains thermal energy
- becoming less dense and rising
- air at the top of the room cools
- becoming more dense and sinks
- this continued process is known as a convection current
explain how the design of the radiator above makes it suitable for its purpose (5)
- radiator is painted white
- because white is a poor absorber of heat
- this reflects heat from the room back into the room instead of absorbing it
- the shape of the radiator maximises surface area
- to increase the heat transferred by convection
