Students are each given a 20 gram sample of an unknown solid compound in a clear plastic bag. they are instructed to break the material into smaller parts by gently hitting it with a hammer. some of the parts break into large chunks and some look like a fine powder. each piece contains the same proportion of different elements.

From the question given above, it can be inferred that EACH PIECE CONTAINS THE SAME NUMBER OF ATOMS.
All substance are made up of atom and atom is the smallest unit division that a a substance can be divided into. So, all the pieces, both the fine powered and the large chunk are made up of atoms.

Pending the correct answer