Let's Do Science 4 – Text Book B by Regal_Education

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P mary 4 Prr i ma 2 Textbook

The 5E Model – Guided Inquiry

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The Let’s Do Science series is based on the Biological Sciences Curriculu Curriculum riculu Study (BSCS) 5E teaching and learning instructional model. The he 5E E model is centered on the idea that students understand science concepts oncepts pts best by using prior knowledge to pose questions and find answers rs through hrough guided inquiry. This hands-on approach, integrated with engineering ng g and design skills, sk s has students learn science by doing science. Teachers chers guide the llearning process and are able to assess student performance evaluating student mance ce by evalua explanations and the application of newly acquired quired d knowledge knowledg knowled and skills.

Engage

The Engage phase of the 5E model provides videss students with w the opportunity to demonstrate their prior knowledge and understanding of the topic or understand concept. Students are presented with which serves to h an n activity or question q motivate and engage students as they hey begin the llesson. Teachers identify and correct any misconceptions and d gather data dat from students which will guide informed teaching and learning. earning. ng Essential to stimulating and students is the use of mixed media d engaging gaging stude st such as colorful photos, illustrations found throughout the trations tions and diagrams d textbooks and activity books. Let’s Science also includes extensive bo boo t’s Do S digital resources such narrated videos, interactive lessons, virtual labs, h as narra nar id slideshows and more. re.

Explore

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This phase encourages exploration of concepts and skills through gh handshan on activities and investigations. Students are encouraged to work togethe together red learning earn and apply various process skills while gaining concrete, shared ch students experiences. These experiences provide a foundation for which epts.. This studentstuden can refer to while building their knowledge of new concepts. centered phase comes before formal explanations and d definitions of tthe concept which are presented by the teacher.

Explain

This phase follows the exploration phase and iss more ore teacher-directed. teacherteache Students are initially encouraged to draw on their learning experiences and earning ex e oncept ept through explanations e demonstrate their understanding of the concept and he opportunity pportunity to t demonstrate discussion. After the students have had the their understanding of the concept, the formal e teacher cher then introduces in definitions and scientific explanations. also clarifies any s. The teacher eache al erged during the th Explore phase. misconceptions that may have emerged

Elaborate

In the Elaborate phase, students nts refine ne and consolidate co c their acquired knowledge and skills. Opportunities for students to further rtunities nities are provided pro apply their knowledge and skillss to new situations in order to broaden si and deepen their understanding rst ng g of the concept. Students may conduct additional investigations, share information and ideas, or apply their ns, sh shar orm knowledge and skillss to other ther disciplines. d disc

Evaluate

This final phase se includes cludes both formal form and informal assessments. These can include concept models, journals as well as more traditional cept maps, physical phys ummative ative assessm assess forms of summative assessment such as quizzes or writing assessments. e encouraged to review and reflect on their own learning, and Studentss are on theirr newly wly acquired knowledge, kn understanding and skills.

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Let’s Do Science Let’s Do Science is based on the United States Next Generation Science Standards (NGSS). The series consists of full-color textbooks and full-color activity books for Grades K to 6.

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Anima

Let’s Do Science engages students with a highly visual al presentation of the disciplinary core ideas in the textbooks xtbooks books and places an emphasis on applying scientific knowledge nowledge ledge using NGSS practices through numerous scientific tific investigations. Let’s Do Science sees engineering ring ass an essential element of science education and tightly d as such is tight integrated into both the textbooks and activity ctivity books.

r als are Animals es res ure or structur os malss to anim i id iv be divid n be an can ca c ess a tures tur ctur stt uc sstru

s u nall str n rnal terrn Exte Exte m warm birds wa bir birds bird ym fly o fly birdss to bird bi

Amazing Fact!

Great white sharks are the largest of all predatory fish in the world. They can reach lengths of up to seven meters and weigh up to 3,000 kilograms!

great white sh

The Let’s Do Science textbooks include e the following ffeatures:

Think Deeply

d In the Field

Topic-related questions for group discussion aimed at deepening students’ understanding of the topic.

Energy Engineer ble En Renewable

wn ffossil dow osing down closing re cl are a e s ar ents ments overnm governm go round tthe world, govern aro trie around trie ntries un countries In many coun ss.. natives. g alterrnative ergy e energy able energ wable new en ene renew with rene th m with g them l ing d replac nd tionss and ations ation ower station fuel pow oduce od p oduce hatt pr ess tthat o ogies olo hnolo chnolo tech w ttechno nd new and farmss a a ms,, wind farm so s r ffarm nclu e sola These includ on tion oduction rod produ pro itty p city lectricity the elect e these se ecause ecau Becau energy. B ve energy. wave a wa da and dal tida g tidal ng sing y using icity ctricity ec electr . e en lean energy clean a clea t as red to ferred re refer y are ey hey miss ns, they missio du em produc o not produce hods do method

ns ns, is ons, mis missi u emissi r uce g to reduc elp ng helpin nd h and ya rgy an energ ean clean cl ed in cle rested intere ou are interest you If yo ewab energy ew rene e neer. A renewable gy engi energy energ ble ene e able b a renewable u may like to be ou o you yo es n no w technologi new ts ne nd tests and dev es, develops researches th t researche ngineer is a scientist that ng en e ergy. duce clean energy. tto produce

ng b burning y by elec of electricity r uction of produc p the pr ne , th n ine in ineer gineer engine g gy e rrg n rgy ne le ene ewable o a renewab To s ers see e ee eer gineer y engineers le energy en ene e em. Renewab em llem. problem. proble ed as a prob iffied entifi identifi fue iss id fuel ossill fuels ffoss fo as ve a ive na iv tern terna alternat energy al ble energy of a renewab o o io ttio tion ation at atio nt na en ent e entation ment men eme lement m leme iimp d im gn and e design he h th the lution.. olution h so th the

off yo ty aiillabilility aila ailab vailab o the availab a on ngin rss collect data ng y enginee rgy rg energy able energy wa w ewa enewa ene Ren Re Renewa n, Sun e Su he th from the ne energ ook at how energy o e look hey h They T Th field The h field. tthe y in th rgy rgy energy le e ble ewab newa enew enewa enewable re renewa y tly. i tly. cien cie fiicien e ficien y ef ty e ectricity generate el ed to gener ssed use be use c n be nd ca d wind nd ater and at n water oving o moving m nd testt and rss to te ters computers u compu n use e and m dels models ey build mo hey ess, the ies, iie orries o tor to ator a orator n lab In d nd or and monitor o monit T y also The s.. Th d ei design thei ss off their t ctivene effec te the effe uate lu alua eval eva ucted. ucted ructe con tructe cons o ec ologiess onc technologi y technologi energy e energ ble re ewab int iin ren inta mainta renewable ou were a renew you work on if you uld y What would eer? engineer? gy engin energy

Engineer It!

Goes beyond inquiry uiry by encouraging students udents to design, model and build utions to to engineer solutions oblems. defined problems.

In the Field

Inspirational sc sciencerelated to ated professions p stir interest rest in sciencerelated careers.

A Closer Look Features of the Eart

h’s Surface

For Forces such ch ass mov movin oving gw water,, w wind in and the movem moveme Earth’s tect ent of the ent t ect ctonic onic o nic plates plates lat are contin continua ntin ti lly sh s aping ping the Earth’s Earth’s surfac and water sources. su f e

111

1 10

lake

plateau

canyon

A Closer Look

Invokes enthusiasm in science by presenting interesting topics beyond the syllabus.

island

lagoon

peninsula ocean

Amazing Fact! eagle de bald bal

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Interesting facts to bui build interest and enthusiasm. nthusiasm.

l Structures

artss a par ntt pa n rent ren iffff re iffe diffe p off d ade up made p the stt ucturess help se str These s These s. ent and environm ir e th the n i in ve rvive u survi r ernal ded into two types – exte e es. urres. u tur tu ctur c r ctu ructur tru nd internall sstru n

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p n orpio scorpio sco

Did You Kno Know?

o ger to nger ng stinge and a sti rs and incers have pince onss have ion orrpion o Sco Scor ea ave gs have ugs u ug ybugs adyb Ladyb y. Ladyb pray. eir pra heir killll tthei a dk ch an catc c ctt e ec te ote ot r pr c to p pss to elps hat hel ng that o ing over cover d outterr c rd ard har hard gs dy and wings. ody od its bod

e p ke kee h eatthers fea uc ass feat such re such ures tu tures ctu uctu t e p the lp ig t help eig eigh l htt we d their lig nd an . y y. sily s ea re easily ore mo mor

green palm snake

e and dolphins es snakes ks, snak ks s h as shar An als ssuch Anim boness to ac bone back ele ons and ba kelet l sk e erna inter have int have es odie nside the bodi inside gans Or Organs . es. ies dies eir bo hei h thei th ortt tthe upport supp gss ngs things thi g the th ge th m to get p the lso help also alss al ma aniima of anim duce. du duce duc ro pro ep repro grow and repro i , grow ive vive urvive ur su ed to sur ee y nee they they the Discuss some animals you know of and the structures they have that help them survive.

hark

Try This!

sea turtle

Optional ptio hands-on activities to be conducted activ in groups or at home.

dolphin

Science Words

13.

are blood vessels that at carry blood high h in oxyge heart to all parts of an ox n from the animal’s body. b

14.

Most mammals have specia alized li hairs, called their mouth and nose.

Use the words to comp lete the sentences. vertebrates invertebrates exoskeleton herbivore carnivore camouflage

endoskeleton lungs gills arteries capillaries

veins nocturnal whiskers antennae brain

2. 3. 4.

The is an internal structure that processes and interpr information and instruc ets ts the body how to respon d to change. Insects have a pair of sense receptors called . animals are active at night and rest during the day. are blood vessels that carry blood high in carbo from the cells back to n dioxide the lungs.

Arteries branch out into a fine

plants.

is an a anima i l that eats

other animals.

Animals without a backb ones

Use a chart to descri cribe how each h animal’s external structu to survive. res he help it External Structures

Animal

(a) a)

network of

is an animal that eats

are called

, surrounding

Review

Body Cover overin ng g

Moveme ent

(b)

. Some have a

Gettin etting gF Food

List and nd describe three interna l structures re of a dolphi do to survive n that help it surviv urvive i e.

mountain

A monkey eats a sweet rose ro apple. Draw aw and label a flow chart show how the sensory to input in is received by the monke process y and how it is ssed in the brain to help it surviv vive.

glacier

Links students to the Let’s Do Science Activity Book at the appropriate juncture.

Discussion

Activities 7.3 – 7.4

AB Activity

(c)

Describe the landforms and water sources shown in the diagram. Which of these can be found in your area?

Extra ra information to t build students’ dents’ knowledge know se of the cu base current topic.

Topic-related questions and situations for class discussion to build a deeper understanding of topics.

hill

river

Review

plain

delta

beach

sand bar

Topical questions at the end of each chapter for formative assessment.

Science Words

Lists the essential science vocabulary covered in each chapter.

Contents

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Unit 6 - Processes That Shape the Earth th

Minerals, Rocks and Soil Changes to the Earth Weathering and Erosion n Rapid Changes Natural Hazard Impactss Na Earth Long Ago Ea Review Re

4 12 13 30 42 44 50

Unit 7 - Mapping the Earth’s rth’s Surface Sur

50 52

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Earth’s Landforms rms ms Earth’s Water M Maps atterns Landform Patterns Ocean Pa Patterns rns Review w

Unit 8 - Using Using Earth’s Ea Resources N Natural Resources Re NonN Non-renewable Energy Ren Renew R Renewable Energy Environmental Impacts E Rev R Review

54 60 66 74 78 83

86 88 90 98 1 102 1 109

112

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Unit 9 - Energy and d Motion M ti

What Is Energy? Energy, Motion and Force E Collisions C F Forms of Energy Transformation of Energy T gy Electric Charge and Circuits E ts Review R eview

Unit 10 - Waves and Information nformation What Are Waves? aves? Characteristics Wavess ics of W Properties Waves rtie of Wave rties Types off Wa Waves Light ht Waves es and In Waves Information Review eview

114 119 120 126 131 134 13 14 145

146 148 151 154 158 160 166 170

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Processes That Shape the Earth

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In this chapter you will ...

• describe minerals, rocks and soil and their properties. es

ow they form. form • list the three main types of rocks and describe how

th’s surface rapidly • list and describe processes that shape the Earth’s and slowly.

rmations and fossils in • identify evidence from patterns in rock formations or changes in a landscape rock layers to support an explanation for over time.

rements to p • make observations and measurements provide evidence of e rate of erosion er the effects of weathering or the by water, ice, wind and vegetation.

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What are minerals, rockss and soil? How are they used by people?

Go Online!

Access interactive content relating to this topic on the NGScience website. ngscience.com

What processes change the shape of the Earth’s surface?

talc lc c mine mi e

Minerals, s, Rocks and a Soil What Are Minerals? Mineral Mineralss are are naturally naturally o occurring inorganic substances are in rocks and soil nces that that a re ffound o on and surface. Inorganic nd under under the the Earth’s Ea means eans they they do do not no come from the remains of ving tthings. hing ngs. living Many M any minerals minera are metals. Gold, silver and copper are er a re minerals. Other common minerals salt, talc and diamond. iinclude nc

Using Minerals Plants, animals and other organisms need minerals to survive. Plants take iin n minerals salts through their roots. The e minerals are essential for the healthy growth of the plant. They are also important for photosynthesis.

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Animals and people need minerals. Many of these essential minerals come from water and food. Calcium is a mineral that helps animals develop healthy, strong bones and teeth. Iron is a mineral essential to animals for the transport of oxygen a and nd production of energy.

gold

Minerals are also mined and used by used b y people people in i many ways. They are used in n the the construction constructi of roads, buildings and cars. used rs. They They are are u se in manufacturing, the production off c cosmetics tion o osm and in cleaning products. cts Gemstones tones and diamonds are often u used sed to to make jjewelry.

Activity 6.1

Properties of Minerals Scientists who study minerals, called d mineralogists, identify minerals by y looking king closely closel at their properties. By observing and measuring ey are re able to the properties of minerals, they usefu to t determine how the minerals can be useful people.

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Try This! Use a mineral collection to observe, test and describe the properties of different minerals. Describe their color, luster and hardness.

nerals ls include c Some properties of minerals color, luster, d cleavage. eavage streak, hardness and The color of a mineral neral is often the th most obvious property of a mineral. ral. However, However many minerals occur in more e than one color, color colo making this property not ot very ry useful.

Opals have an iridescent luster.

The luster ter er of a mineral describes its appearance when it reflects may be eflects light. Minerals M transparent, translucent or opaque. Some sparent, ent, translu minerals luster – they look similar inerals als have a metallic m metal. to a shiny metal meta Others have an earthy luster – they dull, clay-like appearance. A mineral hey y have a d can also hav have an iridescent luster. This means its color changes as light hits its surface from ch different directions. diffe differe dif diff

kaolinite

magnetite

Did You Know? Mineralogists ts measure measu the hardness ess of minerals minera using the Mohs ohs hardness ha scale. They compare compar the hardness ardness of a mineral with 10 minerals hardness. of known hard Diamond is the hardest and has a score of 10. Talc is the th softest and has score of 1. a scor

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Different minerals may be similar in color and luster which can make them difficult to identify. A more accurate way to identify a mineral is by its streak. Streak is the color of a mineral in powdered form. Streak is obtained by scratching a mineral on a hard, rough plate called a streak plate. The color of the streak can be used to help identify the mineral. The hardness of a mineral is how easily it can be scratched. Hardness can be determined by scratching a mineral with another mineral of known hardness. Knowing the hardness is an important property in determining a mineral’s eral’s potential uses. It is also used to help identify ntify a mineral.

