Let's Do Science 4 – Textbook B by Regal Education

Pri ma ry 4 Textbook

Aligned to the Next Generation Science Standards

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Textbook

The 5E Model – Guided Inquiry

The Let’s Do Science series is based on the Biological Sciences Curriculum Study (BSCS) 5E teaching and learning instructional model. The 5E model is centered on the idea that students understand science concepts best by using prior knowledge to pose questions and find answers through guided inquiry.

Engage

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This hands-on approach, integrated with engineering and design skills, has students learn science by doing science. Teachers guide the learning process and are able to assess student performance by evaluating student explanations and the application of newly acquired knowledge and skills.

The Engage phase of the 5E model provides students with the opportunity to demonstrate their prior knowledge and understanding of the topic or concept. Students are presented with an activity or question which serves to motivate and engage students as they begin the lesson. Teachers identify and correct any misconceptions and gather data from students which will guide informed teaching and learning.

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Essential to stimulating and engaging students is the use of mixed media such as colorful photos, illustrations and diagrams found throughout the textbooks and activity books. Let’s Do Science also includes extensive digital resources such as narrated videos, interactive lessons, virtual labs, slideshows and more.

Explore

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This phase encourages exploration of concepts and skills through handson activities and investigations. Students are encouraged to work together and apply various process skills while gaining concrete, shared learning experiences. These experiences provide a foundation for which students can refer to while building their knowledge of new concepts. This studentcentered phase comes before formal explanations and definitions of the concept which are presented by the teacher.

Explain

Elaborate

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This phase follows the exploration phase and is more teacher-directed. Students are initially encouraged to draw on their learning experiences and demonstrate their understanding of the concept through explanations and discussion. After the students have had the opportunity to demonstrate their understanding of the concept, the teacher then introduces formal definitions and scientific explanations. The teacher also clarifies any misconceptions that may have emerged during the Explore phase.

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In the Elaborate phase, students refine and consolidate their acquired knowledge and skills. Opportunities are provided for students to further apply their knowledge and skills to new situations in order to broaden and deepen their understanding of the concept. Students may conduct additional investigations, share information and ideas, or apply their knowledge and skills to other disciplines.

Evaluate

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This final phase includes both formal and informal assessments. These can include concept maps, physical models, journals as well as more traditional forms of summative assessment such as quizzes or writing assessments. Students are encouraged to review and reflect on their own learning, and on their newly acquired knowledge, understanding and skills.

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Let’s Do Science

Animals are or structures animals to s can be divid structures a

External stru birds warm birds to fly m

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

Animal

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.

Amazing Fact!

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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!

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The Let’s Do Science textbooks include the following features:

Think Deeply

In many countries around the world, governments are closing down fossil fuel power stations and replacing them with renewable energy alternatives. These include solar farms, wind farms and new technologies that produce electricity using tidal and wave energy. Because these electricity production methods do not produce emissions, they are referred to as clean energy.

If you are interested in clean energy and helping to reduce emissions, you may like to be a renewable energy engineer. A renewable energy engineer is a scientist that researches, develops and tests new technologies to produce clean energy.

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

In the Field

Renewable Energy Engineer

To a renewable energy engineer, the production of electricity by burning fossil fuels is identified as a problem. Renewable energy engineers see the design and implementation of a renewable energy alternative as the solution.

In laboratories, they build models and use computers to test and evaluate the effectiveness of their designs. They also monitor and maintain renewable energy technologies once constructed. What would you work on if you were a renewable energy engineer?

Engineer It!

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

In the Field

Inspirational sciencerelated professions to stir interest in sciencerelated careers.

Renewable energy engineers collect data on the availability of renewable energy in the field. They look at how energy from the Sun, moving water and wind can be used to generate electricity efficiently.

A Closer Look Features of the Eart

h’s Surface

Forces such as movin g water, wind and the movement of the Earth’s tectonic plates are continually shapin g the Earth’s surface and water sources.

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1 10

lake

plateau canyon

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

lagoon

peninsula island

ocean

Amazing Fact! Interesting facts to build interest and enthusiasm.

bald eagle

l Structures

ladybug

Did You Know?

scorpion

Scorpions have pincers and a stinger to catch and kill their pray. Ladybugs have a hard outer covering that helps to protect its body and wings.

uctures such as feathers keep and their light weight help the more easily.

green palm snake

Animals such as sharks, snakes and dolphins have internal skeletons and backbones to support their bodies. Organs inside the bodies of animals also help them to get the things they need to survive, grow and reproduce.

hark

dolphin

vertebrates invertebrates exoskeleton herbivore carnivore camouflage

endoskeleton lungs gills arteries capillaries

veins nocturnal whiskers antennae brain

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

14.

Most mammals have specialized hairs, called their mouth and nose.

are blood vessels that carry blood high in carbo from the cells back to n dioxide the lungs. Arteries branch out into a fine

network of

(a)

Movement

Getting Food

(b)

AB Activity

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

(c)

plants.

A is an animal that eats other animals. Animals without a backb ones are called hard outer covering called . Some have a an . 9. Animals with a backb one are called . They have an interna structure of bones called Descri l be the landforms and an . water sources shown in the diagram. Which of 10. An anima ability to blend these can be l’s into its surroundings is found in your area? called . 11. are internal structures used to take in oxyge AB Activities 7.3 – 7.4 n from the air. 12. are internal structures used to take in oxyge n from water.

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External Structures

Body Covering

rest during the day.

is an animal that eats

Animal

Use a chart to describe how each animal’s extern al structures help it to survive.

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receptors called

animals are active at night and

, surrounding

Review

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

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

13.

lete the sentences.

sea turtle

Science Words Use the words to comp

Try This!

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Discuss some animals you know of and the structures they have that help them survive.

Extra information to build students’ knowledge base of the current topic.

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e made up of different parts s. These structures help the survive in their environment and ded into two types – external and internal structures.

List and describe three internal structures of a dolphin that help it to survive.

Discussion

A monkey eats a sweet rose apple. Draw and label a flow chart to show how the sensory input is received by the monkey and how it is processed in the brain to help it survive.

glacier

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

hill

river

plain

delta

beach

sand bar

Review

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

Science Words Lists the essential science vocabulary covered in each chapter.

Contents

Unit 7 - Mapping the Earth’s Surface

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Earth’s Landforms Earth’s Water Maps Landform Patterns Ocean Patterns Review

Unit 8 - Using Earth’s Resources Natural Resources Non-renewable Energy Renewable Energy Environmental Impacts Review

4 12 13 30 42 44 50

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Minerals, Rocks and Soil Changes to the Earth Weathering and Erosion Rapid Changes Natural Hazard Impacts Earth Long Ago Review

Unit 6 - Processes That Shape the Earth

50 52 54 60 66 74 78 83

86 88 90 98 102 109

112 114 119 120 126 131 134 145

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What Is Energy? Energy, Motion and Force Collisions Forms of Energy Transformation of Energy Electric Charge and Circuits Review

Unit 9 - Energy and Motion

Unit 10 - Waves and Information

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What Are Waves? Characteristics of Waves Properties of Waves Types of Waves Light Waves Waves and Information Review

146 148 151 154 158 160 166 170

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Processes That Shape the Earth

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• describe minerals, rocks and soil and their properties.

In this chapter you will ...

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

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

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

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

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What are minerals, rocks 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?

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Minerals, Rocks and Soil What Are Minerals?

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Minerals are naturally occurring inorganic substances that are found in rocks and soil on and under the Earth’s surface. Inorganic means they do not come from the remains of living things.

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Many minerals are metals. Gold, silver and copper are minerals. Other common minerals include salt, talc and diamond.

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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 and production of energy.

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

Using Minerals

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Minerals are also mined and used by people in many ways. They are used in the construction of roads, buildings and cars. They are used in manufacturing, the production of cosmetics and in cleaning products. Gemstones and diamonds are often used to make jewelry.

Activity 6.1

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Properties of Minerals

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

Scientists who study minerals, called mineralogists, identify minerals by looking closely at their properties. By observing and measuring the properties of minerals, they are able to determine how the minerals can be useful to people.

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Try This!

Some properties of minerals include color, luster, streak, hardness and cleavage.

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The color of a mineral is often the most obvious property of a mineral. However, many minerals occur in more than one color, making this property not very useful.

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The luster of a mineral describes its appearance when it reflects light. Minerals may be transparent, translucent or opaque. Some minerals have a metallic luster – they look similar to a shiny metal. Others have an earthy luster – they have a dull, clay-like appearance. A mineral can also have an iridescent luster. This means its color changes as light hits its surface from different directions.

