# How can thermal effects be explained?

In this area of study students investigate the thermodynamic principles related to heating processes, including concepts of temperature, energy and work. Students examine the environmental impacts of Earth’s thermal systems and human activities with reference to the effects on surface materials, the emission of greenhouse gases and the contribution to the enhanced greenhouse effect. They analyse the strengths and limitations of the collection and interpretation of thermal data in order to consider debates related to climate science.

Outcome 1
On completion of this unit the student should be able to apply thermodynamic principles to analyse, interpret and explain changes in thermal energy in selected contexts, and describe the environmental impact of human activities with reference to thermal effects and climate science concepts.

Key knowledge

Thermodynamics principles

• convert temperature between degrees Celsius and kelvin
• describe the Zeroth Law of Thermodynamics as two bodies in contact with each other coming to a thermal equilibrium
• describe temperature with reference to the average kinetic energy of the atoms and molecules within a system
• investigate and apply theoretically and practically the First Law of Thermodynamics to simple situations: Q = U + W
• explain internal energy as the energy associated with random disordered motion of molecules
• distinguish between conduction, convection and radiation with reference to heat transfers within and between systems
• investigate and analyse theoretically and practically the energy required to:                    – raise the temperature of a substance: Q = mcΔT                                                                              –  change the state of a substance: Q = mL
• explain why cooling results from evaporation using a simple kinetic energy model.

Thermodynamics and climate science

• identify regions of the electromagnetic spectrum as radio, microwave, infrared, visible, ultraviolet, x-ray and gamma waves
• describe electromagnetic radiation emitted from the Sun as mainly ultraviolet, visible and infrared
• calculate the peak wavelength of the re-radiated electromagnetic radiation from Earth using Wien’s Law: lmaxT = constant
• compare the total energy across the electromagnetic spectrum emitted by objects at different temperatures such as the Sun
• describe power radiated by a body as being dependent on the temperature of the body according to the Stefan-Boltzmann Law, P T 4
• explain the roles of conduction, convection and radiation in moving heat around in Earth’s mantle (tectonic movement) and atmosphere (weather)
• model the greenhouse effect as the flow and retention of thermal energy from the Sun, Earth’s surface and Earth’s atmosphere
• explain how greenhouse gases in the atmosphere (including methane, water and carbon dioxide) absorb and re-emit infrared radiation
• analyse changes in the thermal energy of the surface of Earth and of Earth’s atmosphere
• analyse the evidence for the influence of human activity in creating an enhanced greenhouse effect, including affecting surface materials and the balance of gases in the atmosphere.

Issues 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:                                                                                                                                      –   proportion of national energy use due to heating and cooling of homes                     –   comparison of the operation and efficiencies of domestic heating and cooling              systems: heat  pumps; resistive heaters; reverse-cycle air conditioners;                              evaporative coolers; solar hot water systems;  and/or electrical resistive hot                    water systems                                                                                                                                        –   possibility of homes being built that do not require any active heating or cooling         at all                                                                                                                                                            –   use of thermal imaging and infrared thermography in locating heating losses in           buildings and/or system malfunctions; cost savings implications                                   –  determination of the energy ratings of home appliances and fittings: insulation;           double glazing; window size;light bulbs; and/or electrical gadgets, appliances or         machines                                                                                                                                                   – cooking alternatives: appliance options (microwave, convection, induction); fuel         options (gas, electricity, solar, fossil fuel)                                                                                   – automobile efficiencies: fuel options (diesel petrol, LPG and electric); air delivery         options (naturally aspirated, supercharged and turbocharged); and fuel delivery           options (common rail, direct injection and fuel injection)
• explain how concepts  of  reliability, validity and  uncertainty relate to  the  collection, interpretation and communication of data related to thermodynamics and climate science.

(Source: vcaa.vic.edu.au)