FL7

The Nature of Science 2

Science is the study of the natural world. 5CHAPTER INVESTIGATION Coin Game 12

Science depends on accurate observations and measurements. 14

MATH IN SCIENCE Converting Units 22

Science requires clear communication. 23THINK SCIENCE How Do You Write a Hypothesis? 31

Hydrogen: From Rockets to Cars 42

Red Tide 184

Florida’s Biodiversity 292

Everglades Restoration 488

Let’s Bolt! Lightning in Florida 604

Student Resources

Florida Resources 747Florida Content Preview 748FCAT Science Reference 754Appendix 755

Student Resource Handbooks R1Scientific Thinking Handbook R2Lab Handbook R10Math Handbook R36Note-Taking Handbook R45

Glossary R52Index R74Acknowledgments R108

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Introducing Science FL26

Unifying Principles of Science FL28Florida Student Handbook FL34

GRADE 6

Florida Science

Sunshine State Standards

Sunshine State Standards

i d

In “Hydrogen: From Rockets to Cars” you willlearn about the general properties of theatom (SC.A.2.3.2) and how energy can bemeasured and compared. (SC.B.1.3.1)

In addition, you will learn how the energy oftoday is derived from the stored energy col-lected by organisms millions of years ago.(SC.B.2.3.2)

Hydrogen storage tank atCape Canaveral Florida.

FLORIDA CONNECTIONS

Matter and Energy

Everything that has mass and takes up space

is matter.

Matter has properties thatcan be changed by physical

and chemical processes.

What properties couldhelp you identify thissculpture as sugar? page 78

Introduction to Matter 46

Matter has mass and volume. 49CHAPTER INVESTIGATION Mass and Volume 54

Matter is made of atoms. 56EXTREME SCIENCE Particles Too Small to See 60

Matter combines to form different substances. 61MATH IN SCIENCE Making a Circle Graph 66

Matter exists in different physical states. 67

Properties of Matter 78

Matter has observable properties. 81MATH IN SCIENCE Solving Proportions 89

Changes of state are physical changes. 90CHAPTER INVESTIGATION Freezing Point 96

Properties are used to identify substances. 98CONNECTING SCIENCES Separating Minerals 103

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FL8 McDougal Littell Science Grade 6

UNIT 1

Unit Features

FRONTIERS IN SCIENCE Fuels of the Future 38

FLORIDA CONNECTION Hydrogen: From Rockets to Cars 42

TIMELINES IN SCIENCE About Temperature and Heat 136

Table of Contents FL9

Energy has different forms,but it is always conserved.

What different forms ofenergy are shown in thisphotograph? page 108

Machines help people do work by changing

the force applied to an object.

Energy 108

Energy exists in different forms. 111THINK SCIENCE Gasoline or Electric? 117

Energy can change forms but is never lost. 118CHAPTER INVESTIGATION Energy Conversions 124

Technology improves the ways people use energy. 126MATH IN SCIENCE Using Formulas 131

Forces and Machines 140

Forces can cause change. 143

Machines help people do work. 151MATH IN SCIENCE Changing Ratios to Percents 159

Six simple machines have many uses. 160CONNECTING SCIENCES A Running Machine 169

Modern technology uses compound machines. 170CHAPTER INVESTIGATION Design a Machine 176

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Visual Highlights

States of Matter 69Physical Changes 85Converting Energy 121A Robot at Work 174

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

UNIT 2

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 220

The Cell 188

The cell is the basic unit of living things. 191CHAPTER INVESTIGATION Using a Microscope 198

Microscopes allow us to see inside the cell. 200MATH IN SCIENCE Using Scientific Notation 207

Different cells perform various functions. 208THINK SCIENCE Cells and Spacesuits 215

How Cells Function 220

Chemical reactions take place inside cells. 223SCIENCE ON THE JOB Natural Dyes and Cells 228

Cells capture and release energy. 229MATH IN SCIENCE Interpreting Graphs 237

Materials move across the cell’s membranes. 238CHAPTER INVESTIGATION Diffusion 246

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FL10 McDougal Littell Science Grade 6

Unit Features

FLORIDA CONNECTION Red Tide 184

How can you tell if thesestructures, magnified2800x, are alive? page 252

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 FL11

Single-Celled Organisms and Viruses 252

Single-celled organisms have all the characteristics of living things. 255

MATH IN SCIENCE Making a Line Graph 261

Bacteria are single-celled organisms without nuclei. 262CHAPTER INVESTIGATION Bacteria 268

Viruses are not alive but affect all living things. 270EXTREME SCIENCE The Virus and the Tulip 275

Protists are a diverse group of organisms. 2764

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Bacteria and protists have the characteristics

of living things, while viruses are not alive.

