substance. A sample of matter that cannot be separated into simpler components without chemical change. Physical changes can alter the state of matter but not the chemical identity of a pure substance. Pure substances have fixed, characteristic elemental compositions and properties.

see substance.

is a substance that has a fixed chemical composition throughout.

a form of matter that has a definite composition and distinct properties

a homogeneous collection and has associated parameters such as mass, volume, temperature and specific volume that are constant throughout the substance

a substance that contains only one kind of matter; elements and compounds are pure substances raw materials processed material that can be converted by manufacture, processing, or combination into a new and useful product

matter with a constant molecular formula free of "contamination" by other elements.

A substance—either an element or compound—that has an unvarying composition. This means that by changing the proportions of atoms, the result would be an entirely differentsubstance. Compare with mixture.