Next Generation Science Level 5 - Textbook B by Blue Ring Media Pty Ltd

Science for the Next Generation

Science Gra d e F i ve

Textbook

The 5E Model – Guided Inquiry The Next Generation 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. 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.

Engage

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. 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. Next Generation Science also includes extensive digital resources such as narrated videos, interactive lessons, virtual labs, slideshows and more.

Explore

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 are presented by the teacher.

Explain

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.

Elaborate

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

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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Next Generation Science Next Generation 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.

Wallac

Amphibians

The word amphib term which mean to their unique life amphibians, begin land. Amphibians fertilization, and h

Next Generation 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. Next Generation Science sees engineering as an essential element of science education and as such is tightly integrated into both the textbooks and activity books.

There are three m Frogs are amphib They often have s legs for moving a Toads are similar often have drier a

European tree frog

The Next Generation Science textbooks include the following features:

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

In the Field

Sir Alexander Fleming

“One sometimes finds what one is not looking for. When I woke up just after dawn on September 28, 1928, I certainly didn’t plan to revolutionize all medicine by discovering the world’s first antibiotic, or bacteria killer. But I suppose that was exactly what I did.“ – Sir Alexander Fleming. Sir Alexander Fleming was a Scottish physician and microbiologist, best known for discovering the drug penicillin – the first effective antibiotic used to kill bacteria. In his laboratory in 1928, Fleming was investigating the properties of the bacteria Staphylococci. On returning from a family holiday, Fleming noticed that bacteria growing in a petri dish were being killed by the fungus Penicillium, a type of mold.

He observed that the bacteria immediately surrounding the fungus had been killed, and that the bacteria farther away were normal. “That’s funny” he famously remarked to his assistant. Fleming’s discovery led to the development of the antibiotic penicillin. The discovery was a medical breakthrough for the treatment of many illnesses caused by bacteria. Today, modern antibiotics are still tested using a method similar to how Fleming discovered penicillin.

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

moor frog with eggs

Fleming received many awards A Closer Look for his hard work and scientific Nobel Prize discoveries including the Arth ropod Life Cycles in Physiology or Medicine in 1945. After hatching, most arthro pods do not resemble their parents. The young, called larvae, go through a series of chang es in a process called metamorphosis. During metamorphosis, a larva goes into an inactive pupa stage. When an arthropod emerges has all of the characterist from the pupa, it ics of its parent. 31 The life cycle of a mosqu ito goes through four distinct phases – egg, larva, pupa and adult. The organism looks, feeds and moves differently in each stage.

raft of eggs

egg

In the Field Inspirational sciencerelated professions to stir interest in sciencerelated careers.

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

aquatic larva

Amazing Fact! Interesting facts to build interest and enthusiasm.

ce’s flying frog

Did You Know?

tadpoles

bian comes from a Greek ns ‘double life’. This is due e cycle which, for many ns in water and moves on to reproduce sexually by external hatch from eggs.

Salamanders are amphibians that are similar in appearance to lizards. They have long, slender bodies with a tail. Caecilians are limbless, worm-like amphibians. Most live underground. spotted salamander

Most amphibians get the oxygen they need using lungs to breathe in air. Many amphibians are also able to take in oxygen through their moist skin.

main groups of amphibians. bians we are most familiar with. short bodies with powerful hind about on land and in water. in appearance to frogs, but and rougher skin.

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

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

Some poison dart frogs carry their young on their backs to a source of water.

What are the characteristics of amphibians?

AB Activity 3.12 85

Science Words

12.

Use the words to comp

lete the sentences.

biotic factors abiotic factors individual population community

producer consumer primary consumer secondary consumer tertiary consumer

13.

decomposers food chain food web energy pyramid

14.

An animal that feeds

on a producer is a

on primary consumers

is a

An is a model that shows how much energy is availa each level in an ecosy ble at stem.

Review

break down organic mater ial and absorb the broken down remains.

List three biotic factor s you would expect to find in a tropical rainforest ecosystem.

A is an organism that gets energy by eating other organisms.

List three abiotic factor s you would expect to find in a tropical rainforest ecosystem.

An animal that feeds

is an organism that make s food through photosynthe sis. on secondary consumers is a . 5. A single organism in an ecosystem is called an . 6. All of the organisms in an ecosystem are called . 7. All of the non-living things in an ecosystem are called . 8. All of the organisms of the same kind that interact and reproduce within an ecosystem make up a .

