15
Table of Contents
15
Unit 4: The Nature of Matter
Chapter 15: Classification of Matter
15.1: Composition of Matter
15.2: Properties of Matter
Composition of Matter
15.1
Elements
• All substances are built from atoms.
• element – Pure Substance- all the atoms in a
have the same identity
• Examples: ?
Composition of Matter
15.1
Elements
• About 90 elements are found on Earth.
• More than 20 others have been made in
laboratories, but most of these are unstable
and exist only for short periods of time.
Composition of Matter
15.1
Compounds
• Compound- two or more elements combine
to form substances (has a specific chemical
composition)
• Examples?
Composition of Matter
15.1
Compounds
Composition of Matter
15.1
Mixtures
• A mixture- Material
made up of two or
more substances that
can be easily
separated by physical
means.
• Examples?
Composition of Matter
15.1
Heterogeneous Mixtures
• heterogeneous mixture -A mixture in which
different materials can be distinguished easily
• Examples?
Composition of Matter
15.1
Heterogeneous Mixtures
Composition of Matter
15.1
Homogeneous Mixtures
Composition of Matter
15.1
Homogeneous Mixtures
• Homogeneous mixture two or more
gaseous, liquid, or solid substances blended
evenly throughout.
• Examples?
Composition of Matter
15.1
Homogeneous Mixtures
• Solution –
• (AKA- homogeneous mixture)
• Particles cannot be seen with a microscope
• Will never settle to the bottom of their
container.
Composition of Matter
15.1
Colloids
• colloid -Mixture with particles that are larger
than those in solutions but not heavy enough
to settle out.
• Not homogeneous or heterogeneous
• Examples?
Composition of Matter
15.1
Detecting Colloids
• Tyndall effectscattering of light
by colloidal
particles
Composition of Matter
15.1
Suspensions
• suspension, which is a heterogeneous
mixture containing a liquid in which visible
particles settle.
• Examples?
Composition of Matter
15.1
Suspensions
• The table summarizes the properties of
different types of mixtures.
Section Check
15.1
Question 1
A _______ is a type of matter with a fixed
composition.
A. colloid
B. mixture
C. substance
D. solution
Section Check
15.1
Answer
The answer is C. A substance can be either
an element or a compound.
Section Check
15.1
Question 2
How many elements are found on Earth?
A. 5
B. 10
C. 30
D. 90
Section Check
15.1
Answer
The answer is D. About 90 elements are
found on Earth, and more than 20 have been
made in laboratories.
Section Check
15.1
Question 3
How are compounds different from
mixtures?
Section Check
15.1
Answer
The atoms in compounds are combined in
fixed proportions and cannot be separated by
physical means. A mixture is made of two
or more substances that can be easily
separated by physical means.
Properties of Matter
15.2
Physical Properties
• physical property - characteristic of a
material that you can observe without
changing the identity of the material.
• Examples: color, shape, size, density,
melting point, and boiling point.
• Item Examples:
Properties of Matter
15.2
Behavior
Properties of Matter
15.2
Physical Change
The Identity Remains the
Same
• physical change -A change in size, shape, or
state of matter.
• Examples?
Properties of Matter
15.2
The Identity Remains the
Same
Properties of Matter
15.2
Using Physical Change to
Separate
• Distillation- Separating substances in a
mixture by evaporating a liquid and
recondensing its vapor
Properties of Matter
15.2
Distillation
Properties of Matter
15.2
Chemical Properties and
Changes
• chemical property- characteristic of a
substance that indicates whether it can
undergo a certain chemical change.
• Examples?
Properties of Matter
15.2
Detecting Chemical Change
• If you leave a pan of chili cooking unattended
on the stove for too long, your nose soon tells
you that something is wrong.
• This burnt odor is a clue telling you that a
new substance has formed.
Properties of Matter
15.2
The Identity Changes
• chemical change - A change from one
substance to another
• Indications of chemical
change:
• Odor
• Temperature Change
• Formation of gas/solid
• Color
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Properties of Matter
15.2
The Conservation of Mass
Properties of Matter
15.2
The Conservation of Mass
• Law of conservation of mass, the mass of
all substances equal the mass of all the
substances that remain after the change.
• no mass is lost during a chemical or physical
reaction.
Section Check
15.2
Question 1
Which of the following is a chemical
property?
A. boiling point
B. density
C. flammability
D. melting point
Section Check
15.2
Answer
The answer is C. Flammability indicates
whether a substance will undergo the
chemical change of burning.
Section Check
15.2
Question 2
A characteristic of a material that can be
observed without changing the identity of
the substances that make up the material is a
_______.
Section Check
15.2
Answer
The answer is physical property. Examples
of physical properties include color, shape,
and density.
Section Check
15.2
Question 3
What is the law of conservation of mass?
Section Check
15.2
Answer
According to the law of conservation of
mass, the mass of all substances that are
present before a chemical change equals the
mass of all substances that remain after the
change.
15
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