Please help me, i am stuck this is driving me nuts?

Question

to determine if a substance is pure, looking for this, in a standard reference tabl, will help you identifly the substance.
a. crystal structure
b. colour
c. state
d. density

Answer 1

I'm assuming that this is a multiple-choice question.

Out of the four, a crystal structure helps show that the substance is pure, because all of the atoms are aligned a certain way to form the structure (and by definition, a pure substance contains the same number of atoms of the same element(s) in each molecule). For example, each element has its own crystal structure, as do inorganic compounds.

It can't be the colour; many metals have relatively the same colours, and gases in the air are invisible to the naked eye.

It can't be the state; mixtures can be in the same state as the pure substances they were made from.

It can't be the density; everything has its own density, but it is not an indicator of whether a substance is pure.

Answer 2

These characteristics can be easily observed or measured.