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Opals have an iridescent luster.

kaolinite magnetite

Mineralogists measure the hardness of minerals using the Mohs hardness scale. They compare the hardness of a mineral with 10 minerals of known hardness. Diamond is the hardest and has a score of 10. Talc is the softest and has a score of 1.

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The hardness of a mineral is how easily it can be scratched by other minerals. 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 potential uses. It is also used to help identify a mineral.

Did You Know?

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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.

diamond

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

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

talc calcite

AB Activity 6.2 7

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Types of Rocks

Igneous rocks form when molten rock, called magma, cools beneath the Earth’s surface. Granite is an igneous rock formed in this way.

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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

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Go Online!

Geologists are scientists that study rocks and the processes that shape them. They classify rocks into three main types based on how they form. There are igneous rocks, sedimentary rocks and metamorphic rocks.

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With enough heat and pressure, magma can also break through the Earth’s surface as lava. When the lava cools, the igneous rock basalt is formed.

kimberlite

granite

basalt

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Sedimentary rocks form when minerals and organic particles, called sediment, settle in layers on or just below the Earth’s surface.

The rock that forms the steep cliffs of the Grand Canyon are made of the sedimentary rocks sandstone and mudstone.

The process of the particles settling is known as sedimentation. Over millions of years, the sediment layers are slowly compacted and bind together to form rock in a process called cementation.

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Despite only making up a small percentage of the Earth’s crust, sedimentary rocks cover a large area of the Earth surface, estimated to be up to 80%.

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Unlike sedimentary rocks, metamorphic rocks form deep below the Earth’s surface. Metamorphic rocks were once other types of rocks that have gone through a process known as metamorphosing, meaning ‘to change form’. Metamorphosing occurs when rock is subject to immense heat and pressure deep below the Earth’s surface. Metamorphic rocks make up a large part of the Earth’s crust, but only a small percentage of the rock on the Earth’s surface.

Marble is a metamorphic rock often mined in deep quarries.

AB Activity 6.3 9

Soil Soil is a mixture of weathered rock, air, water and humus. Humus is decomposing organic matter. It is often the darkest part of soil and contains nutrients needed by plants and other organisms.

Humus-rich soil is dark in color.

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There are three types of rock particles that make up soil – sand, silt and clay. The particles come from the weathered parent rocks which they were once part of. Different types of soil contain different amounts of sand, silt and clay. This affects the size of air pockets in the soil and how much water the soil can hold.

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Sand are the largest particles. Soil with mostly sand has the largest spaces for air and water drains through it quickly.

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Most soils have a combination of all three soil particles. The amount of each type of particle and the amount of humus determine the types of organisms that live and grow in the soil. 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.

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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.

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

Changes to the Earth

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What landforms can you see around your school or home? You might see mountains in the distance or a river flowing by. Maybe the land stretches out flat in front of you or perhaps it slopes down into a valley. The Earth has a variety of different landforms and although we often cannot see it from day to day, or even from year to year, these landforms are always changing.

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Some changes, like volcanic eruptions and earthquakes, occur rapidly. Others, like weathering and erosion, have been changing the surface of the Earth over millions of years and are still doing so today.

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What processes change the surface of the Earth?

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

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Weathering and Erosion One of the ways the surface of Earth changes is by weathering. Weathering is the breaking down of rocks into smaller pieces.

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The rocks on Earth are constantly being weathered by crashing waves, roaring rivers, torrential rains and other processes. Weathering changes the Earth’s landforms. Such changes occur too slowly to notice from day to day or even from year to year. The changes usually occur slowly over millions of years.

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

Chemical weathering occurs when chemicals come in contact with rocks causing a chemical reaction. Oxygen in the air and acid rain are two common examples of chemical weathering. Acid rain occurs when harmful gases combine with the oxygen and water vapor in the air causing the rain that falls back to Earth to be acidic.

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

Chemical Weathering

Did You Know?

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When acidic rain falls on limestone, a chemical reaction breaks down the rock leaving holes. The reaction changes the limestone rock into clay and soluble salts. Over time, the holes in the rock can get bigger and break down the rock completely.

Holes in the limestone rock are caused by chemical weathering.

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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.

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AB Activity 6.6

Chemical weathering of the Belogradchik Rocks rocks in the Balkan Mountains.

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

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Physical weathering occurs when rocks are broken down by forces. Examples of physical weathering include moving water, wind, the freezing and melting of water and the actions of organisms.

Think Deeply

River canyons are landforms caused by the weathering of the river bed and rock by the moving water of the river.

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

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Mule pack train in the Grand Canyon National Park.

Moving water, such as the constant battering of coastal rocks by waves and the flow of water in rivers and streams, causes physical weathering. The contact between the water and the rocks slowly wears the rock, breaking it into small pieces.

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Go Online!

Discover how the Grand Canyon formed and the processes that continue to shape it today on the NGScience website. QuickCode: K2F2

The rock formations in Bryce Canyon National Park in Utah, USA, are a great example of frost wedging in action. Each year the rocks are weathered by up to 200 cycles of the melting of ice and freezing of water. The weathering gives the rocks, called hoodoos, their chimney-like appearance.

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

Amazing Fact!

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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.

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

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

Hoodoos in Bryce Canyon National Park.

During the day, the heat from the Sun causes rocks to heat up and expand. When the Sun sets and the temperature drops, the rocks contract. This expanding and contracting causes cracks in the rocks. Over time, those cracks get bigger and the rocks break into smaller pieces.

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

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Try This!

Differences in temperature between night and day can cause physical weathering. Most materials expand as they heat up and contract, or get smaller, when they cool down.

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

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Animals can also cause weathering when they walk or climb on rocks. This can break the rocks apart or give them a smooth surface. How do organisms contribute to the weathering of rock?

Activities 6.7 – 6.8

Erosion

Think Deeply

Waves crashing into the weathered coastline move rock particles to new places. Fast-moving water in rivers pick up rock particles and move them downstream.

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

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

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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.

The particles from weathered rock are often moved to new places. This process of moving weathered rock particles to a new location is called erosion. The main causes of erosion are moving water, wind and gravity. The slow movement of glaciers down mountains can also cause erosion.

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Amazing Fact!

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Wind can carry sand and rock particles over very long distances. Scientists have found weathered rock particles from Africa carried by wind over the Atlantic Ocean and dropped in South America.

Planting vegetation and building sand-breaks are two ways people can slow down or prevent erosion. Make a model of a sandy beach affected by wind and wave erosion. Design and build a solution to the erosion problem. Use your model to test the effectiveness of your solution.

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.

Engineer It!

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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.

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Try This!

Animals help contribute to erosion when they dig holes, tunnels and caves. In doing so, they loosen soil and expose rocks. Large groups of animals can cause erosion too. Overgrazing on vegetation can leave soil bare. The bare soil is no longer held together by the roots of plants and is more easily eroded by wind and water.

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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.

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

Moving in large herds can also contribute to erosion. Sand and soil are thrown into the air as dust where they are moved by wind.

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Wildebeest move in large herds.

Do you know how glaciers form? Find out in a video on the NGScience website. QuickCode: J9Y1

Amazing Fact!

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

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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 changes the surface of the Earth gradually over millions of years.

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.

AB Activities 6.9 – 6.10

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glacier

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

Factors Affecting Erosion

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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 due to weathering and erosion can be affected by a number of factors. Such factors include the steepness of slopes, temperature and the speed and motion of water and wind.

The steepness of the land can affect the rate of erosion. Generally, the steeper the slope, the faster the flow of water over the land. This increases the rate of erosion.

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Try This!

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Temperature can affect the rate of weathering and erosion. The weathering of rock is often occurs faster in places with a greater difference in daily temperatures. This can cause the rock to expand and contract more, which leads to increased weathering.

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Temperature differences can also affect the frequency of frost wedging. The more frequently ice forms and melts, the greater the rate of weathering.

The Port Campbell coastline in southern Australia has been shaped by the harsh weather conditions of the Southern Ocean for millions of years. The soft limestone cliffs develop caves, which then form arches. The arches eventually collapse leaving giant rock stacks. Over time, the rock stacks are weathered and eroded, changing the shape of the land.

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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 of weathering and erosion.

Amazing Fact!

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

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The types of vegetation in an area also affects the rate of weathering and erosion. Tall trees and dense shrubs can reduce the strength of wind and reduce the rate of weathering. The roots of plants grow down into the soil, holding it in place. This reduces the rate of erosion from water and wind.

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AB Activities 6.11 – 6.12

Weathering and Erosion by People

In what ways do people contribute to weathering and erosion?

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Human activities are continually contributing to both weathering and erosion.