Cleavage of a mineral describes the e way it breaks. A mineral with perfect cleavage, leavage, vage, such as a calcite, will break into flat, smooth ooth sheets heets along alon its lines of weakness.

diamond

Why is it useful to know the properties of a min mineral?

talc calcite

AB Activity 6.2 7

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Go Online! Rocks on Earth are continually being formed, broken down and formed again in a repeating pattern called the rock cycle. Watch a video and find out more about the rock cycle on the NGScience website. QuickCode: B6B8

kimberlite im imberl

Geologists are scientists ntists that sstudy rocks and the processes shape them. cesses es that shap They classify three main types ify rocks cks into thr th n how w they form based on form. There are cks, sedimentary sedim sedimen igneouss rocks, rocks and metamorphic amorphic morphic rocks. gneous us rocks fo fform when molten rock, Igneous called magma magma, cools beneath the Earth’s Granite is an igneous rock surface. urface. Gran this way. formed ormed in th With en enough heat and pressure, magma c also break through the Earth’s can as lava. When the lava cools, the sur surface igneous rock basalt is formed. ig igneou

granite

basalt b l

Re ga le du ca ti Sedimentary rocks form when minerals and organic particles, called sediment, settle in layers yers on or just below the Earth’s surface.

The rock tthat forms the steep cliffs of the c Grand Canyon are made Ca C of the sedimentary rocks s sandstone and mudstone. sand

The process of the particles settling is known nown as sedimentation. Over millions of years, ars, the e sediment layers are slowly compacted ted and bind together to form rock in a process ocess cess called d cementation. Despite only making up a small mall percentage of the Earth’s crust, sedimentary ntary ry rocks cover a large area of the Earth’s rth’s ’s surface, surface estimated to be up to 80%. 80

Unlike sedimentary rocks, ks, metamorphic metam metamo rocks form deep below ow the Earth’s Earth surface. s Metamorphic rocks ocks were once other othe types of rocks that have e gone throu through a process known as metamorphosing, ‘to morphosin meaning me change form’. orm’.

Metamorphosing rock is subject morphosing hosing occurs when w to immense deep below the mmense heat and an pressure pr Earth’s rth’s surface.

Metamorphic etamorphic rocks etamo rock make up a large part of the Earth’s crust, crus but only a small percentage of the rock on the surface. e Earth’s Ea

Marble is a metamorphic rock often mined in deep quarries.

AB Activity 6.3 9

Soil Soil is a mixture of weathered rock, ck, air, water and humus. Humus is decomposing wat wa ecomposing mposing organic matter. It is often the darkest or rga est part par soil and contains nutrients off so ts needed eeded by plants pla an and other organisms. m ms.

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Humus-rich soil is dark in color.

There are three types particles T pess of rock par partic tthat make up soil oil – sand, and, silt and an clay. The particles icless come from the weathered parent which they nt rocks w wh were once Different types of e part art of. Differ Differe soil contain amounts of sand, tain different am silt and the size of d clay. This affects affec affe air pockets ockets ts in the soil soi and how much water w er the he soil can hold. h

Sand largest particles. Soil with Sa an n nd are the large mostly mo mos m stly y sand has the largest spaces for air and a an nd d water drains dra dra aiin ns through th hrough h itit quickly. quick kly.

Silt are medium-sized particles. Soil with h mostly silt has small pockets of air and can hold more water than sandy soil.

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Clay are the smallest particles. Soil with mostly clay has the smallest pockets of air. With the particles closely packed together, water cannot drain well through soil made mostly of clay. ee e soil Most soils have a combination of all three arrticle e particles. The amount of each type of particle he e types typ ypes pess and the amount of humus determine the of organisms that live and grow in the soil.l. How does the composition of soil affect its properties?

Activities 6.4 – 6.5

Soil samples with varying amounts of sand, silt and clay.

Try This!

In small groups, go into your schoolyard and collect some soil in a dish. Use a magnifying glass or a microscope to closely observe the soil. Draw and describe the rock particles you observe. y

Changes to the Earth th What landforms can you see around ound d your school or home? You might see e mountains unttai in the distance or a river flowing ng by. by. Maybe the land stretches out flat in n front front nt of of you you or or perhaps it slopes down into to o a valley. valley. The Earth has a variety of different ffferent ferent landforms landfor lan ndform and although we often n cannot nnot see it from f day to day, or even from m year to year, ye these landforms are always ways changing.

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Some changes, s, like like volcanic volcanic eruptions e and earthquakes, Others, akes, occur occur rapidly. rap like weathering ering and and erosion, erosio have been changing g the the surface surface of of the Earth over millionss of of years years and ye and are a still doing so today.

What processes proc change the surface Earth? of the Ea

Rocky cliffs are weathered by the waves crashing into the coastline.

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Wave Rock in Western Australia was formed by the weathering and erosion of rock for over 2,700 million years.

Weathering and a d Erosion Eros Erosi One of the ways the e surface surfac rface of o Earth changes is by weathering. is the atheri ring. Weathering Weathe breaking down of of rocks roc ocks into into smaller smalle pieces. n Earth Eart rth are are constantly constant being The rocks on weathered by crashing waves, db yc rashin ng gw ave es roaring rivers, torrential rrential rrains aiin a nss and and other oth processes. o Weathering landforms. ering g changes ch changes es the Earth’s E chan nges gess occur occ ccur ur too too oo slowly to notice Such changes from m day day to o day da day or or even eve from year to year. The he changes he ang s usually usually occur slowly over millions miillions m llionss off years. yearss. yea

Think Deeply What factors could affect the rate of weathering of a coastal cliff?

Did You Know? Lichens are plant-like organisms that often grow on rock surfaces. They produce oxalic acid which contributes to chemical weathering g of the rock.

Chemical Weathering Chemical weathering occurs when en chemicals chem hem mic ica ca in ng a chemical chemical come in contact with rocks causing d acid acid id rain rain reaction. Oxygen in the air and of chemical chemical hemical are two common examples of weathering. Acid rain occurs urs rs when when n harmful harmf harmfu gases combine with the oxygen and water wa g the he rain that falls ffa back vapor in the air causing to Earth to be acidic.

When acidic rain falls o a chemical on n limestone, limeston im m stto reaction breaks down do own the rock k leaving holes. The reaction changes rock into changes ges the the llilimestone im clay and soluble luble e salts. salts. Over Over time, the holes in the rock can get and break down the et bigger a rock completely. mpletely mpletely.

Holes in the limestone rock are caused by chemical weathering.

Rocks with iron will also rust. The rust breaks down the rock into smaller pieces. The pieces are often washed away by water. The rust also causes the rocks to have a distinctive orange or brown color.

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Many rocks contain iron. A chemical reaction between the iron and oxygen in the air or water can cause rust. We often see rust on metals like the iron and steel used to make cars. The rust breaks down the metal causing it to become brittle.

AB Activity y 6.6 6

Chemical hem he mi weathering of o the he Belogradchik Rocks R cks rocks in the Balkan Mountains. Mou u

Amazing Fact! Chemical and physical weathering have been shaping the Belogradchik Rocks in Bulgaria for millions of years. Many rocks have strange and fascinating shapes and can reach heights of over 200 meters.

Physical Weathering ng Physical weathering occurs urs when when rocks are broken down by by forces. force orrce es. Examples of physical w weathering eathering athering er, wind, the include moving water, ing ng of water wa and an the freezing and melting actions of organisms. nisms. s s.

Mule pack train in the Grand Canyon National Park.

Think Deeply

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What landforms can be found in the Grand Canyon National Park? What processes have shaped these landforms?

Go Online! ne

Discover how the Grand nd Canyon formed and the he processes that continue ontinue to shape it today y on o the NGScience ence website. websit QuickCode: ode: K2F2

er, such uch as the c Moving water, constant battering of coastal oastal rocks by waves and the flow of water in rivers and streams, physical ms, causes auses physi physic weathering. The contact act between betwe betwee the water and the wears the rock, e rocks cks slowly we w pieces. breaking ng it into small s canyons River R iver canyon c anyon are landforms caused weathering of the river bed and by the by the w ea the rock by rock by th th moving water of the river.

Amazing Fact! The rock formations mations in Bryce Canyon yon National Park in Utah, USA, A, are a great gre example in ple of frost wedging we action. n. Each year yea the rocks by up to are weathered b 200 00 cycles of the th melting of freezing of water. ice and free weathering gives the The weathe called hoodoos, their rocks, cal chimney-like appearance. chimn

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In cold climates, water enters the crevices and cracks in rocks. When the temperature cools, the water freezes. When water freezes into ice, its volume increases. The ice pushes against the sides of the crack and can often cause the rock to break into small pieces. This process is called frost wedging.

Wind also causes physical weathering, particularly in places with little vegetation. Wind d is moving air. It also often contains particles such as sand and soil. When strong winds hit h it a rock, the particles slowly chip away at the e rock, rock, breaking it into smaller pieces.

Re ga l

How is chemical weathering g similar to physical weathering? g? How are they different?

Go Online! Learn more about frost wedging during a virtual field trip to Bryce Canyon National Park on the NGScience website. QuickCode: W4B2

Hoodoos in Bryce Canyon National Park.

Try This! Draw a diagram to show how changes in daily temperatures can cause erosion. Present and explain your diagram to a classmate.

Differences in temperature between night and day can cause physical weathering. p Most materials expand as they heat up ey and contract, or get smaller, when they cool down. m the t e Sun Su During the day, the heat from n expand. xp pand d. causes rocks to heat up and e temperature tem eratu When the Sun sets and the drops, the rocks contract. This h expanding expand racks in tthe h rocks. and contracting causes c cracks get b gge and the Over time, those crackss get bigger aller pieces. eces rocks break into smaller

The growth of plants can cause physical physical weathering. The roots of a tree can can break break e grows. grows. This This apart the sidewalk as the tree oo. Plant Plant roots roots happens to rocks in nature ttoo. can grow in the cracks of rocks. rocks. As As the the plant grows and the roots get et bigger, bigger, r, they th push the sides of the c cracks, rac breaking eaking the rock into pieces.

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Animals can also cause weathering oc ause w au eathering when they walk lk or or climb clim imb on on rocks. rocks This he rocks roc ocks apart apart or or give giv them a can break the rface. smooth surface.

How w do organism organisms contribute to the of rock? weathering o

Activities 6.7 – 6.8

Erosion In the Sahara Desert in Africa, wind erosion can carry dust particles across the Atlantic Ocean which settle in the Amazon basin in South America. The dust particles provide the Amazon Basin ecosystem with essential nutrients.

Think Deeply Look at the erosion caused by the moving water in the river. In small groups, discuss possible solutions to reduce the rate of erosion.

The particles from weathered rock are often oft fte en moved to new places. This process off moving weathered rock particles to a new location atio on is called erosion. The main causes of erosion are moving water, wind and d gravity. The slow s movement of glaciers down n mountains can ca also cause erosion. Waves crashing into the weathered coastline move rock particles to new place places. Fast-moving water in rivers pick up particles and move p rock part them downstream.

Amazing Fact!

How does erosio erosion change the shape of the Earth’s surface? s

Engineer It! Planting vegetation etation and a building sand-breaks and-breaks are a two ways people can slow down or prevent erosion. ero Make a model of o a sandy beach affected by wind and and wave erosion. Design D solution to the erosion build a solu Use your model to problem. U of test the effectiveness e your ssolution.

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Wind erosion is constantly changing the shape of the Earth’s surface. Wind lashes coastal cliffs, moving particles to new places and changing the shape of the cliffs.

On beaches, sea and land breezes move sand from place to place. This forms large piles of sand, called sand dunes, that change the shape of the coastline. Wind can carry sand and rock particles over very long distances. Scientists have found weathered rock particles from Africa carried by y wind over the Atlantic Ocean and dropped in South America.

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Moles can contribute e to erosion when they dig and loosen soil.

Try This!

Find examples of erosion taking place in a natural environment. Identify what’s causing the erosion and describe how it is changing the shape of the land.

Animals help contribute ibute to ero erosion when they dig holes, tunnelss and so, they loosen d caves. In doing d soil and expose pose rocks. roups of animals anima can cause erosion too. Large groups Overgrazing can leave soil bare. grazing zing on vegetation vege The e bare e soil is no llonger held together by the roots oots of plants and an is more easily eroded by wind and water.

Moving herds can also contribute to ng in large la erosion. Sand and soil are thrown into the air as e ero S wh w dust where they are moved by wind. Wildebeest move in large herds. W Wildeb

Erosion is a continual process that occurs in many ways. Sometimes, erosion can occur quickly, such as the movement of particles by wind and water during a storm or flood. Erosion also changess ver the surface of the Earth gradually over millions of years.

Do you know w how gla glaciers form? Find d out in a video vide on the NGScience nce website. w QuickCode: Code: J9Y1

Amazing Fact! Ama

The large largest glacier on Earth is the Lambert at present pres Glacier ac in East Antarctica. measured 85 kilometers It m wide, 400 kilometers long and 2,500 meters deep.

AB Activities 6.9 – 6.10 .10

Go Online!

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A glacier is a large body of ice that is slowly pulled over land by the force of gravity. As it moves, it collects and moves rocks of all shapes and sizes. When the glacier melts, the rocks and rock particles are dropped in new places.

glacier

What are some factors that could increase the rate of erosion?

Factors Affecting Erosion rosion sion Try This! Does sedimentary rock erode faster than igneous rock? Plan and conduct an investigation to find out. What will be your controlled variable in the investigation?

Changes to the Earth’s surface ace due to weathering and erosion can an be affected by ch h factors includ inclu a number of factors. Such include the emperature erature an and the steepness of slopes, temperature win speed and motion of water and wind.

The steepness of the affect the rate e land can a of erosion. Generally, steeper the slope, nerally, ally, the stee the faster the e flow flow w of water wate over the land. This increases th the erosion. he rrate ate off erosi ate erossi Temperature can errature c an affect affe the rate of weathering The weathering the ering in ng and and erosion. eros eros of rrock often occurs ock o fte ft en o ccu faster in places with a greater difference greater differenc d ifferenc in daily temperature. This can cause can c ause use the the rock to expand and contract more, which more, w hich leads to increased weathering. hich Temperature differences can also affect Te a the frequency of frost wedging. The more the fr frequently frequent ice forms and melts, the greater the rate off weathering. ra atte o

Amazing Fact! The Port Campbell mpbell c coastline in southern Australia has ha been shaped ed by the t harsh weather er conditions of the Southern ern Ocean for millions of years. The soft limestone cliffs which iffs develop caves, c then form arches. The arches collapse leaving eventually c giant rock stacks. Over time, rock stacks are weathered the roc eroded, changing the and e shape of the land. sha

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Hot temperatures can also cause soil to become dry. This can increase weathering by wind.

The motion of water and wind can directly affect the rate of weathering and erosion. The stronger the wind blows or the more water that runs over the land, the greater the rate of weathering and erosion. The size of waves and the strength of tides affect the rate of weathering and erosion in coastal areas. The bigger the waves and the stronger the tides, the greater the rate e of weathering and erosion.

The types of vegetation in an area also allso o affects the rate of weathering and d erosion. erosion. Tall trees and dense shrubs can rreduce the educe th the strength of wind and reduce the he rate rate of of weathering. The roots of plants nts grow grow down down into the soil, holding it in place. ace. This This reduces reduce the rate of erosion from water ater and and wind. wind

AB Activities 6.11 .11 – 6.12 6

Weathering and Erosion by People In what ways do people contribute tribute to weathering and erosion? n?

Human activities are continually on ntinually contributing contrib to both weathering and nd erosion. erosion.

People cause large-scale weathering ge-scale w eathe when they dig m mines and quarries ines a nd q uarr to take rocks and minerals In erals ffrom rom tthe he Earth. E constructing mines and quarries, trees and gm ines a nd q ua other vegetation are This can etation on a re re rremoved. emo lead to increased ncreased erosion erosio in the area. If the area w where mine here the he the m ine or quarry is built is not restored, and erosion can estored, weathering weathe continue ntinue after aft fte er the the mine or quarry has closed.

People build dams to store w water ater that that is is used us in surrounding cities. Damss a are also created re a lso c rea ce e lectr le to control water flow to produce electricity. Changing the natural fflow of the rivers low o rive can increase erosion downstream wnstream of the dam.

People often cutt down down trees trre ees and and remove re vegetation to make make way way for for farms, farm roads and cities. Without ut plants plants with with roots roots that hold the soil in place, e, erosion erosion by by wind wind and a water can wash away way the the top top layers layers of o soil.

