Chemistry Reference
In-Depth Information
CHEMISTRY
C
S
HEMICAL
UBSTANCES
Matter
All substances
Element
A substance that cannot be split into simpler substances by a
chemical reaction
Atom
The smallest particle of an element that retains the chemical
properties of that element
Compound
A combination of two or more elements held together in some
way. It has different physical and chemical properties from
the elements it contains. The proportion of each element in
a compound is constant, for example, the compound known
as water always contains two atoms of hydrogen and one
of oxygen
Molecule
The smallest particle of an element or compound that exists
on its own and still retains its properties
All matter is composed of elements. Most matter contains two or more
elements and some in the form of compounds contain thousands or even
millions of atoms. Water, for example, is a compound that contains two
elements: hydrogen and oxygen. The chemical compound we know as sugar
contains three elements: carbon, hydrogen, and oxygen. Table salt is com-
posed of the elements sodium and chlorine.
are blends of two or more elements and/or compounds that are
not chemically bound to each other. Mixtures can usually be separated by
physical means.
Mixtures
