Question

The Second Law of Thermodynamics states that the overall entropy of the universe (or any other isolated system) can never decrease. Identify the systems to which the Second Law of Thermodynamics would apply.

a reaction vessel that is completely sealed and insulated

an open beaker containing an aqueous solution

a sealed glass flask that is not insulated

the Earth

Answer 1

The Second Law in the form "entropy of an isolated system never decreases" applies only to isolated systems (or to the universe as a whole). For the listed items:

- reaction vessel completely sealed and insulated: isolated — the Second Law directly applies (its entropy cannot decrease).
- open beaker containing an aqueous solution: not isolated (mass and energy can be exchanged) — the beaker’s entropy can decrease locally; only the beaker+surroundings must obey the Second Law.
- sealed glass flask that is not insulated: closed (no matter exchange) but not isolated (heat exchange allowed) — its entropy can change up or down; the Second Law guarantees non‑decrease only for the flask+surroundings.
- the Earth: not isolated (receives solar radiation and radiates to space) — the law does not force Earth’s entropy alone to never decrease, only the total entropy of Earth plus its surroundings (or the universe) is non‑decreasing.