Visual Highlights

Parts of a Eukaryotic Cell 204Levels of Organization 212Photosynthesis 231Cellular Respiration 233Making New Viruses 273

Diversity of Living Things

Scientists have developed a system for classifying

the great diversity of living things.

Multicellular organisms livein and get energy from avariety of environments.

How does an organismget energy and materialsfrom its environment?page 330

Classification of Living Things 296

Scientists develop systems for classifying living things. 299MATH IN SCIENCE Writing Percents 306

Biologists use seven levels of classification. 307EXTREME SCIENCE The Undiscovered 315

Classification systems change as scientists learn more. 316CHAPTER INVESTIGATION Making a Field Guide 324

Introduction to Multicellular Organisms 330

Multicellular organisms meet their needs in different ways. 333

MATH IN SCIENCE Using Circle Graphs 340

Plants are producers. 341

Animals are consumers. 348SCIENCE ON THE JOB An Animal’s World 355

Most fungi are decomposers. 356CHAPTER INVESTIGATION What Do Yeast Cells

Use for Energy? 362

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FL12 McDougal Littell Science

UNIT 3

Unit Features

FRONTIERS IN SCIENCE Chilling Changes 288

FLORIDA CONNECTION Florida’s Biodiversity 292

TIMELINES IN SCIENCE Discoveries in Biodiversity 368

Table of Contents FL13

Plants 372

Plants are adapted to living on land. 375

Most mosses and ferns live in moist environments. 382

Seeds and pollen are reproductive adaptations. 388CHAPTER INVESTIGATION Which Seeds Will Grow? 394EXTREME SCIENCE Seed Survivors 396

Many plants reproduce with flowers and fruit. 397MATH IN SCIENCE Using Grids to Estimate 405

Invertebrate Animals 410

Most animals are invertebrates. 413MATH IN SCIENCE Line Symmetry 417

Cnidarians and worms have different body plans. 418CHAPTER INVESTIGATION Worm Behavior 424

Most mollusks have shells, and echinoderms have spiny skeletons. 426

THINK SCIENCE Eating Well 431

Arthropods have exoskeletons and joints. 432

Vertebrate Animals 444

Vertebrates are animals with endoskeletons. 447MATH IN SCIENCE Dividing by Decimals 453

Amphibians and reptiles are adapted for life on land. 454CONNECTING SCIENCES Sticky Feet 462

Birds meet their needs on land, in water, and in the air. 463CHAPTER INVESTIGATION Bird Beak Adaptations 470

Mammals live in many environments. 4724

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Plants are a diverse group of organisms that

live in many land environments.

Invertebrate animals have a variety of body plans and adaptations.

Vertebrate animals live in most of Earth’s

environments.

Visual HighlightsClassifying Organisms 311Dichotomous Key 313Six Kingdoms 318Adaptations in Different Environments 337Inside a Leaf 379Life Cycle of a Pine Tree 391Life Cycle of a Cherry Tree 399Three Major Groups of Arthropods 434Wood Frog Life Cycle 456Adaptations for Flight 467

UNIT 4

Ecosystems and Biomes 492

Ecosystems support life. 495CHAPTER INVESTIGATION Soil Samples 500

Matter cycles through ecosystems. 502MATH IN SCIENCE Adding Integers 507

Energy flows through ecosystems. 508CONNECTING SCIENCES Biomagnification 515

Biomes contain many ecosystems. 5164

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Ecology

Matter and energy togethersupport life within

an environment.

FL14 McDougal Littell Science Grade 6

How many living and nonliving things can you identify in this photograph? page 492

Unit Features

FRONTIERS IN SCIENCE Ecosystems on Fire 484

FLORIDA CONNECTION Everglades Restoration 488

TIMELINES IN SCIENCE Wilderness Conservation 560

Visual HighlightsEnergy Flows Through Ecosystems 513Aquatic Biomes 522Levels in the Environment 535Symbiotic Relationships 546Ecosystem Recovery 587

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.

1

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

2

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

3

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

4

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

5

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

49

Table of Contents FL15

Interactions Within Ecosystems 528

Groups of living things interact within ecosystems. 531CHAPTER INVESTIGATION Estimating Populations 538

Organisms can interact in different ways. 540THINK SCIENCE Where Are the Salamanders? 548

Ecosystems are always changing. 549MATH IN SCIENCE Multiplying a Fraction by a Whole Number 555

Human Impact on Ecosystems 564

Human population growth presents challenges. 567SCIENCE ON THE JOB Ecology in Urban Planning 574

Human activities affect the environment. 575MATH IN SCIENCE Finding Volumes 583

People are working to protect ecosystems. 584CHAPTER INVESTIGATION Cleaning Oil Spills 592

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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 528

Earth’s Atmosphere

Earth’s atmosphere is a blanket of gases that

supports and protects life.

