Explain why the knowledge that matter is made up of small particles (atoms) is useful?

Question

informative answer please.

Answer 1

ummm, for openers, it allows people to use an  incredible

tool for calculations of the *chemistry* flavor.

the modelling of the "mole" is incredible

Answer 2

A short answer would be that it impacts nearly everything in physics and chemistry.  That in turn affects medicine, for a start.  Our understanding of it has also helped us do amazing things with fuels, new materials (e.g. polymers and kevlar), and any number of discoveries coming out of chemistry.