P8 Heat Flashcards
how is heat transferred by CONDUCTION?
particles VIBRATE + BUMP into each other → vibration (energy) spreads
how is heat transferred by CONVECTION?
particles MOVE from place to place
how is heat transferred by RADIATION?
INFRARED WAVES
no particle required
why are metals good conductors?
- tightly packed ions: pass vibration/energy faster
- free electrons: move, collide, pass energy
why does sun’s thermal energy only reach us through radiation?
space is VACUUM → NO PARTICLE means no conduction/convection, but radiation needs no particle
explain CONVECTION CURRENT
Hotter at bottom → more KE → particles move more/further apart → less dense → rises
Cools at top → less KE → particles move less/closer together → more dense → sinks
in which medium does CONDUCTION take place?
solid, liquid, gas
in which medium does CONVECTION take place?
liquid, gas (fluids)
what surface is GOOD at absorbing and emitting radiation?
dull/matt
black
what surface is BAD at absorbing and emitting radiation?
shiny
white
what surface is GOOD at REFLECTING radiation?
shiny
white
how is a thermos flask designed to minimize heat loss?
- PLASTIC LID prevents heat loss through conduction and convection
- VACUUM WALLS prevent heat loss through conduction and convection
- SHINY OUTSIDE prevents heat loss through radiation (poor emitter)
what is thermocouple used for?
very high or rapidly changing temp.
how does thermocouple work?
TWO DIFFERENT METALS
heat joint → V created (directly related to temp.)
thermocouple: why is a cold beaker with ice needed?
FIXED REFERENCE TEMP. for the COLD JUNCTION because ice water is 0˚C
