Practice question · Sort into groups
Sort each process by whether it is reversible in principle or irreversible.
Groups: Reversible in the limit · Always irreversible
- Infinitely slow isothermal expansion with no friction
- Free expansion into a vacuum
- Warmth spreading between bodies at unequal temperature
- Quasistatic compression by a frictionless piston
- Two gases mixing spontaneously
Hints
- Look for a finite gradient driving the change.
- Any spontaneous flow driven by a finite difference generates entropy.
Show the answer
Reversible in the limit: Infinitely slow isothermal expansion with no friction, Quasistatic compression by a frictionless piston
Always irreversible: Warmth spreading between bodies at unequal temperature, Free expansion into a vacuum, Two gases mixing spontaneously
Why
Reversible processes are the zero-gradient limit. Every irreversible one here has a finite driving difference — of temperature, pressure or composition — and each generates entropy as it proceeds.
Practise Reversibility and Irreversibility
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