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Vicphysics Teachers’ Network Zeroth Law of Thermodynamics A late addition to physics, for completenessA late addition to physics, for completeness A definition of temperature.A definition of temperature. “All heat is of the same kind”“All heat is of the same kind”TRANSCRIPT
Vicphysics Teachers’ Network
• New concepts
• Practical Activities
• Assessment Tasks
Prepared with material from NPL (UK), IPCC, BOM (Aus)Prepared with material from NPL (UK), IPCC, BOM (Aus)
Thermodynamics
Vicphysics Teachers’ Network
Thermodynamics: New ConceptsThermodynamics: New Concepts
Zeroth law of ThermodynamicsZeroth law of Thermodynamics Internal EnergyInternal Energy First Law of ThermodynamicsFirst Law of Thermodynamics Thermal Radiation: Thermal Radiation:
– Wien and Stefan & BoltzmannWien and Stefan & Boltzmann Energy FlowEnergy Flow
Vicphysics Teachers’ Network
Zeroth Law of ThermodynamicsZeroth Law of Thermodynamics• A late addition to physics, for completenessA late addition to physics, for completeness• A definition of temperature.A definition of temperature.• ““All heat is of the same kind”All heat is of the same kind”
Vicphysics Teachers’ Network
Internal EnergyInternal Energy
You are heating a substance, what happens to its atoms You are heating a substance, what happens to its atoms and molecules?and molecules?Gas:Gas:
Monatomic: NeMonatomic: NeDiatomic: ODiatomic: O22
Multi atom: HMulti atom: H22OOLiquid:Liquid:Solid:Solid:Atoms and molecules have different types of energy.Atoms and molecules have different types of energy.Only Only translationaltranslational kinetic energy relates to Temp. kinetic energy relates to Temp.
Vicphysics Teachers’ Network
Internal energy Internal energy
Vicphysics Teachers’ Network
First Law of ThermodynamicsFirst Law of Thermodynamics• Energy is conserved, Energy is conserved, • but done quantitatively and best with a gas examplebut done quantitatively and best with a gas example• Three terms:Three terms:
• Energy can be added Energy can be added toto a a systemsystem, Q, Q• Work can be done Work can be done byby a a systemsystem, W, W• Internal energy can change as a result, Internal energy can change as a result, UU
U = Q – WU = Q – WOnly simple calculations.Only simple calculations.
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Energy Transfer by RadiationEnergy Transfer by Radiation
Radiation and Greenhouse EffectRadiation and Greenhouse EffectA significant section with many new physics concepts:A significant section with many new physics concepts:
• SpectrumSpectrumTemperature meansTemperature meansatoms jiggleatoms jiggleelectrons jiggleelectrons jiggle accelerating chargesaccelerating charges electromagnetic radiationelectromagnetic radiation
• Freq, wavelength Freq, wavelength • Energy, powerEnergy, power Increasing frequency
Decreasing wavelength
Increasing energy
Vicphysics Teachers’ Network
Energy Transfer by RadiationEnergy Transfer by Radiation
Radiation and Greenhouse EffectRadiation and Greenhouse Effect• Increased temperature meansIncreased temperature means
atoms jiggle fasteratoms jiggle fasterelectrons jiggle fasterelectrons jiggle fasterhigher frequency radiationhigher frequency radiationhigher energyhigher energy
Vicphysics Teachers’ Network
Thermal RadiationThermal RadiationWien’s Law: Wien’s Law: How does the wavelength of maximum intensity vary with How does the wavelength of maximum intensity vary with
temperature? temperature? (CBMR)(CBMR)
maxT = constant
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Thermal RadiationThermal RadiationStefan-Boltzmann Law: Stefan-Boltzmann Law: How does total energy emitted How does total energy emitted
vary with temperature?vary with temperature?Consider Area under the graph: Consider Area under the graph: PowerPower ∝ ∝ TT44..
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What determines the Earth’s surface temperature?What determines the Earth’s surface temperature?
Light reflected from EarthAverage Value
100 watts per square metre
Light from the SunLight from the SunAverage ValueAverage Value
340 watts 340 watts per square metreper square metre
Vicphysics Teachers’ Network
What determines the Earth’s surface temperature?What determines the Earth’s surface temperature?
Light from the Sun heats the Earth…Light from the Sun heats the Earth…
Average Value 240 watts per square
metre
Average Value240 watts
per square metre
Vicphysics Teachers’ Network
What determines the Earth’s surface temperature?What determines the Earth’s surface temperature?
How hot must the Earth be to radiate 240 W/mHow hot must the Earth be to radiate 240 W/m22 ? ?
Average Value 240 watts per square
metre
-18 °C
Vicphysics Teachers’ Network
What determines the Earth’s surface temperature?What determines the Earth’s surface temperature?
