Similarly, the total particle volume is found to be
 | (8–7) |
where 
[g/cm 3 ] is the bulk density of the particle core.
By assuming that the particles are spherical, an average particle diameter can be obtained
as
 | (8–8) |
The total sphere-equivalent surface area of a particle population is given as
 | (8–9) |
With these equations, all basic properties of a particle population are defined for the moment method. Several sections in the Chemkin Theory Manual, Method of Moments chapter, discuss the kinetics models used by the Particle Tracking feature to describe formation, growth, reduction, and interaction of the particles.