Eventually objects reach the temperature
of their surroundings
The unit of temperature is
degrees Celsius
Heat is a measurement of energy
The unit of energy is joules
Heat flows from a warmer to a
colder body
When energy flows away from a warm
object it's temperature decreases
Temperature is a measure of how hot something is
When a substance is heated; it's
temperature increases and particles vibrate
faster. The average kinetic energy increases.
Temperature is a measure of the average
kinetic energy of particles
Heat is a measure of the total
internal energy of an object
Energy needed to change the
temperature of a liquid depends on 3
things; it's mass, what the liquid is and
the rise in temperature
Heat is needed to melt a solid at
it's melting point. Heat is needed to
boil a liquid at it's boiling point
Latent Heat- the heat needed to change
a state without a change in temperature
When an object is heated and it's
temperature rises, energy is transferred
Specific heat capacity (J/kg degrees Celsius) - the amount of energy needed to
change the temperature of one kilogram by one degree celsius
energy transferred= mass x specific heat capacity x temp change
Specific Latent Heat (J/kg) - the amount
of energy needed to change the state of
one kilogram of a substance without a
change in temperature
energy transferred= mass x specific latent heat
When a substance changes state from solid to
liquid or liquid to gas, energy is needed to break the
bonds that hold the molecules together. This is why
there is no change in temperature
Keeping homes warm
INSULATION- Air is a good insulator. Because there is air
trapped inside coats, it does not allow energy to
transfer from a warmer body to cold
surroundings
CONDUCTION- Particles in a solid are close together so energy is
easily transferred as the particles vibrate
INFRA RED RADIATION- Reflected from a shiny reflector. Used for cooking or generating
electricity. A device at the focus of the reflector converts heat energy into electricity. It's absorbed
by dull or rough surfaces
Electromagnetic wave. Energy transfer by infra red radiation does not need a material. Energy can be transferred through a vacuum as in space
A solid is a good conductor of heat and a vacuum is the best insulator because there are no air particles
CONDUCTION- Electrons in metals can leave their atoms and move about freely. The atoms
become charged ions. These ions are close together and are continually vibrating. When heated
kinetic energy of the vibrations increases
CONVECTION- When a gas is heated it expands. The
same mass of gas occupies a greater volume. As the
volume increases, the density decreases
density (g/cm3) = mass/volume
Air is a good convector. As air in the cavity is warmed it rises
through the cavity. Colder air falls and a convection current is
formed. The convection current transfers energy. The air
trapped in the foam stops convection from taking place
Energy efficiency= useful energy output (x100)/ total energy input
The home is the energy source and the atmosphere is the sink
A sink is a large object that does not change it's temperature by
a noticeable amount when it absorbs energy from the source
Payback time= cost of insulation/ annual saving
Energy from a coal fire warms the room by radiation. The hot air
rises up the chimney by convection and energy is transferred
through the surrounding bricks by conduction