Discuss the ways in which people have contributed to erosion in your local area. contribut

Activity 6.13 27

Deposition Weathered rock particles are moved ved to to ne new ew places by erosion. Eventually, the eroded ee roded oded d ace. This process proce material will settle in a new place. of laying down rocks and rock new ck particles articles in n ne places is called deposition.. Like weathering and erosion, is a rosion, sion, deposition depositio deposit continual process that of at changes hanges the shape s the Earth’s surface.

Think Deeply The downstream ream area ar where a river ver flows into the ocean is called lled an estuary. pening of the estuary The opening to the the e ocean is called c Deposition can often mouth. Depositi mouth to close, cause the mou the flow of water blocking th into out of the estuary. nto and o could this affect the How cou animals in the estuary? anima

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Weathering occurs when rain and moving water break down rocks or river beds on a mountain. Erosion occurs as gravity pulls the water downstream bringing the rock particles with it. As a river nears the ocean, it usually gets wider which slows the flow of water.

As it slows, the eroded material is deposited in a new place. This can change the shape of the coastline forming sand bars, deltas and lagoons.

How does deposition change the shape of the Earth’s surface?

AB Activity 6.14

Rapid Changes

What are some ways the Earth’s surface can change rapidly?

Many processes can change nge the the surface surface of the Earth rapidly. These processes processses es iinclude nclu natural hazards such a ass ffloods, loo ood ods, llandslides ands and hurricanes.

Floods Floo During periods of high rainfall, the water Dur D ur sources in an area can fill up. A flood can c occur when the water in rivers and a lakes overflows onto land. This can cause the rapid erosion of soil and rock. Increased water flow in rivers during a flood also increases the rate of the erosion of river banks. The erosion caused by floods rapidly changes the shape of the land. The shape of the land can also be changed by the deposition of eroded sediment to different areas.

ca Landslides Heavy rain and melting snow ow can can increase increase the flow of water over land. On steep sslopes, lopes, ssuch uch as a mountains and hills, this can cause a landslide. is the rapid e A landslide lan ands erosion of soil, rocks and a slope. The d vegetation v tiion down d eroded material is pulled down ed d dow wn the slope by the force of gravity. The movement off rrocks, and nt o ocks, ssoil oil a nd vegetation during a landslide rapidly changes of mountains and hills. pidly c hanges tthe he sshape h The removal val of of vegetation vegetation can ca also increase weathering and erosion sion in in the the future. future. The falling falling rocks rocks during during a landslide can be dangerous. Large can cause damage to roads, cars, homes rge landslides landsl slides c an c and entire a nd even even e ntire towns. tow

Monsoons Think Deeply The word monsoon is often incorrectly used to describe a local thunderstorm with heavy rain. What is the difference between a thunderstorm and a monsoon?

Tropical areas close to the Earth’s e equator qua uat ator have two seasons – a dry season and on n an nd a monsoon season. A monsoon is a wea weather weather ather pattern of strong winds and rrain lasts ain n that th t la las asts for fo several months. Monsoons can be helpful much pfull by bringing b ing gin ng m needed fresh water to an following n area rea follow folllow the dry seasons. Monsoons onsoons oons can ca also als al cause flooding which can weathering and an increase crease w wea ea erosion and change ange ge e the th shape shape of the land.

Hurricanes

The heavy precipitation and large coastal waves increase the rate of weathering and erosion. They can cause flooding and landslides. Hurricanes can be dangerous to people and cause widespread damage to land, roads and buildings.

A hurricane is a large rotating storm that forms over warm ocean waters. Hurricanes have strong winds and heavy rain. A hurricane makes landfall when it moves from the ocean to coastal areas of land.

Meteorologists monitor weather patterns and are able to predict where and when na hurricane will form. They can also predict its movement and warn people that may ay be affected by its landfall.

Go Online! Hurricanes, cyclones and typhoons are all tropical storms. Find out how they are different on the NGScience website. QuickCode: C8G4

A Closer Look

Structure of the Earth The Earth is made up of three layers – the core, mantle and crust.t The core is the inner-most part of the Earth. It is also the e hottest part. The center of the core is the inner core. It is made of solid rock. Surrounding the ock. Surroundi inner core is the outer core. The outer core is made off molten rock. ro The mantle lies between the core and the crust. It iss made up mostly of solid m rock, with parts of the mantle closest to the core made of m molten rock.

crust

ma mantle

Re g

outer core

Think k Deeply

Scientists are not exactly sur sure of the temperature emperature of the inner core. ore. It is estimated to be between ween 5,000 5,0 and 7,000 degrees Celsius. elsius.

inner core

The crust is the thinnest, outer-most part of the Earth and the part we live on. The crust is made up of solid rock and minerals.

Activity 6.15

The outer part of the Earth is divided into large, slow-moving pieces of solid rock called tectonic plates. The plates are constantly moving over a layer of molten rock in the mantle. As nd interact interac the plates move, the boundaries of the plates touch and with each other in different ways. The interactions of the plate thquakes, boundaries is why we experience events such as earthquakes, tsunamis, volcanoes and the formation of mountains.

Go Online! The process by which continents move about on tectonic plates is called continental drift. About 250 million years ago, the continents on Earth were not positioned as they are today. Most continents were joined together forming a massive supercontinent called Pangaea. Slowly, Pangaea broke up and drifted apart to form the continents on Earth today. In millions of years from now, many more supercontinents will form and be broken apart. Discover more about continental drift on the NGScience website. QuickCode: R3Z1

Earthquakes The point in the Earth’s crust where an earthquake originates is called its epicenter. Vibrations caused by an earthquake are greatest at the epicenter and get weaker the further the vibrations travel from the epicenter.

During an earthquake, vibrations move outwards from the faults.

An earthquake is a shaking of the Earth’s th’s surface caused by the movementt of tectonic ate boundaries. boundar plates and interactions at the plate

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Did You Know?

r, the crust, is sitting ssit The Earth’s outer-most layer, on several large rocky plates tes that are in constant co ur when the pla p motion. Interactions occur plates rub h other or pull apart. together, press againstt each ur along plate b The interactions occur boundaries. The interaction of the plate boundaries causes a late bound ure. The release of the pressure buildup of pressure. ns att cracks in tthe Earth’s crust. causes vibrations alle faults. fault au These cracks are called All of the places where plates es meet eet are faults. fau Faults can also hin a plate. occur within

Every year, millions of earthquakes occur all over the Earth. Most of the time, an earthquake is too small to be felt by people. During a more powerful earthquake, the Earth’s crust shakes violently and can cause extensive damage to roads, houses, buildings and bridges.

le du c

Scientists that study earthquakes, called seismologists, are able to measure the strength of an earthquake. An instrument called a seismograph detects and records the vibrations caused by earthquakes. An earthquake is given n a score between 1 and 10 using a scale called the Richter scale. The higher the score, the more powerful p owerful the the earthquake.

How do earthquakes change hange the surface of the Earth?

Volcanoes Go Online! Not all volcanoes have a mountain-like shape. Discover the many other types of volcanoes on the NGScience website. QuickCode: C4Z7

A volcano is an opening in the Earth’s surface, surfac or crust. Beneath a volcano is a magma ma chamber containing hot molten rock called magma. A volcanic eruption occurs urs when the magma pushes up from m inside the Earth Ea and flows onto the Earth’s surface. Magma urface. Magm that flows on the Earth’s surface urface is called calle lava. Volcanic ash, water vapor and other gases also g erupt from a volcano.

Amazing Fact!

Re ga

The Hawaiian islands are a great example of how volcanic eruptions shape the surface of the Earth. All of the Hawaiian islands formed from volcanic eruptions. There are currently four active volcanoes in Hawaii, including the world’s second largest, Mauna Loa. It last erupted in 1984.

Lava has a distinct red or orange glow. Ass it olid cools, it stops flowing and hardens into so solid igneous rock. The new rock formations change the surface of the Earth.

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Volcanic eruptions can also change the Earth slowly. As the volcano erupts, new rock forms on top of older rock. Gradually, the volcano gets bigger and forms a mountain. The time it takes to form a mountain depends on the size and frequency of the eruptions.

Scientists who study volcanoes, called volcanologists, classify volcanoes based on the likelihood of them erupting. pt g. Volcanoes that have erupted recently tly and an a d are likely to erupt again are called active volcanoes. e vo olcano olcanoes can es. canoes s Volcanoes that have not erupted forr thousands thousan ousand and ds of years, but may erupt again in n the future are a called dormant volcanoes. Volcanoes canoes that th have not erupted for 10,000 years orr more are ar called extinct volcanoes.

Re g

Most of the volcanoes on Earth, a about 70 percent, are underwater. erupt, they ater. When they t send lava into the ocean ean which hardens to form rock. As an underwater rwater volcano volca erupts more and more, it getss bigger and an taller. Eventually it may reach the ocean surface surfa as an island.

Mayon Volcano is an active volcano on the island of Luzon in the Philippines.

Try This! In small groups, find out how many volcanoes are in your country. How many are active volcanoes?

How do volca volcanoes change the surface Earth? of the Eart

Tsunamis are sometimes called tidal waves. This can be misleading as the occurrence of a tsunami is not related in any way to tides. All tsunamis are caused by disturbances on the ocean floor.

Engineer It! Tsunamis can cause widespread damage to coastal areas and endanger human lives. In small groups, design, build a model and test a solution to help protect a coastal area from a tsunami.

Tsunami caused by an underwater earthquake.

Tsunamis A tsunami is a series of fast-moving g waves aves caused by a disturbance in the ocean. cean. n. Such disturbances can include an underwater derwater ater earthquake, volcanic eruption or underwater landslide. Although very rare, e, a meteorite landing la in the ocean can also cause se e a tsunami.

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Did You Know?

The waves travel away disturbance, y from m the distur distu towards the shore. If the disturbance is powerful, resulting in large sets ets off waves, they th the may reach the shore and flow w onto nto land. land On land, they damage y can cause extensive exte ext and changes es to coastal areas. are They can cause erosion off sand nd and coastal coa coas banks and remove coastal vegetation. The They can cause widespread damage buildings and coastal towns. age to roads, bu

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The most common cause of tsunamis h are underwater earthquakes. Although we cannot control when or where an underwater earthquake will take place,, we can monitor and detect them as they occur. Monitoring instruments are used to measure and communicate the location and size of the earthquake, along with the height of the waves produced. People in coastal areas can then be warned and move to safety before the destructive waves reach the shore.

mi In 2004, a large and destructive tsunami nd destroyed coastal areas in Indonesia and e llost. ost. surrounding countries. Many lives were Since then, global tsunami warning systems systems ms have been developed to warn people le around around the world of a potential tsunami reaching land. ch and

Amazing Fact! In 2011, a large tsunami caused by a powerful underwater earthquake devastated the town of Fukushima in Japan. As a solution to future tsunamis impacting the area, giant sea walls were constructed. In some places they are more than 12 meters tall and stretch for hundreds of kilometers.

Natural Hazard Impacts Engineer It! Tornado Alley is a large area in central United States that gets frequent supercells. A supercell is like a giant rotating thunderstorm. There are very strong winds, lightning and hail. In small groups, design and build a model of a house that can withstand the forces of nature in Tornado Alley. Test your design. Compare it with the designs of other groups. As a class, evaluate the effectiveness of each design.

Along with causing rapid changes to the he Earth’s Earth surface, many natural hazards can also impact lso im act humans in a number of ways. Such natural namis, volca hazards include earthquakes, tsunamis, volcanic does and flood eruptions, hurricanes, tornadoes floods. ake to people peop The impact of an earthquake depends on its size. Most earthquakes arthquakes are too small to cause any noticeable impact. Larger ceable impa earthquakes can cause e widespread widespre damage to buildings, roads and Buildings nd other property. pro may collapse which result in injuries h can resul and death. Floods can near water an cause land, often o sources, to be covered in water. This can cause damage to farmland, farmland roads, homes and buildings.. Tsunamis can flood coastal areas. The movement ment of water wa from the ocean to land can destroy roads, farmland, homes and buildings. troy road During g large larg ge volcanic eruptions, the release of lava and rocks can damage nearby infrastructure. The gases and ash released during an eruption can also be harmful to people.

Activities 6.16 – 6.17

Reducing Natural Hazard Impacts acts

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Humans cannot eliminate natural hazards, but ut can take steps to reduce their impacts. Scientists tissts and engineers are continually studying the Earth’s processes that cause natural hazards and their effect on humans. They use the data they collect to design solutions that reduce the impacts on people. In the past, one of the greatest impacts of large earthquakes was the damage and collapse of houses and buildings. Today, many buildings in areas where earthquakes es occur are designed to withstand shaking. g. This reduces the damage to buildings and the e chance of a building collapsing. Homes and buildings in areas prone one to hurricanes or tornadoes are built uilt from om strong materials and designed ed to o withstand strong winds.

Think Deeply

To reduce the severity and impacts acts of floods, f floodways, levees and can d sandbags sandba sandb an be installed to divert floodwaterr away homes or cities. ay from ho Planting vegetation can help to on in flood plains ca slow erosion during ring a flood. flood

Warning systems are often used to inform people that a dangerous or harmful natural hazard may impact an area. Why are warning systems important?

Discuss some othe other ways we reduce the impacts caused by natural hazards. n

Earth Long Ago Think Deeply Antarctica is the coldest continent on Earth. The ground is covered in ice and snow and almost no plants can survive in the harsh conditions. Scientists have discovered a variety of different plant fossils in Antarctica. What can they infer from this discovery?

Continual processes like weathering, erosion rosion and deposition, along with natural hazards zards like earthquakes and volcanic eruptions, s, have been b changing the Earth’s surface for billions of years. ye Scientists are able to learn what the Earth was like long ago by studying ying patterns in rock formations and fossils in rock ck layers. The discovery of marine e shell fossils foss above rock layers with plant fossils indicates sils and no shells, s a change from land time. By d to water over o studying the fossils iin n an a area, are scientists are also able to infer things gs about the t climate, vegetation and otherr organisms organ s that th lived there.

In the United States, the discovery of shells and marine fossils in the center of the country led scientists to infer that a large body of water, called the Western n Interior Seaway, ran through the centerr of the country long ago.

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Scientists are also able to learn about the Earth long ago by observing land formations. A canyon with different rock layers in the walls and a river at the bottom, indicates that over time a river cut through the rock. How can scientists find out what an area of the Earth’s surface was like long ago?

Marine fossils in sedimentary rock.

A Closer Look

Geological gical Time Scale Fossils appear pear in layers of mostly sedimentary rock called d strata. Over many years, scientists discovered d that the fossils appear in strata in a pattern. By studying the patterns, scientists developed d the geological time scale. The scale allows ws scientists all over the world to explain the e age of rock and the fossils within them. m. The geological ogical time scale is based on observations vations that fossils of the oldest organisms ganisms on Earth appear er strata and the fossils in the lower of more recent ecent organisms appear in the strata above them. The e scale uses this data to show when different kindss of organisms sms first appeared d on Earth and when they became extinct.

ogical time e scale ale The geological allows scientists entists to o quickly uickly find out the he age e of rocks and fossilss anyw anywhere nywhere here in the world..

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Tyrannosaurus rex

The geolo geological ologica ica al time sca scale shows that the well-known rex lived on Earth during the dinosaur ur Tyrannosaurus Tyran Tyran nnosa nnosaur Cretaceous was roughly 85 to 65 million ta s period pe eriod which w years If scientists discover a Tyrannosaurus rex ears ars ago. ago a s ien fossil in a rock ro roc strata, they will know that the strata was formed somewhere between 85 to 65 million so years ago. ag Trilobites Trilo tes were ancient marine animals that Trilobite became be ame extinct about 250 million years ago. beca They Th The hey had an exoskeleton that was easily fossilized and many trilobite fossils have been fo discovered discovere all over the world. When a scientist discovers a trilobite fossil in rock strata, the geological geologic time scale can tell them the strata was formed at least 250 million years ago. for

Activities 6.18 – 6.19 47

Science Words

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Use the words to complete the sentences. minerals luster streak hardness igneous rock magma sedimentary rock metamorphic rock soil

humus weathering chemical weathering physical weathering erosion deposition flood landslide

monsoon on hurricane cane tectonic plates plate earthquake arthquake fault fau volcano magma chamber tsunami tsuna

A is a series of fast-moving g waves caused ca by a disturbance in the ocean.

is a large rotating storm that forms f over warm A ocean waters.

h is divided iinto large, slow-moving pieces of The outer part of the Earth solid rock called .

forms when whe molten rock, called beneath the Earth’s surface. urfac

The appearance mineral when it reflects light is its e of a mine

is the color of a mineral in powdered form.

