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Chapters5&6Combined
5Sec5onsTotal
Energy&EnergyResources
WhatisEnergy
Sec5on1
• Energy‐istheabilitytocausechange.– Kine5c– Poten5al
• Kine)cenergy‐energyofmo5on– Increasesasanobjectmovesfaster
– Increasesasthemassofanobjectincreases.• Whereelsehaveyouheardthis?
• Poten5alenergy‐energystoredinanobjectduetoitsposi5on.
Energycomesindifferentforms:
• Thermalenergy‐increasesastemperatureincreases.
• Chemicalenergy‐energystoredinchemicalbonds.
• Radiantenergy‐lightenergy• Electricalenergy‐fromelectricity• Nuclearenergy‐comesfromthenucleusofanatom.
Poten5alenergyVS.Kine5cenergy• MeasuredinJoules.• Lawofconserva)onofenergy‐energycannotbe
createdordestroyed.
Poten5alenergy=50JKine5cenergy=0J
1.
2. Poten5alenergy=25JKine5cenergy=25J
Poten5alenergy=0JKine5cenergy=50J
3.
ThermalEnergy
• Manydifferentformsofenergycanbeconvertedintothermalenergy:– Diges5ngfood(chemicalenergy)‐‐>youstarttogethot&sweat(thermalenergy)
– Electricityflowingthroughawire(electrical)getshot(thermal).
– EVERYTHINGHASTHERMALENERGY!– Actsasamediumforotherenergytransfers
• Heatiron(thermal)getsredhot&glows(radiant)
Chemicalenergyexamples:
• Eatfood(bodyconvertsenergyfromfoodintoenergysoyoucanfunc5on)
• Putgasintoacar(convertsitintokine5cenergysoitcanrun)
Electricalenergy
• Causebyfastmovingpar5cles.• Thesepar5cleshavechargesthata`ractandrepeleachother.
• Thereinterac5oncauseswhatwecallelectricity.
• Mostmodernhomesrelyonelectricitytofunc5on.
• Teslavs.Edison
Lightorradiantenergy
• Lightenergy‐anythingthatproduceslight.• Fastmoving(186,000m/s)that’s416,082milesperhour.
• Ourmainsourceofradiantenergyis~93millionmilesaway…ittakes8min20sectoreachus.
Nuclearenergy
• Radioac5vedecay‐causesbyunstableelectrons&protonssplikngfromatoms
• Fusion‐2nucleifusetogethertoformaheavieratom
• Fission‐breaking2nucleiintolighternuclei• Starsarefueledbyfusion,powerplantsarefueledbyradioac5vedecay,nuclearweaponsusefission.
• Lead???
EnergyTransforma5ons
Sec5on2
Energyconstantly:
• Changesfromoneformtoanother• Ormovesfromplacetoplace
• Remember:energycannotbecreatedordestroyed‐thatisthelawofconserva5onofenergy
• Energycanbetransformedfromkine5ctopoten5alenergyandbacktokine5c.
P=0JK=10J
P=10JK=0J
P=5JK=5J
P=5JK=5J
P=0JK=10J
Machines
• Transformenergyfromoneformtoanother:– Chemicalenergycanbetransferredtokine5c,radiant,thermal,orelectrical
– Electricalenergycanbetransformedtokine5cchemicalelectricalorthermal
– Unlikeotherformsofenergy,THERMALenergyisnoteasytostore.
• Duringallenergytransforma5onssomeenergyislostduetoTHERMALENERGY.
• Ifyouareonamovingswingyouwilleventuallystopbecauseofairresistance,whichisfric5on,andyourkine5cenergyistransformedintothermalenergy.
ElectricityProduc5on:
• Inmostformsofelectricalenergygenera5oninpowerplantsthelast2stepsarethesame:– TheKine5cenergyofsteamturnsaTURBINE.– Thekine5cenergyoftheturbinepowerstheGENERATOR.
Ifyoudidn’tknowalready?
• Turbine‐setofsteam‐poweredfanbladesthatspinsageneratoratapowerplant.
• Generator‐devicethattransformskine5cenergyintoelectricalenergy.
PowerPlants
Sourcesofenergy
Sec5on3
• EnergycomesfromeithertheSUNorfromRADIOACTIVEATOMSwithintheEarth.
FOSSILFUELS
• Includeoil,naturalgas,&coal– FossilfuelscontainchemicalenergyfromtheSun’sradianenergyviaphotosynthesis.
