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:

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6