Conservation of Mass

In thermodynamics, you learned that energy can neither be created nor destroyed, only altered in form. The similar is true for mass. The conservation of mass is a principle of engineering that expresses that all mass flow rates into a control volume are equivalent to all mass flow rates out of the control volume plus the rate of change of mass inside the control volume. This principle is stated mathematically by the equation given below.

Here:

Δm/Δt = the rise or reduce of the mass inside the control volume over a particular time period.