Question

For an isolated system, the entropy:

• A. either increases or remains constant
• B. either decreases or remains constant
• C. can never decrease
• D. can never increase

Answer 1

Answer: (A), (C)

can never decrease

Explanation for correct option:

Option (A): either increases or remains constant

• As the second law of thermodynamics states, the total entropy of the system always increases or else remains constant.
• Also the entropy of an isolated system always tends to increase over time, conditioned to be not in equilibrium and approaches maximum value at equilibrium.

Option (C): can never decrease

• Entropy of an isolated system always increases or remains constant.
• Entropy for an isolated system or the universe never decreases.

Explanation for incorrect option:

Option (B): either decreases or remains constant

• For an Isolated system entropy can never decrease over time.
• But the option states, that it can either decreases or remains constant, which does not obey the second law of thermodynamics.

Option (D): can never increase

• We know entropy of the universe or an isolated system always increases or remains constant considering the process to be reversible
• But the option states, it can never increase, which doesn't coincide with the second law of thermodynamics.

Therefore, for an isolated system, the entropy either increases or remains constant Option (A) and can never decrease Option (C).