P1.1.3 (Energy transfer by heating) Flashcards
In what 3 ways can heat be transferred?
Conduction
Convection
Radiation
What are the best conductors of heat?
Metals
How is heat conducted?
In metals, electrons can leave their atoms, this leaves behind ions. The closely packed ions vibrate together and when the metal is hotter the more kinetic energy the vibrations have. The free electrons transfer thekinetic energy as they move throughout the metal and collide with ions.
Why aren’t liquids and gases very good conductors?
Because their particles aren’t packed closely together
Where does convection mostly take place?
Convection mostly takes place in liquids and gases
Why can liquids and gases transfer energy through convection?
Their particles are more spread out and easy to move as they are both fluids. When the liquid or gas is heated it expands as the particles have more energy and spread out more.
How is heat transferred through convection?
Due to being more spread out, the liquid or gas in hot areas is less dense and so it rises into the colder areas. The colder, more dense fluid falls into the warmer areas. The cold fluid is heated and rises while the less dense fluid cools and falls, a current is formed.
Why can we still feel the suns heat on earth even though space is a vacuum?
Infrared radiation involves no particles, only waves, so it can travel through a vacuum.
What surfaces are the best for absorbing and emitting thermal radiation?
Dark, matt surfaces
Which colours will keep you coolest in the summer?
Light/white colours as it absorbs the least heat.
If two objects are made from the same material and with an identical volume but one is thin and flat and the other is fat, which will radiate heat energy faster?
The thin flat object will, which is why radiators are thin and flat.
Why aren’t radiators painted dark black to be able to emit more heat?
Because they actually spread more heat energy through convection.
In which ways can heat be lost from a house?
Through the roof Through the windows Through the gaps around the door Through the walls Through the floor
How can heat loss be reduced in a house?
Curtains, double glazing, draught excluder, insulation, carpets
How does double glazing reduce heat loss?
The gap between the two panes of glass is filled with air. Air is a is a poor conductor of heat as the particles are so spread out and so heat loss by conduction is reduced.
