Matter and Energy

Everything that has mass and takes up space

is matter.

Matter has properties thatcan be changed by physical

and chemical processes.

Unit Features

FRONTIERS IN SCIENCE Fuels of the Future 2

TIMELINES IN SCIENCE About Temperature and Heat 96

What properties couldhelp you identify thissculpture as sugar? page 38

Introduction to Matter 6

Matter has mass and volume. 9CHAPTER INVESTIGATION Mass and Volume 14

Matter is made of atoms. 16EXTREME SCIENCE Particles Too Small to See 20

Matter combines to form different substances. 21MATH IN SCIENCE Making a Circle Graph 26

Matter exists in different physical states. 27

Properties of Matter 38

Matter has observable properties. 41MATH IN SCIENCE Solving Proportions 49

Changes of state are physical changes. 50CHAPTER INVESTIGATION Freezing Point 56

Properties are used to identify substances. 58CONNECTING SCIENCES Separating Minerals 63

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UNIT 1

Table of Contents vii

Energy has different forms,but it is always conserved.

What different forms ofenergy are shown in thisphotograph? page 68

Heat is a flow of energy dueto temperature differences.

Energy 68

Energy exists in different forms. 71THINK SCIENCE Gasoline or Electric? 77

Energy can change forms but is never lost. 78CHAPTER INVESTIGATION Energy Conversions 84

Technology improves the ways people use energy. 86MATH IN SCIENCE Using Formulas 91

Temperature and Heat 100

Temperature depends on particle movement. 103MATH IN SCIENCE Metric Conversions 109

Energy flows from warmer to cooler objects. 110SCIENCE ON THE JOB Cooking with Heat 115

The transfer of energy as heat can be controlled. 116CHAPTER INVESTIGATION Insulators 122

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Visual Highlights

States of Matter 29Physical Changes 45Converting Energy 81Insulation 120

The process of turning wool into a sweater requiresthat the wool undergo physical changes. Changes inshape, volume, texture, and color occur as raw woolis turned into a colorful sweater.

Physical Changes

Preparing the wool produces physicalchanges. The wool is removed fromthe sheep and then cleaned beforethe wool fibers are separated.

Further physical changes occur as amachine twists the wool fibers intoa long, thin rope of yarn.

Dyeing produces color changes but does not change the basic substance of the wool.

How does the yarn in the sweater differfrom the wool on the sheep?

Chapter 2: Properties of Matter 45

Shearing1 Spinning2 Dyeing3

The final product, a woolsweater, is still wool.

4

AB

Electricity and Magnetism

Moving electric chargestransfer energy.

Circuits control the flow of electric charge.

Unit Features

FRONTIERS IN SCIENCE Electronics in Music 130

TIMELINES IN SCIENCE The Story of Electronics 200

How can circuits control theflow of charge? page 168

Electricity 134

Materials can become electrically charged. 137CONNECTING SCIENCES Electric Eels 145

Charges can move from one place to another. 146CHAPTER INVESTIGATION Lightning 154

Electric current is a flow of charge. 156MATH IN SCIENCE Using Variables 163

Circuits and Electronics 168

Charge needs a continuous path to flow. 171SCIENCE ON THE JOB The Science of Electrical Work 178

Circuits make electric current useful. 179MATH IN SCIENCE Solving Percent Problems 184

Electronic technology is based on circuits. 185CHAPTER INVESTIGATION Design an Electronic Communication Device 194

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UNIT 2

Table of Contents ix

Current can produce magnetism, and magnetism

can produce current.

