DP Physics (first assessment 2025)

Question EXE.2.HL.TZ0.b

Date	Example questions Example questions	Marks available	[Maximum mark: 3]	Reference code	EXE.2.HL.TZ0.b
Level	HL	Paper	2	Time zone	TZ0
Command term	Deduce	Question number	b	Adapted from	N/A

[Maximum mark: 3]

EXE.2.HL.TZ0.b

Deduce, with reference to entropy, that the expansion of the gas from the initial configuration A is irreversible.

[3]

Markscheme

The entropy of the gas is related to the number of microstates

$S_{A} = k_{B} \ln Ω_{A}$ and $S_{A} = k_{B} \ln Ω_{B}$ ✓

Since $Ω_{B} > Ω_{A}$ , the entropy in configuration B is greater ✓

A process that results in an increase of entropy in an isolated system is irreversible ✓

Syllabus sections