Question

1. how can you distinguish a pure substance from a mixture? a pure substance may be separated by physical means; a mixture may be separated only by chemical means. none of the above a pure substance has a fixed composition; a mixture has a composition that may vary. a pure substance has a composition that may vary; a mixture has a fixed composition.

Explanation:

A pure substance is made of only one type of particle and has a definite and constant composition. Mixtures are composed of two or more substances in varying proportions. Pure substances can't be separated by physical means easily (elements and compounds), while mixtures can be separated by physical methods like filtration, evaporation etc.

Answer:

A pure substance has a fixed composition; a mixture has a composition that may vary.