affinity.

A mixture is composed of two or more elements or compounds
blended together, but not held by any chemical attraction.

To which of these three classes does sugar belong? Carbon? The
solution of sugar in water?

Carbon is an element; we call its smallest particle an atom.

An atom is the smallest particle of an element that can enter
into combination. Atoms are indivisible and usually do not exist
alone. Both elements and compounds have molecules.

The molecule of an element usually contains two atoms; that of a
compound may have two, or it may have hundreds. For a given
compound the number is always definite.

Chemism is the force that binds atoms together to form molecules.
The sugar molecule contains atoms, forty-five in all, of three
different elements: carbon, hydrogen, and oxygen. That of salt
has two atoms: one of sodium, one of chlorine. Should we say "an
atom of sugar"? Why? Of what is a mass of sugar made up? A
molecule? A mass of carbon? A molecule? Did the chemical affinity
of the acid break up masses or molecules? In this respect it is a
type of all chemical action. The distinction between physics and
chemistry is here well shown. The molecule is the unit of the
physicist, the atom that of the chemist. However large the masses
changed by chemical action, that action is always on the
individual molecule, the atoms of which are separated. If the