N = property =M; Therefore,
Apply Reynold’s Transport Theorem:
(Fig. 12a)
(Particle-mass cannot be created or destroyed)
The 1st term of the right-hand-side is zero: particle-mass cannot be created or destroyed.
Therefore, : conservation of mass equation
Note that of a fluid in a CV may change with time, for example, in a tank filled with air and water. If water is drained out, of the mixture (air + water) will vary with time. Message: Be careful while evaluating the integral, whether under evaluation refers to the density of a pure fluid or fluids-mixture.
: conservation of mass equation
of a fluid in a CV may change with time, for example, in a tank filled with air and water. If water is drained out, 
of the mixture (air + water) will vary with time. Message: Be careful while evaluating the integral, whether 
under evaluation refers to the density of a pure fluid or fluids-mixture.