An animal that feeds

A is a model used to show the interconnected food in an ecosystem. chains

10. A is a simple and often graphical model that energy and nutrients shows how flow through an ecosy stem. Think Deeply 11. A consists of all of the interac Mosqu itoes are within ting popula insects that an ecosystem. tions can spread

diseases to humans. Female Anophe les mosquitoes can spread the disease malaria which infects more than 200 million people every year. How can learning about the life cycle of Anopheles mosquitoes help control the spread of malaria?

1 12

Draw and label a simple diagram to show an individ and a community in a ual, a population grassland ecosystem.

What role does each

(a) hawk

organism play in a desert

(b) rattlesnake

What does a food web

How is an energy pyram

(d) wood rat

web?

Explain how all of the food within an Arctic Ocean ecosystem can be traced back to the energ y in sunlight.

Riley thinks most of the material for plant growt h comes from the soil. Do you think Riley is correc t? Explain your answe r.

1 13

A female Anopheles mosqu ito feeding on human blood.

emerging adult

aquatic pupa

Go Online! Watch a video about the life cycle of a mosquito on the NGScience website. QuickCode: V1J4

Links students to the Next Generation Science Activity Book at the appropriate juncture.

ecosystem?

show? id different from a food

AB Activity

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

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

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

Contents

Unit 6 - Earth’s Systems Earth’s Spheres Earth’s Cycles Review

Unit 7 - Space Movements of the Earth Movements of the Moon The Sun The Solar System Beyond the Solar System Review

2 4 18 29

32 34 38 40 42 56 63

Unit 8 - Forces and Interactions

Describing Motion Forces Contact Forces Non-contact Forces Laws of Motion Review

68 73 78 84 89 95

Unit 9 - Matter and Materials Properties of Materials What Is Matter? Changes in Matter Mixtures and Solutions Review

Unit 10 - Energy Energy What Is Energy? Thermal Energy Light Review

96 98 106 110 116 125

124 126 128 132 141 153

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Science Skills Scientists ask questions about the world around them. To find the answer to these questions, scientists use special skills to collect, analyze and interpret data. They communicate the things they find out. Let’s look at how you can use these skills so you can be a scientist too.

Observing You make observations when you gather information about something using your senses. You can observe how something looks, feels, sounds, smells or tastes. Scientists often use tools and instruments that allow them to observe things closely. Such tools include hand lenses, microscopes and telescopes. It is important to accurately record your observations in a way that can be easily understood by others. You can make notes, and create charts and tables. You can also draw and label diagrams.

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Comparing and Classifying Scientists compare the things they observe. To compare means to observe the properties or characteristics of two or more things and identify their similarities and differences. Classification is the process of placing things into groups based on similarities in their properties or characteristics. Objects around us can be classified by the properties of the materials they are made of. Organisms can be classified by their features, such as the presence or absence of a backbone.

Measure Measuring is an important science skill. It allows you to quantify your observations. Distance, time, volume, mass and temperature are some quantities that can be measured. To measure accurately, you often need to use tools such as rulers, beakers, thermometers and stopwatches.

Make a Model Scientists often construct models to predict, test and observe real-life phenomena. Models can be physical objects, such a model of a miniature wind turbine to simulate electricity generation or a model of the Earth’s surface to simulate weathering and erosion. Models can also be in the form of diagrams. A food web diagram is a model that shows the flow of energy in an ecosystem. A map is a diagrammatic model of an area of land or water.

Infer You infer when you make a guess about something based on what you know or what you observe. If you see footprints in the snow, you can infer that an animal has passed by after the last snowfall. If you discover an animal jaw bone with large canine teeth, you can infer that the animal likely ate other animals.

Communicate You communicate when you show or tell other people what you find out. Communication can be in the form of a written report, visual displays or an oral presentation.

Scientific Method Scientists ask questions based on observations of the world around them. To find the answers to their questions, they carry out tests and investigations following the scientific method. Why is it useful for scientists to follow the same scientific method?

The scientific method is a logical set of steps that is followed to help guide an investigation. It also helps to ensure the investigation is carried out fairly and in a manner that can be understood and repeated by other scientists.

Make Observations The scientific method begins by making observations about the world around you. You may observe that plants in one area grow faster and taller than plants in other areas. You may notice that you feel hotter in a darker-colored shirt than a lighter-colored shirt. You may observe that ice melts faster in a cup made of one material than a cup made of another material. Such observations lead you to ask questions about why these things occur.

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Ask Questions Before a science investigation begins, it’s important to ask questions about what you would like to find out. Asking questions helps you to define the investigation. Your investigation should be designed to find the answer to your questions. You can also use prior knowledge and experiences to provide possible answers to your questions.