– Nonrenewableresourcessuchasfossilfuelsareusedupfasterthancanbereplaced.• ourcoaltodaystartedoffasaplant(~300millionyearsago)
NuclearEnergy
• ComesfromthenucleiofURANIUMATOMS
h`p://www.pplweb.com/NR/rdonlyres/7C32A442‐3C42‐4978‐9BE4‐7128585258E0/0/nuclear.swf
Hydroelectricity• Comesfromthepoten5alenergyofwater.• Isarenewableresource– Meaningitisreplenishedcon5nuously
Alterna5veResources
• Maybesaferforpeople&theenvironment.• Willhelpconservefossilfuels
• Conservingenergywillhelppreventenergyshortages&allowfossilfuelstolastlonger.
SomeAlterna5veResources
• SolarenergycanbecapturedinthermalcollectorsorPHOTOVOLTAICcollectors.
• Geothermalenergy‐thermalenergycontainedinhotmagma.
• Windmillscangenerateelectricitywithoutpollu5ngtheenvironment
Chapter6
ThermalEnergy
Sec5on1
Temperature&ThermalEnergy
Temperature
• A.Temperatureisthemeasureoftheaveragevalueofthekine5cenergyofthemoleculesinasubstance
• Thehigherthetemperature,thefasterthemoleculesaremoving.
• 1.Objectstendtoexpandwithincreasedtemperaturebecausetheirmoleculesspeedupandmovefartherapart
• Objectscontractwhentheyarecooled.– a.theamountofexpansionorcontrac5ondependsonthematerialandtheamountofchangeintemperature
– b.Liquidsusuallyexpandmorethansolids.
examples
• Solids:– Inthesummer5mepowerlineswillsag,whereasinthewintertheywillbepulledmore5ghtly.
• Liquids:– Youprobablybeentoldnevertoputaglassbo`leofsodainthefreezer.Why?Itcanexplodeandyouwillhaveglassalloveryoufreezer.
• Gases:– Placeaballooninaverywarmroomanditwillexpand,thenplaceitinaverycoldroomanditwillshrink.
• 2.TemperatureiscommonlymeasuredusingaThermometer.
Thermometer
• A thermometer is a device that measures the temperature of things.
• The name is made up of two smaller words: – "Thermo" means heat – "meter" means to measure.
• One of the earliest inventors of a thermometer was probably Galileo.
• Galileo is said to have used a device called a "thermoscope" around 1600 - that's about 400 years ago!!
Howdoesathermometerwork?• When you look at a regular outside bulb thermometer,
you'll see a thin red or silver line that grows longer when it is hotter. The line goes down in cold weather.
• This liquid is sometimes colored alcohol but can also be a metallic liquid called mercury. Both mercury and alcohol grow bigger when heated and smaller when cooled.
• Inside the glass tube of a thermometer, the liquid has no place to go but up when the temperature is hot and down when the temperature is cold.
• Numbers are placed alongside the glass tube that mark the temperature when the line is at that point.
Anothertypeofthermometer
• "spring" thermometer. • A coiled piece of metal that is sensitive
to heat is used. • One end of the spring is attached to
the pointer. • As the air heats, the metal expands
and the pointer moves higher. • As the air cools, the metal contracts
and the pointer moves lower. • Typically, these type of thermometers
are less accurate than bulb or digital thermometers.
• 3.Thermometersneednumbersonascaletogiveitatemperaturereading.– a.Fahrenheitscale:• Waterfreezesat32°F
• Waterboilsat212°F
– b.Celsiusscale:• Waterfreezesat0°C• Waterboilsat100°C
– c.Theformulatoconverttemperaturefrom°Fto°Cis:
°C=(5/9)(°F‐32)
Ifitis78°Fintheclassroomhowmany°Cisit?°C=(5/9)(°F‐32)°C=(5/9)(78°‐32)°C=(.55555556)(46)°C=25.6°C
– d.Theformulatoconverttemperaturefrom°Cto°Fis:
°F=(9/5)(°C)+32Iftheclassroomwas21°Cwhatwoulditbein°F?
°F=(9/5)(°C)+32°F=(9/5)(21°)+32°F=(1.8)(21°)+32°F=(37.8°)+32°F=69.8°F°F=70°F
– e.TheKelvinscalegivesthetemperatureof0Ktothelowesttemperatureanobjectcanhave
– knownasABSOLUTEZERO
– f.FormulafortheKelvinscale
KelvintoCelsius
°C=K‐273_____________________________ CelsiustoKelvin
K=°C+273
• B.Anobject’sThermalenergyisthesumofthekine5c&poten5alenergyofallthemoleculesintheobject.– 1.Poten5alenergyisenergythatcanbeconvertedintokine5cenergy.• Poten5alenergychangesasmoleculesmoveclosertogetherorfartherapart.
