Table of Contents
Texas Essential Knowledge and Skills Correlation Chart. . . . . . . 7
TEKS
Chapter 1 Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Lesson 1
Atoms and Elements . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Lesson 2
6.5A*, C; 8.3B, D; 8.5A, B
The Chemical Composition of Earth
and Living Things. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.5B*, 7.6A
Lesson 3
The Periodic Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
6.6A; 8.3D; 8.5B, C
Lesson 4
Physical and Chemical Changes . . . . . . . . . . . . . . . . . 27
6.5D*, 8.1A, 8.4B, 8.5E
Lesson 5
Chemical Formulas and Reactions . . . . . . . . . . . . . . . 32
8.3D; 8.5D, F
Chapter 1 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Chapter 2 Energy, Force, and Motion . . . . . . . . . . . . . . . . . . . . 43
Lesson 6
Describing Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
6.8C, D; 8.2C, D; 8.4A; 8.6B
Lesson 7
Force, Motion, and Inertia . . . . . . . . . . . . . . . . . . . . . . 49
6.8B; 8.6A, C
Lesson 8
Work and Machines. . . . . . . . . . . . . . . . . . . . . . . . . . . 53
6.8E*, 7.7A
Lesson 9
Energy and Its Transformations. . . . . . . . . . . . . . . . . . 58
6.8A, 6.9C
Lesson 10
Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
6.9A*, B*; 8.2A, C, D, E; 8.4A
Lesson 11
Energy Resources and Their Environmental Impact . . 68
6.7A*, B*; 8.1B
Chapter 3 Space Science . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Lesson 12 Days, Years, and Seasons. . . . . . . . . . . . . . . . . . . . . . 82
6.11A*, 8.7A
Lesson 13
Phases of the Moon and Tides . . . . . . . . . . . . . . . . . . 86
8.2A, D, E; 8.7B, C
Lesson 14
The Sun and Other Stars . . . . . . . . . . . . . . . . . . . . . . . 92
6.11A*; 7.9A*; 8.8A, B
Lesson 15
The Solar System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
6.11A*, B; 7.9A*
Lesson 16
Exploring the Solar System and Beyond. . . . . . . . . . 101
6.11C*, 7.9B*, 8.8C
Lesson 17
Deep-Sky Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
8.3D, 8.8A
Lesson 18
Galaxies and Distances in Space . . . . . . . . . . . . . . . 109
8.2A; 8.8A, B, D
Lesson 19
Studying the Universe . . . . . . . . . . . . . . . . . . . . . . . . 114
8.3B–D; 8.8C, E
Chapter 3 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
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4
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Chapter 2 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
TEKS
Chapter 4 Earth Science . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
Lesson 20 Earth’s Internal Structure. . . . . . . . . . . . . . . . . . . . . . 126
6.10A*; 8.3B, C
Lesson 21
The Theory of Plate Tectonics. . . . . . . . . . . . . . . . . . 130
6.10D*, 8.3D, 8.9A
Lesson 22
Plate Motion and Earth’s Changing Surface . . . . . . . 133
6.10C*, D*; 8.9B
Lesson 23
Rocks and Minerals . . . . . . . . . . . . . . . . . . . . . . . . . . 138
6.5B*, C; 6.6B, C*; 6.10B*
Lesson 24
Weathering and Erosion . . . . . . . . . . . . . . . . . . . . . . 142
7.8A*, B*, C; 8.2E; 8.9C
Lesson 25
Using Maps to Study Earth’s Surface . . . . . . . . . . . . 147
7.8B*, 8.9C
Lesson 26
Global Winds and Ocean Currents . . . . . . . . . . . . . . 152
6.9A*; 8.10A, C
Lesson 27
Local and Global Weather . . . . . . . . . . . . . . . . . . . . . 157
8.2E, 8.10B
Chapter 4 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
Chapter 5 Cells and Organisms . . . . . . . . . . . . . . . . . . . . . . . . 171
Lesson 28 Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
6.12A*, B*; 7.7B*; 7.12D, E*, F
Lesson 29
Levels of Organization and Human Body Systems . . . 176
7.12B, C*
Lesson 30
Digestion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
7.6B*, C*; 7.12B
Lesson 31
Photosynthesis and Cellular Respiration. . . . . . . . . . 184
7.5A*, 7.7B, 7.12D, 8.5F
Lesson 32
How Animals Respond to Stimuli . . . . . . . . . . . . . . . 187
7.13A*, B*
Lesson 33
How Plants Respond to Stimuli. . . . . . . . . . . . . . . . . 191
7.7C*; 7.13A*, B*; 8.2B, 8.4A
Lesson 34
Heredity and Reproduction . . . . . . . . . . . . . . . . . . . . 196
7.12D, 7.14A*, B, C
Lesson 35
Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
6.12C*, D; 7.11A; 8.2A
Lesson 36
Adaptations, Variations, and Survival . . . . . . . . . . . . 207
7.11B*, C; 7.12A*; 8.3D; 8.11C
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Chapter 5 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
Chapter 6 Organisms and the Environment . . . . . . . . . . . . . . 219
Lesson 37 Ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
