Coach is the leader in standards-based, state-customized instruction for grades K–12 in English
language arts, mathematics, science, and social studies. Our student texts deliver everything you
need to meet your state standards and prepare your class for grade-level success!
Coach lessons have just what you’re looking for:
✔✔ Easy-to-follow, predictable lesson plans
✔✔ Focused instruction
✔✔ Higher-level thinking activities
✔✔ Two Laboratory Investigations
PLUS Chapter Reviews that target assessed
New Jersey ASK8 Coach, Gold Edition, Science, Grade 8
Your complete ASK8 program!
content and skills
Used by more students in the U.S. than any other state-customized series, Coach books are
proven effective. Triumph Learning has been a trusted name in educational publishing for more than
40 years, and we continue to work with teachers and administrators to keep our books up to date—
improving test scores and maximizing student learning.
Please visit our Web site for detailed product descriptions of all our instructional materials, including
sample pages and more.
www.triumphlearning.com
This book is printed on paper containing
a minimum of 10% post-consumer waste.
167NJ_Sci_G8_SE_Cvr.indd✔✔✔1
167NJ
Phone: (800) 221-9372 • Fax: (866) 805-5723 • E-mail: [email protected]
Developed in Consultation
with New Jersey Educators
7/21/10✔✔✔4:12✔PM
Table of Contents
New Jersey Core Curriculum Content Standards
Correlation Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
CPIs
Chapter 1 Physical Science: Properties of Matter . . . . . . . . . . 17
Lesson 1
Atoms and Elements . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.2.8.A.1, 5.2.8.A.2
Lesson 2
States of Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.2.8.A.3
Lesson 3
The Periodic Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5.1.8.C.1, 5.2.8.A.4, 5.2.8.A.5,
5.2.8.A.6
Lesson 4
Chemical Reactions. . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.1.8.B.2, 5.2.8.A.5, 5.2.8.B.1,
5.2.8.B.2
Lesson 5
Acids and Bases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.1.8.D.3, 5.2.8.A.5, 5.2.8.A.7
Chapter 1 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Chapter 2 Physical Science: Motion, Forces, and Energy . . . 47
Lesson 6
Motion and Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
5.1.8.B.2, 5.2.8.E.1
Lesson 7
How Forces Affect Motion. . . . . . . . . . . . . . . . . . . . . . 52
5.2.8.E.2
Lesson 8
Potential and Kinetic Energy . . . . . . . . . . . . . . . . . . . . 55
5.2.8.D.1
Lesson 9
The Transfer of Light and Heat . . . . . . . . . . . . . . . . . . 60
5.2.8.C.2
Lesson 10
Energy from the Sun . . . . . . . . . . . . . . . . . . . . . . . . . . 64
5.2.8.C.1, 5.2.8.C.2, 5.2.8.D.2
Chapter 3 Life Science . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Lesson 11 The Organization of Living Things . . . . . . . . . . . . . . . . 76
5.3.8.A.1, 5.3.8.A.2
Lesson 12
Food: Energy and Materials for Cells . . . . . . . . . . . . . 80
5.3.8.B.1
Lesson 13
The Flow of Energy in Ecosystems . . . . . . . . . . . . . . . 84
5.3.8.B.2, 5.3.8.C.1
Lesson 14
Relationships in Ecosystems . . . . . . . . . . . . . . . . . . . . 88
5.3.8.C.1
Lesson 15
DNA, Genes, and Chromosomes . . . . . . . . . . . . . . . . 91
5.3.8.D.1
Lesson 16
Asexual and Sexual Reproduction . . . . . . . . . . . . . . . 95
5.3.8.D.1, 5.3.8.D.2
Lesson 17
Inherited Traits and Environmental Influences . . . . . . 99
5.3.8.D.3
Lesson 18
Adaptations, Survival, and Extinction . . . . . . . . . . . . 103
5.3.8.E.1
Lesson 19
Evidence of Evolution . . . . . . . . . . . . . . . . . . . . . . . . 107
5.3.8.E.2
Chapter 3 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Duplicating any part of this book is prohibited by law.
