What can one say about the Chow group of zero-cycles (up to rational equivalence) for a product of smooth projective varieties and Chow motives (so, I am interested in the kernel $Chow_0(P)\otimes Chow_0(Q)\to Chow_0(P\times Q)$)? I am interested in Chow groups with rational, torsion and $l$-adic coefficients; for rational coefficients I consider motives over universal domains (say, over complex numbbers), but for $l$-adic ones I am interested in arbitrary (perfect) base fields.
I would like to treat certain smash-nilpotens questions. So, I am interested in Chow groups of high powers of $P$ for $\dim P>1$ and also in Chow groups of the product of a large number of curves whose genus is bounded by some constant.