To clarify, H and O and H2O are weakly emergent entities out of the artifacts of electrons/protons, similar to the copper in your example. The behavior of electrons and protons/neutrons completely explain the behavior of atoms and molecules.

And when electrons say annihilate by combining with a positron, then the artifact in this case is the say particle physics and energy conservation, whose behavior completely explains electrons and positrons, which then are emergent entities.

The naturalist claim is this happens all the way down to the base rules, which are the core never changing artifacts out of which all properties/behavior is emergent.