1. have distinctly
visible parts
Look at a Periodic Most materials we encounter in the
Table. There are 113 world are mixtures. The air we
elements in the breathe is a mixture of oxygen,
Periodic Table nitrogen, and other gases. The
oceans are mixtures of water, salts
and other substances

2. A pure substance has a
definite and constant
composition — like salt
or sugar. The
composition of a pure
substance doesn’t vary.
An element is composed of
a single kind of atom. A compound is composed of two or more
Chemists CAN’T separate elements in a specific ratio.
For example, water is a compound made up
the components of a
of two elements, hydrogen (H) and oxygen
compound AT ALL. (O).
Chemists can’t easily separate the
components of a compound: They have to
resort to some type of chemical reaction.

3. the different
parts of a mixture
can be easily
separated by
physical means,
such as filtration.
For example,
suppose you
have a mixture of
salt and sand,
and you want to
purify the sand by
removing the
salt. You can do
this by adding
water, dissolving
Mixtures are physical the salt, and then
filtering the
combinations of pure substances mixture. You then
that have no definite or end up with pure
constant composition — the sand.
composition of a mixture varies
according to who prepares the
mixture.