-18 °C
Actual average surface
temperature
33 °CGreenhouse
EffectTemperature for radiation
balance
+15 °C
Vicphysics Teachers’ Network
What determines the Earth’s surface temperature?What determines the Earth’s surface temperature?
The Earth’s surface is The Earth’s surface is 33 °C 33 °C warmer warmer than it would be if it had no atmospherethan it would be if it had no atmosphere
So So howhow does the atmosphere does the atmosphere warm the Earth’s surface?warm the Earth’s surface?
Vicphysics Teachers’ Network
What determines the Earth’s surface temperature?What determines the Earth’s surface temperature?
Nitrogen (NNitrogen (N22),), Oxygen (OOxygen (O22)) & & Argon (Ar) Argon (Ar) • More than 99% of the atmosphere More than 99% of the atmosphere
• These molecules have These molecules have oneone or or twotwo atoms atoms
• They block some They block some ultra-violetultra-violet light, but light, but
• Allow Allow infra-redinfra-red and and visiblevisible radiation through. radiation through.
Vicphysics Teachers’ Network
What determines the Earth’s surface temperature?What determines the Earth’s surface temperature?
With an atmosphere of With an atmosphere of Nitrogen Nitrogen OxygenOxygen & & Argon, Argon, what would be what would be
the surface temperature?the surface temperature?
-18 °C
Average Value 240 watts per square
metre
Average Value240 watts
per square metre
Vicphysics Teachers’ Network
What determines the Earth’s surface temperature?What determines the Earth’s surface temperature?
Greenhouse warming is caused by Greenhouse warming is caused by
Water (HWater (H22O)O)
Carbon Dioxide (COCarbon Dioxide (CO22))
Vicphysics Teachers’ Network
What determines the Earth’s surface temperature?What determines the Earth’s surface temperature?
What is special about What is special about HH22O and COO and CO22??
• Their molecules have Their molecules have threethree atoms, atoms,
• Their Their natural frequenciesnatural frequencies of vibration are in the of vibration are in the infra-red,infra-red,
• They are the earth’s blanket for reflecting certain They are the earth’s blanket for reflecting certain infra-redinfra-red frequencies back down to earth. frequencies back down to earth.
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Infra RedUltra Violet Visible
Infrared Radiation absorbed by Water and COInfrared Radiation absorbed by Water and CO22
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What determines the Earth’s surface temperature?What determines the Earth’s surface temperature?
Greenhouse Warming33 °C
H2O
CO2
+15oC
–18oC
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Global Energy Flows (W/mGlobal Energy Flows (W/m22))
Vicphysics Teachers’ Network
Practical ActivitiesPractical Activities• Introductory activities on phenomena to stimulate Introductory activities on phenomena to stimulate
curiosity and generate students’ questionscuriosity and generate students’ questions• ExperimentsExperiments
Heat capacity: Heat capacity: i) mixing liquids, i) mixing liquids, ii) adding heated block to waterii) adding heated block to wateriii) heat capacity of thermosiii) heat capacity of thermosiv) microwave oven exptiv) microwave oven expt11stst Law: Law: Calorimeter prac (link to elec)Calorimeter prac (link to elec)Latent Heat:Latent Heat: i) Add ice to hot wateri) Add ice to hot waterMechanical Equivalent of heatMechanical Equivalent of heat
Vicphysics Teachers’ Network
Practical ActivitiesPractical Activities• Experiments ctdExperiments ctd
Absolute Zero from Volume vs TempAbsolute Zero from Volume vs TempRadiation:Radiation: i) Spectra of hot objects, i) Spectra of hot objects,
ii) Stefan-Boltzmann Exptii) Stefan-Boltzmann Expt
• Investigation: Investigation: Keeping it Hot – design, build & testKeeping it Hot – design, build & test
* Discount craft supplies* Discount craft supplies* Reverse Art Truck* Reverse Art Truck
• Spreadsheet: Investigation of a Climate modelSpreadsheet: Investigation of a Climate model
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Assessment TasksAssessment Tasks
Written response to a selection of context questions
Exploration of an issue related to thermodynamics
Vicphysics Teachers’ Network
Assessment TasksAssessment Tasks
Issue related to thermodynamics Apply thermodynamic principles to investigate at least one
issue related to the environmental impacts of human activity with reference to the enhanced greenhouse effect.Consider: * other topics such as solar thermal power, geo-engineering, blog related discussion ....* integrating the task into the work program.* a team approach with a group presentation.* how much resourcing do you supply.* how much guidance and structure.
Vicphysics Teachers’ Network
Useful websitesUseful websites
http://www.vicphysics.org/courseplanning.htmlhttp://www.vicphysics.org/courseplanning.html
http://www.vicphysics.org/thermodynamics.htmlhttp://www.vicphysics.org/thermodynamics.html
http://www.vcaa.vic.edu.au/Pages/vce/studies/fuhttp://www.vcaa.vic.edu.au/Pages/vce/studies/futuresd.aspx#Physicsturesd.aspx#Physics
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