What you’ll learn13 learning objectivesChoose one objective for a focused lesson, or study the complete topic.—B.4.1 (HL)—First law of thermodynamics• First law for closed systems: Q = ΔU + W.Syllabus objective—B.4.2 (HL)—Gas work• Work done by/on a gas from pressure-volume change: W = PΔV.Syllabus objective—B.4.3 (HL)—Internal energy change• The change in internal energy: ΔU = 3 2 NkBΔT = 3 2nRΔT of a system is related to the change of its temperature.Syllabus objective—B.4.4 (HL)—Entropy and disorder• Entropy relates to microscopic disorder of particles in a system.Syllabus objective—B.4.5 (HL)—Entropy equations• Entropy change: ΔS=ΔQ/T.• Statistical entropy: S=kB ln Ω.Syllabus objective—B.4.6 (HL)—Second law of thermodynamics• Second law: entropy of an isolated system never decreases.Syllabus objective—B.4.7 (HL)—Irreversibility• Real isolated processes are usually irreversible; entropy tends to increase.Syllabus objective—B.4.8 (HL)—Local entropy decrease• Local entropy can decrease in a non-isolated system if surroundings increase more.• Surroundings must increase entropy enough for total entropy to increase.Syllabus objective—B.4.9 (HL)—Gas processes• Know isovolumetric, isobaric, isothermal and adiabatic gas processes.• Processes keep one state variable or heat transfer condition fixed.Syllabus objective—B.4.10 (HL)—Adiabatic ideal gas• Adiabatic monatomic ideal gas: PV^(5/3)=constant.Syllabus objective—B.4.11 (HL)—Heat engine cycles• Cyclic gas processes underpin heat engines.Syllabus objective—B.4.12 (HL)—Heat engine efficiency• Heat engine efficiency: η=W/QH=1-QC/QH.Syllabus objective—B.4.13 (HL)—Carnot efficiency limit• Carnot efficiency limit: ηCarnot = 1 - TC/TH.Syllabus objective