Heating and Thermal Energy

to take in

to give out

a liquid or gas

the transfer of thermal energy by conduction, convection, radiation from a warmer object to a cooler object

EM waves emitted by all objects
the hotter the object, the more infrared it emits

unit of temperature

Primarily happens in solids
Good conductors are metals and graphite
Poor conductors (insulators) are wood and plastic
Thermal conduction is the process where vibrating particles transfer energy from their kinetic energy store to the kinetic energy stores of the neighbouring particles by colliding with them

Metals have delocalised electrons which are free to move through the structure, therefore they can transfer the kinetic energy much faster than collisions of vibrating particles so the metal starts to heat up as the transfer of the KE of the particles results in the transfer of thermal energy through the metal

Clamp different lengths of copper rods to clamp stand and attach the same amount of vaseline to one end of the rod and attach a pin
Using a bunsen burner, heat the end of each copper rod that doesn't have vaseline, and time with a stopwatch how long it takes for the pin to fall off
Repeat each length at least three times and average
Plot a graph with the length of the copper rod against time taken, drawing a line of best fit
Calculate the rate of conduction by finding gradient of the line

Heat transfer in fluids

Thermal energy means the particles have more KE
This means the particles move faster, collide more frequently and their average separation increases
The fluid becomes less dense
Less dense regions of fluid will rise above more dense regions
On moving away from the heat source, fluid cools, particles move less, density of fluid increases again and the fluid sinks
This creates a convection current

Land heats up faster
Warm air above land rises (convection)
Cooler air from above ocean replaces rising air

Land cools down more quickly than sea
Air above land sinks
Air rises above sea
Cooler air from above land replaces rising air

All objects above absolute zero are continually emitting and absorbing radiation
The hotter the object, the more radiation it emits

Black, matte surfaces are good emitters, good absobers and poor reflectors
White/silver, shiny surfaces are poor emitters, poor absorbers and good reflectors

Conduction: layer of air or vacuum; material that is a poor conductor or good insulator with low thermal conductivity
Convection: reduce fluid movement and prevent convection current from forming; material with air pockets (foam, fur, bubble wrap); layers
Radiation: poor emitter (shiny, white surface), good reflector (keeps heat inside)

deposition

sublimation

-273 degrees celcius
0 kelvin (K)
Coldest that anything can ever get as the particles have as little in their kinetic stores as it's possible to get

The energy in joules required to increase the temperature of 1kg of a substance by 1 degree Celcius

change in energy= mass x specific heat capacity x change in temperature

Because of the heat loss to the environment so the SHC is overestimated