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People cause large-scale weathering when they dig mines and quarries to take rocks and minerals from the Earth. In constructing mines and quarries, trees and other vegetation are removed. This can lead to increased erosion in the area. If the area where the mine or quarry is built is not restored, the weathering and erosion can continue after the mine or quarry has closed.

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People build dams to store water that is used in surrounding cities. Dams are also created to control water flow to produce electricity. Changing the natural flow of the rivers can increase erosion downstream of the dam.

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People often cut down trees and remove vegetation to make way for farms, roads and cities. Without plants with roots that hold the soil in place, erosion by wind and water can wash away the top layers of soil.

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

Activity 6.13 27

Deposition

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Weathered rock particles are moved to new places by erosion. Eventually, the eroded material will settle in a new place. This process of laying down rocks and rock particles in new places is called deposition.

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Like weathering and erosion, deposition is a continual process that changes the shape of the Earth’s surface.

The downstream area where a river flows into the ocean is called an estuary. The opening of the estuary to the ocean is called the mouth. Deposition can often cause the mouth to close, blocking the flow of water into and out of the estuary. How could this affect the animals in the estuary?

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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.

Think Deeply

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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.

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

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AB Activity 6.14

Rapid Changes

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

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Many processes can change the surface of the Earth rapidly. These processes include natural hazards such as floods, landslides and hurricanes.

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Floods

During periods of high rainfall, the water sources in an area can fill up. A flood can occur when the water in rivers and 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.

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Landslides

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Heavy rain and melting snow can increase the flow of water over land. On steep slopes, such as mountains and hills, this can cause a landslide. A landslide is the rapid erosion of soil, rocks and vegetation down a slope. The eroded material is pulled down the slope by the force of gravity.

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The movement of rocks, soil and vegetation during a landslide rapidly changes the shape of mountains and hills. The removal of vegetation can also increase weathering and erosion in the future. The falling rocks during a landslide can be dangerous. Large landslides can cause damage to roads, cars, homes and even entire towns.

Monsoons

Monsoons can be helpful by bringing much needed fresh water to an area following the dry seasons. Monsoons can also cause flooding which can increase weathering and erosion and change the shape of the land.

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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 equator have two seasons – a dry season and a monsoon season. A monsoon is a weather pattern of strong winds and rain that lasts for several months.

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Think Deeply

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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.

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

Hurricanes

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

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

A Closer Look

Structure of the Earth

The Earth is made up of three layers – the core, mantle and crust.

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The core is the inner-most part of the Earth. It is also the hottest part. The center of the core is the inner core. It is made of solid rock. Surrounding the inner core is the outer core. The outer core is made of molten rock.

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The mantle lies between the core and the crust. It is made up mostly of solid rock, with parts of the mantle closest to the core made of molten rock. mantle

crust

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outer core

Think Deeply

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

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

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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 the plates move, the boundaries of the plates touch and interact with each other in different ways. The interactions of the plate boundaries is why we experience events such as earthquakes, tsunamis, volcanoes and the formation of mountains.

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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

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During an earthquake, vibrations move outwards from the faults.

The Earth’s outer-most layer, the crust, is sitting on several large rocky plates that are in constant motion. Interactions occur when the plates rub together, press against each other or pull apart. The interactions occur along plate boundaries. The interaction of the plate boundaries causes a build up of pressure. The release of the pressure causes vibrations at cracks in the Earth’s crust. These cracks are called faults. All of the places where plates meet are faults. Faults can also occur within a plate.

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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.

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

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Did You Know?

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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 a score between 1 and 10 using a scale called the Richter scale. The higher the score, the more powerful the earthquake.

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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.

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How do earthquakes change the surface of the Earth?

Volcanoes

Amazing Fact!

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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.

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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, or crust. Beneath a volcano is a magma chamber containing hot molten rock called magma. A volcanic eruption occurs when the magma pushes up from inside the Earth and flows onto the Earth’s surface. Magma that flows on the Earth’s surface is called lava. Volcanic ash, water vapor and other gases also erupt from a volcano.

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Go Online!

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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.

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

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Scientists who study volcanoes, called volcanologists, classify volcanoes based on the likelihood of them erupting. Volcanoes that have erupted recently and are likely to erupt again are called active volcanoes. Volcanoes that have not erupted for thousands of years, but may erupt again in the future are called dormant volcanoes. Volcanoes that have not erupted for 10,000 years or more are called extinct volcanoes.

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

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

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

How do volcanoes change the surface of the Earth?

Engineer It!

The waves travel away from the disturbance, towards the shore. If the disturbance is powerful, resulting in large sets of waves, they may reach the shore and flow onto land. On land, they can cause extensive damage and changes to coastal areas. They can cause erosion of sand and coastal banks and remove coastal vegetation. They can cause widespread damage to roads, buildings and coastal towns.

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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.

A tsunami is a series of fast-moving waves caused by a disturbance in the ocean. Such disturbances can include an underwater earthquake, volcanic eruption or underwater landslide. Although very rare, a meteorite landing in the ocean can also cause a tsunami.

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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.

Tsunamis

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Did You Know?

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Tsunami caused by an underwater earthquake.

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The most common cause of tsunamis 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.

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

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

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The impact of an earthquake to people depends on its size. Most earthquakes are too small to cause any noticeable impact. Larger earthquakes can cause widespread damage to buildings, roads and other property. Buildings may collapse which can result in injuries and death.

Floods can cause land, often near water sources, to be covered in water. This can cause damage to farmland, roads, homes and buildings. Tsunamis can flood coastal areas. The movement of water from the ocean to land can destroy roads, farmland, homes and buildings.

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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 Earth’s surface, many natural hazards can also impact humans in a number of ways. Such natural hazards include earthquakes, tsunamis, volcanic eruptions, hurricanes, tornadoes and floods.

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Engineer It!

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During large 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

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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 occur are designed to withstand shaking. This reduces the damage to buildings and the chance of a building collapsing.

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Humans cannot eliminate natural hazards, but can take steps to reduce their impacts. Scientists 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.

Reducing Natural Hazard Impacts

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Homes and buildings in areas prone to hurricanes or tornadoes are built from strong materials and designed to withstand strong winds.

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To reduce the severity and impacts of floods, floodways, levees and sandbags can be installed to divert floodwater away from homes or cities. Planting vegetation in flood plains can help to slow erosion during a flood.

Think Deeply 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 other ways we reduce the impacts caused by natural hazards.

Earth Long Ago

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Scientists are able to learn what the Earth was like long ago by studying patterns in rock formations and fossils in rock layers.

The discovery of marine shell fossils above rock layers with plant fossils and no shells, indicates a change from land to water over time. By studying the fossils in an area, scientists are also able to infer things about the climate, vegetation and other organisms that lived there.

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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 and deposition, along with natural hazards like earthquakes and volcanic eruptions, have been changing the Earth’s surface for billions of years.

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Think Deeply

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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.

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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 Interior Seaway, ran through the center of the country long ago.

Marine fossils in sedimentary rock.

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How can scientists find out what an area of the Earth’s surface was like long ago?

A Closer Look

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Fossils appear in layers of mostly sedimentary rock called strata. Over many years, scientists discovered that the fossils appear in strata in a pattern. By studying the patterns, scientists developed the geological time scale. The scale allows scientists all over the world to explain the age of rock and the fossils within them.

Geological Time Scale

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The geological time scale is based on observations that fossils of the oldest organisms on Earth appear in the lower strata and the fossils of more recent organisms appear is in the strata above them. The scale uses this data to show when different kinds of organisms first appeared on Earth and when they became extinct.

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The geological time scale allows scientists to quickly find out the age of rocks and fossils anywhere in the world.

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Tyrannosaurus rex

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The geological time scale shows that the well-known dinosaur Tyrannosaurus rex lived on Earth during the Cretaceous period which was roughly 85 to 65 million years ago. If scientists discover a Tyrannosaurus rex fossil in a rock strata, they will know that the strata was formed somewhere between 85 to 65 million years ago. Trilobites were ancient marine animals that became extinct about 250 million years ago. They had an exoskeleton that was easily fossilized and many trilobite fossils have been discovered all over the world. When a scientist discovers a trilobite fossil in rock strata, the geological time scale can tell them the strata was formed at least 250 million years ago.

Activities 6.18 – 6.19 47

Science Words Use the words to complete the sentences.

monsoon hurricane tectonic plates earthquake fault volcano magma chamber tsunami

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humus weathering chemical weathering physical weathering erosion deposition flood landslide

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minerals luster streak hardness igneous rock magma sedimentary rock metamorphic rock soil

1. A is a series of fast-moving waves caused by a disturbance in the ocean. 2. A is a large rotating storm that forms over warm ocean waters.

