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CHAPTER 15
The Classification of Matter
SECTION 1
Composition of Matter
Different Categories of Matter
Matter fits into 2 major categories…
Pure Substances
Mixtures
• Matter with a fixed
• Matter without a fixed
composition
• Two types:
composition
• Two types:
• Elements
• Compounds
• Heterogeneous mixtures
• Suspensions
• Homogeneous mixtures
• Solutions
• Colloids
Elements
• When all the atoms in
a substance have the
same identity
• Examples:
• Pencil lead is graphite,
which is just carbon in
solid form
• Oxygen tanks contain
pure oxygen to help
people with lung
diseases breathe easier
Compounds
• When two or more
elements are
combined
• Examples:
• Water is a combination
of hydrogen and oxygen
(H2O)
• Air is a combination of
multiple elements
• Salt is a combination of
sodium and chloride
(NaCl)
Heterogeneous Mixtures
• A mixture in which
different materials can
be easily distinguished
• Things like pizza,
salad, chicken noodle
soup, granite, and
concrete are all
heterogeneous
mixtures
Homogeneous Mixtures
• A mixture of two or
more gaseous, liquid,
or solid substances
blended evenly
throughout
• The air we breathe,
Kool Aid, and sweet
tea are all
homogeneous
mixtures
Solutions
• A homogeneous mixture of particles so small they cannot
be seen with a microscope and will never settle to the
bottom of the container
• Vinegar and soft drinks are examples of solutions
because they remain mixed thoroughly
Colloids
• A type of mixture with
particles that are larger
than those in solutions,
but not heavy enough
to settle to the bottom
• Paint, Jell-o, fog, and
smoke are all
examples of colloids
The Tyndall Effect
• To detect a colloid,
shine a light through
the substance
• If there is a definite
beam of light visible, it
is a colloid
Suspensions
• A heterogeneous
mixture containing a
liquid in which large
particles settle out to
the bottom because
they are heavier.
• Muddy water, oil and
vinegar salad dressing,
and snow globes are
suspensions
SECTION 2
Physical & Chemical Properties
Physical & Chemical Changes
Physical Properties
• Any characteristic of a material that you can observe
without changing the identity of the substances that make
up the material is a physical property.
• Color
• Shape
• Size
• Density
• Melting point
• Boiling point
• Freezing point
Chemical Properties
• Any characteristic of a substance that Indicates whether
a material can undergo a chemical change is a chemical
property
• Flammability
• Reaction to light
• Solubility
• Combustion
• Reactivity
Physical Change
• A change in size, shape,
or state of matter
• The identity stays the
same
•
•
•
•
Ice cube melting
Water boiling or freezing
Color changes
Cutting paper into
smaller pieces
• Stretching a rubber band
• Grass growing
Chemical Change
• Change of one
substance to another
• Eggs rotting
• Cars rusting
• Match burning
• Leaves decomposing
• Cooking anything
• Chemical reactions
Weathering
• Physical change: when rocks split after water seeps into
cracks, freezes, then melts
• The pieces of rock that break off still have the same identity, they’re
just smaller
• Chemical change: acid rain causes limestone to change
its chemical makeup and dissolve
• The White Cliffs of Dover have been shaped by this process over
time
Weathering
Physical
Chemical
TRUE OR FALSE: THE EARTH’S
SURFACE HAS STAYED THE SAME
FOR THOUSANDS OF YEARS
TRUE OR FALSE: THE EARTH’S
SURFACE HAS STAYED THE SAME
FOR THOUSANDS OF YEARS
The Earth’s surface is always
changing!
Chemical Change Evidence
The Law of Conservation of Mass
• The mass of all substances present before a chemical
change is equal to the mass of all substances that remain
after the change
• Suppose logs in a fireplace had a mass of 85 kg
• After they burn, all you see is ashes. If you weigh the
ashes, they may not have a mass of 85 kg. Where is the
rest of the mass?