Why does warm water cool faster in a metal cup than in a foam cup? Do plants grow taller when fertilizer is added to soil?

Why do amphibians live near water?

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Make a Prediction Once you have asked questions based on your observations, it’s time to make a prediction and form a hypothesis. A hypothesis is a statement about what you think your investigation will show. A hypothesis is more than just a guess. It is a statement based on knowledge you already have or things you have observed in the past. Based on past gardening experience, you may predict that plants will grow faster and taller in humus-rich potting soil than in sandy soil. Based on a previous investigation, you may already know that metal is a better conductor of heat compared to wood or plastic. These past experiences can help you predict the results of an investigation. Why is it important to write a procedure that can be easily followed by others?

Plan and Carry Out an Investigation Once you have stated your hypothesis, it’s time to plan and conduct an investigation that will test your prediction. In planning your investigation, you should include all the materials you will need and a procedure that clearly shows the steps you will take to conduct the investigation. Your materials and procedure should be written in a way that allows the investigation to be easily followed and repeated by others. In your procedure, include the data you will collect and the way it will be recorded.

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Variables An important part in a science investigation are variables. A variable is any factor that can be controlled or changed during the investigation. There are three main variables – the independent variable, the dependent variables and the controlled variables. The independent variable is the one condition in the investigation that you can change. Usually it is the thing that is being tested. If you were investigating which materials are good conductors of heat, the independent variable would be the type of material. The dependent variable is the factor that you measure or observe. The dependent variable should change due to changes in the independent variable. In an investigation on materials that are good conductors of heat, the dependent variable could be temperature of water in a cup. You would expect the temperature of the water to change as you change the independent variable – the type of material the cup is made of.

Imagine conducting an investigation about the growth rates of different seedlings. What would be the independent variable? What would be the dependent variable?

Imagine you were carrying out an investigation into the effect of temperature on plant growth. What would be your controlled variables?

The controlled variables are variables that do not change during the investigation. Controlled variables could include the type and size of a container, the source and temperature of water and the types of instruments used to take measurements. The purpose of the controlled variables is to ensure that the only influence on changes in your observations is due to the independent variable.

Collecting and Recording Data Make observations and collect data as stated in your procedure. The data should be recorded in an organized way that can be read and understood by others. Often, data is recorded in a visual manner, such as charts, graphs and diagrams. Data can also be entered into computer software which can make it easier to analyze and present the data.

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Analyze and Interpret Data Once your observations have been accurately recorded, it’s time to analyze and interpret the data to see if your hypothesis is supported. You analyze when you look closely at recorded data. You look for patterns to help explain your results. A pattern is when data repeats in a predictable way. You interpret when you understand and explain what the data means. In interpreting data, you use your prior knowledge, experience, and skills to explain patterns and trends identified in the analysis of the data. An important part of analyzing and interpreting is to check the accuracy of the data collected. If there are inaccuracies or inconsistencies in the data, you may need to adjust your procedure and repeat the investigation.

Draw a Conclusion By analyzing and interpreting your data, you reach a conclusion. Your conclusion is a summary of the data collected. Your conclusion should indicate the accuracy of your prediction. Your conclusion should state whether your hypothesis was supported or not supported. If your hypothesis was not supported, you may decide to form a new hypothesis and plan and conduct a new investigation. If your hypothesis was supported, you may wish to do further investigations to confirm the results or improve the accuracy of the data collected.

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Communicate The final step in a science investigation is to communicate your findings to others. This allows you to share what you have discovered and also allows others to assess the accuracy of your investigation. The people you communicate your results with may wish to conduct a similar investigation and compare results. They may also wish to conduct further investigations to find out more. If they do, they’ll also communicate their results so others can learn from their investigations too.

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Scientific Method Flowchart Make Observations

Ask Questions

Construct Hypothesis Plan and Conduct Investigation Analyze and Interpret Data Form a Conclusion Hypothesis Not Supported

Hypothesis Supported

Communicate Results

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Science Safety In the Laboratory

Follow these safety rules when in your science laboratory or when carrying out any science investigation. o not enter the laboratory without D a teacher. ollow your teacher’s instructions. F If you have any questions or are unsure of what to do, raise your hand and ask your teacher. o not eat, drink, play or run in D the laboratory. ash your hands with soap when W entering and before leaving the laboratory. Dry your hands properly, especially if you will be working with electrical equipment. If any chemical or hazardous material gets on your hands, inform your teacher immediately. ear appropriate safety gear when W carrying out scientific investigations. Safety gear includes a lab coat, safety goggles and gloves. Tie long hair back and do not wear open-toed shoes. e careful when handling sharp tools B or working with burners and hot substances.

o not panic if an accident occurs. D Be aware of eyewash stations, fire extinguishers, exit doors and other safety equipment and procedures in case of an emergency. eep your workspace clean and K organized. Report any spills or breakages to your teacher. Clean up any spills straight away and dispose of the cleaning products safely. hen cleaning up, ensure all W materials and substances go into the correct bin or container. Do not pour any liquid down the sink unless your teacher has instructed you to do so. ook after the equipment you use and L return it to its proper location in the same condition you received it. Wipe your workstation down after use.

