Question

what is meant by substance ? ​

Answer 1

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A substance is a pure single form of matter. It cannot be separated into other kinds of matter by any physical process. For example: Sugar, sodium chloride.

Answer 2

A substance is pure if it has a homogeneous chemical composition. At the nanoscale, this only applies to a substance made up of one type of atom, molecule, or compound. ... Examples of pure substances include iron, steel, and water. Air is a homogeneous mixture that is often considered to be a pure substance.