Some features of weatherhave predictable patterns.

Earth’s Changing Atmosphere 608

Earth’s atmosphere supports life. 611CONNECTING SCIENCES Carbon Cycle Chemistry 617

The Sun supplies the atmosphere’s energy. 618

Gases in the atmosphere absorb radiation. 624MATH IN SCIENCE Algebraic Equations 628

Human activities affect the atmosphere. 629CHAPTER INVESTIGATION Observing Particulates 636

Weather Patterns 642

The atmosphere’s air pressure changes. 645

The atmosphere has wind patterns. 649MATH IN SCIENCE Adding Measurements 657

Most clouds form as air rises and cools. 658CHAPTER INVESTIGATION Relative Humidity 666

Water falls to Earth’s surface as precipitation. 668EXTREME SCIENCE Caught Inside a Thunderhead 673

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FL16 McDougal Littell Science

UNIT 5

What weather conditionsdo you see in the distance?page 642

Unit Features

FRONTIERS IN SCIENCE Dust in the Air 600

FLORIDA CONNECTION Let’s Bolt! Lightning in Florida 604

TIMELINES IN SCIENCE Observing the Atmosphere 712

The interaction of air massescauses changes in weather.

Climates are long-termweather patterns that may

change over time.

Weather Fronts and Storms 678

Weather changes as air masses move. 681MATH IN SCIENCE Determining Rates 688

Low-pressure systems can become storms. 689

Vertical air motion can cause severe storms. 694THINK SCIENCE What Type of Weather Buried This Truck? 699

Weather forecasters use advanced technologies. 700CHAPTER INVESTIGATION Design a Weather Center 706

Climate and Climate Change 716

Climate is a long-term weather pattern. 719SCIENCE ON THE JOB Climate and Architecture 726

Earth has a variety of climates. 727CHAPTER INVESTIGATION Microclimates 732

Climates can change suddenly or slowly. 734MATH IN SCIENCE Interpreting Line Graphs 741

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Visual Highlights

Cycles and the Atmosphere 615Temperature Layers 622Global Winds 653Cloud Types 663How Precipitation Forms 671Fronts and Weather 685Climate Classification 729

What types of weathercan move a house?page 678

Table of Contents FL17

Math in Science

NATURE OF SCIENCEConverting Units 22

MATTER AND ENERGYMaking a Circle Graph 66Solving Proportions 89Using Formulas 131Changing Ratios to Percents 159

CELLSUsing Scientific Notation 207Interpreting Graphs 237Making a Line Graph 261

DIVERSITY OF LIVING THINGSWriting Percents 306Using Circle Graphs 340Using Grids to Estimate 405Line Symmetry 417Dividing by Decimals 453

ECOLOGYAdding Integers 507Multiplying a Fraction by a Whole Number 555Finding Volumes 583

EARTH’S ATMOSPHEREAlgebraic Equations 628Adding Measurements 657Determining Rates 688Interpreting Line Graphs 741

Think Science

NATURE OF SCIENCEWriting Hypotheses 31

MATTER AND ENERGYFinding Solutions 117

CELLSMaking Comparisons 215

DIVERSITY OF LIVING THINGSEvaluating Conclusions 431

ECOLOGYInferring 548

EARTH’S ATMOSPHEREEvaluating Hypotheses 699

Connecting Sciences

MATTER AND ENERGYPhysical Science and Earth Science 103Physical Science and Life Science 169

DIVERSITY OF LIVING THINGSLife Science and Physical Science 462

ECOLOGYLife Science and Physical Science 515

EARTH’S ATMOSPHEREEarth Science and Physical Science 617

22 Chapter 1: The Nature of Science

What Units Do You Use?For some purposes, outer space is defined as all altitudes greaterthan 100,000 meters above sea level. The meter is the SI unit oflength. However, the meter is not a convenient unit for measuringsome things. For example, you probably would measure the lengthof a pencil in centimeters, or the distance between two towns inkilometers. How would you express a pencil’s length in meters?Sometimes you need to convert a measurement made with oneunit into a different unit.

SKILL: CONVERTING UNITS

Use the following conversions to answer the questions below:

1. You are asked to make a slit in a piece of cardboard that is0.0055 meters long. How long is this in millimeters?

2. SpaceShipOne was the first private spacecraft to be piloted intospace. SpaceShipOne’s rocket burned for 77 seconds on the firstflight. What is this time in minutes?

3. SpaceShipOne earned a $10 million prize by exceeding an alti-tude of 100 kilometers twice within two weeks. On the secondflight, SpaceShipOne reached an altitude of 112,000 meters.What is this altitude in kilometers?

