Students can use to distinguish pure substances, such as elements and compounds with a constant composition, from other substances. a) color b) density c) particle size d) state of matter

Answer is: B) density.

Pure substance is made of only one type of atom or only one type of molecule, it has definite and constant composition with distinct chemical properties.

Mixtures are physical combinations of pure substances that have no definite or constant composition.

With constant composition density of pure substance is always the same and in other substances it can vary according the composition.

Density is a measure of mass per unit of volume.

The SI derived unit for density is the kilogram/cubic meter, but chemist usually use gram per cubic centimeter.

the answer is barium and copper bromide

the awnser is group 12