Question

What distinguishes a substance from a mixture?

Answer 1

Chemical substances are composed by atoms or molecules without a chemical bond, so they cannot be separated.

On the other hand, chemical mixture are made from different chemical bonds, and can be separated.

Also, substances are homogeneous and mixture are heterogeneous.

Answer 2

Substances are chemically combined and cannot be separated by normal physical means. Mixtures, however, are simply physically combined and can be separated into their component parts.