9..

The

, cools

of a m mineral is how easily it can be scratched.

are inorganic substances found under the Earth’s surface.

is a mixture of weathered rock, air, water and decomposing organic matter called deco .

can occur when the water in rivers and lakes flows

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10. A onto land. 11.

forms when minerals and organic particles settle le in layers.

12.

forms when rock is subject to immense heat at and pressure press deep below the Earth’s surface.

13.

occurs when chemicals come in contact ntact with rocks ro causing a chemical reaction.

is a shaking of the Earth’s surface ace caused cause by the 14 . An movement of tectonic plates.

15 . 16.

occurs when rocks are broken oken down by b forces.

cks and rock pa The process of laying down rocks particles in new places is . called

17.

is the breaking down wn of rock rocks into smaller pieces.

18.

eathered rock particles to a new location is The process of moving weathered . called

19.

20. A 21.

is a crack in the Earth’s crust.

is an opening in the Earth’s crust.

olcano is a Beneath a volcano called magma. m

containing hot molten rock

22. A is is a weather wea pattern of strong winds and rain that lasts for several eral months. mon

occurs when a large piece of land is pulled down a slope 23.. A by the force of gravity.

Review List two minerals used by people.

How could you test the hardness of a mineral?

List the three main types of rock.

Which type of rock forms when lava cools?

List the three main types of soil.

What is the difference between chemical weathering and physical weathering?

What is the difference between erosion n and deposition? dep

How does weathering, erosion and deposition depositio change the Earth’s surface?

List two factors that can affect ect the rate of erosion.

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10. Describe two ways human activities can change the Earth’s surface. 11.

List four ways the Earth’s arth’s surface can change rapidly.

12.

What are tsunamis mis and how do they occur?

13.

How can rock ck layers tell scientists what the Earth was like long ago?

14.

Scientists discovered reptile and dinosaur fossils in the same layer of scovered re sedimentary entary rock. What Wha can they infer about the reptile and dinosaur that formed rmed the fossils?

In the Field

Volcanologists A volcanologist is a scientist who specializes in the study yo off v volcanoes. olcanoes. lcanoes. Volcanologists spend a lot of time in the field observing g and and collecting collectin lle ectting data on volcanoes – including ones that are currently y erupting. erupt erupting g.. anoes formed, fo orm They collect a variety data to help explain when volcanoes when they last erupted and the likelihood of them erupting uptin ng in ng in the future. futu fut An important role of a volcanologist is to predict edict when when and how big a wh volcanic eruption will be. To do this, they need and identify eed d to gather data d patterns about a volcano’s eruptions in the past. indicate past. If If the he e patterns p that the volcano may erupt again, volcanologists canolog ologists ists can can install special monitoring equipment to closely observe serve the e volcano. volc lcan The data collected is interpreted to help make predictions eruption. tiions about about a future fu Predicting volcanic eruptions be ce ruptions iss v very ery y difficult dif dif ifficu cultlt and and can can sometimes sometimes b e inaccurate. Volcanologists are nologists a re continuing in nuing g to to find find d new ways to collect and ct an nd interpret interp terpret data data a tthat tha ha h at will will improve the accuracy off their racy o their predictions. pre edictio on ns.

Mapping the Earth’s Surface

What are Earth’s landforms and water sources? How do they form?

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In this chapter you will ... • describe Earth’s landforms and water sources.

be patterns patter • analyze and interpret data from maps to describe of Earth’s features.

• use maps to identify patterns in the location off mountain ranges, ocean floor structures, earthquakes and volcan volcanoes.

How can we use maps to des describe patterns of Earth’s arth’s features?

Go Online! Access interactive content relating to this topic on the NGScience website. ngscience.com

Earth’s Landforms

Go Online! Watch a video to learn about the great variety of landforms that shape the surface of the Earth on the NGScience website. QuickCode: F9A3

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What are some of Earth’s landforms? forms? How can you describe the landforms? dform

Processes are continually shaping aping g the surface surfac of the Earth. Some processes,, like the weathering weathe and erosion of rock, occur of urr slowly over millions m years. Other processes,, like e a volcanic eruption e or earthquake, change ge the he Earth’s surface su almost instantly.

The combination n off these rapid and slow changes have Earth’s surface into e shaped ped the Ear E physical features landforms. Mountains, turess called land plains, valleys, eys, canyons nyons and an a plateaus are some examples es of landforms.

Mountains untains tains

Amazing Fact!

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Mount Everest is the Earth’s highest mountain above sea level, with a height of 8,849 meters. The mountain was formed by the pushing of the Indian tectonic plate against the Asian tectonic plate. Scientists estimate that hat the mountain is about 50 0 to 60 million years old. Mount un Everest gets taller by about out a quarter of an inch every year.

A mountain landform that rises above the ain is a lla surrounding ounding land. lan A mountain is taller than a hill and usually usua has steep slopes and a sharp or rounded nded ded peak. pea Mountains are formed by the pushing together of the Earth’s tectonic plates p pu to or vo volcanic eruptions. Mountains often form in volc groups group called ca mountain ranges.

Mount Everest

Amazing Fact!

Plains

Many plains were formed over time by the erosion of the land from nearby hills or mountains. Other plains were formed by deposition of sediment by water or wind.

Valleys

One of the largest argest plains pl on Earth is the e West Siberian Siberia Plain in Russian. sian. It stretches for more re than 2,400 kilometers eters (1,491 mi) and of more than covers an area o 2.6 .6 million square squa kilometers square miles). (1 million sq

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Plains are wide, flat landscapes with little elevation. The size of plains can vary between a few hectares to hundreds of thousands of square kilometers. Being wide and flat also make plains suitable for farming.

Many valleys have a stream or river running through the center.

A valley is a low-lying area between mountains or hills. Often, water flows ws through throu ugh a valley as streams or rivers. Some valleys valley are a arre re formed by the weathering and erosion erosion sion of of glaciers and have a u-shape. Others rs are formed by running water such uch as a river or stream and have a v-shape. hape. e.

Canyons Go Online! Take a virtual field trip to Arizona, USA, to learn about one of the most famous canyons on Earth – the Grand Canyon. QuickCode: U8F4

A canyon, also called a gorge, is a deep, p, narr narrow channel that runs through steep slopes es or cliffs. Canyons are created by weathering and erosion erosio of uplifted sedimentary rock usually by a ally caused b river running through it. The formation of canyons usually take takes millions of years. Scientists believe the in he Grand Canyon C the United States took between etween five to six million years to form.

Think Deeply What factors could increase the rate in which a canyon forms? What factors could decrease the rate at which a canyon forms?

Studlagil basalt canyon in Iceland

Plateaus A plateau, also called a high plain or tableland, is flat terrain that elevates sharply from the surrounding land on at least one edge. e. Plateaus can form in a number of ways. A dissected plateau forms as the result of the upward movement of the Earth’s rth’s crust. cru A volcanic plateau is formed by the flow of lava as the result of numerous volcanic eruptions.

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Plateaus can also be formed by the erosion of the surrounding area, leaving part of the terrain above ground, surrounded rounded by b steep ledges. The erosion of the Grand Canyon by the Colo Colorado River has formed many plateaus.

What is the main difference between w plains and plateaus? In whatt way are they similar?

Activities 7.1 – 7.2 2

A Closer Look

Features of the Earth’s Surface

Forces such as moving water, wind and the movement of the Earth’s tectonic plates are continually shaping the Earth’s surface face and water sources.

plateau

lake ake

canyon

lagoon

peninsula ocean island

Describe the landforms and water sources shown in the diagram. Which of these can be found in your area?

Activities 7.3 – 7.4 mountain

glacier

hill

Re g

river

plain lai

delta beach

sand bar

Earth’s Water

Go Online! Beneath the ocean surface, the sea floor is continually forming in a process called seafloor spreading. Find out how this occurs on the NGScience website. QuickCode: H9J9

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When viewed from space, the Earth h looks oks like a blue ball. It’s sometimes called the e ‘blue ue marble’. ut 75 percent per percen The Earth’s blue color is due to about n water. ater. Most of of its surface being covered in a the water on Earth is in the ocean. There is also water in rivers, lakes and under the groun ground.

The Ocean

The ocean is the large rge body of salt sa water that covers more than n three-quarters e-quarters of the Earth’s w surface. The saltt in the ocean’s water comes mical erosion o of rocks on land by from the chemical ater erodes rocks, rock salts from the water. As water rocks are carried to streams and rivers and stream str lly to the ocean ocean. Some salt also comes eventually from openings penings nings on the ocean floor.

island continent

abyssal plain

sea mount

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The ocean is usually shallow close to land. On beaches and coral reefs, the water is typically only a few meters deep. Further out to sea, the ocean can reach depths of over 10 kilometers.

Just like on land, the ocean floor has a variety ety y of features. There are deep ocean trenches, renches renches, abyssal plains and underwater volc lcanoes. noe volcanoes. canoes. anoes.

How are the features of the ocean floor flo similar to Earth’s landforms? ms?

The flow f and cooling i of lava underwater forms new igneous rock.

Activity 7.5 .5

continental shelf

mid-ocean ridge

trench continental slope

Think Deeply What human activities can make fresh water unsuitable for use by people and other organisms? What can we do to protect our fresh water sources?

waterfall

Go Online!

The fresh water on Earth moves in a cycle between the Earth’s surface and the atmosphere. Discover more about the water cycle on the NGScience website. QuickCode: X7H3

Fresh Water The water on Earth that is used ed by peo people and organisms on land is fresh esh water. Only Onl about three percent of the e water er on Earth Eart is fresh water. Most of the he Earth’s arth’s fresh water is unavailable for or use by b people eop and other organisms. s. It is frozen in areas a around the North and nd South Poles Pole and in glaciers and icebergs. bergs. s. This leaves leave less than sh water ava 0.5 percent of fresh available to people and otherr organisms. organism organisms

stream

lake

The fresh water that is available flows from high in the mountains down streams and waterfalls. It flows through rivers into and out of lakes. As it moves over the Earth’s surface, some water seeps into the ground. It gathers in the spaces in rocks and soil as groundwater. The groundwater can be extracted by digging wells.

precipitation precipitat

snow

Go Online!

river

People are able to turn the salt water in the ocean into usable fresh water through a process called desalination. How do you think the process works? Find out on the NGScience website. QuickCode: R7G6

Activity 7.6

groundwater

A Closer Look

The Water Cycle The water on Earth is constantly moving g in a repeating pattern between the surface ace of the Earth and the atmosphere. This process is called the water cycle, or hydrological This ological cycle. Th complex process is driven by the he heat from the Sun which causes water on Earth rth to evaporate evap into the atmosphere, condense nse in clouds and fall back to the Earth’s surface as precipitation. precipita

The T he water water vapo vapor cools as it rises. As iitt d As oes, itit c does, condenses into water d dro rople lettss a an droplets and tiny ice crystals. These d roplets ts combine c droplets together and also join with with other particles in the air to fform orm m clouds.

eg al

Go Online!

Watch the water cycle in action in an animated video de ite. on the NGScience website. QuickCode: L5R3

The heat from the Sun causes the water in the ocean, lakes and rivers to evaporate into water vapor. Plants also release water vapor into the atmosphere through a process called transpiration.

As more water droplets combine, they get larger ger and eventually fall back to Earth as precipitation ation in in the form of rain, snow, hail or sleet.

The T he w he water ater flows flows through th streams and rivers and collects groundwater, lakes and the ocean. c ollects in g roun ro

Maps Draw a map of an area of your schoolyard. Compare your map with your classmates. Do you think your map is accurate? How can it be improved?

A map is a diagram that representss an n area, usually from above. Maps can represent present ent areas of all sizes – from the rooms in a house e to the th entire planet. The features and d information formation n its use. shown on a map depend on

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Try This!

A map of your school might ht include the th location of the classrooms, oms,, cafeteria, library and football field.

This map of San Francisco in the United States shows the location of roads and parks.

tio n

A map of a national park might include the locations of different landforms, water sources, roads and camping grounds. A map of a city usually includes the locations of suburbs, roads, parks and ports.

Wha makes the map of the school and What the city of San Francisco useful?

Types of Maps Maps are used by people in many ways. A map of a building shows hows the location of rooms, offices, elevators, elevat bathrooms and fire escapes. ape es. A road map shows ws the locations location of roads and highways. ways. Road maps m are often used in digita digital form in cars hey y often n display di and phones. They your location and provide directions. provid de d ir A physical shows the locations of al map show features of the Earth’s surface. They Ea often us use se different differen colors to show the e locations l io ons of o mountains, plains, canyons and nd plateaus. They also show water sources ourc such as rivers, lakes and the ocean. Water is commonly shown in blue.

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topographical map topog topogr

A topographical map is similar to a physical map in that it shows the features of the Earth’s arth’ss led surface. A topographical map uses liness called ht of contour lines, to show changes in the height o the land. The contour lines connect points of equal elevation.

ders and A political map shows the borders tates es and countries. count boundaries of towns, cities, states A political map usually doess not physical ot show phys p features of the land or water.

Think Deeply

What are some situations where it would be useful to have a contour map of an area? What about a political map?

political map of the United States

ati on

Navigational g maps, often called charts, are useful for people traveling by sea. They usef ey include inc impo or stances nces important information about the distances bettw he water ater and between places, the depth of the in nfo nt forr avoiding information that is important accidents, such as the location obstacles ac cation on of obstac or o shallow water. navigational map p

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resource map of the United States

A resource is something that is taken from m the Earth and used by people. A resource ce map shows the location of resources such as vegetation, trees, rocks, minerals and nd fuels like l coal, oil and natural gas.

Digital maps are used for a wide wid de range ng of nge purposes. They can include multiple tiple layers to show a variety of information on in n one map. ma There may be layers for physical features, atures, ures, roa road roads, temperature, vegetation on ttyp type and d clim climate.

Amazing Fact!

The Global Positioning System (GPS) is a series of satellites in space. The satellites send out signals of their location. Receivers on Earth, such as those in your mobile phone, use the distance from multiple satellites to calculate exactly where you are.

Activity 7.7

Maps Features

With a classmate, use the map below to take turns in describing the positions of the map features.

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Try This!

Maps have features that provide people eople e with accurate information about the area rea they the represent. Some features include e a title, e, symbols, symbol symbo a key and a scale. Some mapss also grids so have grid that can be used to find the location of things thing on thi the map. The title tells people what hat the he area on the map represents. It may also so include nclude what the intended use of the map is.

Lake Boulder National Park – Hiking ng andd Camping C Map Key campfire toilet campsite bridge lookout Arrow Ridge dge Trail Trail Big M Moose oose TTrail rail

BBrown rown Bear Beeaaarr Trail Trai Tr ail

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Symbols are used on maps to represent the locations of things. Symbols are usually simple and easy for the map reader to understand what they represent. A key is often used to provide an explanation of what the symbols represent. A key can also be called a legend.

Try y This!

List the e main objects obj in your classroom. Create ob a key for the objects by drawing sim simple symbols. See if your classmate can name the symbols.

A scale shows the distance between objects ts on the map. Often, the scale is in the form rm of a bar with distances at different intervals marked. A scale also includes the units of measurement, asurement, such as kilometers or meters.

400 mi

400 km

A compass rose is a feature eature on o most st maps that shows the directionss of north (N), (S), east (N south s (E) and west (W). Common mmon practice practic is i for a map to show an area up. a with north pointing poin

compass rose

Activity 7.8 73

Landform Patterns

Mountains usually form in areas where plate boundaries are moving towards each other. They are called convergent plate boundaries. Go online to learn how this plate movement and others shape the surface of the Earth. QuickCode: E6P1

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Go Online!

