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Kinetic molecular theory (aka KMT): the theorythat all matter is made up of particles (atomsand molecules) moving constantly in randomdirections
Kinetic energy: the energy of a particle due to itsmotion.
When particles collide, kinetic energy is transferredbeteen them (like ho a boling ball transfers energyto the boling pins it hits)
Kinetic Molecular TheoryKinetic Molecular Theory
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solid liquid gas
The particles of a substance move di!erentlydepending on the state of the substance.
"n solids, particles vibrate slightly but do not changeposition.
"n li#uids, particles vibrate more and move around
ithin a set volume. "n gases, particles vibrate greatly and move aroundto take all volume available.
Kinetic Molecular TheoryKinetic Molecular Theory
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Temperature Temperature
Temperature is a measure of theaverage Kinetic $nergy of theparticles in a substance.
◦ %emember K$ is the energy of motion.
◦ The higher the average Kinetic $nergy,the faster the particles move
◦ Temperature and &eat are NOT thesame thing
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Temperature: the measure of the average kineticenergy of all particles in a sample ofmatter.
• The movement of particles is hat e measure astemperature.
• Temperature is measured using ' di!erent temperaturescales:
ahrenheit, elsius, and Kelvin
Temperature Temperature
ahrenheit: *st invented scale
elsius: Waterfree+ing point -boiling point *--
Kelvin: scale based on absolute +ero(here particles have no kinetic
energy)
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Temperature /cale omparisons Temperature /cale omparisons
373 K = 100°C
37°C = 99°F
298 K = 25°C
273 K = 0°C-40°C = -40°F
0 K = -273°C
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Thermal $nergy Thermal $nergy
Thermal energy: the total energy of all theparticles in a substance.
Thermal energy = all kinetic energy + all potential energy
Kinetic energy: the energy of a particle due to itsmotion
0otential energy: the stored energy of an ob1ect orparticle due to its position or state
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Thermal $nergy Transfer Thermal $nergy TransferConduction: the transfer of heat by direct contact
• &eat is transferred from matter ith a higher temperatureand greater kinetic energy to matter ith loer temperature and less kinetic energy.
$2ample: a cold spoon arms up hen placed in a cup ofhot co!ee
• Thermal conductors (such as metals) transfer heat easily.
• "nsulators (such as ood and air) do not transfer heat easily.
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&eat Transfer&eat Transfer
&eat can be transferred in ' ays:
Conduction Convection Radiation
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&eat Transfer&eat Transfer&eat onductors
◦ 3ood thermal conductors transfer heatrapidly
◦ Metals are good thermal conductors
Radiators are metals that transferthe heat in the ater to the air
Fr!in" #ans transfer heat fromthe sto$e to the food
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&eat Transfer&eat Transfer Thermal "nsulators◦ 0oor thermal conductors of heat.◦ 4sbestos, cork, ceramic, cardboard, and
5berglass are e2amples of thermalinsulators
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onductiononduction
Takes place between solids or solids with
liquids
◦ 0articles vibrating or moving faster transfer
some of their energy to nearby atoms
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onductiononductionWhen particles collide and the faster ones pass some
of their energy on to the cooler ones.
This results in a change in energy for each particle
This causes the fasterones to slow down andcool
The slower ones speed upand heat up
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onvectiononvection
6ccurs in luids(li#uids andgases)
aused by achange in
density due to achange intemperature.
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Radiation: the transfer of heat by electromagnetic avesthat carry radiant energy
• &eat radiation infrared radiation.
$2ample: eeling arm hen standing ne2t to a camp5re
• /olar radiation: the transfer of
radiant energyfrom the sun
Earth’s energy sources:
*./olar radiation 7 $isi%le li"ht& infrared
radiation& and other t!#es of radiation
8.%esidual thermal energy from henthe $arth as formed is slolyreleased
'.9ecay of underground radioactive
elements produces energy
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%adiation%adiation The transfer of energy due to "nfrared
and other electromagnetic rays.
%adiation can travel through space.
4ll things radiate heat.
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Thermal $2pansion Thermal $2pansionWhen ob1ects heat up their particles move
faster, hit others harder, and bouncefurther, creating more empty spacebeteen the particles.
4s a result, the entire substance e2pands.
This is knon as thermal e2pansion
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$2amples of Thermal$2amples of Thermal
$2pansion$2pansion
%oads crack asthey e2pand in theheat
6n bridges andother sensitivesections, e2pansionpanels allo it toe2.
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Thermal $2pansion continued Thermal $2pansion continued
The li#uid in a thermometere2pands as it arms.
This causes it to head up the tubeand tell you the temperature
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