Chapter 2
◦ Bamboo has properties that
make it a good choice for
use in chopsticks. It has no
noticeable odor or taste. It
is hard, yet easy to split,
and it is heat resistant. You
will learn how properties
can be used to classify and
identify matter.

Describing Matter
◦ How are properties used to describe matter
classified?
◦ Properties used to describe matter can be classified
as extensive or intensive.
◦ Extensive Properties
 The mass of an object is a measure of the amount of
matter the object contains.
 The volume of an object is a measure of the space
occupied by the object.
 An extensive property is a property that depends on the
amount of matter in a sample.
◦ Intensive Properties
 An intensive property is a
property that depends on the type
of matter in a sample, not the
amount of matter. The hardness
of a bowling ball is an example of
an intensive property.

Identifying Substances
◦ Why do all samples of a substance have the same
intensive properties?
 Matter that has a uniform and definite composition is
called a substance. These kettles are mainly copper.
Copper is an example of a substance.
 This sculpture of a falcon is
made of gold. Gold is an
example of a substance.
 Every sample of a given substance has identical
intensive properties because every sample has the
same composition.
 A physical property is a quality or condition of a
substance that can be observed or measured without
changing the substance’s composition.
 Hardness, color, conductivity, boiling point, density
and malleability are examples of physical properties.
 See reference table S

States of Matter
◦ What are three states of matter?
◦ Three states of matter are solid, liquid, and gas.
◦ Solids
 A solid is a form of matter
that has a definite shape and
volume.
◦ Liquid
 A liquid is a form of matter
that has an indefinite shape,
flows, yet has a fixed volume.
◦ Gases
 A gas is a form of matter that
takes both the shape and
volume of its container.
 Vapor describes the gaseous state of a
substance that is generally a liquid or solid at
room temperature, as in water vapor.

Physical Changes
◦ How can physical changes be classified?
 During a physical change,
some properties of a material
change, but the composition
of the material does not
change.
 As gallium melts in a person’s
hand, the shape of the sample
changes, but the composition
of the material does not
change.
◦ Panning is one way to separate
gold from a mixture of gold and
materials such as sand or gravel.
A pan containing the mixture is
place underwater and shaken
vigorously from left to right. You
will learn how to classify and
separate mixtures.

Classifying Mixtures
◦ How can mixtures be classified?
 A mixture is a physical blend of two or more components.
 A salad bar provides a range of items. Customers choose
how much of each item to use in their salads. Each salad has
a different composition.
◦ Based on the distribution of their components,
mixtures can be classified as heterogeneous
mixtures or as homogeneous mixtures.
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 A mixture in which the composition is not uniform
throughout is a heterogeneous mixture.
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 A mixture in which the composition is uniform throughout
is a homogeneous mixture.
 Another name for a homogeneous mixture is a solution.
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 The term phase is used to describe any part of a
sample with uniform composition and
properties.
 A homogenous mixture consists
of a single phase.
 A heterogeneous mixture consists of two or more
phases.
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 When oil and vinegar are mixed they form layers, or
phases. The oil phase floats on the water phase.
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
Separating Mixtures
◦ How can mixtures be separated?
◦ Differences in physical properties can be used to
separate mixtures.
◦ Filtration
 The process that separates a solid from the liquid in a
heterogeneous mixture is called filtration.
 A colander is used to separate pasta from the water in
which it was cooked. This process is a type of filtration.
◦ Distillation
 During a distillation, a liquid is boiled to produce a
vapor that is then condensed into a liquid.
◦ Take two pounds of sugar, two cups
of boiling water, and one quarter
teaspoon of cream of tartar. Add
food coloring and you have the
sticky, sweet concoction known as
cotton candy. You will learn how
substances are classified as
elements or compounds.

Distinguishing Elements and Compounds
◦
How are elements and compounds different?
 An element is the simplest form of matter that has a
unique set of properties.
 A compound is a substance that contains two or more
elements chemically combined in a fixed proportion.
◦ Compounds can be broken down into simpler
substances by chemical means, but elements cannot.
◦ Breaking Down Compounds
 A chemical change is a change
that produces matter with a
different composition than the
original matter.
 When table sugar is heated, it
goes through a series of
chemical changes.
 The final products of these chemical changes are solid
carbon and water vapor. The following diagram
summarizes the process.
 In general, the properties of compounds
are quite different from those of their
component elements.
 When the elements sodium and chlorine
combine chemically to form sodium
chloride, there is a change in composition
and a change in properties.
 Chlorine is used to kill
harmful organisms in
swimming pools.
 Sodium is stored
under oil to keep it
from reacting with
oxygen or water
vapor in the air.
Sodium vapor
produces the light in
some street lamps.
 Sodium Chloride
(commonly known as
table salt) is used to
season or preserve
food.
How can substances and mixtures be
distinguished?
If the composition of a material is
fixed, the material is a substance. If
the composition of a material may
vary, the material is a mixture.
 This flowchart
summarizes the
process for
classifying
matter.

Symbols and Formulas
◦ What do chemists use to represent elements and
compounds?
◦ Chemists use chemical symbols to represent
elements, and chemical formulas to represent
compounds.
◦ These chemical symbols were used in earlier
centuries.
 Each element is represented by a one or two-letter
chemical symbol.
◦ Iron is abundant, easy to shape
when heated, and relatively
strong, especially when mixed
with carbon in steel. Over time,
objects made of iron will rust if
they are left exposed to air. You
will learn to recognize chemical
changes and to distinguish them
from physical changes.
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
Chemical Changes
◦
What always happens during a chemical change?
 The ability of a substance to undergo a specific
chemical change is called a chemical property.
 Chemical properties can be used to identify a
substance. But chemical properties can be observed
only when a substance undergoes a chemical change.
◦ During a chemical change, the composition of
matter always changes.
◦ Recall that during a physical change, the
composition of matter never changes.
 A magnet separates iron from sulfur. This is an
example of a physical change.
 A mixture of iron and sulfur is heated. The iron and
sulfur react and form iron sulfide. This is an example of
a chemical change.
 A chemical change is also called a chemical reaction.
 One or more substances change into one or more new
substances during a chemical reaction.
 A substance present at the start of the reaction is a
reactant.
 A substance produced in the reaction is a product.
What are four possible clues that a
chemical change has taken place?
◦ Possible clues to chemical change include:
 a transfer of energy
 a change in color
 the production of a gas
 the formation of a precipitate.
 A precipitate is a solid that forms and settles out of a
liquid mixture.
 Clues to chemical changes have practical applications.
How are the mass of the reactants and the mass of
the products of a chemical reaction related?
During any chemical reaction, the
mass of the products is always equal
to the mass of the reactants.
 The law of conservation of mass states that in any
physical change or chemical reaction, mass is
conserved.
 The conservation of mass is easily observed when a
change occurs in a closed container.