In the Field ake sure you are accompanied by an M adult when on field trips or doing other activities outside of the schoolyard. n long trips, make sure you take O enough water and food. Bring insect repellent if necessary. n sunny days, take Sun protection such O as a long-sleeved shirt, hat and sunscreen.

Try This! Create a poster of the rules to be followed in your science laboratory or classroom. Display the poster in a place for everyone to see.

o not touch plants, animals or other D organisms unless instructed to do so by your teacher.

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Earth’s Systems

In this chapter you will ... • list and describe the Earth’s four main spheres. • use models to describe how parts of an individual Earth sphere work together to affect the functioning of that Earth sphere. • identify and describe relationships within and between the Earth’s main spheres. • develop models to describe the interactions that occur between the Earth’s spheres.

What are Earth’s main spheres? What makes up each sphere?

What interactions occur between Earth’s main spheres?

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

Earth’s Spheres The Earth is a complex system. Interactions are continually occurring between the land, water, air and its organisms. Scientists divide the Earth into four subsystems, called spheres. The four main spheres are the geosphere, hydrosphere, atmosphere and biosphere.

The geosphere consists of all of the rock on Earth. This includes the interior of the Earth and its rocky surface.

All of the water on Earth makes up the hydrosphere. This includes all of the salt water, fresh water, groundwater, ice and water vapor in the air.

The layer of gases surrounding the Earth is called the atmosphere. The atmosphere stretches from the Earth’s surface to a height of about 10,000 kilometers (6,214 mi). It is the barrier between the Earth and outer space.

Go Online! Watch an introductory video about Earth’s main spheres on the NGScience website. QuickCode: D5H3

All of the organisms on Earth, from bacteria and other microorganisms to the great variety of plants and animals, make up the biosphere.

Activity 6.1

The Geosphere Did You Know? There are eight planets in our solar system. The four planets closest to the Sun, which includes Earth, are called rocky planets as they are comprised mostly of rock and have a well-defined geosphere. The four planets furthest from the Sun are called gas giants. They lack a well-defined geosphere and are composed mostly of gases.

The geosphere is all of the rock and the inorganic parts of soil on Earth. It includes all of the layers of the Earth from the crust to the inner core. It includes the massive tectonic plates and all of the rocks and minerals beneath them, in both solid and molten form. The parts of the geosphere we are most familiar with are the Earth’s rocky surface and sea floor, along with their landforms. The geosphere interacts with the other Earth systems in many ways. It interacts with the biosphere by providing different amounts of minerals in soil and determining the dominant types of vegetation.

It interacts with the hydrosphere as it directs precipitation down mountains into rivers, streams, groundwater and the ocean. In doing so, the moving water weathers and erodes parts of the geosphere. The geosphere interacts with the atmosphere when wind and chemicals in the air weather and erode rocks. Volcanoes are part of the geosphere. Volcanic eruptions can change the composition of the atmosphere when they release gases and ash into the air. In what other ways does the geosphere interact with Earth’s other spheres?

Activity 6.2

How do people and other organisms interact with the geosphere?

The Hydrosphere

Go Online! Learn more about what makes up the hydrosphere in a video on the NGScience website. QuickCode: S2N7

Niagara Falls

The hydrosphere is the combined mass of all the water on Earth. This includes water in all three states of matter – solid (ice), liquid (water) and gas (water vapor). The vast majority of the hydrosphere is salt water in the ocean, which accounts for about 97.5% of all water on Earth. About 2.5% of water in the hydrosphere is fresh water. Most of this fresh water, about 69%, is frozen at the Earth’s poles, as permanent snow cover or held in glaciers. Groundwater accounts for about 30% of the fresh water in the hydrosphere. The remaining fresh water, less than 0.5%, is found in streams, rivers, lakes and stored water in reservoirs.