4. 5.

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

, cools

The appearance of a mineral when it reflects light is its

is the color of a mineral in powdered form.

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

7. The of a mineral is how easily it can be scratched by other minerals. 8.

are inorganic substances found under the Earth’s surface.

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

10. A onto land. 11.

can occur when the water in rivers and lakes flows forms when minerals and organic particles settle in layers.

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

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

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14 . An is a shaking of the Earth’s surface caused by the movement of tectonic plates. 15 .

occurs when rocks are broken down by forces.

16. The process of laying down rocks and rock particles in new places is called . 17.

is the breaking down of rocks into smaller pieces.

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18. The process of moving weathered rock particles to a new location is called . 19. A

is a crack in the Earth’s crust.

20. A

is an opening in the Earth’s crust.

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21. Beneath a volcano is a called magma.

containing hot molten rock

22. A is a weather pattern of strong winds and rain that lasts for several months. 23. A occurs when a large piece of land is pulled down a slope by the force of gravity.

Review 1. List two minerals used by people.

2. How could you test the hardness of a mineral?

4. Which type of rock forms when lava cools? 5. List the three main types of soil.

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3. List the three main types of rock.

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6. What is the difference between chemical weathering and physical weathering? 7. What is the difference between erosion and deposition?

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

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

10. Describe two ways human activities can change the Earth’s surface. 11. List four ways the Earth’s surface can change rapidly. 12. What are tsunamis and how do they occur?

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13. How can rock layers tell scientists what the Earth was like long ago? 14. Scientists discovered reptile and dinosaur fossils in the same layer of sedimentary rock. What can they infer about the reptile and dinosaur that formed the fossils?

In the Field

Volcanologists

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A volcanologist is a scientist who specializes in the study of volcanoes. Volcanologists spend a lot of time in the field observing and collecting data on volcanoes – including ones that are currently erupting.

They collect a variety data to help explain when volcanoes formed, when they last erupted and the likelihood of them erupting in the future.

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An important role of a volcanologist is to predict when and how big a volcanic eruption will be. To do this, they need to gather data and identify patterns about a volcano’s eruptions in the past. If the patterns indicate that the volcano may erupt again, volcanologists can install special monitoring equipment to closely observe the volcano. The data collected is interpreted to help make predictions about a future eruption.

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Predicting volcanic eruptions is very difficult and can sometimes be inaccurate. Volcanologists are continuing to find new ways to collect and interpret data that will improve the accuracy of their predictions.

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

Mapping the Earth’s Surface

In this chapter you will ...

• describe Earth’s landforms and water sources.

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

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

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

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

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

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

Processes are continually shaping the surface of the Earth. Some processes, like the weathering and erosion of rock, occur slowly over millions of years. Other processes, like a volcanic eruption or earthquake, change the Earth’s surface almost instantly. The combination of these rapid and slow changes have shaped the Earth’s surface into physical features called landforms. Mountains, plains, valleys,canyons and plateaus are some examples of landforms.

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Go Online!

Mountains

A mountain is a landform that rises above the surrounding land. A mountain is taller than a hill and usually has steep slopes and a sharp or rounded peak. Mountains are formed by the pushing together of the Earth’s tectonic plates or volcanic eruptions. Mountains often form in groups called mountain ranges.

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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 the mountain is about 50 to 60 million years old. Mount Everest gets taller by about a quarter of an inch every year.

Mount Everest

Amazing Fact!

Valleys

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

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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.

One of the largest plains on Earth is the West Siberian Plain in Russian. It stretches for more than 2,400 kilometers (1,491 mi) and covers an area of more than 2.6 million square kilometers (1 million square miles).

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.

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Plains

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

Canyons

Think Deeply

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

The formation of canyons usually takes millions of years. Scientists believe the Grand Canyon in the United States took between five to six million years to form.

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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, narrow channel that runs through steep slopes or cliffs. Canyons are created by weathering and erosion of uplifted sedimentary rock usually caused by a river running through it.

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Go Online!

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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.

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Plateaus can form in a number of ways. A dissected plateau forms as the result of the upward movement of the Earth’s crust. 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 by steep ledges. The erosion of the Grand Canyon by the Colorado River has formed many plateaus. What is the main difference between plains and plateaus? In what way are they similar?

Activities 7.1 – 7.2

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A Closer Look

Features of the Earth’s Surface

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

plateau

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lake

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canyon

lagoon

peninsula ocean

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

mountain

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glacier

Activities 7.3 – 7.4

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hill

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river

plain

delta beach

sand bar

Earth’s Water

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continent

The ocean is the large body of salt water that covers more than three-quarters of the Earth’s surface. The salt in the ocean’s water comes from the chemical erosion of rocks on land by water. As water erodes rocks, salts from the rocks are carried to streams and rivers and eventually to the ocean. Some salt also comes from openings on the ocean floor.

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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

The Ocean

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Go Online!

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

island

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 of features. There are deep ocean trenches, abyssal plains and underwater volcanoes.

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

Activity 7.5

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

continental shelf

mid-ocean ridge

trench

continental slope

waterfall

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Go Online!

The water on Earth that is used by people and organisms on land is fresh water. Only about three percent of the water on Earth is fresh water. Most of the Earth’s fresh water is unavailable for use by people and other organisms. It is frozen in areas around the North and South Poles and in glaciers and icebergs. This leaves less than 0.5 percent of fresh water available to people and other organisms.

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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?

Fresh Water

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Think Deeply

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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

stream

lake

precipitation

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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.

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snow

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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

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

The water vapor cools as it rises. As it does, it condenses into water droplets and tiny ice crystals. These droplets combine together and also join with other particles in the air to form clouds.

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Go Online!

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Watch the water cycle in action in an animated video 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.

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

The water flows through streams and rivers and collects in groundwater, lakes and the ocean.

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Maps

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

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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 represents an area, usually from above. Maps can represent areas of all sizes – from the rooms in a house to the entire planet. The features and information shown on a map depend on its use.

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Try This!

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

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.

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

Types of Maps

Maps are used by people in many ways. A map of a building shows the location of rooms, offices, elevators, bathrooms and fire escapes.

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A road map shows the locations of roads and highways. Road maps are often used in digital form in cars and phones. They often display your location and provide directions.

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A physical map shows the locations of features of the Earth’s surface. They often use different colors to show the locations of mountains, plains, canyons and plateaus. They also show water sources such as rivers, lakes and the ocean. Water is commonly shown in blue.

n tio topographical map

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

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

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A political map shows the borders and boundaries of towns, cities, states and countries. A political map usually does not show physical features of the land or water.

Think Deeply

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Navigational maps, often called charts, are useful for people traveling by sea. They include important information about the distances between places, the depth of the water and information that is important for avoiding accidents, such as the location of obstacles or shallow water.

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navigational map

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resource map of the United States

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

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Digital maps are used for a wide range of purposes. They can include multiple layers to show a variety of information in one map. There may be layers for physical features, roads, temperature, vegetation type and 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

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

The title tells people what the area on the map represents. It may also include what the intended use of the map is.

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Try This!

Maps have features that provide people with accurate information about the area they represent. Some features include a title, symbols, a key and a scale. Some maps also have grids that can be used to find the location of things on the map.

Lake Boulder National Park – Hiking and Camping Map Key campfire toilet

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campsite bridge

lookout

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Arrow Ridge Trail Big Moose Trail

Brown Bear Trail

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 This!

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

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

400 mi

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400 km

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A compass rose is a feature on most maps that shows the directions of north (N), south (S), east (E) and west (W). Common practice is for a map to show area with north pointing up.

compass rose

Activity 7.8 73

Landform Patterns

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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

Scientists have identified patterns in the Earth’s landforms. Mountains are landforms that often appear in groups, called mountain ranges. Scientists have observed a pattern whereby many mountain ranges occur at the places where the Earth’s plates meet.

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Go Online!

In science, finding patterns is very useful. A pattern is something that repeats over and over. They can be used to help explain why something is occurring and also to make predictions about where or when it may occur again. Meteorologists are scientists that look for patterns in the weather. When a pattern is identified, it can be used to make predictions about the weather in the future.

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How is identifying patterns in Earth’s landforms useful?

Indian Plate

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Himalayan Mountain Range

This pattern helps with the explanation that mountains form when the boundaries of the plates interact as they bump and slide against each other. The interactions cause the crust to buckle or push upwards.

How is identifying a pattern in mountain formation useful?

