Heat Transfer Notes



Heat (thermal energy) is created by the movement of particles (atoms) that produces heat.
Heat (thermal energy) is transferred from one object to another when the objects are at
different temperatures.
Thermal energy always moves from warmer to cooler objects.
Conduction
o Conduction is the
transfer of heat by
direct contact
(particles collide)
o Conduction occurs
most easily in solids
and liquids
o Conductors:
substances that
transfer thermal
energy very well
o Example: metals
o Insulators:
substances that do
not transfer heat
very well
o Example: wood,
paper, plastic, foam
Convection
o Convection is the flow of
currents in a liquid or gas
o A current is created when
the warmer (less dense)
material rises forcing the
cooler (more dense) material
to sink
o Convection is a cycle in
nature responsible for most
winds and ocean currents.
o Example: Hot water rising in
a pool and cold water
sinking. The water on top of
the pool is warmer, the
bottom is cooler.
o Basement in a house is
cooler than the attic
Radiation
o Radiation is heat transfer
through space by
electromagnetic waves
o Radiation can occur in
empty space, as well as
in solids, liquids and
gases.
o Waves such as visible
light, infrared, and
ultraviolet light are forms
of radiation.
o Examples: Heat from a
light bulb, microwave
oven, getting a sunburn,
cooking hamburgers
over a charcoal flame