In science, finding patterns is very useful. ul. A pattern is something that repeatss over er and a over. They can be used to help explain ain why something is occurring and also lso to o make oc o predictions about where or when it may occur again. Meteorologists are scientists that look lo for patterns in the weather. is her.r. When a pattern pat pa identified, it can be used ed to o make predictions pred about the weather in n the e future. future

Scientists have identified patterns in the Earth’s dentified tified pattern landforms. Mountains that often untains ins are landforms land appear in groups, ranges. oups, s, called mountain mo Scientists have ave observed a pattern whereby many mountain at the places ountain ranges occur o where the he Earth’s plates plate meet. How ow is identifying iden patterns in Earth’s landforms useful?

Indian Plate In

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Himalayan Mountain Range

This pattern helps with the explanation that at mountains form when the boundaries off the e against inst plates interact as they bump and slide he crust rust to each other. The interactions cause the buckle or push upwards. Himalayan Mountain Range

Think Deeply

How is identifying a pattern in mountain formation useful?

Activity 7.9

Asian Plate

A Closer Look

The e Ring ing of Fire As with the formation forma of mountains on the Earth’s surface, earthquakes earthqu earthquake and volcanic eruptions also identifiable patterns. They both occur in occur in ident identifiabl Earth’s crust, called faults. The largest cracks in the Ear aults o faults occur at plate boundaries. There are also faults within plates. wit p

By putting the location of earthquakes kes and volcanic eruptions on a map, scientists ntists ists observed that many occur along g plate ate boundaries and faults around the Pacific ac Ocean. The area is known ass the e Ring of Fire. Fir About 90 percent of volcanic nic eruptions ruptions on Earth occur in the Ring of Fire. e

Re g

quake ake and an volcanic The pattern of earthquake activity around the Ring g of Fire helps help he scientists explain why, when y, where and wh such events occur. cur.

Why do so many earthquakes ea and volcanic occur around the anic eruptions o g of Fire? Ring

Ocean Patterns Just as there are processes that shape shap pe tthe he Earth’s surface on land, many off the the same sa ame me oor. processes shape the ocean floor. ow and and very very llong on Ocean trenches are narrow sunken areas on the ocean ean floor. floo oor. They They have h he d eepest p ar of the steep sides and form th the deepest parts ocean. Scientists have patterns in the ve iidentified dentified p at location of ocean tr trenches which renches w hich help explain their formation. L Like mountains ike m ountains and volcanoes, ocean trenchess c commonly occur at plate ommonl n ly o c boundaries. They They are are formed formed when two plates push against each one plate to st e ach other other causing c slide under er tthe he other. other. This Thi interaction at plate boundaries aries is is called called subduction. su

Like mountains on land, an ocean ridge is a sudden rising of the ocean floor caused by the movement of the Earth’s plates. Many ocean ridges link together forming the mid-ocean ridge. It is the longest series of mountains on Earth, stretching for more than 65,000 kilometers.

Think nk Deeply

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An abyssal plain is a wide, flat area on the deep ocean floor. They are usually found at depths of over 3,000 meters and account for more than 60 percent of the Earth’s surface.

The map ap here shows show the features res of the Earth’s What patterns ocean floor. Wh can identify? What an you identif caused the patterns?

Activities 7.10 – 7.11

Go Online! Discover more about the features of the ocean floor on the NGScience website. QuickCode: S7V5

A Closer Look

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The Mariana Trench

Located in the Pacific Ocean, about bo out 200 kilometers from the Mariana a Islands, lies the deepest part of the ocean, the Mariana Trench. The trench is more than 2,500 kilometers in length, almost 70 kilometers wide and is almost 11 kilometers deep.

Did You Know? Oceans are divided into zones based ed on depth. The deepestt part of the ocean,, at depths of between 6,000 and 11,000 meters is called the hadal zone, named after fter Hades, the th Greek god of underworld. the underw

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Reaching such depths is a challenge to scientists. There is immense pressure, complete darkness and very cold water temperatures. Most of the expeditions to the bottom of the trench are unmanned. Only four people have ever made the journey to its sea floor – two Italian scientists in 1960, the film director James Cameron in 2012 and American retired naval officer, Victor Vescovo.

Science Words

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Use the words to complete the sentences. mountain plain valley canyon plateau

groundwater map key scale compass rose

mountain n range Ring of Fire ocean ean trench tre abyssal plain ocean ridge

A a map.

A group of mountains in the same area a form a

A is low-lying area between moun mountains or hills, often with a river or stream flowing through h it.

is narrow and very ery long ssunken area on the ocean floor.

is a wide, flat lat area o on the deep ocean floor.

A or cliffs.

is flat terrain that t elevates sharply from the surrounding A land on at least one edge.

Underground nd water in spaces in rocks and soil is called

A a map..

10. A 11.

shows the directions of north, south, outh, east and west on

is a deep, de narrow row ch channel that runs through steep slopes

is is an explanation exp of what the symbols represent on

shows the distance between objects on a map.

The is a zone along plate boundaries in the Pacific Ocean where here many earthquakes and volcanic eruptions occur.

A is a landform that rises above the surrounding land and usually has steep slopes and a sharp or rounded peak.

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12.

13.

is a wide, flat landscape with little elevation.

14.

is a diagram that represents an area, usually ally from ab above.

15.

is a sudden rising of the ocean floor oor caused by the t An movement of the Earth’s plates.

Review

Draw a simple diagram to show the following wing landforms. landform (a) mountain (b) plain (c) valley v (d) canyon (e) plateau

What is groundwater and how can it be obtained obtain by people?

What does each map show and d how is it used? (a) physical map (b) topographical pographic map (c) political map (d) navigation navigational map

Why do mountains often form ranges? orm in mountain m

Use the words in the e box to t label the diagram. ocean trench

aby abyssal plain

ocean ridge

How w is identifying patterns on land and on the ocean floor useful?

In the Field

Oceanographer The ocean is a fascinating and diverse environment. There ere are deep trenches, giant underwater mountains and se volcanoes. If you’d like to learn more about the diverse here re, you you features of the ocean and the organisms that live th there, might want to be an oceanographer.

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es ocean ocean cean An oceanographer is a scientist who explores features. Oceanographers study how ocean n features features form and change over time. They often head deep de eep underwater underwate using scuba equipment or submarines. They They also use remotely operated underwater vehicles es (ROVs) (ROVs) Vs) to collect col col data for analysis in a laboratory.

Oceanographers have a diverse set of knowledge dg and skills. They are often trained in geology, chemistry, biology istry, y, b io io and physics. They measure and collect all sorts orts of data. data. From the condition of sea water and the organisms ismss living living iv vin ng ny underwater underwa nderwa ater there, to the geology of the ocean’s many features. They also collect data about the the movement m movemen ovemen nt of water in waves, tides and currents.

An A n important im mpor part of an oceanographer’s job is to iinterpret nte erpre and communicate their information with others. This could be in the form of reports or media o other such as photographs and videos. They often use suc maps to show the condition and features of the m ever-changing ocean floor.

Using Earth’s Resources

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In this chapter you will ...

• describe how energy and fuels are derived from natural atural resources.

able resources. resourc • distinguish between non-renewable and renewable

d how their the uses • list and describe different natural resources and affect the environment. he Earth’s resources. re • explain the importance of conserving the

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What are Earth’s resources? How are they used by people?

How can using the Earth’s resources affect the environment?

Go Online! Access interactive content relating to this topic on the NGScience website. ngscience.com

Natural Resources esources ources Materials or substances bsstances iin nn nature atu that are used by people are called called natural natural resources. We use many different fferent kinds kinds of of natural resources for a range e of of different diifffe feren rent purposes. pu Rocks, soil, soil, metals metals and and wood are natural resources houses and buildings. urces used used to to build b Plants nts and and animals anima mals are natural resources that are a re often oft fte en farmed farrmed me to produce the food we eat and and the the clothes clo lothe we wear. Fossil fuels such as coal, coal, oil oil and and gas are also natural resources.

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Some natural resources, like fossil fuels, take millions of years to form. We use these resources far quicker than they can be replaced. They are called non-renewable resources.

Other natural resources, like the energy nergy y in sunlight, wind and moving water, er, r cannot be used up. They are called alled d renewable resources.

What is the difference between non-renewable and en renewable resources? urces?

Activity 8.1

Think Deeply In a plantation forest, trees are planted, grown and cut down for their timber. Do you think a plantation forest is a renewable or non-renewable resource?

What are some ways people generate electricity?

Non-renewable e Energy nergy

Electricity is very important nt to to people. people. ItIt helps h us to do work in many different different ways. ways. People P have discovered many y ways ways to to produce pro rodu electricity. A common on way way is is by by burning bu fuels to produce heat. The heat he eat. T he h he eat is is often used to change waterr in into The nto st ssteam. team. T h steam is transformed into ntto kinetic kinetic energy energ that spins turbines which ch then then drive drive the th generators that produce electrical energy. le ectri riica al e nergy

Fossil il Fuels Mostt o off the the fuels fue s that th tha h people burn to produce ectric city are are fossil fo foss fuels. Fossil fuels are electricity formed med d from from the tth he remains of organisms that died long ago. ed and an nd decayed deca

ga l

Hundreds dred d re eds of o millions of years ago, the surface of of the th he Earth Earth looked very different than it does Ea today. today. Itt was was covered in shallow seas and swamp-like swamp-lik forests. They were filled with microorganisms, plants and animals. microo

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When these organisms died, they fell to the bottom of the sea or swamp, and were covered by layers of sediment. As more g sediment covered the decomposing organisms, they became more and nd d more compressed over time. Eventually, ventu uall ally, they formed fossil fuels.

The fossil fuels most commonly mon nly used used by by people are coal, petroleum and and natural natu ural ra gas. These fuels are often lo located deep beneath oca de eep b e the Earth’s surface. To o obtain obtain coal, people dig mines. Petroleum um and and natural natura gas are obtained by drilling and ng into in ntto the the Earth’s Ear arrtth’ss surface s pumping the fuels uelss to to the th the surface. su urface e.

Fossil fuels take ta ake millions milllions of of years yea to form. As such, they called resources y are are c alllled non-renewable non--rre because se e tthey hey are he are used used up up much faster than they can be can b e replaced replaced by by nature.

Why are oil, gas and coal non-renewable resources? What will no hap happen when these fuels are used up?

How Fossil Fuels Are Formed

A Closer Look

Re g

Fossil fuels are formed when the remains of organisms buried ried deep eep within w the Earth are subject to heat and pressure over millions of years. ears.

copic plankton an and other 1 Microscopic

organisms lived in the ocean and other environments millions of years aquatic environm ago. o.

2 The organisms die, fall to the

sea floor and are covered in sediment. Over time, layers of sediment buried the dead organisms and formed sedimentary rock.

n Re g

he 3 Over millions of years, heat

beneath the and pressure ben turned the Earth’s surface tu remains fuels such mains into fossil f gas. as oil and ga

4 The fossil fuels are extracted by drilling

deep into the Earth’s crust and pumping the fuels to the surface.

Activity 8.2 93

Generating Electrical Power From Fossil Fuels Coal, natural gas and petroleum are fossil fuels commonly used to produce electricity. In this process, the fuels are burned to transform the chemical energy in the fuel into heat energy. The heat energy is used to heat water and convert it to steam.

coal ssupply coa

boiler

The steam generated spin turbines which then turn a generator. As the generator turns, it converts the kinetic energy into electrical energy.

Go Online!

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Watch how electricit electricity is generated d by burning fossil f fuels in an animated video anima on the e NGScience website. w QuickCode: kC X4U6 X4

The electricity produced by the power station is sent along power lines that connect homes, buildings and cities through an electrical grid.

When fossil fuels are burned, harmful gases are released into the Earth’s atmosphere. This can cause air pollution along with other impacts on the environment.

Activity 8.3

The e electrical energy produced by burning fossil prod ffuels can be traced back to the Sun. Draw a diagram to explain why this is so.

transmission lines

Think T hin Deeply

turbine bine

generator gene g

transformer

water supply

Nuclear Fuel All matter is made up of tiny particles called atoms. The parts inside an atom are held together by strong forces. In the 1930s, scientists discovered that the bonds inside atoms can be broken apart to release a huge amount of energy as light and heat. The energy from inside atoms is called nuclear energy.

control rods

turbine

steam ste generator

condenser

Scientists designed nuclear power stations to convert nuclear energy into electricity. Like in a coal-fired power plant, heat is used to boil water and produce steam. The steam spins turbines which produce electricity. Electricity produced in this way is called nuclear power. transmission lines

cooling tower

generator

transformer

water supply

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generator

Renewable Energy nergy Wind

In most of the ways ys people pro produce electricity, kinetic energy is used sed to spin a generator. Wind has he form of o moving air. kinetic energy in the ne is a very ve large windmill that uses A wind turbine the energy in wind to spin its blades. The blades tha transforms the energy into spin a ge generatorr that cal en electrical energy. Often, en, particula particularly in very windy places, many wind urbines are grouped together to form a wind farm. turbines Wind farm farms can produce enough electricity to er wh power whole cities.

blows all the time, the electricity produced As wind b by wind turbines and wind farms is a renewable so source of energy.

Discuss some advantages and disadvantages of using wind to generate electricity.

Moving Water

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hydroelectric power station

In a similar way that a wind turbine uses the kinetic energy in wind to produce electrical energy, people can also use the energy in moving water to produce e electrical energy. Hydroelectricity is the electricity y produced using the kinetic energy rgy in n flowing rivers and streams. The he water is often held in large dams which ch allow people to control the flow off water. water ater. ater

Tidal energy is electricity using the city produced pr movement of water during in tides. ring changes cha Wave energy uses the e energy in waves and ocean swells to produce electricity. uce electri

generator in a hydroelectric power station

Go Online! Watch how moving water can be used to produce electricity in an animated video on the NGScience website. QuickCode: U2D5

tidal powe power turbine

Solar Power Think Deeply Why is the solar electricity produced in photovoltaic cells a form of renewable energy?

Most of the energy on Earth can be traced ced back b to the Sun. The Sun is more than 140 million nough light ligh kilometers from Earth, yet produces enough wa and heat to light up the Earth and keep us warm. Solar electricity, or solar energy, nergy, can be gy from the Sun S is produced when light energy ene ergy. This Thi is done transformed into electrical energy. alled d photovoltaic hoto through special devices c called cells. The cells are connected ne ed together tog in large groups to form solar panels. pan n lss.

solar panels containing photovoltaic cells

e attache Solar panels can be attached to the roof of buildings and provide ovide home homes with electricity. Large collections ons of solar sola panels are often n open areas are s th h get lots of sunlight. The placed in that y they produce prod duc is used to power towns electricity s. and cities.

Why is producing solar electricity better for the environment than producing electricity by burning fossil fuels?

AB 1 00

Activity 8.4

A Closer Look

Solar-powered Home

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A solar-powered home is a home that meets all or part of its electricity needs using solar power. Solar panels are attached to the roof and positioned in a way to absorb as much sunlight as possible. Photovoltaic cells convert the sunlight into electrical energy. The electrical energy is sent to an inverter which makes the electricity y available to use. The electricity can be used to power electrical ectrical appliances within the home or stored in batteries tteries to use later. If the solar panels produce uce more mo electricity than needed, the electricity city ity can be sent to the electric grid for otherss to use.

1 01

Environmental Impacts cts The generation of electricity can impact mpact ct the environment in a number of ways. s. Impacts mpacts to e take fossil fuels fue the environment occur when we ssil fuels can from the Earth. The burning off fossil harmful gases g also harm the environment when harmfu are released into the atmosphere. osphere.

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Did You Know?

Oil spills in the ocean are harmful to marine animals. The oil can stick to the feathers of marine birds leaving them unable to fly. It also sticks to the fur of marine mammals, such as sea otters, reducing its ability to keep mammals warm.

oil spill

Habitat Loss

Coal is a fossil fuel that hat iss found beneath ben b the surface of the Earth. rth. To get coal, a mine needs to be constructed. Thiss can cause huge changes to ent. Trees rees and plants p the environment. are removed to make way y forr the mine and a the network of roads needed ded to transport transpor transpo people and coal out of the area. that cannot move to new ea. Animals tha ts may die. habitats To get natural atural gas and petroleum, people must drill deep into the Earth’s surface. Sometimes c chem ch micals ar are used to pump the fuels from the chemicals Ea art rtth. h. These chemicals can pollute the land. Earth. Land pollution can also occur when La L and and nd d water w fossil fo oss fuels spill into the natural environment. os

open-pit coal mine

1 02

Emissions Think k Deeply

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When fossil fuels are burned to turn water into steam, emissions are produced. An emission is the release of a substance, often a gas, into the environment. Some emissions can be harmful to organisms and the environment. These harmful emissions are called pollutants. Pollutants released into the air when fossil fuels are burned can combine with oxygen and water droplets in clouds. The rain that falls from the clouds, called acid rain, carries the pollutants back to the surface ace of the Earth. Acid rain can pollute water ater sources, such as lakes and rivers, and is harmful to plants. It can also cause se e the soill to become polluted.