Activity 7.9

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Himalayan Mountain Range

Think Deeply

Asian Plate

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A Closer Look

The Ring of Fire As with the formation of mountains on the Earth’s surface, earthquakes and volcanic eruptions also occur in identifiable patterns. They both occur in cracks in the Earth’s crust, called faults. The largest faults occur at plate boundaries. There are also faults within plates.

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By putting the location of earthquakes and volcanic eruptions on a map, scientists observed that many occur along plate boundaries and faults around the Pacific Ocean. The area is known as the Ring of Fire. About 90 percent of volcanic eruptions on Earth occur in the Ring of Fire.

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The pattern of earthquake and volcanic activity around the Ring of Fire helps scientists explain why, where and when such events occur. Why do so many earthquakes and volcanic eruptions occur around the Ring of Fire?

Ocean Patterns

Just as there are processes that shape the Earth’s surface on land, many of the same processes shape the ocean floor.

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Ocean trenches are narrow and very long sunken areas on the ocean floor. They have steep sides and form the deepest parts of the ocean. Scientists have identified patterns in the location of ocean trenches which help explain their formation. Like mountains and volcanoes, ocean trenches commonly occur at plate boundaries. They are formed when two plates push against each other causing one plate to slide under the other. This interaction at plate boundaries is called subduction.

Activities 7.10 – 7.11

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The map here shows the features of the Earth’s ocean floor. What patterns can you identify? What caused the patterns?

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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 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.

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

A Closer Look

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Located in the Pacific Ocean, about 200 kilometers from the Mariana 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.

The Mariana Trench

Oceans are divided into zones based on depth. The deepest part of the ocean, at depths of between 6,000 and 11,000 meters is called the hadal zone, named after Hades, the Greek god of the underworld.

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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.

Did You Know?

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Reaching such depths is a challenge to scientists. There is immense pressure, complete darkness and very cold water temperatures.

Science Words Use the words to complete the sentences.

mountain range Ring of Fire ocean trench abyssal plain ocean ridge

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

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1. A a map.

groundwater map key scale compass rose

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mountain plain valley canyon plateau

2. A group of mountains in the same area form a

3. A is low-lying area between mountains or hills, often with a river or stream flowing through it. is narrow and very long sunken area on the ocean floor.

5. An

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

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4. An

6. A or cliffs.

is a deep, narrow channel that runs through steep slopes

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7. A is flat terrain that elevates sharply from the surrounding land on at least one edge. 8. Underground water in spaces in rocks and soil is called 9. A a map.

is an explanation of what the symbols represent on

10. A

shows the distance between objects on a map.

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

12. A is a landform that rises above the surrounding land and usually has steep slopes and a sharp or rounded peak. is a wide, flat landscape with little elevation.

14. A

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

13. A

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15. An is a sudden rising of the ocean floor caused by the movement of the Earth’s plates.

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

2. What is groundwater and how can it obtained by people?

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

4. Why do mountains often form in mountain ranges? 5. Use the words in the box to label the diagram.

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ocean trench abyssal plain ocean ridge

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

In the Field

Oceanographer

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

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

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Oceanographers have a diverse set of knowledge and skills. They are often trained in geology, chemistry, biology and physics. They measure and collect all sorts of data. From the condition of sea water and the organisms living there, to the geology of the ocean’s many underwater features. They also collect data about the movement of water in waves, tides and currents.

An important part of an oceanographer’s job is to interpret and communicate their information with others. This could be in the form of reports or media such as photographs and videos. They often use maps to show the condition and features of the ever-changing ocean floor.

Using Earth’s Resources

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

In this chapter you will ...

• distinguish between non-renewable and renewable resources.

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• list and describe different natural resources and how their uses affect the environment.

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• explain the importance of conserving the Earth’s resources.

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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

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Natural Resources

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Materials or substances in nature that are used by people are called natural resources. We use many different kinds of natural resources for a range of different purposes.

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Rocks, soil, metals and wood are natural resources used to build houses and buildings. Plants and animals are natural resources that are often farmed to produce the food we eat and the clothes we wear. Fossil fuels such as coal, oil 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.

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Other natural resources, like the energy in sunlight, wind and moving water, cannot be used up. They are called renewable resources. What is the difference between non-renewable and renewable resources?

Activity 8.1

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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 Energy

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Electricity is very important to people. It helps us to do work in many different ways. People have discovered many ways to produce electricity. A common way is by burning fuels to produce heat. The heat is often used to change water into steam. The steam is transformed into kinetic energy that spins turbines then generators that produce electrical energy.

Fossil Fuels

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Most of the fuels that people burn to produce electricity are fossil fuels. Fossil fuels are formed from the remains of organisms that died and decayed long ago.

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Hundreds of millions of years ago, the surface of the Earth looked very different than it does today. It was covered in shallow seas and swamp-like forests. They were filled with micro-organisms, plants and animals.

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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 sediment covered the decomposing organisms, they became more and more compressed over time. Eventually, they formed fossil fuels.

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The fossil fuels most commonly used by people are coal, petroleum and natural gas. These fuels are often located deep beneath the Earth’s surface. To obtain coal, people dig mines. Petroleum and natural gas are obtained by drilling into the Earth’s surface and pumping the fuels to the surface.

Fossil fuels take millions of years to form. As such, they are called non-renewable resources because they are used up much faster than they can be replaced by nature.

Why are oil, gas and coal non-renewable resources? What will happen when these fuels are used up?

A Closer Look

How Fossil Fuels Are Formed

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

1 Microscopic plankton and other

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

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.

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3 Over millions of years, heat

and pressure beneath the Earth’s surface turned the remains into fossil fuels such as oil and gas.

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

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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.

Generating Electrical Power From Fossil Fuels

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coal supply

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

Go Online! Watch how electricity is generated by burning fossil fuels in an animated video on the NGScience website. QuickCode: X4U6

Activity 8.3

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

generator

transmission lines

transformer

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turbine

Think Deeply

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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.

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

water supply

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control rods

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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.

Nuclear Fuel

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steam generator

condenser

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transmission lines

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Like in a coal-fired power plant, the 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.

Scientists designed nuclear power stations to convert nuclear energy into electricity.

transformer

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generator

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cooling tower

water supply

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generator

Renewable Energy Wind

In most of the ways people produce electricity, kinetic energy is used to spin a generator. Wind has kinetic energy in the form of moving air.

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A wind turbine is a very large windmill that uses the energy in wind to spin its blades. The blades spin a generator that transforms the energy into electrical energy.

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Often, particularly in very windy places, many wind turbines are grouped together to form a wind farm. Wind farms can produce enough electricity to power whole cities. As wind blows all the time, the electricity produced by wind turbines and wind farms is a renewable source of energy.

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

n Moving Water

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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 electrical energy.

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hydroelectric power station

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Hydroelectricity is the electricity produced using the kinetic energy in flowing rivers and streams. The water is often held in large dams which allow people to control the flow of water.

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

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

generator in a hydroelectric power station

tidal power turbine

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

Most of the energy on Earth can be traced back to the Sun. The Sun is more than 140 million kilometers from Earth, yet produces enough light and heat to light up the Earth and keep us warm.

Think Deeply

Solar panels can be attached to the roof of buildings and provide homes with electricity. Large collections of solar panels are often placed in open areas that get lots of sunlight. The electricity they produce is used to power towns and cities.

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solar panels containing photovoltaic cells

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Solar electricity, or solar energy, can be produced when light energy from the Sun is transformed into electrical energy. This is done through special devices called photovoltaic cells. The cells are connected together in large groups to form solar panels.

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

AB 100

Activity 8.4

A Closer Look A solar-powered home is a home that meets all or part of its electricity needs using solar power.

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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 available to use.

Solar-powered Home

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The electricity can be used to power electrical appliances within the home or stored in batteries to use later. If the solar panels produce more electricity than needed, the electricity can be sent to the electric grid for others to use.

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Environmental Impacts

Coal is a fossil fuel that is found beneath the surface of the Earth. To get coal, a mine needs to be constructed. This can cause huge changes to the environment. Trees and plants are removed to make way for the mine and the network of roads needed to transport people and coal out of the area. Animals that cannot move to new habitats may die. To get natural gas and petroleum, people must drill deep into the Earth’s surface. Sometimes chemicals are used to pump the fuels from the Earth. These chemicals can pollute the land. Land and water pollution can also occur when fossil fuels spill into the natural environment.

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oil spill

Habitat Loss

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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 mammal, such as sea otters, reducing its ability to keep mammals warm.

The generation of electricity can impact the environment in a number of ways. Impacts to the environment occur when we take fossil fuels from the Earth. The burning of fossil fuels can also harm the environment when harmful gases are released into the atmosphere.

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Did You Know?

open-pit coal mine

Emissions

Many countries around the world have made an agreement to reduce greenhouse gas emissions. Why is such an international agreement important?

