The first can be filled with an element and the second blank can be filled with a compound.
Iron is an element as it contains only one kind of atom, which combines with the oxygen from the air to produce rust, that is, iron oxide. The rust comprises two kinds of atoms, which signifies that it is a compound. A compound refers to a molecule that comprises at least two types of atoms. In the case, iron oxide is a compound as it comprises Fe and O atom.
.5kg
Because the formula for force is Force = mass multiplied by acceleration, so you would divide Force by the acceleration to find your mass.
