P2 energy transfer by heating (paper 1) Flashcards
what does energy transfer by conduciton depend on
the materials thermal conductivity
if a material conducts well then what is the thermal conductivity like of the material
high
what are the different methods of isulation in the home
- loft insulation
- cavity wall insulation
- aluminium foil
- double glazing
- solar panels
what does the size of a temperature change which increases internal energy depend on
- the mass of the substance
- what it is made of (specific heat capacity)
- the energy input
what is the formula for the energy input when given temp chance, c and mass
E (J) = mass (kg) x specific heat capacity (J/kg) x change in temperature
what is meant by the term ‘specific heat capacity’
the amount of energy needed to raise the temperature of 1kg of a substance by 1°C
does energy material have the same specific heat capacity?
no
if a material needs a LOT of energy inputed to their thermal store to warm up, describe the specific heat capacity
a high specific heat capacity
if a material needs a lot of energy to heat up what will happen when it cools
a lot of energy will be let out
describe the type of thermal conductivity an insulator has
a low thermal conductivity so they retain heat
how can you reduce the energy transfer by heating
- thermal conductivity of material should be as low as possible
- the thickness of the insulating layer should be thick as possible
if a material has a high thermal conductivity describe the rate of energy transfer through it
a high/fast rate of energy transfer
describe how you can investigate specific heat capacities of materials
- get material to be investigated
- measure the mass of the material with a balance (2dp)
- insulate the material to reduce enrgy trasferred to surroundings
- measure the initial temp of material and set power supply to 10 V
- turn on power and start stop watch
- a current will flow and will transfer thermal energy
- as the block heats, measure the temp and current every min for 10 min
- the current shouldn’t change
- once 10 readings collected turn off power supply and calculate power using P = VI
- calculate energy transferred using E = Pt
- reapeat with different materials
when does conduction occur
in solids
what is meant by the term conduction
the process where vibrating particles transfer energy to neighbouring particles
when does convection occur
in liquids and gases
what is meant by the term convection
where energetic particles move away from hotter to cooler regions
what is a perfect black body
an object that absorbs all radiation that hits it
what happens when an object absorbs more infrared radiation than it emits
the temp of the object will increase
is an object is hotter will it emit infrared radiation quickly or slowly
quickly
what direction does heat flow from
hot to cold
what is the difference between temperature and heat
- temperature is a measure of how hot something is (°C)
- heat is a measure of the thermal energy in an object (J)
what is the specific heat capacity of water
4200J/kg°C
what is the radiation emitted by a perfect black body
black body radiation
how does loft insulation help insulate buildings
- fibreglass traps lots of air
- this stops heat loss by conduction
- you can make this insualtion thicker by adding lots of layers
how do cavity wall insulation insulate buildings
- foam is pumped into the cavity between the brick laters in the wall
- this traps pockets of air
- this stops heat loss by conduction
how does aluminium foil insulte buildings
- foil is put behind radiators
- foil reflects heat energy
- this stops heat being lost by radiation
how does double glazing insulte buildings
- formed from two layers of glass with air or a vacuum in between
- stops heat loss by conduction and convection
how do solar panels insulate buildings
- solar cell panels absorb infrared radiation and use it to generate electricity
- solar heating panels absorb infrared radiation and use it to heat water
- both types reduce energy use
