For any quantity that is conserved, an inventory rate equation can be written to describe the transformation of the conserved quantity. Inventory of the conserved quantity is based on a specified unit of time, which is reflected in the term rate. In words, this rate equation for any conserved quantity takes the form ( -)-( output of v ) + ( generation of ) = ( accumulation of y) Rate of Rate Rate of input of Basic concepts upon which the technique for solving engineering problems is based are the rate equations for the Conservation of chemical species, Conservation of mass, Conservation of momentum, Conservation of energy. Why is entropy not included