Vicphysics Teachers’ Network New concepts Practical Activities Assessment Tasks Prepared with material from NPL (UK), IPCC, BOM (Aus) Thermodynamics

Vicphysics Teachers’ Network Thermodynamics: New Concepts  Zeroth law of Thermodynamics  Internal Energy  First Law of Thermodynamics  Thermal Radiation: –Wien and Stefan & Boltzmann  Energy Flow

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”

Vicphysics Teachers’ Network Internal Energy You are heating a substance, what happens to its atoms and molecules? Gas: Monatomic: Ne Diatomic: O 2 Multi atom: H 2 O Liquid:Solid: Atoms and molecules have different types of energy. Only translational kinetic energy relates to Temp.

Vicphysics Teachers’ Network Internal energy

Vicphysics Teachers’ Network First 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 to a system, QEnergy can be added to a system, Q Work can be done by a system, WWork can be done by a system, W Internal energy can change as a result,  UInternal energy can change as a result,  U  U = Q – W Only simple calculations.

Vicphysics Teachers’ Network Energy Transfer by Radiation Radiation and Greenhouse Effect A significant section with many new physics concepts: SpectrumSpectrum Temperature means  atoms jiggle  electrons jiggle  accelerating charges  electromagnetic radiation Freq, wavelengthFreq, wavelength Energy, powerEnergy, power Increasing frequency Decreasing wavelength Increasing energy

Vicphysics Teachers’ Network Energy Transfer by Radiation Radiation and Greenhouse Effect Increased temperature meansIncreased temperature means  atoms jiggle faster  electrons jiggle faster  higher frequency radiation  higher energy

Vicphysics Teachers’ Network Thermal Radiation Wien’s Law: How does the wavelength of maximum intensity vary with temperature? (CBMR) max T = constant

Vicphysics Teachers’ Network Thermal Radiation Stefan-Boltzmann Law: How does total energy emitted vary with temperature? Consider Area under the graph: Power ∝ T 4.

Vicphysics Teachers’ Network What determines the Earth ’ s surface temperature? Light reflected from Earth Average Value 100 watts per square metre Light from the Sun Average Value 340 watts per square metre

Vicphysics Teachers’ Network What determines the Earth ’ s surface temperature? Light from the Sun heats the Earth… Average Value 240 watts per square metre Average Value 240 watts per square metre

Vicphysics Teachers’ Network What determines the Earth ’ s surface temperature? How hot must the Earth be to radiate 240 W/m 2 ? Average Value 240 watts per square metre -18 °C

Vicphysics Teachers’ Network What determines the Earth ’ s surface temperature? -18 °C Actual average surface temperature 33 °C Greenhouse Effect Temperature for radiation balance +15 °C

Vicphysics Teachers’ Network What determines the Earth ’ s surface temperature? The Earth’s surface is 33 °C warmer than it would be if it had no atmosphere So how does the atmosphere warm the Earth’s surface?

Vicphysics Teachers’ Network What determines the Earth ’ s surface temperature? Nitrogen (N 2 ), Oxygen (O 2 ) & Argon (Ar) More than 99% of the atmosphereMore than 99% of the atmosphere These molecules have one or two atomsThese molecules have one or two atoms They block some ultra-violet light, butThey block some ultra-violet light, but Allow infra-red and visible radiation through.Allow infra-red and visible radiation through.

Vicphysics Teachers’ Network What determines the Earth ’ s surface temperature? With an atmosphere of Nitrogen Oxygen & Argon, what would be the surface temperature? -18 °C Average Value 240 watts per square metre Average Value 240 watts per square metre

Vicphysics Teachers’ Network What determines the Earth ’ s surface temperature? Greenhouse warming is caused by Water (H 2 O) Carbon Dioxide (CO 2 )

Vicphysics Teachers’ Network What determines the Earth ’ s surface temperature? What is special about H 2 O and CO 2 ? Their molecules have three atoms,Their molecules have three atoms, Their natural frequencies of vibration are in the infra-red,Their natural frequencies of vibration are in the infra-red, They are the earth’s blanket for reflecting certain infra-red frequencies back down to earth.They are the earth’s blanket for reflecting certain infra-red frequencies back down to earth.

Vicphysics Teachers’ Network Infra RedUltra VioletVisible Infrared Radiation absorbed by Water and CO 2

Vicphysics Teachers’ Network What determines the Earth ’ s surface temperature? Greenhouse Warming 33 °C H2OH2O CO o C – 18 o C

Vicphysics Teachers’ Network Global Energy Flows (W/m 2 )

Vicphysics Teachers’ Network Practical Activities Introductory activities on phenomena to stimulate curiosity and generate students’ questionsIntroductory activities on phenomena to stimulate curiosity and generate students’ questions ExperimentsExperiments Heat capacity: i) mixing liquids, ii) adding heated block to water iii) heat capacity of thermos iv) microwave oven expt 1 st Law:Calorimeter prac (link to elec) Latent Heat:i) Add ice to hot water Mechanical Equivalent of heat

Vicphysics Teachers’ Network Practical Activities Experiments ctdExperiments ctd Absolute Zero from Volume vs Temp Radiation:i) Spectra of hot objects, ii) Stefan-Boltzmann Expt Investigation:Investigation: Keeping it Hot – design, build & test * Discount craft supplies * Reverse Art Truck Spreadsheet: Investigation of a Climate modelSpreadsheet: Investigation of a Climate model

Vicphysics Teachers’ Network Assessment Tasks   Written response to a selection of context questions   Exploration of an issue related to thermodynamics

Vicphysics Teachers’ Network Assessment 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 websites    turesd.aspx#Physics turesd.aspx#Physics turesd.aspx#Physics  Rumford