heatvs tem2

8/20/2019 heatvs tem2

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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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