Energy (convection, conduction & radiation/heat transfer) Flashcards
what is convection?
- Where gases and liquids are free to move around, and this allows them to transfer heat.
- When the more energetic particles move from hotter areas to cooler areas and take energy with them.
what is a poor conductor?
An insulator
what surfaces are good absorbers or infra-red radiation?
black/matt surfaces
what surfaces are good reflectors of infra-red radiation?
white/shiny surfaces
what gives off infra-red radiation?
everything
How does a vacuum flask reduce convection & conduction?
as there is no particles in it, so this prevents air entering or leaving the flask.
what surfaces are slow to emit infra-red radiation?
light/shiny surfaces
what is radiation?
heat energy tends to move away from hot objects to it’s colour surroundings.
what is conduction?
where vibrating particles pass on their extra kinetic energy to neighbouring particles.
what is kinetic theory?
where particles move in solids, liquids and gases.
what are convection currents?
Changes in density
- hot less dense air rises, and denser cool air replaces it
What does the stopper do in a vacuum flask?
- Prevents convection currents escaping
- Uses conduction to keep liquid inside hot.
What does the silvering of a flask do?
Keeps liquid hot because shiny surfaces are good for radiation.
What does the double walled glass do in a flask?
Reduces conduction
What is specific heat capacity?
the amount of energy needed to raise the temperature by 1◦c of 1 kg (of substance)
