Based on a course given to beginning physics, chemistry, and engineering students at the Winterthur Polytechnic Institute, this text approaches the fundamentals of thermodynamics from the viewpoint of continuum mechanics. By describing physical processes in terms of the flow and balance of physical quantities, the book provides a unified approach to hydraulics, electricity, mechanics and thermodynamics. In this way it becomes clear that the entropy is the fundamental property that is transported in thermal processes and that the temperature is its measure. Previous knowledge of thermodynamics is not required, but readers should be familiar with basic electricity, mechanics, and chemistry and should have some knowledge of elementary calculus. Both the theory and applications are included as well as many exercises and solved problems from various fields of science and engineering.