What force is acting onthis compass needle?page 204

Magnetism 204

Magnetism is a force that acts at a distance. 207THINK SCIENCE Can Magnets Heal People? 215

Current can produce magnetism. 216

Magnetism can produce current. 223CHAPTER INVESTIGATION Build a Speaker 228

Generators supply electrical energy. 230MATH IN SCIENCE Using Significant Figures 235

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Visual Highlights

How a Photocopier Works 143How Lightning Forms 149Batteries 161How a PC Works 190How Magnets Differ from Other Materials 211How a Motor Works 221

The Water Planet 246

Water continually cycles. 249THINK SCIENCE Does Mars Have a Water Cycle? 255

Fresh water flows and freezes on Earth. 256MATH IN SCIENCE Multiplying Fractions and Whole Numbers 263

Fresh water flows underground. 264CHAPTER INVESTIGATION Water Moving Underground 272

Freshwater Resources 278

Fresh water is an essential resource. 281MATH IN SCIENCE Volume of Rectangular Prisms 289

Society depends on clean and safe water. 290CHAPTER INVESTIGATION Monitoring Water Quality 298

Water shortages threaten society. 300SCIENCE ON THE JOB Water and Farming 307

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Unit Features

FRONTIERS IN SCIENCE Exploring the Water Planet 242

TIMELINES IN SCIENCE Exploring the Ocean 346

Earth’s Waters

Water moves throughEarth’s atmosphere, oceans,

and land in a cycle.

Fresh water is a limitedresource and is essential

for human society.

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UNIT 3

In what ways do youdepend on water?page 278

Table of Contents xi

Visual Highlights

The oceans are a connectedsystem of water in motion.

Springs and Wells 269Sources of Water Pollution 295The Ocean Floor 320Ocean Waves 331Intertidal Zone 355Coral Reefs 363Life in the Open Ocean 367

Ocean Systems 312

The oceans are a connected system. 315MATH IN SCIENCE Plotting Coordinates 323

Ocean water moves in currents. 324

Waves move through oceans. 329CHAPTER INVESTIGATION Wave Movement 334

Waters rise and fall in tides. 336CONNECTING SCIENCES Tidal Energy 341

Ocean Environments 350

Ocean coasts support plant and animal life. 353MATH IN SCIENCE Making a Double Bar Graph 360

Conditions differ away from shore. 361EXTREME SCIENCE Undersea Hot Spots 369

The ocean contains natural resources. 370CHAPTER INVESTIGATION Population Sampling 378

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The ocean supports life andcontains natural resources.

What causes thesewaves? page 312

Waves transport energy, not water. As a wave crest passes, thewater particles move in circular paths.

Ocean Waves

Chapter 3: Ocean Systems 91

Wave Structure

The movement of the floatinginner tube is similar to themovement of the water particles.

Water particles rise as a wave crest approaches.

At the crest, water particles havemoved in a semicircle.

Water particles drop after thetrough passes.

The wave passes through thewater but the water particles endup in the same place they began.

wave direction

Below a certain depth,waves no longer affectthe water.

What happens to water particles as a wave passes through?

The deeper waterparticles move insmaller circles thanthe water particlesnear the surface.

water particlemovement

Wavelength is the distancebetween one wavecrest and the next.

Wave height is the vertical distance between the top of thecrest and the bottom of the trough.

C

Waves affect only thewater near the surface.

The troughis the lowpoint of thewave.

The crest isthe high pointof the wave.

UNIT 4

Ecosystems and Biomes 390

Ecosystems support life. 393CHAPTER INVESTIGATION Soil Samples 398

Matter cycles through ecosystems. 400MATH IN SCIENCE Adding Integers 405

Energy flows through ecosystems. 406CONNECTING SCIENCES Biomagnification 413

Biomes contain many ecosystems. 4144

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Unit Features

FRONTIERS IN SCIENCE Ecosystems on Fire 386

TIMELINES IN SCIENCE Wilderness Conservation 458

Ecology

Matter and energy togethersupport life within

an environment.

xii McDougal Littell Science Grade 6

How many living and nonliving things can you identify in this photograph? page 390

Visual HighlightsEnergy Flows Through Ecosystems 411Aquatic Biomes 420Levels in the Environment 433Symbiotic Relationships 444Ecosystem Recovery 485

Chapter 2: Interactions within Ecosystems 49

0° 0°Equator

Grassland

Organisms living in an African savannah illustrate the different levels of the environment.