6.12E*, F*; 7.10A*; 8.2A; 8.11B
Lesson 38
Energy Flow in Ecosystems. . . . . . . . . . . . . . . . . . . . 224
7.5A*, B*, C*; 8.11A
Lesson 39
Changes in Ecosystems . . . . . . . . . . . . . . . . . . . . . . 230
7.8A; 7.10C; 8.11B, C
Lesson 40
Biodiversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
7.10B, 8.11B
Lesson 41
Oceans and Other Water Resources. . . . . . . . . . . . . 237
7.8C*; 8.11C, D
Chapter 6 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
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Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
Investigation 1 Testing Conservation of Mass. . . . . . . . . . . . . . . 247
8.1A; 8.2B–E; 8.3A; 8.4A, B;
8.5E, F
Investigation 2 Tracking the Path of a Hurricane . . . . . . . . . . . . 257
8.2A, C–E; 8.4A; 8.10C
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
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6 • Table of contents
Duplicating any part of this book is prohibited by law.
Comprehensive Review. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281
Chapter 1 • Lesson 1
TEKS: 6.5A, C; 8.3B, D; 8.5A, B
Atoms and Elements
Key Words • atom • element • nucleus • proton • charge • neutron • electron • atomic number • ion
• atomic mass • chemical symbol • compound • model • electron cloud model
Getting the Idea
Everything around you is matter. Matter is anything that has mass and volume.
Mass is the amount of matter in a substance. Volume is the amount of space the
substance occupies. All substances—everything you own, everything you touch,
even you yourself—are made up of different types of matter.
Atoms and Elements
Atoms are the basic building blocks of most of the matter around you. There are
different kinds of atoms. Each kind of atom is an element. An element is one of
the basic substances that combine to form all other substances. Elements cannot
be broken down into simpler substances by ordinary chemical means.
Scientists have discovered about 117 elements. These elements are the building
blocks of the matter around you. About 90 of these elements are found in nature.
Carbon, oxygen, gold, silver, and iron are some naturally occurring elements.
The remaining elements are synthetic, or made by humans in the laboratory.
An atom is the smallest particle of an element that has all the properties of that
element. Each element is made up of atoms that differ from those of every other
element. To understand how the atoms of each element differ, you need to look
at the particles that make up an atom.
The diagram below shows the structure of a carbon atom. Notice that this atom
is made up of three different kinds of particles.
Carbon Atom
Neutron
Proton (+)
Electron (–)
12
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Atoms and Their Parts
The center of the atom is called the nucleus. The nucleus of most atoms is made up of two
kinds of particles: protons and neutrons. Protons carry a positive (+) charge. Charge is an
electrical property that can be either positive or negative. Neutrons have no charge. The
masses of protons and neutrons are measured in atomic mass units (amu). Each proton and
neutron has a mass of about 1 amu.
Electrons are subatomic particles that exist in an area outside the nucleus. Electrons have a
negative (−) charge. The mass of electrons is insignificant compared to the mass of protons
and neutrons. The table below compares protons, neutrons, and electrons.
Characteristics of Subatomic Particles
Particle
Mass
Charge
Proton
1 amu
⫹1
Nucleus
Neutron
1 amu
0
Nucleus
Electron
—
⫺1
Location
Outside nucleus
Elements and Subatomic Particles
The properties, or characteristics, of an element are determined by the structure of its atoms.
The main difference between different elements is atomic number. Atomic number is the
number of protons in the nucleus of an atom. The number of protons in the nucleus is unique
for each element. Therefore, no two elements have the same atomic number. Carbon, for
example, has six protons and an atomic number of 6.
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Look at the carbon atom on page 12 again. Notice that the number of protons in the atom is
equal to the number of electrons. Because these numbers are equal, each positive charge in
the nucleus is balanced by a negative charge in the electrons around the nucleus. The atom
as a whole is electrically neutral and has no overall charge. If the numbers of protons and
electrons in an atom are not equal, the atom has a charge. A charged atom is called an ion.