CHALLENGE The Moon takes 27.3 days to orbit Earth once.What is the time of the orbit in seconds? (Hint: Set up a sequenceof conversion fractions.)

ExampleA pencil is 15 cm long. How long is the pencil in meters?

(1) Look up (or recall) the conversion factor. In this case, 100 centimeters = 1 meter.

(2) Set the conversion up as a fraction. Because the top and bottom of the fraction are equal, the resulting fraction isequivalent to 1. Place the unit you want in your answer onthe top of the fraction:

�10

10mcm�

(3) Multiply the original number and unit by the fraction you’veset up. When you simplify the fraction, the original unitsshould cancel out and you will be left with the new unit.

15 cm� p�1010

mcm�� = �1

1050

� m = 0.15 m

MATH TUTORIALCLASSZONE.COM

Click on Math Tutorialfor more help withchanging units.

SpaceShipOne hitched a ridebeneath a special carrier. At analtitude of 15 km, SpaceShipOne’srocket fired and the two craft separated.

1 minute = 60 seconds 1 kilometer = 1000 meters

1 hour = 60 minutes 1 meter = 100 centimeters

1 day = 24 hours 1 meter = 1000 millimeters

Features

FL18 McDougal Littell Science Grade 6

Table of Contents FL19

Science on the Job

CELLS Natural Dyes and Cells 228

DIVERSITY OF LIVING THINGSAn Animal’s World 355

ECOLOGYEcology in Urban Planning 574

EARTH’S ATMOSPHEREClimate and Architecture 726

Extreme Science

MATTER AND ENERGYParticles Too Small to See 60

CELLS The Virus and the Tulip 275

DIVERSITY OF LIVING THINGSThe Undiscovered 315Seed Survivors 396

EARTH’S ATMOSPHERECaught Inside a Thunderhead 673

Frontiers in Science

MATTER AND ENERGYFuels of the Future 38

DIVERSITY OF LIVING THINGSChilling Changes 288

ECOLOGYEcosystems on Fire 484

EARTH’S ATMOSPHEREDust in the Air 600

Florida Connections

MATTER AND ENERGYHydrogen: From Rockets to Cars 42

CELLSRed Tide 184

DIVERSITY OF LIVING THINGSFlorida’s Biodiversity 292

ECOLOGYEverglades Restoration 488

EARTH’S ATMOSPHERELet’s Bolt! Lightning in Florida 604

Timelines in Science

MATTER AND ENERGYUnderstanding Forces 136

DIVERSITY OF LIVING THINGSDiscoveries in Biodiversity 368

ECOLOGYWilderness Conservation 560

EARTH’S ATMOSPHEREObserving the Atmosphere 712

Natural Dyes and CellsWhere does the blue in your blue jeans come from? How about thered, yellow, green, or pink in your favorite wool or cotton sweater?Most fabrics are colored with dyes made up in labs, but somedesigners prefer to use natural dyes and natural cloth. All textiledesigners must understand the science of dyes and fibers to pro-duce the colors they want.

EXPLORE

1. EXPERIMENT Design an experiment using onion skins,beets, or blackberries to color white wool and whitecotton. The procedure should include chopping theplant and heating it with water to make the dye. Besure that your experiment procedure includes only onevariable. Your experiment should start with a question,such as How do the dyes differ? Or Which dye worksbest?

2. CHALLENGE Using different mordants with the samedye can give different colors. For example, dandelionleaf dye gives yellow-green, gray-green, tan, or goldwith different mordants. Explain why this happens.

TEXTILE DESIGNER

Natural fibers come either fromplants or animals. Wool is ananimal fiber. Silk, too, is madeup of animal cells. Cotton, linen,and rayon are fibers made fromplants. Plant fibers have thickcell walls, made mostly of cellu-lose. Animal fibers, on the otherhand, contain mainly proteins.

Fibers

Most natural dyes come from plants, but sometimesinsects are used too. The indigo plant is used for mostblue, including the original blue jeans. Insects are mostoften used to make reds. All dyes are made ofmolecules—carbon, oxygen, hydrogen, and other atoms.The molecules of the dye bind to the molecules of thefibers, adding the dye’s color to the fiber.

Dyes

228 Unit 2: Cells

A mordant is a chemical compoundthat combines with dye as a colorfixer, or color keeper. The mordantmust strengthen the bonds betweennatural dye molecules and fibers.A stronger bond means the color is less likely to fade or wash out of the fibers. Most mordants are liquid solutions containing metals,such as chromium.

