Two substances, x and y, are to be identified. substance x cannot be broken down by a chemical change. substance y can be broken down by a chemical change. what can be concluded about these substances?

The conclusion that can be made about X and Y is that they are element and compound respectively.

An element is a pure substance consisting of the same atom while a compound is formed by the combination of atoms of different elements. the atoms of the different elements are usually joined together by chemical bonds.

Thus, elements cannot be broken down any further by a chemical change while compounds can be broken down by breaking the bonds between the atoms of different elements.

Therefore, the fact that X cannot be broken down by a chemical change makes it an element while the fact that Y can be broken down by a chemical change makes it a compound.

More on elements and compounds can be found here:

particle   p is an electron and particle q is a neutron