What is the Clausius form of the second law of thermodynamics?
(1) For an isolated system, ΔS≥0 .
(2) It is not possible to exchange heat from a colder body to a hotter body without the use of mechanical work input.
(3) It is not possible to make a heat engine that converts all of the heat exchanged into useful work.
(4) A Carnot heat engine is the most efficient of all heat engines operating between the same temperatures.