Burning fossil fuel also produces carbon du uces es c arb a rbon bon dioxide which is released into nto the air. air Carbon dioxide is a greenhouse When ouse se gas. gas. W greenhouse gases are e added add to the air, a a they cause the atmosphere osphere phere to retain more heat. This is slowly Earth y causing using the E ar to get hotter fasterr than would. n it normally normall w o Emissions from m fossil ssil fuel power pow stations s along with vehicle is a major ehicle cle and factories facto cause of climate te change.

Many countries ountries around aro orld have made ma the world an agreement tto reduce greenhouse ga gas emissions. Why is such an a international agreement important?

Go Online!

Head to the NGScience website to learn more about how the release of greenhouse gases and other human activities are contributing to global climate change. QuickCode: W6G2

1 03

Nuclear Nu u Impacts Nuclear N uc u c power plants do not release high gh levels leve e ls o ants into nto the the off greenhouse gases or other pollutants air. However, the process of uranium mining a um m mi inin ng and making electricity produces es radioactive dioa ti wastes such as uranium m tailings and an used u fuel rods. Radioactive materials are v very harmful to people and d other organisms. orga They also remain dangerous g ous ffor or thousands to millions of years. For this th his reason, nuclear wastes need to be carefu carefully and u y contained c isolated. If containment nme fails, fails, the impact on the th environment can can be e catastrophic. c

nuclear waste

Nuclear power plants N uc u an nts also produce a lot of hot water, w at which hich needs nee to be be cooled. This can be done cycling don do o by cyclin ng the the water wa through a larger body off water, such ass the o w t ocean or a lake. This can change the environment and affect the he water w er e organisms nisms living liv ving tthere.

Did You Know?

Re ga

In 2011 in northern Japan, a large tsunami caused extensive damage to a nuclear power plant. Radioactive material was released into the atmosphere phere and the Pacific Ocean. Thousands of people had to be evacuated from m the area.

104

A Closer Look

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Global Climate Change

Climate describes the weather conditions, such as average e temperature eratu and precipitation, in an area over a period of time. Scientists tists are continually continu continua measuring and monitoring climates all over the Earth. They analyze tth the data they collect to identify patterns. One pattern scientists have identified is that the Earth is getting warmer at a w much faster rate than expected. This pattern, called climate change, alled d global clim coincides with increases in greenhouses gases people es produced oduced by p through the burning of fossil fuels. You may recall all that carbon carb dioxide is a greenhouse gas. As trees and other plantss take from the air, ke carbon dioxide d di clearing forests is also contributing to global oball climate change. ch cha Global climate change has many effects Earth and the organisms fects on the Ea Ear living here. Such effects include: • • • •

rising sea levels. melting ice in glaciers and the Earth’s poles. pole more frequent extreme weather ther events. even changes in ecosystem communities. comm mmunities. munities.

Activities s 8.5 – 8.7

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Technology and the Environment Technology plays an important role e in n helping to reduce human impacts ts on on cien cient ntifiic the environment. By applying scientific cientis entissts knowledge to new designs, scientists and engineers are able to improve mp prove existing electricity production methods. tion m eth etho hodss.. They can help make them em m more more ctricity, orr efficient at producing elec electricity, ons. produce less emissions. Scientists also develop new evelop n ew ttechnologies ech that produce electricity ricity from m renewable resources. Solar wind farms olar energy, wi win and wave energy energy are are all all rrelatively new al technologies have gies tthat hat hav h ave far f less impact on the e environment nvironment than th producing electricity ric city by by burning burnin rning fossil fuels. Scientists trying to ntists ts are continually co on iimprove m e these these e new technologies to make efficient and more m ma ake them m more m easily available to people. e asily a as v

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In small groups, ide identify a problem are m where people peo using non-renewable energy. non-renew Provide a solution solutio to the problem that uses renewable u energy. Design and build a Des model of your design.

Electric cars are starting to replace cars that burn petroleum. This reduces our use of fossil fuels. Since electric cars do not produce emissions, they do not release greenhouse gases.

Engineer neer It!

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New technologies can also reduce the amount of electricity we use. Smart homes make use of technology to reduce electricity consumption by using low-energy light bulbs and other electrical devices.

What are the advantages of using an electric car rather than a car that burns ele fuel? What are some disadvantages? fue

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Science Words

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Use the words to complete the sentences. natural resources non-renewable resource renewable resource fossil fuels nuclear energy wind turbine hydroelectricity tidal energy

wave energy solar electricity photovoltaic cells pollutants acid rain greenhouse gas global climate e change

is electricity produced using g the move movement of water during changes in tides. uses the energy in waves and ocean oc swells to produce

electricity.

is the pattern in n which the t Earth is getting warmer at a much faster rate than ha expected. cted

is produced duced using usin special devices called transform light energy nergy from the Sun into electrical energy.

Materials or substances in nature that are used by people are called .

ral resource that is used up faster than it can be replaced is A natural . called a

A natural resource that cannot be used up is called a natu al res

The energy from inside atoms is called

is a gas that causes the atmosphere a to retain more heat.

10. Harmful emissions are called

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that

are formed from the remains of organisms that died and decayed long ago.

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11.

12.

is a very large windmill that uses the energy in n wind to A produce electricity.

13.

is the electricity produced using the kinetic netic energy in flowing water.

14.

Rain that falls when pollutants combine with oxygen gen and water wa droplets in clouds is called .

Review

List four types of natural resources.

Are fossil fuels renewable or non-renewable on-renewable resources? re Explain your answer.

List three types of fossil fuel.

What are two disadvantages electricity by burning ges of producing pro fossil fuels?

What are two advantages ntage of producing electricity using renewable resources? ces?

List three wayss moving water w can be used to produce electricity.

Draw a labeled eled diagram diagra to show how solar electricity is produced.

be two environm Describe environmental impacts of using Earth’s natural resources.

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In the Field

Renewable Energy Engineer In many countries around the world, governments are closing down wn fossil fo fuel power stations and replacing them with renewable energy gy alternatives. alter ati These include solar farms, wind farms and new technologies produce ollo s that t prro lectrr city production prod electricity using tidal and wave energy. Because these electricity methods do not produce emissions, they are referred d to as a clean cllea energy. If you are interested in clean energy and helping to reduce e emissions, mi you may like to be a renewable energy engineer. A renewable renewab energy engineer is a scientist that researches, developss and tests new technologies to produce clean energy.

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To a renewable energy engineer, the production of electricity by burning fossil fuels is identified as a problem. Renewable energy engineers see ea the design and implementation of a renewable energy alternative ass the solution. of Renewable energy engineers collect data on the availability of renewable energy in the field. They look at how energy y from fr m the th Sun, un n moving water and wind can be used to generate electricity ctricity y efficiently. effficie ent In laboratories, they build models and use computers to test tesst and an nd evaluate the effectiveness of their designs. They also monitor and so m onitor a maintain renewable energy technologies once constructed. nstruc ed d What would you work on if you were a renewable ab energy engineer?

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Energy and Motion

In this chapter you will ...

• describe and provide examples of potential and kinetic netic energy. g the speed of • use evidence to construct an explanation relating an object to the energy of that object. he change • ask questions and predict outcomes about the changes in energy that occur when objects collide.

ransferred from f • provide evidence that energy can be transferred place to tric currents. current place by sound, light, heat and electric

onverts energy ener from one form • design and test a device that converts to another.

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How can the energy of a moving object be transferred to another object?

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What are some me different forms f of energy? What at are some som examples of energy transformations? ansforma

Go Online! Access interactive content relating to this topic on the NGScience website. ngscience.com

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What Is Energy? Everything around us happenss because of energy. Energy iss the th ability to do work or cause e change. rgy from the Sun Su to Plants use the energy make food. The food ood gives them the energy they need d to live and grow. ople get ene Animals and people energy from the food they eat. They nee need energy to move aboutt and carry out all life processes. ses.

A panda gets the energy it needs from the stored energy in bamboo leaves.

Energy is needed to power cars, light up our cities and cook our food. Energy makes things move, warm up, produce light and make sound. H How do you use energy in your daily activities?

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Think Deeply

ion

A light bulb uses electrical elec energy. Describe escribe what energy transformation takes nsform place when a light bulb is switched he on.

sforms A television transforms electrical energy y into light, heat and sound.

Energy cannot be made and cannot be destroyed. oyed. It exists exis in many forms and can be transformed from one form to another.

eg al ed

A television is a device that uses electrical ctrical energy. The T electrical energy is transformed into light, heat at and sound energy. e What energy transformations ns take ta place during a motorcycle cle race?

Activity 9.1

Motorcycles use the stored energy in gasoline.

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Potential and Kinetic Energy nerg All forms of energy can be described bed as either stored energy or moving energy. rgy. The stored energy in an object ect iss called potential energy. Food has as potential energy. ene The energy is transformed ed into other forms fo fo when we eat the food and to nd use the energy en move about, keep warm m and and stay sta ay healthy. h Potential energy is also o related tto o the shape and position off an obje object. ectt. If you y yo o hold a ball above your he head, has potential ead, the ball ball ha h energy due e to o its itts position. po ositio on. IIf you drop the ball, the pote potential ential al energy ene erg gy is transformed into moving g energy.

The arrow is not moving. Explain why the arrow has potential energy.

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Did You ou K Know?

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When potential energy is released, it is converted into kinetic energy. Kinetic energy is the energy of an object due to its movement. All moving objects, from the tiny particles that make up our air to an airplane flying in the sky, have kinetic energy.

The amount of kinetic energy in an object depends on how fast it is moving. The faster an object moves, the greater its kinetic energy. The amount of kinetic energy also depends on the mass of an object. If two objects are moving at the same speed, the object with the greater mass has the greater amount of kinetic energy.

Doubling the he mass of a an object in n motion, doubles d its kinetic etic energy. If you speed of an double the spee energy increases object, its energ times. by four times

Think Deeply

A car and a bicycle are moving at the same speed. Which object has more energy? Explain your answer.

Discuss how the kinetic energy gy of the train changes as it leaves the e station.

The kinetic energy of the train increases with its speed.

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A stretched elastic band is an example of an object with potential energy. Design an object that can move by converting the potential energy in a stretched elastic band to kinetic energy.

We can compare the potential energy and kinetic energy of an object by looking at what happens during a roller coaster ride. Ass the cars climb up the track, their potentiall energy increases as they get higher. ck, the cars have ha the At rest on the top of the track, d no kinetic energy. ene most potential energy and he track, the potential As the cars move down the energy is converted into kinetic energy. energ As the etic energy iincreases. As cars get faster, their kinetic tential energy ene they get lower, their potential decreases.

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Engineer It!

Discuss some me other examples of the conversion and kinetic on of potential poten energy park. y at an amusement am

Go Online! Observe how different kinds of potential energy can be converted into other forms of energy on the NGScience website. QuickCode: G9L6

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Activities ctivi 9.2 – 9.3

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Describe the motion of a bowling ball all as it leaves your hand and rolls down ow a bowling lane.

Energy, Motion and d Force Forc Motion is the process of changing ging position. When something is moving oving it is in motion. An object that at is i in motion tion has h descri motion by kinetic energy. We can describe measuring its speed and nd direction. directio

Speed is the time it takes an object to cover ob a certain distance. e. The faster an object covers a distance, greater its speed. ce, the grea Direction is which is moving. h way an object o

The greaterr the speed o of an object, the more re energy it has. Forces can also affect the of an object. Larger e motion and energy e forces orces will cause objects to move faster and have e more mor energy than smaller forces.

Activity 9.4 1 19

Collisions Think Deeply Describe how kinetic energy is transferred when the balls collide in a Newton’s cradle.

A collision occurs when an object hits another an nothe object. A collision can occur between two tw w objects bjectt in motion, or by an object in motion and d an an object at rest. During a collision, kinetic energy is transferred between the colliding objects. s.

A collision occurs when a tennis player hits a tennis ball. Kinetic energy is transferred from the player’s moving tennis racket to the ball, causing it to move. The more kinetic energy that is transferred, the faster and farther the tennis ball will move.

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How is kinetic energy transferred when dominoes collide?

During a collision, the faster an object is moving, ng, the greater the energy transfer and the greater ater the impact on the other object.

Think Deeply D

Use your k knowledge of energy and a collisions to explain why there is more explai damage to the cars in an am accident the faster the cars acc are traveling at the time of the collision.

We can see this by looking at car accidents. dents. s. If the cars are traveling slowly at the time they collide, e, there may be little damage to the cars. If the cars are traveling faster, there is a much more ely to be more observable impact. There is likely damage to the cars.

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The observable impact of a collision reflects how much energy was transferred he amo between objects and relates to the amount of energy of the moving object.. lliards, a pla At the start of a game of billiards, player uses a large force to hit one ball into the other balls. The ball gains kinetic en energy from the billiard cue and moves down the table. As it hits the other ther balls, a loud sound is made. Kinetic energy transferred to the nergy is tran other balls as they y scatter all a over the table. When a player er uses a smaller force, less kinetic energy transferred. The balls ergy is trans produce a softer sou sound when they collide and d move more sslowly.

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Re g

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What effect does hitting a drum harder ard der or softer have on the sound produced? ce ed? What does this tell you about the kinetic energy of the drumstick?

A sledgehammer edgehammer hits a wall. observations would indicate the What observ amount o of energy transferred when the sledg sledgehammer and wall collide?

Try This! Plan and conduct an investigation to demonstrate how changing the size of a collision during a ball sport affects the distance the ball travels.

Activity 9.5

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In the Field

Vehicle Safety Engineer The cars, vans, buses and trucks we use for transportation are very ery important in our daily lives. However, these heavy vehicles travel avel at fast speeds and that means a lot of kinetic energy is transferred erred in the event ev of a collision. Vehicle safety engineers have a very important mportant job. They Th dent in orde study what happens when vehicles collide in an accident order to make vehicles safer for drivers and passengers. Vehicle safety engineers use models and computer simulations of vehicle er simulatio peed and m accidents to observe and record how energy, speed motion interact. They use this information to help design safer vehicles tha that can better withstand collisions.

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They also design safety devices, such as airbags, to protect people during a collision and braking systems that can slow down and stop a vehicle quickly.

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Vehicle safety engineers continue to develop new technologies that make our vehicles and roads safer for everyone.

Go Online! Watch the tests and investigations carried out by vehicle safety engineers on the NGScience website. As a class, discuss how the speed and mass of the vehicles relate to the impact of each collision. QuickCode: N1M7

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As sound waves travel outward from their source, the sound energy becomes more spread out and the sound gets softer. What are some ways people make their voice louder when talking to a large group of people such as a classroom? How does this affect the sound waves formed?

Forms of Energy There are many forms of energy. As you ou have learned, energy can also change from m one form to another.

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Think Deeply

Sound Energy

Sound is the movement off energy through throug throu rates. The vibrations v vi matter when an objectt vibrates. n the e matter around aro cause the particles in it to vibrate.

m a guitar, the kinetic k When you strum energy in uses the guitar sstrings to vibrate. your hand causes ns cause ause the pa The vibrations particles in the air e strings rings to vib vibra around the vibrate too. The vibrating particless travel in waves away from the source nd. We hear sounds when the sound of the sound. es reach each our ears. e ea waves wav wa aves always alway travel outward from Sound waves sourc sou urce of the so the source sound. They can travel throug solids, liquids liquid and gases. through

Wh produces sound What when you strum the whe strings of a guitar? strin

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Thermal Energy

Describe what hat happens happ to the particles es in warm water w when a glass water ss of warm w ced in a refrigerator. refrig is placed

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All matter is made up of tiny particles that are constantly moving about within the matter. The movement of these particles is called thermal energy. The faster the particles are moving within an object, the more thermal energy it has and the hotter it will be.

