<P> where d V (\ textstyle (\ text (d)) V) is the differential that defines the integral over the whole volume of the system . </P> <P> The continuity equation for the mass is part of Euler equations of fluid dynamics . Many other convection--diffusion equations describe the conservation and flow of mass and matter in a given system . </P> <P> In chemistry, the calculation of the amount of reactant and products in a chemical reaction, or stoichiometry, is founded on the principle of conservation of mass . The principle implies that during a chemical reaction the total mass of the reactant is equal to the total mass of the products . For example, in the following reaction </P> <Dl> <Dd> CH 4 + 2 O 2 → CO 2 + 2 H 2O, </Dd> </Dl>

What is mass and what is the law of conservation of mass