Which statement accurately describes the Second Law of Thermodynamics?

• A. Heat flows from cold to hot without work.
• B. Energy cannot be transformed from one form to another.
• C. Heat energy can only flow from a body having a high temperature to a body having a lower temperature.
• D. Perpetual motion machines are possible if insulated.

Answer: (C)

Heat naturally flows from a hotter body to a cooler one when no external work is applied, which is a direct consequence of the Second Law and the way entropy tends to increase. This directionality is what the statement is expressing: heat energy moves from high temperature to lower temperature in spontaneous transfers. It’s important to note that if you do work on a system, you can move heat from cool to hot (as in refrigeration), but without external work the natural flow is hot to cold. The other ideas conflict with fundamental principles: energy can be transformed between forms and conserved, and perpetual motion machines cannot exist because they would violate the Second Law.