Think Deeply

Heat energy is the movement of thermal energy. When heat energy is transferred to an object, the particles within the object move faster ster and collide with each other. This causes the object to get hotter – its temperature increases. eases. es. If you place a glass of cold water in sunlight, nlight, t, the heat from the Sun causes the particles es in n the t water to move faster. This causes the he water to gain thermal energy and get hotter. tter.

Heat always moves from something (with mething hing hotter ((w greater thermal energy) to something colder mething col cold (with less thermal energy).

As the water gains thermal energy, its temperature increases and the particles that make up the water move about more rapidly.

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Light Energy Light is a form of energy we can n see. Anything that gives out light off its own is a source of light. Most of the light energy ergy on Earth c comes from the Sun. It lightss up the sky d during the day and allowss us to see. Li Light energy from the Sun used by n is also us ood. The Sun Su is a natural plants to make food. source of light. Fire and lightning are also lig natural sources ces of light.

Most of the light energy on Earth comes from the Sun.

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urces of light are produced Artificial sources by people. le. Light bulbs, bul mobile phone screens are artificial ns and televisions tele light. sources of ligh Disc Discuss the different ways people use light. What is the pe source of light?

Electrical Energy Try This! his!

ca tio n

Electrical energy, commonly called electricity, is caused by moving electric charges. Electricity is very important to people. We use it in many parts of our daily lives. Devices like flashlights, mobile phones and watches use electrical energy from batteries.

Electricity from power stations is sent all over our cities. It is used to power lights, fans, computers and televisions. It is used to heat and cool our homes and cook our food.

Electrical energy is very useful because it can an be changed into many other forms of energy. nergy. When you switch on a light, the electrical ctricall energy is changed into light and heat. When n you listen tto o music, electrical energy is changed to sound energy.

List the devices ices and a appliances that nces in your home h use electricity. Describe the ectricity. De transformations that energy transform take when the device ke place whe appliance is switched on. or applianc

Go o Online! O

Learn more about energy transformation around the home in a video on the NGScience website. QuickCode: C6U3

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Chemical Energy Ch C C Chemical Ch energy is energy that hat iss stored. stored It is a type of potential energy. rgy. Ene Energy is released when chemical cal reactions ctions takes place. Food is a form m of chemical chemic energy. When we eat at food, a chemical chem reaction converts the chemical e energy into kinetic energy gy that enables enable us to move about, keep eep warm and carry out life li processes.. Fuels coal, gas and Fu such as gasoline, coa F wood A chemical wo have w ve chemical emical energy. ene reaction re ea n occurs curs when the th t fuels are burned and an light gh ht and and nd heat heat are are released.

al e

Batteries atteries teries contain chemical energy. A flashlight fla ashlight hlight converts conve con nver the chemical energy in in batteries bat attteri teries iess into int int light and heat. A batteryoperated op peratted toy to car converts the chemical energy ene erg rgy gy in in its i batteries into kinetic energy.

Why is chemical energy a type of stored energy? What must take place for the energy to be released?

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Activity 9.6

Transformation of Energy

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All around us, energy is changing from one form to another. During photosynthesis, plants use light energy from the Sun to make food. The light energy is converted into chemical energy. When people and animals eat plants for food, the chemical energy is used to help them move from place to place. The chemical energy is converted into kinetic energy.

Describe the energy transformation that takes place ace when plants photosynthesize. e.

Try This! Draw a simple diagram to show how energy is passed from the Sun to the different organisms in an ecosystem.

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Press your hands together and move them quickly back and forth. What do you observe? How is energy changing form??

Think Deeply Many light bulbs used in households today are called LEDs. These lights transform electrical energy into light without producing much heat. What are the advantages of LEDs over incandescent light g bulbs?

When you move your hands dss back and forth, for fort they gain kinetic energy. The he kinetic energy ener is transformed to heat from om the friction created c when the surfaces of your ur hands rub together. Many ovens and stoves use the stored chemical sst energy in gas. When n the gas is burned, it produces the heat we need for fo cooking food. Light is also produced duced when gas is burned. Electricity ty y flowing through throug thin wires can cause them to heat up. Electric Elect heaters and hair dryers convert into heat energy. vert electrical energy e en Devices fans and electric cars convert vices such as fa electrical trical energy into kinetic energy.

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solar panels

The photovoltaic cells in a solar panel convert the energy in sunlight into electrical energy. A wind turbine is spun by the kinetic energy of moving air – wind. A generator inside the turbine changes the kinetic energy into electrical energy.

ical energy e ene erg gy When you turn on a television, electrical und. nd. is converted into light, heat and sound.

The battery that powers your smartphone, martphone, phone, tablet tab bl t b or notebook computer storess chemical emical energy. ener energ emical energy ener energ As you use your device, thiss chemical is transformed into electrical al energy, energy nergy nergy, then the light, heat and sound.

wind turbine

Think Deeply D

What happens happen to your the smartphone when w energy in the chemical ener battery is used up? What transformation of energy transformatio occurs when you y re-charge your smartphone? smartpho

Activity 9.7

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Electric Charge and Cir Circuits

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Electric Charge

Go Online!

Discover some fun science tricks you can do using electric charge on the NGScience website. QuickCode: R2Q6

Try This!

Tear some paper into small pieces. Run a comb through your hair 10 times. Hold the comb near the pieces of paper. What do you observe? Why does this occur?

Clothes othes stick s together toge when opposite pposite charges pposi ch attract each other. oth

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Have you ever opened the clothes es dryer yer and an discovered that some of the clothes othes es are stuck stuc together? This happens because ause some clothes cloth clo gain or lose charge as they y tumble in the dryer. d Charges are small particles ticless that exist in i all forms of matter. They can be positive (+) or negative (-). In most matter, the number of positive and p negative charged d particles rticles is the same. When objectss rub against each other, like ea e the clothes in your particles our dryer, charged ch can move causing an e between tween the objects o imbalance nce ce of charge. An A imbalance of negative or positive sitive e particles in matter causes an electric charge. rge. Just like the th poles of a magnet, like charges each other and opposite charges harges repel eac attract act each other. oth In a dryer, the th clothes stick together when the positively-charged clothes are attracted to the p po y-c negatively-charged clothes. neg negat

Re ga le du ca tio n

Rubbing a balloon with a fabric cloth causes the balloon to have a negative charge. Hold the balloon to a wall and it will attract the positive charges and stick to the wall.

The Th he negative c ch charges in the balloon attract charges in the wall attra act the positive posit posi causing to stick to the caussing the balloon ba wall. w l. wall

Electric Discharge e

Have you ever received an electric ectric ctric shock shoc when touching a metal object? is ct? An A electric ric i shock s an example of an electric discharge. Electric ectric c discha disc discharge is the movement of ement of the th buildup b electric charge from rom one place to another. an

When you walk alk on a surface such suc as carpet, you gain negatively particles – your body ively charged pa partic becomess slightly charged. The electric htly negatively c shock you receive when yo you touch a metal object of the negative ct is the rapid movement movem m charge arge leaving y your bo you body. b

An electric shock is the rapid movement of negative charge leaving your body.

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A Closer Look

Lightning Lightning is an example of an electric discharge. During a storm, small bits of ice and raindrops bump into each other as they move around within a cloud. This creates an electric charge within the cloud. Normally the top off m of the cloud becomes positively charged and the bottom the cloud becomes negatively charged.

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Amazing Fact! The temperature ature of a bolt of lightning g can be up to t five times hotter than the t e of the Sun! surface

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As opposite charges attract each other, the negative charge at the bottom of a cloud causes the ground beneath it to become positively charged. Eventually the buildup of charge is so great that the negative charges race to the positively-charged ground. When the electric charge discharges, we see a bright flash in the sky – lightning. The electric discharge happens very quickly. As the negative charges race towards the ground, they excite the air around them – causing it to light up. The charges also cause the air around them to heat up very quickly and create a pressure wave. We hear this pressure wave as thunder.

Why do we always see a bolt of lightning before we hear thunder?

When lightning strikes the surface of the Earth, it can cause damage to property erty and can injure or kill people. It is very important portant to stay indoors during a thunderstorm. orm.

Think Deeply

Lightning strikes the ssurface of Earth about 1100 times every second.

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Electric Current What properties of plastic make them suitable for wrapping the copper wires in electrical cables?

Electric charge is the buildup of charged arged d particles within matter. Electric current urrent nt is the continuous flow of electric charge. ge.

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Think Deeply

es to move m mor Some materials allow charges more easily than others. Metals, such uch as copper found in wires, allow charges to freely. o move very free fre arges es to move ffreely are Materials that allow charges ductors ctors.. Many metals are called electrical conductors. good conductors. ose used to wrap electrical Plastics, such ass those wires, do not allow charges to move freely. Materials that hat restrict estrict the fl flow of charges are called electrical insulators. ctrical cal insulato insula ulattor Wood, glass and ulato o good iin insula rubber are also insulators. g Why is it us useful to know which materials are electrical conductors which are electrical insulators? and w

Copper wire is a conductor of electric current. Plastic is an insulator of electric current.

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Electricity describes the flow of charges in one direction through a material. Electricity is very useful for transferring and transforming energy into other different forms of energy. When you turn on a light, electricity flows through the wires. In the light bulb, the electrical energy is transformed into light and heat energy.

Discuss the differences between electric charge, electric discharge and electric current.

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Circuits What are some devices that contain electric circuits? What components do they have? What energy transformation takes place when the device is switched on?

Engineer It!

Apply what you know about electric circuits to design, test and refine a useful device that converts the chemical energy in a battery into light or sound energy.

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An electric circuit is a path around which ich electricity flows. In an electric circuit, uit, electrical energy flows from a power source, rce, through rough ices that conducting wires, to different devices y into other forms. form A for change the electrical energy light bulb, for example, can n change the electrical ele energy into light energy and nd heat energy. energ energy A fan cal energy into kinetic k can change the electrical y and nd heat energy. ener energy, sound energy

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Think Deeply

For electric current nt to o flow through throug throu a circuit, there must be a complete mplete path along which the electrical energy flow. A switch is often gy can flow flo used to control ntrol the flow of electrical energy by opening and closing the path. p

When the components are connected correctly and the switch is in the ‘on’ position, the circuit is closed and electric current can flow.

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What do you do to control the flow of electric current in a flashlight?

Try This!

Design and conduct an investigation to find the effect of adding more batteries to a circuit with a light bulb.

When a switch is in the ‘on’ position, there iss a complete path for electrical energy to flow. The circuit is closed. When the switch in n the e ‘off’ position, the circuit is open and electric ic current ent cannot flow. An electric circuit may also be open if the circuit components are not connected nnected way. properly or are broken in some w way y.

A flashligh flashlight uses an electric circuit. circu circ

Whe the switch is in the ‘off’ position, the circuit When is open electric current cannot flow. pen an and elect

Activities 9.8 – 9.10 1 41

Electrical Appliances

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A great way to see the various ways in which electrical energy can be transformed is by looking at the electrical appliances around your home. Kettles, toasters and ovens transform electrical energy into heat.

A Closer Look

Discuss some ways electrical energy is transformed in the appliances and devices around your school. Where does the electrical energy come from?

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A computer transforms electrical energy y into light, heat and sound energy. In a printer, printer err, r, electrical energy is transformed into kinetic energy and sound energy.

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Science Words

Re ga le du ca tio n

Use the words to complete the sentences. energy potential energy kinetic energy motion collision

thermal energy heat energy electrical energy chemical energy electric charge

electric discharge charge electric current electrical ctrical conductors conduc electrical ctrical insulators insulat electric ectric circuit circu

is the process of changing position. n.

An imbalance of negative or positive particles in matter causes an .

is the movement off the buildup of electric charge from one place to another.

occurs when an object hits another object. ob

is the continuous ous flow o of electric charge.

is the ability ab to do work wor or cause change.

The stored energy in an object obje is called

is the e energy of o movement.

is caused by moving electric charges.

10.

is energy tthat is stored. Energy is released when chemical reactions place. ons takes place

11.

An A

12.

is energy possessed by an object due to the movement of particles article within the object.

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is a path around which electricity flows.

13.

Materials that allow charges to move freely are called

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14.

is the movement of thermal energy.

15.

Materials that restrict the flow of charges are called

Review

Provide two examples of an object with potentiall energy. Explain Exp why it has potential energy.

Provide two examples of an object with kinetic why it c energy. Explain E has kinetic energy.

Describe the energy transformation that at takes place pla as a rock starts rolling down a hill.

Describe the kinetic energy of a car as it spe speeds up and slows down.

How does the speed of an object ct affect iits energy?

Describe how energy is transferred ansferred when a tennis racket collides with a tennis ball.

How does the speed object is moving affect the collision that occurs d an o when it strikes another other object? objec

What energy transformat transformation occurs when you turn on an electric fan?

What energy transformation occurs when you turn on a television? gy transform

10. Why are plastic used to make electrical wires? re copper and p 11.

occur for the device in an electric circuit to work? What must occ

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Waves and Information

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In this chapter you will ...

• develop a model of waves to describe patterns in terms n cause of amplitude and wavelength and that waves can objects to move.

ng from objects ob • develop a model to describe that light reflecting and entering the eye allows objects to be seen. een. • generate and compare multiple solutions ns that use patterns to transfer information.

What are some characteristics ch es? of waves?

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du c Go Online!

Access interactive content relating to this topic on the NGScience website. ngscience.com

How are waves used to transfer information? nformation? How Ho is this useful?

1 47

What Are Waves? Go Online!

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Discover more about waves and their properties on the NGScience website. QuickCode: X1D2

Throw a pebble into a still pond and d it will make a splash. Then ripples appear ear and move away from the splash in all directions. ctions. s. When the pebble entered the water,, its energy from motion was transferred to the he water as it pushed pu p the water out of the way. This energy was then spread out in all directions ns through the rripples – which are small wavess in the are he water. Waves W disturbances that carry arry energy and travel in a repeating pattern.

What would uld happen if a larger pebble was thrown wn into the pond? What if the pebble thrown with a greater force? ebble was thro

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Sound travels in waves too. Pluck a guitar string and the vibration pushes the air around the string. The disturbance moves as waves in all directions from the string to the surrounding air. When the waves reach our ears, we hear the disturbance caused by the vibrating string g as sound.

The water waves in n the pond d and an the sound waves in the he air move through thr thro oug matter. The substance bstance ce that a wave wav w ve moves through gh iiss called a medium. me m ediu The particles es of of a medium med dium do do not change or mo move ove very much muc uch as the wave moves es through it. it

Activity 10.1

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Waves travel at different speeds depending on the type of wave and its medium. Sound travels through air at about 330 m/s. Sound travels through water at about 1,500 m/s. Light waves travel at speeds of almost 300,000 km/s.

Think about a Mexican wave at a stadium or concert. The wave of people appearss to m move around the stadium, but the individual ual people producing the wave only stand up p and d sit back down in their seats. The wave iss moving oving around arou the stadium in one direction, but the people are a only moving up and down in n the same position. pos po

ca tio n

Did You Know?

Similarly, the individual water ter molecules molecule in the pond mostly move up p and d down as the th t waves move across. The molecules near the cules of air n vibrating guitar string back and forth ring also so move b as the sound wave ave passes. Not all wavess need ed a medium mediu to propagate. Light from the Sun through empty un moves oves in waves wa space to reach Earth. Light Lig waves are produced when magnetic fields vibrate. These agnetic and electric e vibrations tionss create their the own medium.

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Characteristics of Waves

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Whether they are sound waves moving through the air, waves of water in the ocean or light waves traveling from your television – all waves share certain characteristics.

Amplitude

Amplitude is the measure between a wave’s resting position and its greatest height. For a sound wave, amplitude describes the volume of the sound. Hitting a drum softly will produce a e same me sound wave of a certain amplitude. Hit the drum with a greater force and the amplitude itude eive this of the sound wave increases. We perceive change as a louder sound.

Did You Know? Know

The amplitude of o a sound is measured in de decibels (dB). ere are the decibels d Here of some com common sounds: Whisper: 30 dB Conversation: 60 dB Conve Lawnmower: 90 dB aw Jet engine: 130 dB

drum hit softly

drum hit with greater force

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Wavelength

Try This! Describe the sounds produced by the roar of a lion and the chirp of a bird in terms of amplitude and wavelength.