Color Fixers

linen

wool

cotton

silk

FL20 McDougal Littell Science Grade 6

Simulations

MATTER AND ENERGYWeight on Different Planets 51Gas Behavior 73Physical and Chemical Changes 79Potential Energy and Kinetic Energy 109Applying Force 148Mechanical Advantage 167

CELLSVirtual Cell Tour 189Cells through Different Microscopes 201

DIVERSITY OF LIVING THINGSDichotomous Key 312Seed Dispersal 402

ECOLOGYCarrying Capacity 529

EARTH’S ATMOSPHERELatitude and Altitude 721

Visualizations

MATTER AND ENERGYSolar Cells 128

CELLS Photosynthesis 221Active Transport 242Binary Fission 258Bacteriophage Replication 272

DIVERSITY OF LIVING THINGSPlant Response to Stimuli 346Seeds Sprouting 373Cephalopod Movement 428How Fish Breathe 449

ECOLOGYNitrogen Cycle 506Human Population Growth 568

EARTH’S ATMOSPHERERadiation, Conduction, and Convection 621Greenhouse Effect 626Land and Sea Breezes 643Coriolis Effect 650Warm Fronts and Cold Fronts 684Progress of a Hurricane 690

Career Centers

Electrical Engineering 41

Zoology 291

Ecology 487

Meteorology 603

Internet Resources @ ClassZone.com

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Table of Contents FL21

Resource Centers

NATURE OF SCIENCEResources for the following topics may be found atClassZone.com: Scientists; Units of Measure;Colorized Images.

MATTER AND ENERGYResources for the following topics may be found atClassZone.com: Hydrogen Fuel; Scale Views ofMatter; Volume; Scanning Tunneling MicroscopeImages; Mixtures; Chemical Properties of Matter;Melting Points and Boiling Points; SeparatingMaterials from Mixtures; Kinetic Energy and PotentialEnergy; Electric Cars; Alternative Energy Sources;Force and Motion Research; Machines in EverydayObjects; Artificial Limbs; Nanomachines; Robots.

CELLSResources for the following topics may be found atClassZone.com: Red Tide; Cell Structures; UnicellularOrganisms; Macromolecules; Diffusion; Single-CelledOrganisms and the Human Body; Bacteria; Viruses.

DIVERSITY OF LIVING THINGSResources for the following topics may be found atClassZone.com: Florida’s Biodiversity; Linnaeus;Taxonomy; New Insect Species; Bee Dance; PlantAdaptations; Animal Adaptations; Fungi; BiodiversityDiscoveries and Research; Plant Systems; PlantEvolution; Seeds; Extreme Seeds; InvertebrateDiversity; Worms; Mollusks; Arthropods; Reptile andAmphibian Distribution; Fish; Amphibians; Reptiles;Mammals.

ECOLOGYResources for the following topics may be found atClassZone.com: Everglades Restoration; PrairieEcosystems; Ecosystems; Cycles in Nature; Land andAquatic Biomes; Symbiotic Relationships; Succession;Conservation Efforts; The Environment; UrbanExpansion; Natural Resources; Ecosystem Recovery.

EARTH’S ATMOSPHEREResources for the following topics may be found atClassZone.com: Lightning in Florida; Earth’sAtmosphere; Ozone Layer; Air Pressure; GlobalWinds; Clouds; Lightning; Weather Safety; Weatherand Weather Forecasting; Atmospheric Research; ElNiño; Climate Zones; Climate and Climate Change;Global Warming.

Math Tutorials

NATURE OF SCIENCEChanging Units 22

MATTER AND ENERGYCircle Graphs 66Solving Proportions 89Rates 131Percents and Fractions 159

CELLSScientific Notation 207Interpreting Line Graphs 237Interpreting Line Graphs 261

DIVERSITY OF LIVING THINGSPercents and Fractions 306Interpreting Circle Graphs 340Perimeter and Area 405Line Symmetry 417Dividing by Decimals 453

ECOLOGYAdding Integers 507Multiplying Fractions and Whole Numbers 555Finding the Volume of a Rectangular Prism 583

EARTH’S ATMOSPHEREEquations 628Adding Measures of Time 657Rates as Ratios 688Interpreting Line Graphs 741

NSTA SciLinks

Codes for use with the NSTA SciLinks site maybe found on every chapter opener.

Florida Review

There is a content review and FCAT practice forevery chapter at ClassZone.com.

Nature of Science

Can You Deduce a Shape from Shadows? How Do You Test an Idea? 3

Matter and Energy

What Has Changed? Where Does the Sugar Go? 47

Float or Sink; Hot Chocolate 79A Penny for Your Energy; Hot Dog! 109Changing Direction; Shut the Door! 141

Cells

Seeing and Understanding; Bits and Pieces 189Leaves Underwater; Just a Spoonful

of Sugar 221Where Can You Find Microscopic Life?

