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Moving and Storing Heat
Heat= Measure of energy IF THERE'S A DIFFERENCE OF TEMPERATURE BETWEEN
Temperature= Measure of hotness 2 PLACES, ENERGY WILL FLOW BETWEEN
Energy tends to flow from hot to cold...
SPECIFIC HEAT CAPACITY: how much energy a substance can store
Energy= Mass x SHC x Temperature Change
Eg. How much energy is needed to heat 2kg of water from 10°C to 100°C?
ANSWER: energy needed= 2 x 4200 x 90 = 756 000 J (NEVER FORGET UNITS)
Eg. An empty 200g aluminuim kettle cools down from 115°C to 10°C, losing 19 068 J
of heat energy. What is the specific heat capacity of aluminium?
ANSWER: SHC = Energy 19 068
Mass x SHC x Temp Ch 0.2 x 105 = 908J/Kg/°C…read more

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Melting and Boiling
When you heat a liquid the heat energy makes the particles move
Heating
faster. Eventually when enough of the particles have enough energy
ga to overcome their attraction to each other, big bubbles of gas form
boilin s in the liquid ­ BOILING
g
melting liqui When you heat a solid heat energy makes the particles vibrate
d faster until eventually the forces between them are overcome and
soli the particles start to move around ­ MELTING
d
Cooling When a substance is melting or boiling, you're still putting in energy
ga but the energy is being used for breaking intermolecular bonds
s condensing rather than raising the temperature (hence flat spots on graph)
liqui freezing When a substance is condensing or freezing, bonds are forming
d between the particles, which releases energy. This means the
temperature doesn't go down until all the substance has turned
soli into a liquid (condensing) or a solid (freezing).
d…read more

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Conduction and Convection
Conduction: the process where vibrating particles pass on extra kinetic
energy to neighboring particles.
Convection: the more energetic particles move from the hotter region
to the cooler region, and take their heat energy with them.
Specific Latent Heat ­ the energy needed to change state...
The amount of energy needed to melt 1kg of a substance without changing its temperature
The amount of energy needed to boil 1kg of a substance without changing its temperature
ENERGY = Mass x Specific Latent Heat
E.g. The specific latent heat of water for melting is 334 000 J/Kg. How much energy is
required to melt an ice cube of mass 7g at 0°C?
ANSWER: 0.007 X 334 000 J = 2338 J…read more

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Conduction
· Occurs mainly in a solid
· The particles are held tightly together so when one particles vibrates,
it bumps into the other particles nearby and quickly passes the
vibrations on.
· Particles that vibrate faster than others pass on their extra kinetic
energy to neighboring particles. These then vibrate faster themselves.
· This process continues throughout the solid and gradually the kinetic
energy or heat is spread all the way through the solid.
· This causes a rise in temperature on the other side.
· Liquids and gases conduct heat more slowly than solids. This is
because the particles are not held as tightly together therefore air is a
good insulator.
· Metals are really good conductors of heat and non metals are good
for insulating things.…read more

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Convection
· Occurs mostly in fluids (liquid or gas)
· When you heat up a fluid the particles move faster and the fluid expands becoming
less dense
· The warmer, less dense fluid rises above its colder, denser surroundings
· As the warm fluid rises, cooler fluid takes its place. As this process continues, you
end up with a circulation of heat (convection current). This is how an immersion
heater works.
· Radiators rely on convection to make the warm air circulate around the room.
· Convection cant happen in solids because the particles can't move ­ they just
vibrate on the spot.
· To reduce convection you need to stop the fluid moving. (e.g.. Clothes, blankets,
cavity wall insulation all work by trapping pockets of air. This means the air can't
move so the heat has to conduct very slowly through the pockets of air, as well as
the material in between.…read more

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