Energy transfer by heating Flashcards
Explain why radiators are made of metal
Because metal is a better conductor of heat than non-metals
Which colour out of white,black and silver is best at radiating heat
Black as it is the best emitter of thermal energy.
How does convection from a radiator heat a room?
-Air particles next to radiator gain kinetic energy and speed up
-The distance between particles increases
-The hot air becomes less dense therefore it rises
In terms of energy transfer describe the thermal energy transfer between hot and cold water
-Hot water temperature decreases and cold water temperature increases
-The thermal energy transfer stops when thermal equilibrium is reached
-Some energy will be lost to the surroundings
What is conduction?
The process where vibrating particles transfer energy from their kinetic store to the kinetic store of neighbouring particles.
What is convection?
Occurs when the more energetic particles move from the hotter region to the cooler region, whilst transferring energy.
What is Radiation (Infrared)?
All objects are constantly emitting and absorbing infrared radiation, gives off and takes in thermal energy using IR waves.
What colour is best at absorbing and emitting thermal energy?
Black is better than white
What surface type is best at absorbing and emitting thermal energy?
Dull surface are better than shiny surfaces.
How do you prevent the transfer of heat energy?
By insulation
How does insulation prevent the transfer of heat energy?
It traps pockets of air, meaning the air can’t move so energy has to conduct very slowly through pockets of air.
An objects that hotter than it’s surroundings ______ more radiation than it ______ as it cools down
emits, absorbs
An object that’s cooler than it’s surroundings _______ more radiation than it ______ as it warms up
Absorbs, emits
What materials are bad conductors
Most non-metals e.g. plastics, wood, rubber
What materials are good condcutors?
Metals
Thick objects conduct ______
Slower
How do you reduce convection current in a liquid
Stop the liquid from flowing
Describe convection current using heater and water
-Water near the coils of heater are warmed up
-They gain more kinetic energy so move around faster
-The distance between particles is greater so becomes hotter and less dense
-Rises above the cooler, denser water
-The cooler water is then heated by the coils and repeats.
Can convection occur in solids?
No as the particles in solids can’t move but vibrate.