Chapter 2 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4
167NJ_Sci_G8_SE_PDF.indd 4
7/14/10 2:27:18 AM
CPIs
Chapter 4 Earth Science: Earth in the Universe . . . . . . . . . . . 121
Lesson 20 Gravitation and Orbits . . . . . . . . . . . . . . . . . . . . . . . . 122
5.4.8.A.3, 5.4.8.A.4
Lesson 21
Causes of Earth’s Seasons . . . . . . . . . . . . . . . . . . . . 127
5.4.8.A.2
Lesson 22
Phases of the Moon and Tides . . . . . . . . . . . . . . . . . 131
5.4.8.A.1
Lesson 23
Eclipses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
5.4.8.A.1
Chapter 4 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Chapter 5 Earth Science: Earth’s History,
Structure, and Processes . . . . . . . . . . . . . . . . . . . . 145
Lesson 24 Earth’s History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
5.4.8.B.1, 5.4.8.B.2
Lesson 25
Weathering and Erosion . . . . . . . . . . . . . . . . . . . . . . 152
5.4.8.C.2
Lesson 26
Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
5.1.8.B.2, 5.4.8.C.1
Lesson 27
Earth’s Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . 160
5.1.8.B.2, 5.4.8.C.3
Lesson 28
Earth’s Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
5.4.8.D.1
Lesson 29
Plate Tectonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
5.4.8.D.2
Lesson 30
Earth’s Magnetic Field . . . . . . . . . . . . . . . . . . . . . . . . 174
5.4.8.D.3
Chapter 5 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
Duplicating any part of this book is prohibited by law.
Chapter 6 Earth Science: Weather and Climate . . . . . . . . . . . 183
Lesson 31 Global Winds and Ocean Currents . . . . . . . . . . . . . . 184
5.4.8.E.1
Lesson 32
The Water Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
5.4.8.E.1
Lesson 33
Weather . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
5.4.8.F.1, 5.4.8.F.3
Lesson 34
Climate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
5.4.8.F.2, 5.4.8.F.3, 5.4.8.G.1
Lesson 35
Environmental Issues: Problems and Solutions . . . . 203
5.4.8.G.2
Chapter 6 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
Investigation 1 Testing Soil Permeability . . . . . . . . . . . . . . . . . . . 215
[seeStandards
Correlation Chart]
Investigation 2 Describing a Food Web. . . . . . . . . . . . . . . . . . . . 225
[seeStandards
Correlation Chart]
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
5
167NJ_Sci_G8_SE_PDF.indd 5
7/14/10 2:27:18 AM
Chapter 2 • Lesson 8
CPI: 5.2.8.D.1
Potential and Kinetic Energy
Key Words • energy • potential energy • gravitational potential energy • kinetic energy
• law of conservation of energy • friction
Getting the Idea
Energy is a word you use often in everyday life. You know that you need energy to
climb stairs or to carry your books. When you are advised to eat a good healthy
meal, you are told that it will give you energy. What is energy? The scientific definition
of energy is not very different from the way you use the word in everyday life.
What Is Energy?
Energy is the ability to make matter move or change. You need energy in order
to get things done. For example, you know that your body uses energy when you
perform physical activities. All energy is classified into two broad categories: potential
energy and kinetic energy. Either form of energy can change into the other.
Potential Energy
Potential energy (PE) is stored energy. Potential energy has the “potential” to make
matter move or change. An object can have potential energy because of its position.
A rock at the edge of a cliff has potential energy because of its position. Gravitational
force can pull the rock down to the bottom of the cliff, releasing the stored energy.
Gravitational potential energy (GPE) is energy stored because of an object’s
position. The higher the object, the more gravitational potential energy it has.
Duplicating any part of this book is prohibited by law.
This rock has more
potential energy.
55
167NJ_Sci_G8_SE_PDF.indd 55
7/14/10 2:27:33 AM
Potential energy is measured in units called joules (J). A joule is one kilogram (kg) times one
meter per second squared (m/s2). You can calculate an object’s gravitational potential energy
(GPE) near Earth by the following formula:
GPE mgh
In the formula above, m is mass in kilograms, g is acceleration due to gravity, and h is height
in meters. Suppose a rock at the edge of a cliff has a mass of 10 kg, and its height above
the ground below is 100 m. Acceleration due to gravitational force (g) is 9.8 m/s2. So the
rock’s gravitational potential energy is 9800 J.
GPE 10 9.8 100
GPE 9800 J
An object can also have potential energy because of its composition. This form of potential
energy is stored in the chemical bonds between atoms. The food you eat has chemical
potential energy. So do fuels such as coal, oil, and gasoline. When a fuel burns, the energy
stored in its chemical bonds is released.
Kinetic Energy
Kinetic energy (KE) is the energy of motion. The amount of kinetic energy an object has
depends on two factors: the object’s mass and its speed. An object’s kinetic energy changes
if its mass or its speed changes.
