Classification of Matter
Composition of matter
Physical and chemical properties
Physical and chemical changes
Pure Substances
A
pure substance is a substance that
cannot be broken down into simpler
components by physical means.
 Examples: elements and compounds.
 Elements are substances that are
composed of all the same atoms.
Examples of Elements
 What
elements do we use everyday?
 Carbon- graphite in pencils, diamonds
 Copper- electrical wires, pennies
 Oxygen- breathing
 There are 90 elements found in nature.
 More than 20 others have been
synthesized in the lab.
Compounds
A
compound is a substance in which the
atoms of two or more elements are
combined in fixed proportions.
 Chlorine and Sodium are toxic alone but
when put together in a 1:1 ratio, they
make up salt.
Mixtures

A mixture is a
material made up of
two or more
substances that can
easily be separated
by physical means.

There are two types
of mixtures:
 Heterogeneous
mixtures
 Homogeneous
mixtures
Heterogeneous Mixtures

A mixture in which
the different
materials are easily
distinguishable is a
heterogeneous
mixture.

Heterogeneous
mixtures contain
more than one
phase.
 A phase is a region
with uniform
properties, like
density, structure
and heat capacity.
Homogeneous Mixtures

A homogeneous
mixture contains
gaseous, liquid or
solid substances
blended evenly
throughout.
 Example: cold soft
drink

A solution is a type
of homogeneous
mixture of particles
so small that they
cannot be seen with
a microscope and
will never settle.
 Example: vinegar
Colloids

Colloid comes from a
Greek word for glue.
 Colloids have some
properties of
heterogeneous and
homogeneous
mixtures.
 Examples: milk, paint,
fog

Like a solution, the
components won’t
settle if left standing.
 Like a
heterogeneous
mixture, there are
varying proportions
of components.
Detecting colloids

One way to
distinguish a colloid
from a solution is by
its appearance.
 Colloids scatter light
because the
particles suspended
are large.

The scattering of
light by a colloid is
called the Tyndall
effect.
Suspensions
A
suspension is a heterogeneous
mixture containing a liquid in which
visible particles settle.
 Example: muddy pond water
Physical Properties
A
physical property is any characteristic
of a material that you can observe
without changing the identity of the
substances that make up the material.
 Examples of physical properties:
color, shape, size, melting point, boiling
point, heat capacity, mass
Behavior
 Some
physical properties describe the
behavior of a substance.
 Ductility- the ability of a metal to be
drawn into wires
 Magnetism- the ability to be attracted by
a magnetic field
 Malleability- the ability of a metal to be
hammered into thin sheets
Behavior
 Viscosity-
the resistance of a fluid to flow
Using Physical Properties to Separate
 How
might you separate a mixture of iron
and sand?
 What approach would you take to separate
salt from water?
 What does it mean if a sample has two
different boiling points?
Physical Change
A
change in shape size or state of
matter is called a physical change.
 These changes may require energy
changes, but the material itself remains
unchanged.
 Examples of state changing processes:
freezing, melting, evaporation,
sublimation, boiling, condensation
Distillation

The process of
distillation involves the
physical separation of
substances in a
mixture by the
evaporation of a liquid
and recondensing of
its vapor.

This process is often
used in industry.
Natural oils, such as
mint and lavender,
are separated using
distillation.
Closed v. Open Systems


A closed system is a
system which is isolated
so that it cannot
exchange matter or
energy with its
surroundings and can
therefore attain a state
of thermodynamic
equilibrium.
Example: hand-boiler
distillation

An open system is a
system across
whose boundaries
both matter and
energy may pass.
 Example: water
cycle
Chemical Properties
A
chemical property is a characteristic
of a substance that indicates whether it
can undergo a chemical change.
 One such property is flammability.
Some chemicals are photosensitive and
decompose when exposed to light.
 Chemical properties are often related to
the structure of a particular molecule or
compound.
Detecting Chemical Change
 There
are 4 clues that a chemical change
is taking place:
1. A color change is observed.
2. Heat is released or absorbed.
3. A precipitate is formed.
4. A gas is released.
☺A precipitate is a solid that forms as a
result of mixing two or more solutions.
Chemical Changes
 The
only real proof that a chemical
change or reaction has occurred is a
new substance is produced.
 For example, what forms on iron when
exposed to oxygen? Is this a chemical
or physical change?
 Does the separation of an element from
its ore require chemical or physical
changes?
Intensive and Extensive
Properties

Intensive properties
do not depend on
the amount of
matter present.
 Examples: melting
point, boiling point,
density and
conductivity of
electricity and heat

Extensive properties
depend on the
amount of matter
present.
 Examples: mass,
volume and amount
of energy
Is mass lost during a chemical
reaction?
 Wood
is combustible, meaning that it will
readily burn. Will the pile of ash
remaining after the wood is burned weigh
the same as the original log?
 Where did the excess weight go?
 You might realize that if you combined all
of the oxygen that escaped along with the
other gases… the before and after
products would be the same!!!
The Law of Conservation of Mass

This law states that
the reactants and
the products in a
chemical reaction
have exactly the
same mass.
 Antoine Lavoisier
came up with this
law.