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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 of the Earth. Acid rain can pollute water sources, such as lakes and rivers, and is harmful to plants. It can also cause the soil to become polluted.

Think 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.

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

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Burning fossil fuel also produces carbon dioxide which is released into the air. Carbon dioxide is a greenhouse gas. When greenhouse gases are added to the air, they cause the atmosphere to retain more heat. This is slowly causing the Earth to get hotter faster than it normally would. Emissions from fossil fuel power stations along with vehicle and factories is a major cause of climate change.

Go Online!

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Nuclear Impacts

Nuclear power plants also produce a lot of hot water, which needs to be cooled. This can be done by cycling the water through a larger body of water, such as the ocean or a lake. This can change the water environment and affect the organisms living there.

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nuclear waste

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Nuclear power plants do not release high levels of greenhouse gases or other pollutants into the air. However, the process of uranium mining and making electricity produces radioactive waste such as uranium tailings and used fuel rods. Radioactive materials are very harmful to people and other organisms. They also remain dangerous for thousands to millions of years. For this reason, nuclear wastes need to be carefully contained and isolated. If containment fails, the impact on the environment can be catastrophic.

Did You Know?

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

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A Closer Look

Global Climate Change

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Climate describes the weather conditions, such as average temperature and precipitation, in an area over a period of time. Scientists are continually measuring and monitoring climates all over the Earth. They analyze the data they collect to identify patterns.

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One pattern scientists have identified is that the Earth is getting warmer at a much faster rate than expected. This pattern, called global climate change, coincides with increases in greenhouses gases produced by people through the burning of fossil fuels. You may recall that carbon dioxide is a greenhouse gas. As trees and other plants take carbon dioxide from the air, clearing forests is also contributing to global climate change. Global climate change has many effects on the Earth and the organisms living here. Such effects include:

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rising sea levels. melting ice in glaciers and the Earth’s poles. more frequent extreme weather events. changes in ecosystem communities.

Activities 8.5 – 8.7

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• • • •

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Technology and the Environment

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Technology plays an important role in helping to reduce human impacts on the environment. By applying scientific knowledge to new designs, scientists and engineers are able to improve existing electricity production methods. They can help make them more efficient at producing electricity, or produce less emissions.

Scientists also develop new technologies that produce electricity from renewable resources. Solar energy, wind farms and wave energy are all relatively new technologies that have far less impact on the environment.

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Scientists are continually trying to improve these new technologies to make them more efficient and more easily available to people.

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

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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 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 fuel? What are some disadvantages?

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Science Words

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

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natural resources non-renewable resource renewable resource fossil fuels nuclear energy wind turbine hydroelectricity tidal energy

Use the words to complete the sentences.

1. is electricity produced using the movement of water during changes in tides. 2. electricity.

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

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3. A

uses the energy in waves and ocean swells to produce

4. is the pattern in which the Earth is getting warmer at a much faster rate than expected. 5. is produced using special devices called transform light energy from the Sun into electrical energy.

that

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6. Materials or substances in nature that are used by people are called . 7. A natural resource that is used up faster than it can be replaced is called a . 8. A natural resource that cannot be used up is called a 9. The energy from inside atoms is called 10. Harmful emissions are called

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. .

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

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

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

Review

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

1. List four types of natural resources.

2. Are fossil fuels renewable or non-renewable resources? Explain your answer. 3. List three types of fossil fuel.

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4. What are two disadvantages of producing electricity by burning fossil fuels? 5. What are two advantages of producing electricity using renewable resources?

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6. List three ways moving water can be used to produce electricity. 7. Draw a labeled diagram to show how solar electricity is produced. 8. Describe two environmental impacts of using Earth’s natural resources.

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In the Field

Renewable Energy Engineer

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In laboratories, they build models and use computers to test and evaluate the effectiveness of their designs. They also monitor and maintain renewable energy technologies once constructed.

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What would you work on if you were a renewable energy engineer?

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Energy and Motion

In this chapter you will ...

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• describe and provide examples of potential and kinetic energy. • use evidence to construct an explanation relating the speed of an object to the energy of that object.

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• ask questions and predict outcomes about the changes in energy that occur when objects collide.

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

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

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

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What are some different forms of energy? What are some examples of energy transformations?

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 happens because of energy. Energy is the ability to do work or cause change.

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.

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

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Plants use the energy from the Sun to make food. The food gives them the energy they need to live and grow. Animals and people get energy from the food they eat. They need energy to move about and carry out all life processes.

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How do you use energy in your daily activities?

Think Deeply

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

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

Energy cannot be made and cannot be destroyed. It exists in many forms and can be transformed from one form to another. A television is a device that uses electrical energy. The electrical energy is transformed into light, heat and sound energy.

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What energy transformations take place during a motorcycle race?

Activity 9.1

Motorcycles use the stored energy in gasoline.

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Potential and Kinetic Energy All forms of energy can be described as either stored energy or moving energy.

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The stored energy in an object is called potential energy. Food has potential energy. The energy is transformed into other forms when we eat the food and use the energy to move about, keep warm and stay healthy.

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Potential energy is also related to the shape and position of an object. If you hold a ball above your head, the ball has potential energy due to its position. If you drop the ball, the potential energy is transformed into moving energy.

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

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.

Think Deeply

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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 mass of an object in motion, doubles its kinetic energy. If you double the speed of an object, its energy increases by four times.

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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.

Did You Know?

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

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

The kinetic energy of the train increases with its speed.

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At rest on the top of the track, the cars have the most potential energy and no kinetic energy. As the cars move down the track, the potential energy is converted into kinetic energy. As the cars get faster, their kinetic energy increases. As they get lower, their potential energy decreases.

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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. As the cars climb up the track, their potential energy increases as they get higher.

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Engineer It!

Discuss some other examples of the conversion of potential and kinetic energy at an amusement park.

Go Online!

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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 9.2 – 9.3

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

Energy, Motion and Force

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Motion is the process of changing position. When something is moving it is in motion. An object that is in motion has kinetic energy. We can describe motion by measuring its speed and direction.

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Speed is the time it takes an object to cover a certain distance. The faster an object covers a distance, the greater its speed. Direction is which way an object is moving. The greater the speed of an object, the more energy it has. Forces can also affect the motion and energy of an object. Larger forces will cause objects to move faster and have more energy than smaller forces.

Activity 9.4 119

Collisions

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

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

Think Deeply

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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.

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

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

Think Deeply

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How is kinetic energy transferred when dominoes collide?

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

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The observable impact of a collision reflects how much energy was transferred between objects and relates to the amount of energy of the moving object.

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At the start of a game of billiards, a player uses a large force to hit one ball into the other balls. The ball gains kinetic energy from the billiard cue and moves down the table. As it hits the other balls, a loud sound is made. Kinetic energy is transferred to the other balls as they scatter all over the table.

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When a player uses a smaller force, less kinetic energy is transferred. The balls produce a softer sound when they collide and move more slowly.

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

A sledgehammer hits a wall. What observations would indicate the amount of energy transferred when the 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 9.5 123

In the Field

Vehicle Safety Engineer

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The cars, vans, buses and trucks we use for transportation are very important in our daily lives. However, these heavy vehicles travel at fast speeds and that means a lot of kinetic energy is transferred in the event of a collision. Vehicle safety engineers have a very important job. They study what happens when vehicles collide in an accident in order to make vehicles safer for drivers and passengers.

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Vehicle safety engineers use models and computer simulations of vehicle accidents to observe and record how energy, speed and motion interact. They use this information to help design safer vehicles that can better withstand collisions.

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

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.

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

Sound Energy

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

Sound is the movement of energy through matter when an object vibrates. The vibrations cause the particles in the matter around it to vibrate.

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Think Deeply

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When you strum a guitar, the kinetic energy in your hand causes the guitar strings to vibrate. The vibrations cause the particles in the air around the strings to vibrate too. The vibrating particles travel in waves away from the source of the sound. We hear sounds when the sound waves reach our ears.

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Sound waves always travel outward from the source of the sound. They can travel through solids, liquids and gases.

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

Thermal Energy

Think Deeply

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.

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Describe what happens to the particles in warm water when a glass of warm water is placed in a refrigerator.

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

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Heat always moves from something hotter (with greater thermal energy) to something colder (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 see. Anything that gives out light of its own is a source of light.

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Most of the light energy on Earth comes from the Sun. It lights up the sky during the day and allows us to see. Light energy from the Sun is also used by plants to make food. The Sun is a natural source of light. Fire and lightning are also natural sources of light. Artificial sources of light are produced by people. Light bulbs, mobile phone screens and televisions are artificial sources of light.

