What does the second law state?

• A. Energy is conserved in all processes.
• B. Entropy decreases in the universe with every transfer.
• C. Every energy transfer or transformation increases the entropy of the universe.
• D. Temperature is invariant in all processes.

Answer: (C)

The main idea here is how energy changes flow in real processes: the second law says that every energy transfer or transformation increases the entropy of the universe. This captures why energy tends to spread out and become less available to do work—some energy becomes dispersed as heat and disorderly energy. It also explains why most processes are irreversible in practice; only idealized reversible processes keep the universe’s entropy the same. Energy conservation is a separate concept (the first law) and doesn’t speak to entropy changes, which is why that option isn’t the focus. Entropy decreasing or temperature staying invariant in all cases aren’t accurate descriptions of how real processes behave, so the statement that best reflects the second law is that each energy transfer or transformation increases the entropy of the universe.