Atoms have mass. The atomic mass of an atom is equal to the total mass of protons,
neutrons, and electrons in the atom. The unit for atomic mass is the atomic mass unit (amu).
Each proton has a mass of about 1 amu. Each neutron also has a mass of 1 amu. Electrons
have almost no mass. You can therefore determine the atomic mass by counting the protons
and neutrons in an atom.
13
The table below gives the atomic masses of several common elements.
Atomic Masses of Some Elements
Element
Protons
Neutrons
Electrons
Atomic Mass
Carbon (C)
6
6
6
12 amu
Oxygen (O)
8
8
8
16 amu
Sodium (Na)
11
12
11
23 amu
Potassium (K)
19
20
19
39 amu
Iron (Fe)
26
30
26
56 amu
Notice the letters in parentheses beside the name of each element in the table above. These
letters are the chemical symbol of the element. A chemical symbol is a code, normally
composed of one or two letters, used to represent an element. Each element has its own
chemical symbol. C always represents carbon, Ca always represents calcium, Fe always
represents iron, and so on.
Elements Form Compounds
A compound has different properties from those of the elements that make it up. For
example, table salt is a compound of sodium and chlorine. Sodium (Na) is a soft metal that
explodes when combined with water. Chlorine (Cl) is a poisonous gas. When these elements
combine to form sodium chloride (NaCl), they form table salt, an edible white solid. Hydrogen
and oxygen are both gases at room temperature. They can combine to form water, which is
liquid at room temperature.
Atomic Theory
Scientists use atomic theory to describe the particles that make up matter. Atomic theory
states that atoms are the basic building blocks of all matter and atoms are composed of
subatomic particles. Atomic theory began in ancient Greece more than 2,500 years ago.
Since that time, many different models of the atom have been developed as scientists have
learned new information. A model is a representation of an object, system, or process.
Scientists use models to study, show, or explain how something functions. Diagrams, threedimensional replicas, and computer simulations are some models used in science. Models
are used to describe atoms because atoms are too small to be seen with the unaided eye or
even with most microscopes.
14 • Chapter 1: Matter
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A compound is a substance that forms when two or more elements join chemically in a
fixed proportion. The atoms that make up a compound bond to one another. Bonds form
when the elements making up a compound join by sharing or transferring electrons. The
bonds mean the atoms cannot be broken apart easily.
Lesson 1: Atoms and Elements
A useful model of the atom was developed by a Danish physicist, Niels Bohr. In the Bohr
model, electrons move around the nucleus in orbits called energy levels. An energy level is
a region in which electrons having similar amounts of energy are likely to be located. The
closer electrons are to the nucleus, the lower their energy. The Bohr model is shown below.
Bohr Model
Nucleus
(contains protons [+]
and neutrons)
Electron (–)
In the Bohr model, electrons can shift position from one energy level to another. Higher
energy areas (those farther from the nucleus) can hold more electrons. The maximum
numbers of electrons normally held by energy levels 1, 2, 3, and 4 are 2, 8, 18, and 32.
The modern model of the atom is the electron cloud model. Electrons exist in an
area around the nucleus of an atom called a “cloud.” Scientists describe electrons as
existing everywhere in the electron cloud. An electron can be found anywhere within
the electron cloud.
Modern Electron Cloud Model
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Electrons in the cloud absorb and release energy. This changes their location within the
atom. When electrons give off energy, they move to lower levels. Energy absorbed or
emitted as light, heat, or other forms of energy can be detected. The electron cloud model
explains why substances have color, release heat, or give off different types of radiation.
This model is not the end, however. The atomic model will continue to change as scientists
make discoveries.
15
Discussion Question
How are compounds and elements similar and different?
Lesson Review
1.
2.
3.
4.
What are the smallest building blocks of most ordinary matter?
A. carbon
C. mass
B. atoms
D. compounds
Sodium is an element found in table salt. It contains 11 protons and 12 neutrons.
How many electrons are found in a neutral atom of sodium?
A. 11
C. 23
B. 12
D. 1
A substance that forms when two or more elements join chemically is
A. an ion.
C. a formula.
B. a compound.
D. an atom.
The nucleus of an atom contains
A. only neutrons.
C. protons and neutrons.
D. only electrons.
5.
What is the most current model used to describe the structure of the atom?
A. solar system model
B. Bohr model
C. solid sphere model
D. electron cloud model
16 • Chapter 1: Matter
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B. protons and electrons.