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

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Discuss the different ways people use light. What is the source of light?

Electrical Energy Electrical energy, commonly called electricity, is caused by moving electric charges.

Go Online!

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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.

List the devices and appliances in your home that use electricity. Describe the energy transformations that take place when the device or appliance is switched on.

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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.

Try This!

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

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

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Chemical Energy

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Chemical energy is energy that is stored. It is a type of potential energy. Energy is released when chemical reactions takes place. Food is a form of chemical energy. When we eat food, a chemical reaction converts the chemical energy into kinetic energy that enables us to move about, keep warm and carry out life processes.

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Fuels such as gasoline, coal, gas and wood have chemical energy. A chemical reaction occurs when the fuels are burned and light and heat are released.

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Batteries contain chemical energy. A flashlight converts the chemical energy in batteries into light and heat. A batteryoperated toy car converts the chemical energy in its batteries into kinetic energy.

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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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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.

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During photosynthesis, plants use light energy from the Sun to make food. The light energy is converted into chemical energy.

All around us, energy is changing from one form to another.

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Describe the energy transformation that takes place when plants photosynthesize.

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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Many ovens and stoves use the stored chemical energy in gas. When the gas is burned, it produces the heat we need for cooking food. Light is also produced when gas is burned.

Electricity flowing through thin wires can cause them to heat up. Electric heaters and hair dryers convert electrical energy into heat energy. Devices such as fans and electric cars convert electrical energy into kinetic energy.

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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 bulbs?

When you move your hands back and forth, they gain kinetic energy. The kinetic energy is transformed to heat from the friction created when the surfaces of your hands rub together.

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Think Deeply

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

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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.

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When you turn on a television, electrical energy is converted into light, heat and sound.

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The battery that powers your smartphone, tablet or notebook computer stores chemical energy. As you use your device, this chemical energy is transformed into electrical energy, then light, heat and sound.

wind turbine

Think Deeply What happens to your smartphone when the chemical energy in the battery is used up? What transformation of energy occurs when you re-charge your smartphone?

Activity 9.7

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Electric Charge and Circuits Electric Charge

Try This!

Charges are small particles that exist in all forms of matter. They can be positive (+) or negative (-). In most matter, the number of positive and negative charged particles is the same. When objects rub against each other, like the clothes in your dryer, charged particles can move between the objects causing an imbalance of charge. An imbalance of negative or positive particles in matter causes an electric charge. Just like the poles of a magnet, like charges repel each other and opposite charges attract each other.

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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?

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

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Go Online!

Have you ever opened the clothes dryer and discovered that some of the clothes are stuck together? This happens because some clothes gain or lose charge as they tumble in the dryer.

Clothes stick together when opposite charges attract each other.

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In a dryer, the clothes stick together when the positively-charged clothes are attracted to the negatively-charged clothes.

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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 negative charges in the balloon attract the positive charges in the wall causing the balloon to stick to the wall.

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Electric Discharge

Have you ever received an electric shock when touching a metal object? An electric shock is an example of an electric discharge. Electric discharge is the movement of the buildup of electric charge from one place to another.

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When you walk on a surface such as carpet, you gain negatively charged particles – your body becomes slightly negatively charged. The electric shock you receive when you touch a metal object is the rapid movement of the negative charge leaving your body. An electric shock is the rapid movement of negative charge leaving your body.

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A Closer Look

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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 of the cloud becomes positively charged and the bottom of the cloud becomes negatively charged.

Lightning

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The temperature of a bolt of lightning can be up to five times hotter than the surface of the Sun!

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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.

Amazing Fact!

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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.

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

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

Think Deeply

Lightning strikes the surface of Earth about 100 times every second.

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Electric Current

Some materials allow charges to move more easily than others. Metals, such as copper found in wires, allow charges to move very freely. Materials that allow charges to move freely are called electrical conductors. Many metals are good conductors.

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

Electric charge is the buildup of charged particles within matter. Electric current is the continuous flow of electric charge.

Think Deeply

Plastics, such as those used to wrap electrical wires, do not allow charges to move freely. Materials that restrict the flow of charges are called electrical insulators. Wood, glass and rubber are also good insulators.

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Why is it useful to know which materials are electrical conductors and which are electrical insulators?

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

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

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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.

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.

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Circuits

Engineer It!

For electric current to flow through a circuit, there must be a complete path along which the electrical energy can flow. A switch is often used to control the flow of electrical energy by opening and closing the path.

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

An electric circuit is a path around which electricity flows. In an electric circuit, electrical energy flows from a power source, through conducting wires, to different devices that change the electrical energy into other forms. A light bulb, for example, can change the electrical energy into light energy and heat energy. A fan can change the electrical energy into kinetic energy, sound energy and heat energy.

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Think Deeply

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

n A flashlight uses an electric circuit.

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

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

Try This!

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

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

Activities 9.8 – 9.10 1 41

A Closer Look

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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 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.

Electrical Appliances

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

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Science Words Use the words to complete the sentences.

electric discharge electric current electrical conductors electrical insulators electric circuit

is the process of changing position.

2. A

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thermal energy heat energy electrical energy chemical energy electric charge

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energy potential energy kinetic energy motion collision

occurs when an object hits another object.

3. An imbalance of negative or positive particles in matter causes an . 4. is the movement of the buildup of electric charge from one place to another.

is the continuous flow of electric charge.

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is the ability to do work or cause change.

7. The stored energy in an object is called is the energy of movement.

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8. 9.

is caused by moving electric charges.

10. is energy that is stored. Energy is released when chemical reactions takes place. 11. An

is a path around which electricity flows.

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

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13.

is the movement of thermal energy.

14. Materials that allow charges to move freely are called

. .

15. Materials that restrict the flow of charges are called

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Review

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

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2. Provide two examples of an object with kinetic energy. Explain why it has kinetic energy. 3. Describe the energy transformation that takes place as a rock starts rolling down a hill. 4. Describe the kinetic energy of a car as it speeds up and slows down. 5. How does the speed of an object affect its energy?

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6. Describe how energy is transferred when a tennis racket collides with a tennis ball. 7. How does the speed an object is moving affect the collision that occurs when it strikes another object?

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8. What energy transformation occurs when you turn on an electric fan? 9. What energy transformation occurs when you turn on a television? 10. Why are copper and plastic used to make electrical wires? 11. What must occur for the device in an electric circuit to work?

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Waves and Information

In this chapter you will ...

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

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

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What are some characteristics of waves?

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n tio du ca Access interactive content relating to this topic on the NGScience website. ngscience.com

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Go Online!

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

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What Are Waves?

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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 it will make a splash. Then ripples appear and move away from the splash in all directions. When the pebble entered the water, its energy from motion was transferred to the water as it pushed the water out of the way. This energy was then spread out in all directions through the ripples – which are small waves in the water. Waves are disturbances that carry energy and travel in a repeating pattern.

Go Online!

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

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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 strings as sound.

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The water waves in the pond and the sound waves in the air move through matter. The substance that a wave moves through is called a medium. The particles of a medium do not change or move very much as the wave moves through it.

Activity 10.1

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Similarly, the individual water molecules in the pond mostly move up and down as the waves move across. The molecules of air near the vibrating guitar string also move back and forth as the sound wave passes.

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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 appears to move around the stadium, but the individual people producing the wave only stand up and sit back down in their seats. The wave is moving around the stadium in one direction, but the people are only moving up and down in the same position.

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Did You Know?

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Not all waves need a medium to propagate. Light from the Sun moves in waves through empty space to reach Earth. Light waves are produced when magnetic and electric fields vibrate. These vibrations create their own medium.

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Characteristics of Waves

Whisper: 30 dB Conversation: 60 dB Lawnmower: 90 dB Jet engine: 130 dB

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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 sound wave of a certain amplitude. Hit the same drum with a greater force and the amplitude of the sound wave increases. We perceive this change as a louder sound.

The amplitude of a sound is measured in decibels (dB). Here are the decibels of some common sounds:

Amplitude

Did You Know?

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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.

drum hit softly

drum hit with greater force

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

Hit the shortest bar of a xylophone and it will produce a high-pitched sound. This is because the bar vibrates quickly. Hit the longest bar of the xylophone and a lower-pitched sound is produced. This is because the bar vibrates at a slower rate compared to the shortest bar.

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

For a sound wave, wavelength describes the pitch of a sound. The shorter the wavelength, the higher the pitch of the sound. The longer the wavelength, the lower the pitch of the sound.

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Try This!

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Higher-pitched sounds produce shorter wavelengths.

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Lower-pitched sounds produce longer wavelengths.