How Quickly Do Bacteria Multiply? 253

Diversity of Living Things

How Are Fingerprints Different? How Would You Sort Pennies? 297

Where Does It Come From? How Can a Multicellular Organism Reproduce on Its Own? 331

How Are Plants Alike, How Are They Different? How Are Seeds Dispersed? 373

Worm-Watching; Insects and You 411What Animals Live Near You? How Is a

Bird like a Frog? 445

Ecology

How Do Plants React to Sunlight? What Is Soil? 493

How Do Living Things Interact Where You Live? How Many Roles Can a Living ThingHave in an Ecosystem? 529

How Many is Six Billion? How Easily DoesPolluted Water Move Through Plants? 565

Earth’s Atmosphere

How Heavy Is Paper? How Does Heating Affect Air? 609

Are You Stronger Than Air? How Does Air Motion Affect Balloons? 643

How Does Cold Air Move? How Does Weather Move? 679

Why Are Climates Different? How DoMicroclimates Form? 717

Explore the Big IdeaExplore the Big IdeaChapter Opening Inquiry

Each chapter opens with hands-on explorations that introduce the chapter’s Big Idea.

FL22 McDougal Littell Science Grade 6

Chapter 1: The Nature of Science 3

Can You Deduce aShape fromShadows?Three beams of light hit anobject from different direc-tions. The resulting shadowsare shown in the diagram. Thedashed lines may help youimagine the beams of light.

Observe and Think Try to picture what theobject would look like from different direc-tions. Can you tell whether the object is anorange, a paperback book, or a can of soup?

How Do You Test an Idea?Rub a radish on a blank index card until themark on the card becomes dark pink. Use a cotton swab to wipe lemon juice onto the mark on the card. Observe the color of the radish mark.

Observe and ThinkDid the change occur because the lemon juice was wet? Test this idea by repeating the procedure with tap water instead of lemon juice.

Internet Activity: ScientistsGo to ClassZone.com to learn about differenttypes of scientists and the many ways they dotheir work.

Observe and ThinkWhich scientists’ work surprised you? Explain.

NSTA scilinks.org

Scientific Methods Code: MDL068

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?

Prepare and practice for theFCAT.• Section Reviews, pp. 11,

21, 30• Chapter Review, pp. 32–34• FCAT Practice, p. 35

CLASSZONE.COM• Florida Review: Content

Review and FCAT Practice

2 Chapter 1: The Nature of Science

The Natureof Science

Science is both a bodyof knowledge and aprocess for gainingknowledge.

Key Concepts

Science is the study ofthe natural world.Learn how scientists think andhow they test ideas.

Science depends onaccurate observationsand measurements.Learn about measurementsand about variables.

Science requires clearcommunication.Learn about record keeping,communication, and criticalevaluation.

3SECTION

2SECTION

1SECTION

Why might a scientist beexploring this sunken ship?

Nature of Science

Coin Game 12

Matter and Energy

Mass and Volume 54Freezing Point 96Energy Conversions 124Design a Machine Design Your Own 176

Cells

Using a Microscope 198Diffusion 246Bacteria 268

Diversity of Living Things

Making a Field Guide 324What Do Yeast Cells Use for Energy? 362Which Seeds Will Grow? 394Worm Behavior 424Bird Beak Adaptations 470

Ecology

Soil Samples 500Estimating Populations 538Cleaning Oil Spills Design Your Own 592

Earth’s Atmosphere

Observing Particulates 636Relative Humidity 666Design a Weather Center Design Your Own 706Microclimates 732

name of lab, skill?, mod-ule and page number

Chapter InvestigationsChapter InvestigationsFull-Period Labs

The Chapter Investigations are in-depth labs thatlet you form and test a hypothesis, build a model,or sometimes design your own investigation.

Table of Contents FL23

Place the coin behind the starting line. Hold theruler behind the coin. Flick the coin toward thetarget by pulling one end of the ruler back andreleasing it.

Practice flicking the coin for 2 minutes. Try to getthe coin to stop on or near the target. Once youhave discovered a successful method you maywish to mark the paper to remind yourself howfar to pull the ruler back.

Flick the coin. Measure the distance from the target to the nearest edge of the coin.

Have your partner measure the distance andrecord the results in her or his notes. If the dis-tance is greater than 20 cm, discard the resultand do a new trial.

Repeat steps 8 and 9 for a total of five trials.

Switch roles with your partner. Repeat steps 6–10.

1. RECORD Describe the ways you tried toreduce possible hazards.

2. RECORD Organize your measurementsand your partner’s measurements in a table.

3. CALCULATE Find the mean, or average,of each set of five measurements.

4. COMPARE How similar were your measure-ments and your partner’s measurements?

1. ANALYZE Answer the question in the problem.

2. EVALUATE How safe were your trials?How would you change the procedure toimprove safety further?

3. INTERPRET Which of you is more skilledat getting the coin near the target? How doyou know?

4. ANALYZE LIMITATIONS How couldyou improve the way you test and compareyour skills?

5. APPLY Choose a sport or other type ofcompetition and list some of the possiblevariables that are controlled in order toensure fairness.

