Question

Thermodynamics.Entropy-2nd-Law.MS.KC.5: Molten lead is poured into a mold to make a tool. As it cools and hardens, which of the following statements are true?

(a) The entropy of the lead decreases more than the surrounding environment’s entropy increases.
(b) The entropy of the lead decreases less than the surrounding environment’s entropy increases.

(c) The entropy of the lead increases while the surrounding environment’s entropy remains constant.
(d) The entropy of the lead + environment increases.
(e) The entropy of the lead + environment remains constant.

Answer 1

from the given statements, as the solidification of molten lead is an irreversible process, total entropy chage should be +ve from second law of thermodynamics
hence entrpy change f lead + entropy change of environment > 0
hence entropy decrease in lead is less than increase in entropy of the environment ( as lead's entripy is decreasing as it is giving off heat and cooling down)

hecne
(b) The entropy of the lead decreases less than the surrounding environment’s entropy increases.
d) The entropy of the lead + environment increases.