Question

Scientists use what properties to help them identify and classify matter

Answer 1

Scientists use the physical and chemical properties to help them identify and classify matter. These physical and chemical properties are in a macro-perspective, in which these matter contains compounds, elements and atoms. Hence, matter can be classified in various ways, 
1.    Atomic number either atomic mass each element has 
2.    By substance of that matter either pure substance or mixed substance 
3.    If they cannot reduce a certain substance into a much smaller quantified atomic structure then they they’ll use (2) to identify and classify it.