CHALLENGE Some sports and other competi-tions average the effects of several trials or shortcompetitions. Others combine skill and luck byusing the best of several trials. List several sportsor other competitions with multiple trials.Evaluate the amount of skill and the amount ofluck involved in each.

INVESTIGATE Further

ConcludeWriteIt Up

Observe and AnalyzeWriteIt Up

Coin Game

Problem How do multiple trials affect results?

Observe and Analyze

Table 1. Distance of Coin’s Edge

from Target

Conclude

Chapter 1: The Nature of Science 13

Distance (cm)

Trial Trial Trial Trial Trial Mean

1 2 3 4 5

My scores,

measured

by me

My scores,

measured

by partner

Partner’s scores,

measured

by me

Partner’s scores,

measured

by partner

CHAPTER INVESTIGATIONCHAPTER INVESTIGATION

12 Chapter 1: The Nature of Science

Coin GameOVERVIEW AND PURPOSE In a contest, how do youknow if the winner had more skill or just more luck? In gamesplayers often repeat what they do, such as firing arrows into a target. Scientists also may repeat a procedure several times.Each repetition is called a trial. Scientists try to keep factors thesame each time, but this may not be possible for all factors.Averaging the results of several trials may reduce the effect of afactor that is uncontrolled—that is, unintentionally different fromone trial to another. In this lab you will

• test your ability to flick a coin close to a target• make the procedure as safe as possible• do multiple trials to average out unidentified

and uncontrolled factors

How do multiple trials affect results?

Work with a partner. Tape the corners of a large piece of paperto a tabletop or desk. Make sure the paper is smooth and flat.

Use the ruler to draw a straight line across the paper near oneend, as shown below. This is your starting line.

Draw two short lines that cross at a point 20 cm from the starting line. The crossing point is your target.

You and people around you will be flicking coins. Wear safetygoggles to protect your eyes from accidents.

As you go through the procedure, develop other ways to reducepossible hazards to people and materials. For example, you mightput up a soft barrier to prevent the coin from flying off the table.

Procedure

ProblemWriteIt Up

MATERIALS• tape• large piece of paper• flexible plastic ruler• pencil• coin

12 Chapter 1: The Nature of Science

Nature of Science

Warmth 14Communication 23

Matter and Energy

Similar Objects 49Mixed Substances 61Solids and Liquids 67Physical Properties 81Identifying Substances 98Energy 111Solar Cells 126Motion 143Machines 151Changing Forces 160

Cells

Activity and Life 191Specialization 208Food Molecules 223Diffusion 238Organisms 255Viruses 270

Diversity of Living Things

Classification 307Stored Energy 341Mushrooms 356Leaf Characteristics 375Moss Plants 382Fruit 397Worm Movement 418Arthropods 432Streamlined Shapes 447Moving on Land 454Feathers 463

Ecology

Your Environment 495The Water Cycle 502Energy 508Counting Animals 531Population Growth 549Sharing Resources 567Environmental Impacts 584

Earth’s Atmosphere

Air Resistance 611Radiation 624Air Pollution 629Air Pressure 645Solar Energy 649Condensation 658Air Masses 681Hurricanes 689Lightning 694Weather Maps 700Solar Energy 719

ExploreExploreIntroductory Inquiry Activities

Most sections begin with a simple activity that lets youexplore the Key Concept before you read the section.

Chapter 1: The Nature of Science 23

VOCABULARY

experimental bias p. 27

BEFORE, you learned

• Scientific results must bereproducible

• Measurements are used tocompare observations

• The accuracy of measurementscan be evaluated

NOW, you will learn

• Why it is important to keepdetailed records

• How to evaluate results• About methods for sharing

results

KEY CONCEPT

Science requires clearcommunication.

EXPLORE Communication

How do you describe a shell?

PROCEDURE

Observe one of the shells in detail.Do not change it in any way.

Record your qualitative and quantitative observations.

WHAT DO YOU THINK?Exchange your recorded observations with those of a classmate. Determine which shell your classmate examined. What additional observations, if any, would be helpful?

2

1

MATERIALS• several shells• ruler • other observing

tools as needed

Sunshine StateSTANDARDSSC.H.1.3.4: The studentknows that accuraterecord keeping, open-ness, and replication areessential to maintainingan investigator’s credibility.SC.H.1.3.7: The studentknows that when simi-lar investigations givedifferent results, the sci-entific challenge is toverify whether the dif-ferences are significantby further study.SC.H.2: The studentunderstands that mostnatural events occur incomprehensible, consis-tent patterns.SC.H.3.3.6: The studentknows that no matterwho does science, orwhen or where they doit, the knowledge caneventually becomeavailable to everyone.

