ABSTRACT
Chemical species, total mass, momentum, and energy are the conserved quantities encountered in engineering analysis. Conservation equations for chemical species, total mass, momentum, and energy are also called basic concepts. The basic concepts are applied at all levels, that is, subatomic, atomic, molecular, microscopic, and macroscopic. Integration of the equations of change over the volume of a system gives the basic concepts at the macroscopic level. Integration eliminates position dependence, and the resulting equations are ordinary differential equations, with time as the only independent variable. In engineering calculations, students are interested in the determination of the rate of momentum, heat, and mass transfer from one phase to another across the phase interface. Materials behave differently when subjected to the same gradients. Constitutive equations identify the characteristics of a particular material.
