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Chapter 10 (briefly!)
HEAT TRANSFER
Energy transfer
(3 TYPES)
Conduction
Convection
Radiation
Conduction

Heat transfer from one particle to the next
– Particles at the warm end move faster and this
then causes the next particles to move faster and
so on.

In this way heat in an object travels from:
the HOT end
the cold end
Conduction cont…

Occurs when particles hitting each other
and so energy is transferred.

Can happen in solids, liquids and gases

Happens best in solids-particles very close
together
Conductors
Conductors: Materials that conduct heat
quickly
 All metals are good conductors of heat

– Pans for cooking are usually made with a
copper or aluminium bottom and plastic
handles (plastic is a poor conductor…you
won’t get burned)
Insulators/poor conductors

Insulators: materials that conduct heat
slowly or poorly
– Glass, wood, plastic and rubber are poor
conductors (good insulators)
Convection

Convection: Heat transfer by movement of
fluids

Convection Currents: heat carried by the
particles.
Convection Currents

Hot liquids and gases expand and rise
while the cooler liquid or gas falls (all
caused by a difference in densities!)
2. Goes across
3. Then down
1. Hot air rises
4. And across
Radiation

Radiation: Transfer of heat directly from the
source to the object by a wave, travelling as rays.
– Heat radiation is also known as
INFRA-RED RADIATION

Heat transfer by radiation does not need particles
to occur and is the only way energy can be
transferred across empty space
Emission of Radiation (canned
heat lab 2)
Hotter objects emit (give out) heat
 Different surfaces emit heat at different speeds
 A dull black surfaces loses energy more
quickly – it is a good radiator
 A bright shiny or white surface is a poor
radiator

– Survival kits have shiny heat blankets in them,
covering in a shiny blanket reduces radiation and
therefore heat loss.
Emitters of heat
Bright shiny can
Poor radiator
Dull black can
Good Radiator
Absorption of Heat (canned
heat lab 1)
Cooler
objects absorb (take in) heat
Substances
Dull,
absorb heat at different speeds
black surfaces absorb heat quickly
Bright,
shiny surfaces absorb heat slowly
In
hot countries, people wear bright white
clothes and paint their houses white to reduce
absorption of energy from the sun.
Gas/Oil
storage tanks are sprayed silver to
reflect sun’s rays
Absorbers
Shiny, bright can
Poor absorber
Dull black can
Good absorber
Evaporation is Cooling!!
Sweating is cooling…
dogs have no sweat glands, so they pant
Chapter 10 bonus questions
Why is boiling a cooling
process??