Thermal Energy Flashcards
what does thermal energy tend toy do
flow away from a hotter object to its cooler surroundings
heat energy can be transferred by …
radiation
conduction
convection
thermal (infrared) radiation is the transfer of heat energy by…
electromagnetic waves
conduction and convection involve what
the transfer of energy by particles
what is the main form of heat transfer in solids
conduction
what is the main form of heat transfer in liquids and gases as solid particles cannot move
convection
emission of thermal radiation occurs in what
solids liquids and gases
any object can both … and … heat radiation, even when conduction and convection are taking place
absorb
emit
all objects are … emitting and absorbing heat radiation
continually
an object that’s hotter than its surroundings emits … radiation than it absorbs (as it cools down)
more
an object that’s cooler than its surroundings absorbs .. radiation than it emits (as it warms up)
more
in a solid, the particles are held … together
tightly
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
collides
vibrations
what out of the 3 heat transfer methods work in a vacuum
heat radiation (as doesn’t rely on particles)
what is convection
it occurs when the more energetic particles move from the hotter region to the cooler region - and take their heat energy with them
how do immersion heaters work
- 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
convection is most efficient in what type of containers
round/squarish ones
insulating your house … heat transfer
reduces
explain what it does: loft insulation
a thick layer of fibreglass wool laid out across the loft floor and ceiling reduces heat loss from the house by conduction and convection
explain what it does: draught proofing
strips of foam and plastic around doors and windows stop draughts of cold air blowing I’m, reduce convection
explain what it does: cavity wall insulation
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
explain what it does: hot water tank jacket
lagging such as fibreglass wool reduces conduction and radiation
explain what it does: double glazing
two layers of glass with a narrow air/vacuum gap between reduces conduction and convection
explain what it does: thick curtains
big bits of cloth over the window to reduce heat loss by conduction and radiation
how does human hairs on the skin insulate us
stand up to trap a thicker layer of insulating air around the body, limits the amount of heat loss by convection
how do humans reduce heat loss by wearing layered clothes
the pockets of air trapped in the clothes and between layers mainly reduce heat transfer by conduction and convection (as air is an insulator)
how do humans reduce heat loss by wearing just clothes
reduce heat loss by radiation from the body, as the material absorbs some heat radiated out by our bodies
