Chapter 2
Matter & Change
Properties of Matter
– 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
– Properties used to describe matter can be
classified as extensive or intensive.
Describing Matter
– 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.
Describing Matter
– 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
• Identifying Substances
– Why do all samples of a substance have the same
intensive properties?
Identifying Substances
• Matter that has a uniform and definite composition
is called a substance. These kettles are mainly
copper. Copper is an example of a substance.
Identifying Substances
•This sculpture of a falcon
is made of gold. Gold is
an example of a
substance.
Identifying Substances
• Every sample of a given substance has identical
intensive properties because every sample has the
same composition.
Identifying Substances
• 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, and malleability are
examples of physical properties.
Identifying Substances
States of Matter
• States of Matter
– What are three states of matter?
– Three states of matter are solid, liquid, and gas.
States of Matter
– Solids
• A solid is a form of
matter that has a definite
shape and volume.
States of Matter
– Liquid
• A liquid is a form of
matter that has an
indefinite shape, flows,
yet has a fixed volume.
States of Matter
– Gases
• A gas is a form of matter
that takes both the shape
and volume of its
container.
The Three States of Matter
States of Matter
– Animation 1
– Relate the states of matter to the arrangements
of their particles.
States of Matter
• Vapor describes the gaseous state of a
substance that is generally a liquid or solid
at room temperature, as in water vapor.
Physical Changes
• Physical Changes
– How can physical changes be classified?
Physical Changes
• 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.
Physical Changes
•Physical changes can be classified as reversible or
irreversible.
• All physical changes that involve a change from
one state to another are reversible.
• Cutting hair, filing nails, and cracking an egg are
examples of irreversible physical changes.
Section Quiz.
– 1.
Which of the following would be
described as an extensive property of matter?
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temperature
color
mass
hardness
Section Quiz.
– 2.
Which properties can be observed
without changing the composition of a
substance?
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all properties of a substance
intensive properties
chemical properties
physical properties
Section Quiz.
– 3.
Match the states of matter with the following
descriptions:
(1) takes the volume and shape of its container
(2) has a definite shape and volume
(3) has a definite volume but an indefinite shape
• (1) liquid, (2) solid and (3) gas
• (1) gas, (2) solid, and (3) liquid
• (1) gas, (2) liquid, and (3) solid
Mixtures
– 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
• Classifying Mixtures
– How can mixtures be classified?
Classifying Mixtures
•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.
Classifying Mixtures
– Based on the distribution of their components,
mixtures can be classified as heterogeneous
mixtures or as homogeneous mixtures.
Classifying Mixtures
–Heterogeneous Mixtures
•A mixture in which the composition is not uniform
throughout is a heterogeneous mixture.
Classifying Mixtures
–Homogeneous Mixtures
•A mixture in which the composition is uniform throughout is a
homogeneous mixture.
•Another name for a homogeneous mixture is a solution.
Classifying Mixtures
• 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.
Classifying Mixtures
• When oil and vinegar are mixed they form layers, or phases.
The oil phase floats on the water phase.
Separating Mixtures
• Separating Mixtures
– How can mixtures be separated?
Separating Mixtures
– Differences in physical properties can be used to
separate mixtures.
Separating 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.
Separating Mixtures
– Distillation
• During a distillation, a liquid is boiled to produce a
vapor that is then condensed into a liquid.
– 1.
Which of the following phrases
describes a mixture?
• composition varies
• composition may vary
• components cannot be separated
– 2.
Which of the following is a
homogeneous mixture?
• vinegar
• iron filings in sand
• chicken noodle soup
• muddy water
– 3.
Which technique is used to separate
homogeneous mixtures?
• filtration
• distillation
• magnetism
• dissolving
Elements and Compounds
– 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
• Distinguishing Elements and Compounds
– How are elements and compounds different?
Distinguishing Elements and
Compounds
• 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.
Distinguishing Elements and
Compounds
– Compounds can be broken down into simpler
substances by chemical means, but elements cannot.
