P2 Flashcards
SPECIFIC HEAT CAPACITY PRACTICAL
REFER TO GOODNOTES
What is specific heat capacity?
It is the amount of energy needed to raise the temperature of 1kg of a substance by 1°c.
Do some materials need more energy to increase temp?
Yes. More energy needs to be transferred to the thermal energy store of some materials to increase their temperature than others.
(Materials that need lots of energy in thermal energy store to heat up they also need lots to cool down. They store lots of energy.)
What is conduction?
Conduction is the process where vibrating particsles transfer energy to enighbouring particles.
Describe conduction through a solid
.Energy transferred to object by heating is transferred to thermal store of object.
.This energy shared across kinetic energy stores of particles in object.
The particles in part of the object being heated vibrate more + collide with each other.
.collisions cause energy to be transferred between particles’ kinetic energy stores.
This is conduction.
This process continues through the object
until energy is transferred to other side
of object.
.then usually transferred to thermal store of surroundings.
Thermal conductivity is measure of how quickly energy is transferred through a material.
Materials with high thermal conductivity transfer energy between their particles quickly.
What is convection?
Convection is where eneegetic particles move AWAY from HOTTER to COOLER REGIONS in only liquids and gases
Describe how convection occurs in liquids and gases?
: Energy is transferred by heating to thermal store of liquid/gas. This is chared across kinetic stores of gas/liquid particles.
: the particles are able to move and they move faster in hotter regions and the gap between particles increases. Causing densityof heated region to decrease.
: cause liquids/gases can flow, the warmer and less dense region will rise above denser, cooler regions. If there is a constant heat source, a convection current can be created
How do radiators create convection currents?
:: heating a room with radiator relies on creating convec currents in air of room.
:: energy is transferred from radiator to nearby air particles by conduction.
:: air by the radiator becomes warmer and less dense.
:: this warm air rises and is replaced by cooler air. The cooler air is then heated by the radiator
:: at same time, previously heated air transfers energy to the surroundings. It cools, becomes denser and sinks.
:: this cycle repeats
Reducing unwanted energy transfers: Lubrication (reduces frictional force)
::: When something moves, usually there is at least 1 frictional force acting against it. Causing some energy to be dissipated.
:::When objects are rubbed together, lubricants can be used to reduce the friction between them.
:::Lubricants are usually liquids(oils) so can flow easily.
Insulation reduces the rate of energy transfer by heating—— (how to prevent energy loss)
. Have thick walls made of material of low thermal conductivity. Thicker the walls and the lower the thermal conductivity, the slower the rate of energy transfer will be.
Thermal insulation examples: (cavity walls, double glazed windows, cavity wall insulation, loft insulation
Cavity walls, made up of an inner and an outer wall with an air gap in the middle. The air gap reduces the amount of energy transferred by conduction through the walls.
Cavity wall insulation, where the cavity wall air gap is filled with a foam, can also reduce energy transfer by convection in the wall cavity
Double-glazed windows - work in the same way as cavity walls - they have an air gap between two sheets of glass to prevent energy transfer by conduction through the windows.
Loft insulation can reduce convection currents being created in lofts
Insulation RP
GOODNOTES