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Frequency is the measure of how quickly a wave repeats in a given amount of time. A wave of high frequency means that the wave repeats in a short amount of time. Similarly, a wave of low frequency will repeat in a longer amount of time. In sound waves, this is also related to the pitch of the sounds. High-pitched sounds are produced from high frequency waves. Low-pitched sounds are produced from low frequency waves.

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Frequency

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.

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.

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

Try This!

high frequency

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

low frequency

Activity 10.2 1 53

Some bats use echolocation to ‘see’.

Properties of Waves

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Reflection

Just as different waves share similar characteristics, waves also share similar properties.

Go into a large empty room such as the school gymnasium and clap your hands. What do you notice? You may hear the clapping sound repeat. This is because the sound waves produced from clapping bounce off hard surfaces in the room such as bricks and concrete and travel back to your ears. The reflected sound is called an echo.

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Go Online!

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When you look at yourself in the mirror each morning, light travels from your face, bounces off the mirror and then enters your eyes. The bouncing of waves off a surface is called reflection. The direction a wave bounces depends on the angle that it hits the object. Drop a tennis ball and it will bounce straight up off the ground. If you throw the tennis ball at an angle to the ground, it will bounce away at the same angle.

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

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Activities 10.3 – 10.4

Refraction

The pencils appear broken due to the refraction of light.

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

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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 direction. This change in speed and direction is called refraction.

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

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Light can be refracted to bring the light rays closer together and make objects appear closer. It can also be refracted to spread out the rays and cause objects to appear further away.

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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Did You Know?

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Absorption

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

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Light waves can also be absorbed when they hit an object. Materials that absorb light are dark in color because they don’t reflect much light. They also tend to be warmer because they absorb heat that is being transferred by the light waves. White objects reflect most of the light waves that hit them. They tend to be cooler 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.

Different objects and materials can interact with light waves in different ways.

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

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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

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Light Waves and Transparency

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

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

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Some objects, such as tissue paper, absorb some light waves. They allow some light to pass through.

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

movement of energy

Try This!

Take a length of rope and attach one end to a tree. Holding the other end of the rope, quickly move it up and down. What do you notice? You will see waves move along the rope from your hand to the tree it is attached to. As the waves travel through, the rope moves up and down, perpendicular to the direction of the wave. Waves in which matter moves perpendicular to the direction of the wave are called transverse waves.

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

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Types of Waves

Did You Know?

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

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Waves moving over the deep ocean surface is an example of transverse waves. Boats floating on the ocean surface move up and down as the waves moves perpendicular to the boats. The boats are not moved in the direction of the wave. Light moves from its source to your eyes in transverse waves too.

movement of energy

direction of wave

Think Deeply

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

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

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The motion of the spring is parallel to the direction of the wave.

As the disturbance moves, the spring gets packed tightly together, and then spreads out as the waves passes. The packing together is called a compression and the spreading apart is called a rarefaction. The motion of the spring coils is parallel to the direction of the wave. Such waves are called longitudinal waves. Sounds waves are an example of longitudinal waves. When an object vibrates, the particles of air around the object get compressed and spread out over and over again.

Go Online!

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

amplitude

source

Sound moves in longitudinal waves.

rarefaction

compression

Activity 10.6 159

Light Waves

wavelength

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source

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amplitude

Light waves are the vibration of magnetic and electric fields. These fields vibrate perpendicular to one another and also perpendicular to the direction the light wave is traveling. Light waves are transverse waves.

Light We Can See

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Sunlight appears white, but it is actually a mixture of many different colors. When white sunlight enters a glass prism, the light separates into the colors of a rainbow. Droplets of water in the sky can also act like prisms and separate the Sun’s white light to produce a rainbow.

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In a prism, light separates into the colors 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 appears white because it reflects all of the light waves that hit it.

Think Deeply Describe how is light being reflected and absorbed by the clothes you 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.

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

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Stained glass windows are an example of filters. White light enters from the outside and the different filters only allow certain colors to pass through.

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Some traffic lights use white light that passes through red, green and orange filters.

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Light, Sight and Our Eyes

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Our eyes take in light and allow us to see the world around us. Sources of light such as the Sun and televisions produce light of their own. Light from these objects enters our eyes directly. Other objects such as a vase of flowers do not produce light on their own. We are able to see these objects when a source of light shines on them and the light is reflected to our eyes.

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sclera

iris

pupil

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lens cornea

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Anatomy of the human eye.

retina

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

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Once the light passes through the pupil, it goes through the lens. Just like the lens of a camera, the lens of your eye bends the light and focuses it before it reaches the retina. The retina is a light-sensitive tissue at the back of the eye. It converts the light into electrical signals which travel to our brain via the optical nerve.

Did You Know?

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The size of the pupil is controlled by the iris which is also 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.

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.

lens

Activity 10.7

retina

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cornea

pupil

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

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The color of light is determined by the wavelength of the light waves. Short wavelengths give us blue and purple light, while longer wavelengths give us red and orange light.

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

When the wavelength becomes very short or very long, our eyes are not able to see the light as colors. This light is invisible to our eyes.

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Did You Know?

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Ultraviolet light, also called UV light, is an example of light we cannot see due to its very short wavelength. We can feel the effects of ultraviolet light because it causes sunburn. Germs and viruses die or are destroyed when exposed to ultraviolet light. UV lamps can be used to sterilize surfaces, preserve food and treat water.

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radio waves

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infrared

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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 cameras are used to produce images that show the temperature of objects.

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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.

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Radio waves are light waves with very large wavelengths. We can use these waves to send and receive messages.

x-rays

gamma rays

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ultraviolet

visible light

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Waves and Information

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

Think of a wave in the ocean. A point of water that the wave passes through will continuously rise and then fall. The height of the waves, the amplitude, will also take on a range of values as the wave passes.

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Go Online!

Just as waves transfer energy, waves can be used to send and receive information. Messages or signals are often sent with sound waves, light waves or radio waves. Signals sent along these waves are analog signals. Analog signals have a range of continuous values.

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Similarly, the sound waves produced by a guitar has a range of continuous values. As the sound wave moves through the air, the particles of air experience compressions and rarefactions continuously. Sound wave are analog signals.

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However, in today’s modern world, the signals have to be sent and received a certain way in order for computers and electronics to process them. Computers and electronics are not able to 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.

n tio AB

Activity 10.8

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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.

A Closer Look

Radio Waves and Cell Towers

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You probably talk on a cell phone every day. When you talk, the phone converts your voice into a digital signal which is sent to a nearby cell tower as radio waves. The tower then sends the signal to a central computer that relays the message to the correct cell tower closest to the receiving cell phone. The tower sends the signal to the recipient’s phone that then processes the signal and converts it back into an analog signal that the recipient can hear.

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Radio waves are a useful method of sending and receiving signals as they can do so over long distances without the signal getting lost or becoming weaker. Radio waves can also be used in a similar way to send television signals and Internet data.

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Optical Fiber

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Light waves can also be used to send and receive information across large distances through optical fiber. Optical fiber are thin, transparent fibers that are about the thickness of 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.

Science Words Use the words to complete the sentences.

refraction longitudinal wave ultraviolet light infrared light analog signals digital signals optical fiber

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rarefaction transparency transparent translucent opaque transverse wave compression

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waves medium amplitude wavelength frequency reflection echo

1. is the distance between two similar points in the repeating pattern of a wave. 2. is the measure of how quickly a wave repeats in a given amount of time. 3. The bouncing of waves off a surface is called

, the motion of the disturbance is parallel to the direction

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4. In a of the wave.

5. Light we can’t see due to its very short wavelength is called 6. Light we can’t see due to its very long wavelength is called object blocks light.

8. An

is produced when sound waves are reflected.

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7. An

9. The change in speed and direction of a wave as it passes from one medium to another is called . 10. The amount of light that can pass through an object is called . 11. A

object allows almost all light to pass through it.

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12. A

object allows some light to pass through it.

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

14. The substance that a wave moves through is called a

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15. The measure between a wave’s resting position and its greatest height is its . have a range of continuous values.

17.

have specific values.

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16.

18. Waves in which matter moves perpendicular to the direction of the wave are called . 19. The part of a wave where the particles are close together is . a .

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

21. are thin, transparent fibers that can be used to send information through light waves, often across large distances.

Review

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1. Describe how increasing the volume and changing the pitch of a sound affects the sound waves produced. 2. Provide an example of transverse waves and longitudinal waves. 3. How are transparent materials different from opaque materials? 4. Provide an example of how waves can be used to send messages. 5. What is the difference between analog and digital signals? 6. Provide an example of how digital signals are used to send information.

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