Download Untitled - Triumph Learning

Contents
Ohio Revised Standards and Model
Curriculum Correlation Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Chapter 1 Earth Science . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Lesson 1 Earth’s Internal Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Lesson 2
Learning from Seismic Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Lesson 3
The Theory of Plate Tectonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Lesson 4
Plate Motion and Earth’s Changing Surface . . . . . . . . . . . . . . . . . 29
Lesson 5
The Effects of Erosion and Deposition . . . . . . . . . . . . . . . . . . . . . . 35
Lesson 6
Studying Earth’s Surface from Above . . . . . . . . . . . . . . . . . . . . . . 41
Lesson 7
Evidence of Earth’s History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Chapter 1 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Chapter 2 Life Science . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Lesson 8 Sexual and Asexual Reproduction . . . . . . . . . . . . . . . . . . . . . . . . . 62
Lesson 9
Patterns of Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Lesson 10 Adaptations, Survival, and Extinction . . . . . . . . . . . . . . . . . . . . . . . 76
Lesson 11 Fossils and Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Chapter 2 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Chapter 3 Physical Science . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Lesson 12 Force, Motion, and Inertia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Lesson 13 Friction and Gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Lesson 15 Potential Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Chapter 3 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
Investigation 1 Modeling Plate Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
Investigation 2 Making and Testing an Electromagnet . . . . . . . . . . . . . . . . . 133
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
Comprehensive Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
Duplicating any part of this book is prohibited by law.
Lesson 14 Electricity and Magnetism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
4 245OH_Sci_G8_SE_PDF.indd 4
05/06/12 11:53 AM
Chapter 1 • Lesson 1
Earth’s Internal Structure
Key Words • crust • continental crust • oceanic crust • mantle • asthenosphere • core • lithosphere
• tectonic plate • convection • theory of plate tectonics • model
Getting the Idea
Earth resembles a hard-boiled egg with a cracked shell. A hard-boiled egg has three
main parts: the shell, the egg white, and the yolk. Earth also has three parts: the
crust, the mantle, and the core. Like a cracked eggshell, Earth’s crust is made up of
smaller pieces, known as plates.
The Formation of Earth
Earth’s internal structure is the result of how the planet formed, about 4.6 billion years
ago. Early Earth was hot—so hot that it was completely melted. Heavier elements,
such as iron and nickel, sank to the center and formed Earth’s core. Lighter elements
remained near the surface. These lighter materials cooled to produce a solid outer
layer of rock. The process in which heavier and lighter elements separated is called
planetary differentiation. Other planets in our solar system were formed by the same
process at around the same time.
Earth’s Crust
Earth has two kinds of crust, continental crust and oceanic crust. Continental crust is
the lighter, older, and thicker part of the crust that makes up the continents. Oceanic
crust is the thinner, denser rock that makes up the ocean floor.
In the 1970s and 1980s, scientists drilled a hole into
Earth’s crust in what was then the Soviet Union.
They reached a depth of more than 12 kilometers
before they had to stop. At that point, increasing
heat made drilling impossible.
Duplicating any part of this book is prohibited by law.
Earth’s outermost layer is the crust. The crust is Earth’s thinnest layer, ranging from
about 5 kilometers to about 100 kilometers thick. The crust makes up only about
1 percent of Earth’s mass.
14
245OH_Sci_G8_SE_PDF.indd 14
05/06/12 11:54 AM
Earth’s Mantle
The mantle is the layer of Earth beneath the crust. The mantle is about 2900 kilometers thick
and makes up nearly 67 percent of Earth’s mass.
Crust
5–100 km
thick
Lithosphere
Asthenosphere
Mantle
Outer core
2 90 0 k m
Upper mantle
Lower mantle
5100 km
Inner core
NOTE: To scale
6378 km
NOTE: Not to scale
There are two main layers in the mantle: the upper mantle and the lower mantle. The top
of the upper mantle is solid, but great heat and pressure make the middle of the upper
mantle soft. This region of hot, soft rock is called the asthenosphere. The rock in the
asthenosphere flows slowly, like a very thick liquid. Below this region is a transition zone.
Scientists believe the lower mantle is solid, although it is even hotter than other parts of the
mantle. In the lower mantle, the pressure is so great that it keeps the rock from melting.