You can calculate the amount of kinetic energy an object has using the formula:
1 mv 2
KE __
2
In the formula above, m is mass in kilograms, and v is speed in meters per second. At one
point in its fall from the cliff, the 10-kg rock is moving at a speed of 20 m/s. You can
calculate its kinetic energy as follows:
1 10 202
KE __
KE 0.5 10 400
KE 2000 J
Potential and Kinetic Energy Transformations
Potential energy can change to kinetic energy, and vice versa. Picture a car on a roller
coaster track. At the top of a hill, the car has mostly potential energy. As the car rolls down
the hill, it moves faster and faster. More and more of its potential energy changes to kinetic
energy. At the bottom of the hill, it has mostly kinetic energy. As the kinetic energy moves
the car up the next hill, some of the kinetic energy changes back to potential energy.
Duplicating any part of this book is prohibited by law.
2
56 • Chapter 2: Physical Science: Motion, Forces, and Energy
167NJ_Sci_G8_SE_PDF.indd 56
7/14/10 2:27:33 AM
Lesson 8: Potential and Kinetic Energy
In the diagram below, the roller coaster car has mostly potential energy at points A, C, and
E. At points B, D, and F, the car has mostly kinetic energy.
A
C
E
B
D
F
Whenever energy is transformed, the total amount of energy stays the same. This principle
forms the basis of an important scientific law. The law of conservation of energy states
that although energy may change from one form to another, energy is neither created nor
destroyed. According to the law of conservation of energy, the total amount of energy of
a roller coaster car should stay the same. The car’s potential energy at the top of the hill
should equal its kinetic energy at the bottom of the hill. In such a system, the roller coaster
car could go up and down hills forever. But in real life, this does not happen. The roller
coaster car runs out of energy and stops moving.
Duplicating any part of this book is prohibited by law.
Although the car runs out of energy, this energy is not destroyed. Instead, it is transformed
to another form of energy. Friction changes some of the energy to thermal energy. Recall
that thermal energy is the energy of the moving particles that make up matter. Friction is
a force that acts between two surfaces that touch each other. Friction is present whenever
two objects are in contact with each other. Friction causes the wheels of the roller coaster
car to get hot. Because the energy that is changed to thermal energy is not useful energy, it
is sometimes described as “lost” energy. But the energy is not really “lost.” It is just changed
to another form of energy.
A swinging pendulum eventually stops because of air resistance. Air resistance is a form of
friction that opposes the motion of an object moving through air. When air resistance acts on
the pendulum, some of the pendulum’s kinetic energy is transformed to thermal energy.
57
167NJ_Sci_G8_SE_PDF.indd 57
7/14/10 2:27:33 AM
Discussion Question
As a pendulum swings, its energy is constantly changed from potential energy to kinetic energy
and back again. Study the diagram below.
A
E
B
C
D
At which point in its swing does the pendulum have the least potential energy and the most
kinetic energy? Explain your answer.
Lesson Review
1.
An apple is hanging from a tree branch. A gust of wind blows the tree, and the apple falls.
Which of the following describes the apple’s energy just as the apple hits the ground?
A. Its potential energy is zero.
B. Its kinetic energy is zero.
D. Its kinetic energy equals its potential energy.
2.
As a ball rolls down a hill, it has less potential energy than it did at the top of the hill. Some
of the ball’s potential energy
A. disappears.
B. decreases friction.
C. creates even more energy.
D. changes to kinetic energy.
Duplicating any part of this book is prohibited by law.
C. Its kinetic energy is twice its potential energy.
58 • Chapter 2: Physical Science: Motion, Forces, and Energy
167NJ_Sci_G8_SE_PDF.indd 58
7/14/10 2:27:33 AM
Lesson 8: Potential and Kinetic Energy
3.
Which of the following correctly describes the law of conservation of energy?
A. Energy cannot be created or destroyed but can be changed from one form to another.
B. Energy can be created or destroyed and can also be changed from one form to another.
C. Energy is created when it is changed from one form to another.
D. In some systems, energy is destroyed by friction.
4.
A ball with a mass of 5 kg is rolling at a speed of 4 m/s. What is its kinetic energy?
A. 20 J
B. 40 J
C. 80 J
D. 100 J
Duplicating any part of this book is prohibited by law.
59
167NJ_Sci_G8_SE_PDF.indd 59
7/14/10 2:27:33 AM