Chemistry Reference
In-Depth Information
Matter
Anything that has
both mass and
volume.
Ex. Sodium chloride,
oxygen
Substance
Matter with constant
composition. All
particles have the
same properties.
Ex. Water, helium
Mixture
Matter with variable
composition. Made
from two or more
substances.
Ex. Sand, soil
Element
A substance made up
of atoms with the
same atomic number.
Compound
A substance made
from two or more
elements, chemically
combined.
Ex. Carbon dioxide
Homogeneous
Mixture
A mixture made up
of particles that are
uniformly distributed.
Ex. Salt water
Heterogeneous
Mixture
A mixture made up of
particles that are not
uniformly distributed.
Ex. Raisin bran
Ex. Lead, sodium
right now. Although the diagram is concise, it may not be completely clear
unless I explain the categories in more detail. Once you understand the
categories, the chart should be all that you need to review.
Matter is anything that is made up of atoms, and because all atoms have
mass and volume, so does all matter. Even colorless gases, which you can't
see, contain atoms that have both mass and volume. If you doubt that invis-
ible air has volume, blow up a balloon and see how much space the air takes
up. All objects that you encounter in your day are examples of matter.
A substance is a type of matter that has a consistent composition. What
I mean is that no matter where you find a specific substance, its composi-
tion will be the same. In other words, a molecule of water from India has
the same composition as a molecule of water from Canada. There is no
real variation in the composition of a substance (except, perhaps, on the
subatomic level, as you will learn when we discuss isotopes). There are two
major types of substances: elements and compounds.
Elements are substances that are made up of only one type of atom. By
“type of atom,” I mean that all of the atoms in this type of substance have
the same atomic number, which is the number of protons. For example,
all samples of pure oxygen (O
2
) are only made up of atoms of oxygen,
with 8 protons in their nuclei. So oxygen is a substance, because it has a
consistent composition (it is the same, wherever you find it) and it is an
