The total energy of the universe is constant; the total entropy is continually increasing.

The entropy of the universe tends to a maximum.

The energy of the universe is constant.

The total energy of the universe is constant; the total entropy is continually increasing.

Heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time.

The algebraic sum of all the transformations occurring in a cyclical process can only be positive, or, as an extreme case, equal to nothing. Statement of the second law of thermodynamics, 1862

In all cases where work is produced by heat, a quantity of heat proportional to the work done is expended; and inversely, by the expenditure of a like quantity of work, the same amount of heat may be produced.