– 2.Temperatureandthermalenergyaredifferentconcepts• Thermalenergyisrelatedtothequan5tyofmolecules.
Whyistemperatureandthermalenergydifferent?
• Letssayyouhad2glassesofwateratexactlythesametemperature.
• Youpouredthemintoapot.• Willthetemperatureofthewaterchange?NO• Willthethermalenergychange?YESwhy?BECAUSETHEREAREMOREMOLECULES.
• Howcanweknowthisforsure?– ITTAKESLONGERFORMOLECULESTOHEATUPORCOOLDOWNWHENTHEREAREMOREOFTHEMASOPPOSEDTOLESS.
– ITTAKESLONGERFORASWIMMINGPOOLOFWATERTOWARMUPINTHEHOTSUNCOMPAREDTOJUSTAGLASSOFWATER.
Sec5on2
Heat
Heat• A.Heatisthethermalenergythatistransferredfromoneobjecttoanotherwhentheobjectsareatdifferenttemperatures.– 1.Thermalenergyalwaysmovesfromwarmertocoolerobjects.
Howdoweknowthis?Easyexperiment:takesomethingwarmlikehotsoupandputanicecubeinit.Whathappenstotheicecube?
Kitchen5p:Youwanttodefrostafrozensteakwithoutitamicrowavecookingtheedgesevenwhenyouhaveitondefrost:placethefrozenmeatonacastironpan.Castironisheavy,thereforeithaslotsofmolecules.Theheatfromthemoleculeswilltransferintothemeatanddefrostyousteakinaboutanhours5meorless.
• 2.Thetransferofheatbydirectcontactbetweenthepar5clesofasubstanceiscalledCONDUCTION.
• Conduc5onoccursmosteasilyinsolids,wheremoleculesareclosetogether.
Ifyouplacedapotofwaterandametalspoononahotburner.Thespoonwillgetho`ermuchquicker.Commonsensesaysdon’tpickupthespoonunlessyouareusingahotpad.Sodon’ttrythisathome…ifyouhavenocommonsense!
• 3.HeattransferbyRADIATIONoccurswhenelectromagne5cwavescarryenergythroughspaceorma`er.
Whydoestheroadgethotinthesummer?BECAUSETHESUN’SRAYSTRAVELABOUT92MILLIONMILESTHROUGHSPACEDOSO.
Peoplegototanningbedsandbecometan.Why?BECAUSETHERADIATIONCOOKSTHEIRSKIN.
• 4.CONVECTIONdescribesthetransferofthermalenergybythemovementofmoleculesfromonepart(warmer)ofthematerialtoanother(cooler)part.
– a.Convec5onoccursnaturallyashotgasorliquidmovesfromoneplacetoanother
– Windiscausedbyconvec5onintheair
– Risingwarmerairformsaconvec5oncyclewithfallingcoolingair.
• WherewecanseeConvec5ontakingplace.• Wind:airheatsuplandinoneareamorethananother.Likeyousawontheotherpage.
• Inthemantle,IntheSun,EveninaBowlofsoup.
• B.CONDUCTORSarematerialsthattransferheatreadily.– Metalssuchascopperandgoldarethebestheatconductors
• C.INSULATORSarematerialsthatdoesnottransferheatreadily.– Liquidsandgasesareusuallybe`erinsulatorsthansolids.
• D.Objectsabsorbheatatdifferentratesdependingonwhatmaterialstheyaremadeof.– 1.SPECIFICHEAT‐amountofheatneededtoraisethetemperatureof1kgofasubstanceby1°C
– 2.Moreheatisneededtochangethetemperatureofamaterialwithahighspecificheat(suchaswater)thanonewithalowspecificheatsuchassand.
Land&SeabreezesDay5mewhenthesunisshiningthegroundheatupmuchfasterthanthewaterdoes.
80°F70°F
60°F70°F
Night5methelandcoolsmuchquickerthanthewaterdoes
• E.ThermalPollu)oncausedbyaddingwarmerwatertoabodyofwater.– 1.Thermalpollu5oncankillfishandotheraqua5corganismsduetoareduc5oninoxygeninwarmerwater.
– 2.Thermalpollu5oncanbereducedbycoolingwaterfromfactories,powerplants,andrunoffbeforeitisreleasedintoabodyofwater.