Levels in the Environment

Biome The African savannah ispart of a grassland biome.

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EcosystemThe community of organisms, along withwater, soil, and otherabiotic factors, make upan ecosystem.

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CommunityPopulations of wildebeests, gazelles,lions, and grasses sharethe same living areasand resources. These andother populations form asavannah community.

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PopulationGazelles travel togetherin herds looking forareas to graze in. Thetotal number of gazellesin an ecosystem is calleda population of gazelles.

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OrganismThe gazelle lives in various grassland habitatsin eastern Africa and fillsa particular niche.

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Describe the gazelle’s place ineach level of the environment.

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Table of Contents xiii

Interactions Within Ecosystems 426

Groups of living things interact within ecosystems. 429CHAPTER INVESTIGATION Estimating Populations 436

Organisms can interact in different ways. 438THINK SCIENCE Where Are the Salamanders? 446

Ecosystems are always changing. 447MATH IN SCIENCE Multiplying a Fraction by a Whole Number 453

Human Impact on Ecosystems 462

Human population growth presents challenges. 465SCIENCE ON THE JOB Ecology in Urban Planning 472

Human activities affect the environment. 473MATH IN SCIENCE Finding Volumes 481

People are working to protect ecosystems. 482CHAPTER INVESTIGATION Cleaning Oil Spills 490

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Humans and human population growth affect

the environment.

Living things within anecosystem interact

with each other and the environment.

How do living thingsinteract? page 426

UNIT 5

Cells

All living things are made up of cells.

All cells need energy and materials for

life processes.

How do plants like these sunflowerschange energy from the Sun? page 530

The Cell 498

The cell is the basic unit of living things. 501CHAPTER INVESTIGATION Using a Microscope 508

Microscopes allow us to see inside the cell. 510MATH IN SCIENCE Using Scientific Notation 517

Different cells perform various functions. 518THINK SCIENCE Cells and Spacesuits 525

How Cells Function 530

Chemical reactions take place inside cells. 533SCIENCE ON THE JOB Natural Dyes and Cells 538

Cells capture and release energy. 539MATH IN SCIENCE Interpreting Graphs 547

Materials move across the cell’s membranes. 548CHAPTER INVESTIGATION Diffusion 556

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xiv McDougal Littell Science Grade 6

GlucoseC6H12O6

�Oxygen

6O2

Carbondioxide

6CO2

Water6H2O ��

Glucose (C6H12O6)

Oxygen (6O2 )

Carbon dioxide (6CO2)

Water (6H2O)

What part of the diagram shows starting materials being changed?

Leaf cell (magnified 2200�)

Chloroplast

The starting materialsCarbon dioxide from the airand water from the soil enter the chloroplasts.

The process Inside thechloroplasts, chlorophyll captures energy from sunlight. This energy is usedto change starting materialsinto new products.

The products Glucose supplies energy and is asource of materials for theplant; most oxygen isreleased into the air.

321

Chloroplast

Photosynthesis

LightEnergy

LightEnergy

Chapter 2: How Cells Function 49 EA

Table of Contents xv

Cell Division 562

Cell division occurs in all organisms. 565CONNECTING SCIENCES Chemical Dyes Show Nerve Growth 571

Cell division is part of the cell cycle. 572CHAPTER INVESTIGATION Stages of the Cell Cycle 578

Both sexual and asexual reproduction involve cell division. 580

MATH IN SCIENCE Using Exponents 585

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Organisms grow,reproduce, and maintain

themselves through cell division.

Visual Highlights

Parts of a Eukaryotic Cell 514Levels of Organization 522Photosynthesis 541Cellular Respiration 543Cell Division 575

Some of these bacterial cellsare dividing. How are thecells formed in cell divisionlike the other cells in thephotograph? page 562