Earth’s Core
Duplicating any part of this book is prohibited by law.
Earth’s innermost layer is the core. It is about 3500 kilometers thick and makes up about
33 percent of Earth’s mass. The core is made up mainly of iron, with a small amount of
nickel and other elements. It consists of two parts: the inner core and the outer core. The
outer core is liquid. It consists of extremely hot, melted rock. Enormous pressures keep the
inner core solid. At the center of the core, the temperature is greater than 6000°C, and the
pressure is 4 million times greater than the air pressure at Earth’s surface.
Tectonic Plates
The crust and the solid part of the upper mantle make up the lithosphere. The lithosphere is
divided into giant, slow-moving chunks of rock called tectonic plates. You can think of the
lithosphere as a jigsaw puzzle. Each tectonic plate is a piece of the puzzle. Tectonic plates
float on the asthenosphere below.
245OH_Sci_G8_SE_PDF.indd 15
15
05/06/12 11:54 AM
Tectonic plates move because of convection currents in the asthenosphere. Convection is
the transfer of heat by the movement of a fluid—that is, a liquid or a gas. When a region of
a fluid absorbs heat energy, that region expands and becomes lighter. The warm fluid floats
upward as cooler, heavier fluid sinks beneath it. This process creates circular convection
currents of warmer fluid rising and cooler fluid sinking.
Because rock in the asthenosphere is so soft, it can transfer heat through convection, as a
fluid does. Heat coming from the core causes rock in the lower part of the asthenosphere
to expand and rise. As the rock gets closer to Earth’s surface, it cools and sinks. Rising
currents in the asthenosphere push the plates in the lithosphere apart. Sinking currents pull
plates toward each other. The theory that describes these processes is called the theory of
plate tectonics. You will learn more about this theory in Lesson 3.
Atlantic Ocean
Africa
South America
Plate
Plate
te
Pla
Heated material
expands and rises.
Duplicating any part of this book is prohibited by law.
Denser
material sinks.
16 • Chapter 1: Earth Science
245OH_Sci_G8_SE_PDF.indd 16
05/06/12 11:54 AM
Lesson 1: Earth’s Internal Structure
Focus on Inquiry
A model is a representation of an object, system, or process. A model may be a diagram, a
three-dimensional object, or a computer program. A model may also be an idea or a mathematical
formula. The diagram on page 15 is a model of Earth’s internal structure. Comparing the layers
of Earth to the layers of a hard-boiled egg is also a model.
Scientists use models for a number of reasons. Here are some ways in which models are used:
■
■
■
■
to represent an object that is too small or large to be directly observed
to show how the sizes of the parts of an object are related
to show how objects affect each other
to show how objects change over time
All models have advantages and limitations. A hard-boiled egg and the diagram on page 15
are both useful for learning about Earth’s internal structure, which cannot be directly observed.
However, as a model of Earth, a hard-boiled egg has limitations because it is not very detailed.
The diagram has much greater detail but is limited by being two-dimensional. Also, it shows each
of Earth’s layers as having exactly the same thickness throughout, but the thickness of the layers
can vary.
Think of another way to model Earth’s structure. Your model should show the inner core, outer
core, upper mantle, lower mantle, and crust. Describe your model below.
Duplicating any part of this book is prohibited by law.
Identify at least one advantage of your model.
Identify at least one disadvantage of your model.
245OH_Sci_G8_SE_PDF.indd 17
17
05/06/12 11:54 AM
Lesson Review
1.
Which layer of Earth consists mostly of iron?
A. continental crust
B. oceanic crust
C. mantle
D. core
2.
Which of these layers makes up most of Earth’s mass?
A. continental crust
B. oceanic crust
C. mantle
D. core
3.
On a cross-sectional diagram of Earth, you would label the center of the planet as the
A. inner core.
B. outer core.
C. mantle.
D. crust.
4.
Which layer of Earth is soft and somewhat fluid, like a very thick liquid?
B. the lithosphere
C. the crust
D. the inner core
Duplicating any part of this book is prohibited by law.
A. the asthenosphere
18 • Chapter 1: Earth Science
245OH_Sci_G8_SE_PDF.indd 18
05/06/12 11:54 AM