MAIN IDEA WEBRemember to make notesof main ideas and relatedterms and ideas.

Scientists look for patterns.If you observe a shell, you might sketch the pattern of its colors.Scientists look for other types of patterns too. They look for patternsof behavior, patterns of change, and patterns in relationships. Onerelationship might be that larger shells have more twists. Scientistsseek patterns that are universal—ones that apply under many differentconditions. A scientist would ask if the relationship between shell sizeand number of twists applied to other shells of the same type and toother types of shells.

When you find a pattern, you need to describe it so others can test it. Remember that reproducible results are the same for differentpeople under different conditions. It can be hard to make your workreproducible. You have to identify all of the important factors that ledto your results so that others can duplicate your work.

check your reading Why might you need to describe a pattern carefully?

FL24 McDougal Littell Science Grade 6

InvestigateInvestigateSkill Labs

Each Investigate activity gives you a chance to practice a specificscience skill related to the content that you’re studying.

Nature of Science

Variables Controlling variables 17Copper Pennies Measuring 25

Matter and Energy

Mass Modeling 57Mixtures Inferring 64Liquids Measuring 71Chemical Changes Measuring 87Separating Mixtures Design Your Own 101Potential Energy Design Your Own 115Solar Energy Observing 129Speed Design Your Own 146Efficiency Analyzing data 157Pulleys Inferring 163

Cells

Plant and Animal Cells Observing 203Cell Models Making models 213Oil and Water Observing 226Fermentation Observing 235Cells Making models 244Microorganisms Observing 259Viruses Analyzing 271Protists Observing 277

Diversity of Living Things

Classifying Leaves Classifying 302Binomial Nomenclature Classifying 308Specialization Making models 334What Plants Need to Grow Design Your Own 342Owl Pellets Inferring 350Capturing the Sun’s Energy Measuring 384Pinecones Observing 392

Flower Parts Observing 401Invertebrates Observing 414Mollusks and Echinoderms Observing 428Insect Metamorphosis Observing 436Eggs Observing 460How Body Fat Insulates Making models 474

Ecology

Carbon Observing 505Decomposers Observing 511Climate Graphing data 521Species Interactions Analyzing data 543Limiting Factors Design Your Own 551Resources Interpreting 570Particles in the Air Observing 577

Earth’s Atmosphere

Gas in the Air Predicting 612Solar Radiation Measuring 619Greenhouse Gases Graphing 626Air Pressure Collecting data 647Coriolis Effect Modeling 657Condensation Observing 661Precipitation Measuring 669Air Masses Inferring 683Ice Observing 692Updrafts Inferring 696Heating and

Cooling Rates Comparing 721Climate Change Measuring 735

Chapter 1: The Nature of Science 25

Later, you learn about pumice, which is a low-density type of rock formed by volcanoes. Densityis a measure of the amount of mass in a givenvolume of a substance. A dense object is heavy forits size. You read that pumice has a low density,sometimes less than 1 gram per cubic centimeter,because it contains air bubbles. Looking back at yournotes, you see that the unusual rock was lightweight andbubbly looking. You think the rock might be pumice. Inscience class, you learn that objects with a density of less than1 gram per cubic centimeter can float in water. This might be a testfor pumice. Your friend agrees to test the rock, and it floats. The newevidence strengthens your identification. You were able to identify therock because you recorded your observations and put them togetherwith information you gained later.

How dense are pennies?PROCEDURE

Estimate an amount of copper that will fill the graduated cylinder abouthalfway. Use the balance to find the mass of this copper. Record the mass.

Fill the graduated cylinder about halfway with water and record the waterlevel. Add the copper and record the new water level.

Find the difference between the water level measurements. The result is the volume of the copper.

Divide the mass of the copper by its volume to get the density. Use this formula: Density = �Vo

mluamss

e�

Repeat steps 1–4 with pennies. Record all measurements and calculations.

Repeat steps 1–4 twice more with different pennies.

WHAT DO YOU THINK?• How similar were your three results for the pennies’ density?

• Compare the density of copper with these three results. What can you infer about the material pennies are made of?

CHALLENGE How can you tell if silver-colored coins or jewelry are made of silver, coated with silver, or just look like silver? What additional information would you need?

6

5

4

3

2

1

Copper PenniesCopper PenniesSKILL FOCUSMeasuring

MATERIALS• pieces of copper• graduated

cylinder• balance• water• pennies

TIME30 minutes

Pumice has such a low densitythat some samples can floatin water.

Table of Contents FL25