If the particles are infinitely small they don't actually require any space, so they could exist within a volume of any size from infinitely small to infinitely large. In terms of the volume they completely fill, the only one such is also infinitely small (but existent). As to mass, Isaacs take makes the most sense if we recognize infinity as a theoretical limit rather than a true quantity, but if you're saying the particles are ACTUALLY "infinite" in number and of "infinitely" small mass it seems inevitable that the total mass is Unity. Of course, seeming is not believing, and asking the value of ∞/∞ is similar in many ways to asking the value of 0/0 (recently investigated in another thread); it depends on how you look at it, because different axioms argue that BOTH are 1, 0 or ∞. I think Unity is the only logical answer, which is why I think everything reduces to either Unity or Void; which has precedence depends, in turn, on whether you ask me or Dan. In terms of this question, I think an infinite number of infinitesimally massive particles would have a large mass, simply because Unity is "large" relative to the "smallness" of Void, and one of the few things we can say with certainty is that the particles would NOT be Void.

UT (the one in TX, not TN) has forever ruined orange for me, beyond even the power of the other UT to redeem; not only can I not stand the Austin attitude, but their particular shade or orange is one I refer to as "puke orange" (they prefer "burnt" ). Green is OK, if it's a dark, emerald, green but I prefer blue; everything in the middle of the road is either dead or yellow (or green, which is right next door to yellow). Green, however, improves markedly in the context of your final question....

Reluctantly and under protest.

EDIT: Smiley overload.