Heat can be transferred from place to place by conduction,
convection and radiation. Dark matt surfaces are better at absorbing
heat energy than light shiny surfaces. Heat energy can be lost from
homes in many different ways and there are ways of reducing these
heat losses.
Annotations:
Conduction: the transfer of heat energy through a material - without the material itself moving.
Convection: the transfer of heat energy through a moving liquid or gas.
Radiation: electromagnetic radiation emitted from a hot object.
INFRARED RADIATION
All objects emit (give out) and absorb thermal radiation,
which is also called infrared radiation. The hotter an
object is, the more infrared radiation it emits.
Infrared radiation is a type of electromagnetic radiation,
which involves waves rather than particles. This means that
unlike conduction and convection, radiation can even pass
through the vacuum of space.
This is why we can still feel the heat of the sun,
although it is 150 million km away from earth.
KINETIC THEORY
The kinetic particle theory explains the properties of the different
states of matter. The particles in solids, liquids and gases have
different amounts of energy. They are arranged differently and move
in different ways.
CONDUCTION
Heat energy can move through a substance by conduction. Metals
are good conductors of heat but non-metal and gases are usually
poor conductors of heat.
Poor conductors of heat are called insulators.
Heat energy is conducted from the hot end of an
object to the cold end.
Heat conduction in Metals: the electrons in
piece of metal can leave their atoms and
move about in the metal as free electrons.
The parts of the metal atoms left behind are
now charged metal ions.
The ions are packed closely together and they
vibrate continually. The hotter the metal, the more
kinetic energy these vibrations have. This kinetic
energy is transferred from hot parts of the metal to
cooler parts by the free electrons. These move
through the structure of the metal, colliding with ions
as they go.
CONVECTION
Liquids and gases and fluids. The particles in these fluids
can move from place to place. Convection occurs when
particles with a lot of heat energy in a liquid or gas move
and take the place of particles with less heat energy.
Heat energy is transferred from hot places to cooler places by
convection.
Liquids and gases expand when they are heated.
This is because the particles in liquids and gases move
faster when they are heated than they do when they
are cold. As a result, the particles take up more
volume. This is because the gap between particles
widens, while the particles themselves stay the same
size.
The liquid or gas in hot areas is less dense than the liquid or
gas in cold areas, so it rises into the cold areas. The denser
cold liquid or gas falls into the warm areas. In this way,
convection currents that transfer heat from place to place are
set up.