there are 3 unknown substance a,b and c that need to be classified as element mixture compound
Substance a is classified as an element because it is a pure substance made up of only one type of atom.
Substance b is classified as a mixture because it is made up of multiple different substances that are physically mixed together but not chemically bonded.
Substance c is classified as a compound because it is made up of two or more different elements that are chemically bonded together in a fixed ratio.