IB Physics HL B 4 4 Hl Entropy and Disorder Questions

Explain entropy and disorder in HL thermodynamics, comparing system and surroundings during melting, gas cycles, heat transfer and spontaneous change.

Exam points

Determine whether entropy increases, decreases or stays constant from heat transfer, temperature and the associated change in microscopic disorder.
Compare entropy between states or points on a thermodynamic cycle using disorder, heat-transfer direction and process conditions.
Recognise that entropy returns to its original value after a complete cycle and identify the state of greatest entropy from a process description or diagram.

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Study B.4.4 (HL)—Entropy and disorder conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

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The p V diagram shows a heat engine cycle consisting of adiabatic, isothermal and isovolumetric parts. The working substance of the engine is an ideal gas.

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The following data are available:

\begin{aligned} & p_{\mathrm{A}}=5.00 \times 10^{5} \mathrm{~Pa} \\ & V_{\mathrm{A}}=2.00 \times 10^{-3} \mathrm{~m}^{3} \\ & T_{\mathrm{A}}=602 \mathrm{~K} \\ & p_{\mathrm{B}}=3.00 \times 10^{4} \mathrm{~Pa} \\ & p_{\mathrm{C}}=4.60 \times 10^{3} \mathrm{~Pa} \end{aligned}

Suggest, for the change $A \Rightarrow B$ , whether the entropy of the gas is increasing, decreasing or constant.

Increasing because thermal energy/heat is being provided to the gas « and temperature is constant, $\Delta S=\frac{\Delta Q}{T} \gg$

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IB Physics HL B 4 4 Hl Entropy and Disorder Questions question 1