(Comparison of two compression methods of the same gas sample)
(a) A sample of an ideal gas initially at 1 atm and 300 K is compressed to one-fifth of its initial volume in two different ways.
Method A: The piston is pushed so slowly that the gas remains in thermal equilibrium with a large water bath at 300 K during the entire compression.
Method B: The piston is suddenly pushed in, completing the volume change in a fraction of a second; no heat flows during this step.
(b) (i) For each method, predict whether the entropy change of the universe (ΔSuniv) is zero, positive, or negative. State the classification of the process as reversible or irreversible.
(c) (ii) Give a qualitative explanation, based on molecular behaviour or energy exchanges, for the difference in ΔSuniv obtained in the two methods.