heat

temperature measured

degree celcius

si unit of temperature

kelvin ; k

expansion gap for train tracks

trains track may buckle if it is not present

two different materials of expansion and contraction

the different materials expands at different rates when heated

conduction

transfer of heat energy without movement of medium. can happen to solid, liquid and gas

convection

transfer of heat from one place to another by movement of medium. only can happen to liquid and gas. sets up an convection current that let the colder denser air float and warmer air float up

radiation

transfer of energy from a hotter body to a cooler body without the need of a medium and can happen to solid, liquid and gas

conduction rate

different materials conduct heat and different rates

radiation good absorbers of heat

dark colour, rough surface, large surface area

poor absorbers of heat

bright colour, smooth surface, small surface area

thermal conductors

silver, copper, brass, aluminium

thermal insulators

air, styrofoam, fat, water