Distinguishing Elements and
Compounds
– 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.
Distinguishing Elements and
Compounds
• The final products of these chemical changes are
solid carbon and water vapor. The following
diagram summarizes the process.
•
Distinguishing Elements and
Compounds
–Properties of Compounds
–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.
Distinguishing Elements and
Compounds
• Chlorine is used to kill
harmful organisms in
swimming pools.
Distinguishing Elements and
Compounds
• 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.
Distinguishing Elements and
Compounds
• Sodium Chloride
(commonly
known as table
salt) is used to
season or
preserve food.
Distinguishing Substances and
Mixtures
• Distinguishing Substances and Mixtures
– How can substances and mixtures be
distinguished?
Distinguishing Substances and
Mixtures
– 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.
Classification of Matter
Matter
Yes
Can it be separated?
No
Mixtures
Blend
of two or more
Is composition
uniform?
Pure Substances
kinds of matter, each of
No
Can it be decomposed by
Yes
which retains its own Has a fixed composition;
ordinary chemical means?
identity and propertieshas exactly the same
properties
throughout;
Yes
Nohas
exactly the same
Homogeneous
Heterogeneous
composition
Compounds
Elements
Symbols and Formulas
• Symbols and Formulas
– What do chemists use to represent elements
and compounds?
Symbols and Formulas
– Chemists use chemical symbols to represent
elements, and chemical formulas to represent
compounds.
– These chemical symbols were used in earlier
centuries.
Symbols and Formulas
• Each element is represented by a one or two-letter
chemical symbol.
– 1.
Passing an electric current through a
certain substance produces oxygen and sulfur.
This substance cannot be a(n)
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compound.
mixture.
element.
solution.
– 2.
Which of the following is a
mixture?
• sodium chloride
• carbon dioxide
• sucrose
• air
– 3.
The symbol for the element
potassium is
• K.
• Po.
• P.
• Pt.
Chemical Reactions
– 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.
Chemical Changes
• Chemical Changes
– What always happens during a chemical change?
Chemical Changes
• 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.
Chemical Changes
– During a chemical change, the composition of
matter always changes.
– Recall that during a physical change, the
composition of matter never changes.
Chemical Changes
• A magnet separates iron from sulfur. This is an
example of a physical change.
Chemical Changes
• 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.
Chemical Changes
–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.
Recognizing Chemical Changes
• Recognizing Chemical Changes
– What are four possible clues that a chemical
change has taken place?
Recognizing Chemical Changes
– Possible clues to chemical change include:
• a transfer of energy
• a change in color
• the production of a gas
• the formation of a precipitate.
Chemical Changes
• A precipitate is a solid that forms and settles out of
a liquid mixture.
• Clues to chemical changes have practical
applications.
Conservation of Mass
• Conservation of Mass
– How are the mass of the reactants and the mass of the
products of a chemical reaction related?
Conservation of Mass
– During any chemical reaction, the mass of the
products is always equal to the mass of the
reactants.
Conservation of Mass
• 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.
– 1.
Which of the following is a chemical
reaction?
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melting of lead
dissolving sugar in water
rusting of iron
crushing of stone
– 2.
Which of the following is NOT a
possible clue that a chemical change is taking
place?
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a change of state
a change in color
production of a gas
formation of a precipitate
– 3.
During any chemical change, the mass of the
products is
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always equal to the mass of the reactants.
always greater than the mass of the reactants.
always less than the mass of the reactants.
sometimes different than the mass of the reactants.
Pure
Substances
and Mixtures
Pure Substances and Mixtures
• If matter is not uniform throughout, then it is a
heterogeneous mixture.
• If matter is uniform throughout, it is
homogeneous.
• If homogeneous matter can be separated by
physical means, then the matter is a mixture.
• If homogeneous matter cannot be separated by
physical means, then the matter is a pure
substance.
• If a pure substance can be decomposed into
something else, then the substance is a compound.
Groups
Periodic Table
Metalloids
Periods
Noble
Gases