Heat Flashcards
Heat definition
a form of energy which causes temperature to rise when added or fall when drawn out
heat capacity
- the heat energy required to change the temperature of a substance by 1 kelvin
- symbol - c
- unit - J/K
- equation - Q = cΔθ
specific heat capacity
- the heat energy required to change 1 kg of a substance by 1 Kelvin
- symbol - mc
- units - J/kg/K
- equation - Q = mcΔθ
(higher means more energy required to change)
specific heat capacities of substances
copper - 385
aluminium - 900
ice - 2100
water - 4190
latent heat
- the heat required to change a substances state without a change in temperature
- symbol - “L”
- unit - J
specific latent heat
- the heat required to change the state of 1 kg of a substance without a change in temperature
Latent heat of fusion of ice
330,000
Latent heat of vaporisation of water
2300000
Inside of a fridge
- heat pump
- volatile liquid = low specific heat capacity
(B.F.C) - 1) valve - high pressure liquid to low
pressure gas (Lv)
- absorbed heat; cold - 2) compressor - low pressure gas to high
pressure liquid (Lv)
- releases heat energy; hot
Latent heat in the body
- hot
- plasma sent to surface capillaries
- sweat
- sweat evaporates (Lv)
- body loses heat energy and cools down
conduction
the transfer of heat energy in a solid by passing on kinetic energy from molecule to molecule
(frying pan)
Conduction experiment
- water bath
- temperature probe
- wax and thumbtacks
- first to fall = best conductor
Convection
the transfer of heat energy by the circulation of heated parts of a fluid
(kettle)
Convection experiment
- heat water in a beaker with potassium permanganate
- pp moves with convection currents
Radiation
the transfer of heat energy as an electromagnetic wave without the need for a medium
(sun)
Radiation experiment
- black can, white can
- thermometer
- boiling water
- black loses heat faster - better radiator
solar constant
the amount of heat energy striking 1 m² of the earth’s atmosphere every second
(average = 1.37 Kw/m²)
Solar Panels
- dark pipes heat in the sun
- heat moves from warm pipes into cold water
insulation in a house
- foam between walls (conduction)
- block draughts (convection)
- silver foil in walls
insulation in a flask
- plastic between layers (conduction)
- lid (convection)
- silver on inside (radiation)
u value
the amount of heat energy that is transmitted across 1m² of the surface of a material - so long as there is a temperature difference of 1 kelvin on each side of the material
high u value
- good conductor
- old chapel
low u value
- bad conductor
- modern house