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Waves move in a repeating pattern.. Wavelength Wavelen avelen is the distance between two similar ar points oints in the repeating pattern of a wave.

For a sound wave, wavelength gth describes the t pitch of a sound. The shorter ter er the wavelength, waveleng wavelen the higher the pitch of the the he sound. The longer lo l wavelength, the lower the pitch of the sound. Hit the shortest barr of a xylophone xylophon and it will produce a high-pitched pitched hed sound. This T is because the bar vibratess quickly. ickly. Hit the longest bar of the xylophone sound is e and a lower-pitched lower-p lowerproduced. This iss because the t bar vibrates at a slower rate te compared ompared to t the shortest bar.

Higher-pitched sounds produce shorter wavelengths.

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Lower-pitched sounds produce longer wavelengths.

In light waves, the wavelength tells us about the color of the light. The colors of the rainbow show the changing wavelengths of light. The violets and blues of the rainbow have shorter wavelengths than the reds and oranges of the rainbow.

Frequency

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y Frequency is the measure of how quickly a wave repeats in a given amount of time. e. A wave of high frequency means that the wave wa ave ve repeats in a short amount of time. Similarly, rly, ya y, wave of low frequency will repeat in a longer nger amount of time. In sound waves, this is also o related to the pitch of the sounds. High-pitched gh-pitched ed sounds are produced from high frequency equency quency waves. Low-pitched sounds are produced duced from low frequency waves.

Just as frequency is related to pitch in sound, soun frequency is related to the color or of light. Violet V light has waves of a higher frequency quency compared c to red light.

Try This!

Hold your ruler over the edge of your desk. Pluck it to make different sounds. Describe the sound waves produced in terms of amplitude, wavelength and frequency.

high frequency

Us amplitude, wavelength and Use frequency to describe common freq sounds around you.

low frequency

Activity 10.2 153

Some bats use echolocation to ‘see’.

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Properties of Waves Pr es Just as different waves share similar imilar ar characteristics, waves also share hare similar properties.

Reflection

urself elf in the mirror mirr mir When you look at yourself each els from om your face, fac fa morning, light travels bounces off the mirror and your eyes. The o d then enters yo bouncing of waves surface is called bo aves off a surfac reflection. The wave bounces ref e direction ection a wa w depends on n the angle that iit hits the object. Drop a tennis will bounce straight up nnis ball and it w off the ground. If you th throw the tennis ball at an angle ground, it will bounce away at gle to the groun the same e angle.

Go Online!

Bats reflect sound waves to ‘see’ in the dark. Find out more on the NGScience website. QuickCode: F4P9

empty room such as the Go into nto a large e gymnasium and clap your hands. What school ool gymn gymna do you notice? You may hear the clapping ou notic sound repeat. so epe This is because the sound wav produced from clapping bounce off waves surfaces in the room such as bricks and hard ssurf and travel back to your ears. The conc concrete reflected sound is called an echo. ref reflecte

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Activities 10.3 – 10.4

Refraction The pencils in the glass of water appear to be broken. Can you explain why?

Spectacles, binoculars and telescopes refract ct light through their arrangement of lenses. As light passes from air through the glass off the lenses, it slows down and bends. As it leaves eavess the lens and enters the air again, it speeds ds up.

Light can be refracted to bring the e light ght rays closer together and make objects cts appear ppear closer. It can also be refracted d to spread read out the t rays and cause objects to appear ppear ear further away. aw

The pen pencils appear broken d due to the refraction of light. refrac refract

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When waves pass from one medium to another, the speed of the waves changes. The change in speed causes the waves to change nge on is direction. This change in speed and direction called refraction.

Did You Know?

Lenses are transparent objects that refract light. Eyeglass lenses use refraction to make objects look clearer. Refracting telescopes use lenses to make objects appear closer than they are.

Activity 10.5

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Absorption When waves hits an object, they can an also be taken in, or absorbed, by the object. ect. Look at the size and placement of the rocks ks along the t signed ed so that th sea wall. They have been designed the n’t pass through, through but waves from the ocean can’t also don’t get reflected directly the irectly rectly back to th boats. The sea wall absorbs orbs bs the wave waves.

Lig Light ght waves wavess can also be absorbed when they hit an n object. obje Materials that absorb light are dark in color because they don’t reflect much da light. They T also tend to be warmer because heat that is being transferred by th they hey absorb abs the light the ligh waves. White objects reflect most of tthe he light lig waves that hit them. They tend to be cooler c oo than dark objects. Just as hard materials are good at reflecting sound waves, soft materials such as foam and carpets do a good job of absorbing sound. Waves that hit these objects are absorbed and are not reflected back. The energy being carried by the sound wave does not disappear. Instead, it is transformed, for example, to the movement and heating of the material.

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ca tio

How is the interaction of light waves with a piece of wood different from the interaction with a glass window?

Light Waves and Transparency Different objects and materials can interact with light waves in different ways. Wood is an example of a material that is usually opaque. An opaque object absorbs light waves. It does not allow light to pass through.

Think Deeply D

Many wind windows have two layers of curtains – a translucent curtain and an translu opaque curtain. pa How is this useful?

A glass window is usually made to be transparent. A transparent object allows allow ws almost all light to pass through.

e paper r, absorb r, abso orb Some objects, such as tissue paper, some light waves. They allow ow some light lig ght to to pass through.

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movement of energy

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The up and down motion of the rope is perpendicular ar ve. to the direction of the wave.

Types of Waves

Try This! With a classmate, use a skipping rope to demonstrate how transverse waves can change in amplitude, wavelength and frequency.

You will see along the rope ee waves move m from om yourr hand to t the tree it is attached to. travel through, the rope moves As the he waves tra up and down, down perpendicular to the direction of the he e wave. Waves in which matter moves perpendicular pe dicu to the direction of the wave called transverse waves. are c

Waves over the deep ocean surface Wav moving m is an of transverse waves. Boats a example ex floating on the ocean surface move up and fl floati down dow as the waves move perpendicular to the t boats. The boats are not moved in the th direction of the wave.

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Did You Know?

Take a length of rope pe and attach att a one end to a tree. Holding olding g the other end of the rope, quickly move What do you ove it up and down. d do notice?

During an earthquake, transverse waves move ve out in all directions. They ey h rock for can travel through hundreds of kilometers. meters.

Light moves from its source to your eyes in transverse waves too.

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movement of energy

direction of wave

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The motion of the t spring is parallel to t the direction ction of the wave. w

Take one end of a slinky spring and give the other end to a friend. Spread apart so that there e is some tension in the spring. Gather a small ether. section of spring at your end and hold it together. ve Let go quickly and you will see a wave move down the slinky to the other end.

Think T h Deeply

How would you use a slinky spring to demonstrate sp the transfer of energy in transverse waves?

g gets As the disturbance moves, the spring preads out as packed tightly together and then spreads the waves passes. The packing together ogether ther is called ding apart is calle ca a compression and the spreading called ring coils is a rarefaction. The motion of the spring he wave. Such waves w parallel to the direction of the are called longitudinal waves. ves. Sounds waves w are an example of longitudinal an itu waves. When W object vibrates, the particles the articles rticle of o air around aro object get compressed spread sed and nd sp spre out over and over again.

amplitude mplitu

source our

Go Online!

Watch a video on transverse and longitudinal waves on the NGScience website. QuickCode: F3Q4

rarefaction

compression

Sound moves mov in longitudinal waves.

Activity 10.6

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Light Waves

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Light waves are the vibration of magnetic agnetic etic and electric fields. These fields vibrate e perpendicular rpendicular ndicular ular to the th to one another and also perpendicular veling. g. Light waves wave wav direction the light wave is traveling. are transverse waves. amplitude

source

wavelength

Light We e Can See

Sunlight appears but it is actually a mixture ears white, b of many y different colors. color When white sunlight enterss a glass prism, the t light separates into the colors ors of a rainbow. rainbow Droplets of water in the sky can prisms and separate the Sun’s an also so act like p white a rainbow. te light to produce pro pr

In a prism, light separates into the colors ors seen in a rainbow.

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The color of an object is determined by how it absorbs and reflects light. A white piece of paper ab an appears white because it reflects all of the light appe appea waves that tha hit it.

Think Deeply

Describe how w is light being reflected and absorbed absorbe by the clothes you a are wearing.

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A ripe lemon is yellow because it reflects yellow light and absorbs the other colors. A green avocado reflects green light and absorbs other colors.

sing white Colored light can be produced by passing ects only light through a filter. Just as colored objects reflect certain colors of light, filterss only allow certain colors of light to pass through ough h them.

n example xample of filters. filt fil Stained glass windows are an side and the White light enters from the outside different filters only allow certain rtain in colors to pass sss through. ligh that t Some traffic lights use white light passess through red, green n and nd orange filters. filter fi

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Light, Sight and Our Eyes E

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Our eyes take in light and allow ow us to ssee the world around us. Sources th ces of light such suc as the Sun and televisions ns produce duce light of their own. Light from these th hese e objects enters en ent our ou eyes directly. Other er objects such suc as a vase of flowers do o not produce light lil on their own. We are re able to see se these objects when a source on ob rce of light shines s them and the th e light ht is reflected to our eyes.

retina

sclera

iris pupil

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lenss ea cornea

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Anatomy of the human eye.

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Light enters our eyes through the cornea, which is like a clear round window at the front of the eye. It bends the light before it passes through the pupil – a dark circular opening into the eye.

The size of the pupil is controlled by the iris which is the part of the eye that gives eyes their color. If the light is bright, the iris will make the pupil smaller to reduce the amount of light entering. Similarly, the iris will make the pupil larger when it’s dark to allow more light in. Once the light passes through the pupil, it goes oes through the lens. Just like the lens of a camera, mera, a, the lens of your eye bends the light and d focuses cuses it before it reaches the retina. The retina na is a light-sensitive tissue at the back of the he eye. It converts the light into electrical signals gnals als which travel to our brain via the optic nerve. e.

cornea

lens ens

Did You Know?

Light bend bends as it passes through the eye lens, creating throug upside-down image on an ups the rretina. The brain interprets the image the right way up.

Activity 10.7

retina

pupil

Light entering the eye is refracted by the cornea, forming an upside-down image on the retina.

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Long exposure to the Sun’s ultraviolet light can damage skin cells and lead to skin cancer. Sunscreens contain chemicals that protect your skin by absorbing ultraviolet light. Some sunscreens, such as zinc cream, also contain physical particles that block the light waves and provide added protection.

Light We Cannot See The color of light is determined by the he wavelength of the light waves. Short ort wavelengths give us blue and purple urple light, ight, while longer wavelengths give e us red and orange light.

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Did You Know?

When the wavelength becomes short ecomes comes very sh or very long, our eyes are not able to see s the ght iss invisible to our eyes. light as colors. This light

Ultraviolet light, also o called UV llight, is an example of light ht we e cannot see due to its very short wavelength. avelength. gth. We can ca c feel the effects of ultraviolet it causes ltraviolet iolet light because be sunburn. Germs die or are ms and viruses viru vir destroyed exposed to ultraviolet light. ed when expos expose UV lamps mpss can be used use to sterilize surfaces, preserve water. serve food and treat t

dio waves radio

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infrared

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X-rays have even shorter wavelengths than ultraviolet light. They are high in energy and are able to pass through our bodies. X-rays pass through our bodies’ soft tissues more easily than our bones. This allows doctors and medical technicians to create images of the inside of our bodies.

Our eyes also cannot see infrared light, which has wavelengths that are longer than that of red light. We can feel infrared light as heat. Infrared how cameras are used to produce images that show the temperature of objects. Radio waves are light waves with very large arge e wavelengths. We can use these wavess to send end and receive messages.

aviole ultraviolet

x-rays

gamma rays

visible ble light lig

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Waves and Information o

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Just as waves transfer energy, waves es can be used to send and receive information. ation. n. Messages ound waves, light ligh l or signals are often sent with sound nt along these thes waves or radio waves. Signalss sent h waves are analog signals. Analog signals have a range of continuous values. es.

Go Online! Are you still a bit confused about the difference between analog and digital signals? Watch an animated video on the NGScience website. QuickCode: D8E9

an. A point of water Think of a wave in the ocean. es through rough will co that the wave passes continuously rise and then fall. The height eight of the waves, the amplitude, will also range of values as so take ake on a ra ran es. the wave passes. Similarly, the he sound und waves produced by a guitar has a range nge of continuous continuou values. As the sound continuo wave moves oves through the th t air, the particles of air experience and rarefactions xperience ience compressions comp continuously. ntinuously. usly. Sound Soun wave are analog signals.

However, in today’s modern world, the signals Howe have to be sent and received a certain way in or order for computers and electronics to process them. them Computers and electronics are not able to t process analog signals. They are only able to process digital signals. Unlike analog signals that take on a range of values, digital signals have specific values.

Digital signals are transmitted as short pulses that represent different digits. A digital signal only has two values – 0 or 1. You can think of a digital signal like a light switch – it can only be one of two values – off or on.

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Re ga le du ca tio n Digital signals are much better at sending information over long distances than analog signals. Information transmitted and received by televisions, computers and cell phones are sent using digital signals.

AB A B

Activity 10.8

A Closer Look

Radio Waves and Cell Towers owers er

You probably talk on a cell phone every very day. When Whe you talk, the phone converts your voice into a digitall signal nal which is sent to a nearby cell tower as radio waves. The tower then en sends ds the signal sign to a central computer that relays the message to the correct cell tower closest to the receiving t cell phone. The tower sendss the e signal to tthe recipient’s phone that then processes the signal and converts back into an analog signal that the verts erts it bac recipient can hear. Radio waves are a useful eful method of o sending and receiving signals as they can do so over long the signal getting lost or becoming ong distances without withou w weaker. Radio waves used in a similar way to send television ves can also be u signals and Internet nternet net data.

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Optical Fiber Light waves w can also be used to send and receive information across large distances receiv through optical fiber. Optical fiber are thin, hro transparent fibers that are about the thickness of tra a human hair. A digital signal is fed into a bright light connected to the fiber. The light sends the signal through the fiber by turning off and on very quickly. A receiver at the other end of the fiber takes in the light pulses and processes the signal. Optic fibers are able to send and receive large amounts of data very quickly over large distances.

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Science Words

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Use the words to complete the sentences. waves medium amplitude wavelength frequency reflection echo

rarefaction transparency transparent translucent opaque transverse wave compression

refraction longitudinal udinal wave ultraviolet light ligh infrared nfrared light analog signals sig digital signals sign optical fiber f

is the distance between two similar points point in the repeating pattern of a wave.

is the measure of how quickly a wave w repeats in a given amount of time.

urface is called ca The bouncing of waves off a surface

In a of the wave.

Light we can’t see due tto its very short wavelength is called

Light we can’t see very long wavelength is called e due to its v

object blo blocks light.

is produced produ when sound waves are reflected.

ange in sspeed eed and direction of a wave as it passes from one The change ano . medium to another is called

, the motion on of the disturbance is parallel to the direction

. .

10. amount of light that can pass through an object is 0. The e amoun called calle .

11.

object allows almost all light to pass through it.

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object allows some light to pass through it.

13.

are disturbances that carry energy and travel in a repeating pattern.

Re ga le du ca tio n

12.

14.

The substance that a wave moves through is called a

15.

The measure between a wave’s resting position and its greatest height . is its

16.

have a range of continuous values. s.

17.

have specific values.

18.

Waves in which matter moves perpendicular dicular to the th direction of the wave are called .

19.

The part of a wave where the particles are close together is c a .

he particles are spread out is a 20. The part of a wave where the 21.

are thin, transparent parent fibers fib that can be used to send information through across large distances. gh llight waves, ves often o

Review

creasing th Describe how increasing the volume and changing the pitch of a sound affects the sound ound waves produced.

Provide an example of transverse waves and longitudinal waves.

How are re transparent materials different from opaque materials?

P vide an ex Provide example of how waves can be used to send messages.

Wh is the difference between analog and digital signals? What

d an example of how digital signals are used to send information. Provide

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