Chapter 3
Matter – Properties
and Changes
I. Substances
• A substance is matter that has a uniform
and unchanging composition
- table salt is a substance, it is always 100%
sodium chloride (NaCl)
- water is a substance, it is always
composed of hydrogen and oxygen (H2O)
- salt water, or seawater, is not a substance;
different samples from multiple locations
may not have the same levels of water,
salts, and other dissolved particles
II. Physical Properties of Matter
• A physical property is a characteristic that
can be observed or measured without
changing the sample’s composition
i.e. density, color, odor, taste, hardness,
melting point, boiling point,
conductivity
A. Extensive properties
• Extensive properties are dependent upon
the amount of substance present
i.e. mass, length, volume, height
B. Intensive properties
• Intensive properties are independent of the
amount of substance present
i.e. density, appearance
• Some unknown substances can be
identified by their unique intensive
properties
ex. Real gold and “fools” gold have the
same appearance but real gold has its
own unique density that is different
from “fools” gold
III. Chemical Properties of Matter
• A chemical property is the
ability of a substance to
combine with or change into
one or more other
substances as a result of its
contact with other
substances or the
application of thermal or
electrical energy
• The inability of a substance
to change into another
substance is also a chemical
property
IV. Observing Properties of Matter
• Observations of properties may vary
depending on the conditions of the
immediate environment
• It is important to state the specific
conditions in which observations are made
because both chemical and physical
properties depend on temperature and
pressure
V. States of Matter
A. Solids
• A form of matter that has its own definite
shape and volume
• Particles of matter are very tightly packed
• Expands only slightly when heated
• Because its shape is definite, a solid may
not conform to the shape of the container
in which it is placed
B. Liquids
• A form of matter that flows, has constant
volume, and takes the shape of its
container
• Particles are not rigidly held in place and
are less closely packed than are the
particles in a solid
• Tend to expand when heated
C. Gases
• A form of matter that flows to
conform to the shape of its
container and fills the entire
volume of its container
• Particles are very far apart
• Easily compressed
• The word gas refers to a
substance that is naturally in
the gaseous state at room
temperature
- The word vapor refers to the gaseous state of
a substance that is a solid or a liquid at room
temperature; is should not be confused with
gas
ex. Water is a liquid at room temperature;
steam, its gaseous state, is a vapor
VI. Physical Changes
• A physical change alters a substance
without changing its composition
• Temperature and pressure alter a
substances state of matter which is also a
physical change that does not change its
composition
- these properties are listed as the melting
point and boiling points of a substance
and can help identify unknown substances
(p.914-916)
VII. Chemical Changes
• A chemical change, or chemical reaction,
involves one or more substances changing
into new substances
• The new substances formed in the reaction
have different compositions and different
properties from the substances present
before the reaction occurred
• In chemical reactions, the starting substances
are called reactants and the new substances
that are formed are called products
• Terms referring to chemical changes include
explode, rust, oxidize, corrode, tarnish,
ferment, burn, or rot
VIII. Conversion of Mass
• The law of conservation of mass states that
mass is neither created nor destroyed
during a chemical reaction – it is conserved
massreactants = massproducts
IX. Mixtures
• A mixture is a combination
of two or more pure
substances in which each
pure substance retains its
individual chemical
properties
A. Heterogeneous Mixtures
• A mixture that does not
blend smoothly
throughout and in which
the individual
substances remain
distinct
B. Homogeneous Mixtures
• A mixture that has constant
composition throughout
• Homogeneous mixtures are also
referred to as solutions
- solutions can contain solids,
liquids, or gases
- solid-solid solutions are called
alloys
X. Separating Mixtures
• Because the substances in a mixture are
physically combined, the processes used to
separate a mixture are physical processes
that are based on the difference in physical
properties of the substances
A. Filtration
• Heterogeneous
mixtures composed of
solids and liquids are
separated by filtration
• Filtration is a technique
that used a porous
barrier to separate a
solid from a liquid
B. Distillation
• Homogeneous mixtures
composed of two liquids can be
separated by distillation
• Distillation is a technique that is
based on differences in boiling
points of the substances
involved
- a mixture is heated until the
substance with the lowest
boiling point boils to a vapor
that can be condensed into a
liquid and collected
C. Crystallization
• Homogeneous mixtures composed of a solid
dissolved in a liquid can be separated by
crystallization
• When a solution contains as much dissolved
substance as it can possible hold, the addition
of a tiny amount more often causes the
dissolved substance to come out of solution
and collect as crystals on some available
surface
D. Chromatography
• Chromatography is a technique that
separates the components of a mixture
(called the mobile phase) on the basis of
the tendency of each to travel or be drawn
across the surface of another material
(called the stationary phase)
http://www.youtube.com/watch?v=gpFb635N2wo&feature=related
XI. Elements
• An element is a pure substance that cannot
be separated into simpler substances by
physical or chemical means
• Each element has a unique chemical name
and symbol that are universally accepted
A. A first look at the periodic table
• As many new elements were
being discovered in the early
nineteenth century, schemes
for organizing the elements on
the basis of patterns of
similarities in chemical and
physical properties were being
proposed
• Dmitri Mendeleev devised the
first accepted chart by
organizing the elements in rows
and columns based on their
similarities and masses
• Mendeleev was able to predict the properties
of elements that were yet to be discovered
and where they belonged on the table
• Mendeleev’s table was further developed into
the periodic table of elements
- elements are organized into horizontal rows
called periods and vertical columns called
groups or families
XII. Compounds
• A compound is a combination of two or
more different elements that are combined
chemically
i.e. water, table salt, aspirin
• Compounds can be broken down into
simpler substances by chemical means
- often requires external energy such as
heat or electricity
• The properties of a compound are
different from those of its individual parts
XIII. Law of Definite Proportions
• The law of definite proportions states that a
compound is always composed of the same
ratio of the mass of each element that
compose it, or percent by mass
Percent by mass (%) = mass of element/mass
of compound X 100
O
H
H
• The law of definite proportions also suggests
that the mass of the compound is equal to the
sum of the masses of the elements that made
up the compound
• Compounds with different mass proportions
must be different compounds
H
O
H
H
H
O
O
XIV. Law of Multiple Proportions
• The law of multiple proportions states that
when different compounds are formed by a
combination of the same elements,
different masses of one element combine
with the same relative mass of the other
element in a ratio of small whole numbers