Question

a chemical reaction is the only way to separate a(n) element pure substance mixture solution

Explanation:

Elements are the simplest substances and cannot be separated into simpler substances by chemical reactions. Pure substances include elements and compounds. Compounds can be separated into elements or simpler compounds by chemical reactions. Mixtures can be separated by physical methods like filtration, evaporation etc. Solutions are homogeneous mixtures and also separated by physical means. So a chemical reaction is the only way to separate a compound which is a type of pure - substance.

Answer:

pure substance