P2 - Energy Transfer by Heating Flashcards
define thermal energy
thermal energy is the name for the KE stored by a particle. how much a particle vibrates
define temperature
the measure of how hot or cold a body is
list the 3 types of heat transfer
- conduction
- convection
- radiation
define conduction
the process of thermal energy transfer where vibrations are passed through tightly packed particles
list 3 properties of electromagnetic waves
- can travel through a vacuum
- travel at the speed of light
- are reflected or absorbed
define a black body
a theoretical body that absorbs and emits all wavelengths of electromagnetic radiation
define black body radiation
the radiation emitted by a black body
describe the greenhouse effect (6 marks)
- most radiation travels through Earth’s atmosphere while some are reflected into space
- Earth absorbs the radiation that reaches the surface
- Earth emits IR back into atmosphere
- Some IR escapes atmosphere
- Some IR is absorbed by gases in atmosphere
- gases re-emit IR back to Earth which causes the lower atmosphere to warm up
define specific heat capacity
the amount of energy that is required to heat 1kg of a substance by 1°C
formula for thermal energy using specific heat capacity
energy = mass x SHC x temperature
E = mcΔT
J = kg x J/kg°C x °C
list 4 good thermal insulators
- wool
- ceramics
- plastics
- air
link poor insulation to global warming
Poorly insulated houses lose more thermal energy. This means it costs more and it requires more energy to continue to heat the house. Fossil fuels are usually burnt to create energy which causes more greenhouse gasses to be released which links to pollution and global warming.
explain how vacuums are good for insulating
vacuums stop conduction and convection because they require particles to occur and since there is no air in a vacuum the particles can’t get the thermal energy needed for those processes
list 5 common ways that houses are insulated
- double-glazed windows
- loft insulation
- cavity wall insulation
- radiator reflectors
- draught excluders and curtains
define payback time
the time it takes (in years) for the cost of insulation to be equalled by savings made from reduced energy costs
(Time to break even)
formula for payback time
payback time (years) = cost of insulation / savings yearly
explain how a thermos works
- vacuum- to stop conduction and convection
- insulator in lid - reduce thermal energy lost through conduction, convection and radiation
- shiny walls - reflect radiation back into bottle
order these from longer to shorter wavelengths:
- blue
- infrared
- ultraviolet
- infrared
- blue
- ultraviolet
list the steps for finding the specific heat capacity for copper
- record the mass of the copper block using a scale
- Insert the thermometer and immersion heater into holes in the copper block
- Leave for a few minutes to allow the thermometer to reach equilibrium then record the starting temperature of the thermometer
- Connect the ammeter and immersion heater to the power pack. Then connect the voltmeter
- turn on the power pack and record the values on the ammeter and the voltmeter
- Measure the temperature of the block each minute for 10 minutes
List 3 errors in finding the specific heat capacity experiment
- gaps of air between copper and immersion heater
- analogue thermometer so measurements might be read wrong
- takes time to heat the immersion heater at the start