The hydrosphere is continually interacting with Earth’s other systems. It shares part of the atmosphere as water vapor in the air. It also interacts with the atmosphere as water moves in a repeating pattern from the surface of the Earth, into the atmosphere and back to Earth – a process called the water cycle. The hydrosphere interacts with the geosphere when the processes of sea floor spreading and the movement of tectonic plates change the shape and positions of water sources. It also interacts with the geosphere as precipitation and the movement of water shapes the Earth’s surface through weathering, erosion and deposition. The hydrosphere interacts with the biosphere when the distribution of water determines the types of organisms living in different regions of the Earth. In what ways do humans interact with the hydrosphere?

Activity 6.3

The Atmosphere

Go Online! Take a journey from the Earth’s surface through the atmosphere on the NGScience website. QuickCode: A6R6

The Earth’s atmosphere is the layer of air that surrounds the Earth. It is held in place by Earth’s gravitational force. Scientists divide the atmosphere into different layers. The air in the layer closest to the surface of the Earth is being pressed by the layers of air above it. This means the air pressure in the layer closest to the surface of the Earth is higher than the air pressure in the layers above it. The air in the atmosphere consists mostly of the gases nitrogen (78%) and oxygen (21%). There is also argon (0.93%), carbon dioxide (.04%) and smaller traces of other gases. Argon, carbon dioxide and other gases (1%) Oxygen (21%)

Nitrogen (78%)

composition of air in the atmosphere

The atmosphere interacts with all of Earth’s other systems. It absorbs damaging ultraviolet light from the Sun and enables the biosphere to flourish. It also helps to absorb heat from the Sun thereby reducing the temperature difference between day and night. The Earth’s atmosphere provides the organisms that make up the biosphere with the air they need to survive. It provides organisms with the oxygen they need to get energy from food – a process called respiration. It provides plants and other photosynthesizing organisms with the carbon dioxide they need to make food. The air pressure created by the atmosphere allows water to exist in its liquid form. The atmosphere interacts with the hydrosphere through the movement of water in the water cycle and the creation of weather patterns such as sea breezes.

Did You Know? A weather balloon is a device used by scientists to gather information about the Earth’s atmosphere. They carry a range of instruments as high as 40 kilometers (25 miles) above the Earth’s surface and send back data on air pressure, temperature, wind speed and humidity.

Think Deeply Why do spacecraft heat up when re-entering the Earth’s atmosphere? What do spacecraft have to protect them from burning up?

The atmosphere interacts with the geosphere when wind and the heating and cooling of rocks cause weathering and erosion. Geosphere features, such as mountains, can affect atmospheric conditions which cause changes in weather patterns. How does the atmosphere interact with the hydrosphere?

A Closer Look

Layers of the Atmosphere Scientists divide the Earth’s atmosphere into layers based on the properties of air. The lowest layer of the atmosphere, called the troposphere, is the part that contains life. It stretches from the Earth’s surface to a height of about 20 kilometers (12 miles). Air pressure and temperature in the troposphere decreases with height. The troposphere contains about 75% of all of the air in the atmosphere and almost all of the water vapor. Clouds and precipitation take place in the troposphere. Above the troposphere lies the stratosphere, which stretches from about 20 to 50 kilometers (12 to 31 miles) above the Earth’s surface. This layer contains ozone – a gas composed of three oxygen atoms. exosphere

thermosphere

mesosphere

stratosphere troposphere

Ozone absorbs heat from the Sun along with harmful ultraviolet light. Due to the absorption of light and heat, the temperature in the stratosphere increases with height, while the air pressure decreases. Above the stratosphere is the mesosphere, which stretches from about 50 to 90 kilometers (31 to 56 miles) above the Earth’s surface. Air temperature in the mesosphere is the coldest in the atmosphere with a temperature of about –90°C (–130°F). Air temperature in the mesosphere decreases with height until reaching the next layer, the thermosphere, stretching from about 90 to 700 kilometers (56 to 435 miles). Air temperature is at its hottest in the thermosphere and increases with height. The outermost layer is the exosphere. The exosphere is the boundary between the Earth’s atmosphere and outer space. Air is very thin in the exosphere and the force of the Earth’s gravity is very weak. How does the atmosphere change with altitude?

Activity 6.4

Go Online! In the 1970s, scientists discovered that certain ozone-depleting chemicals used by people were lowering the amount of ozone in the stratosphere. This was causing an increase in the amount of harmful ultraviolet light reaching the Earth’s surface. Head to the NGScience website to discover how scientists and the international community came together to overcome this problem. QuickCode: K8C2

The Biosphere The biosphere is a system on Earth that makes the Earth a very unique planet. The biosphere includes all of the living organisms on a planet and so far, no other planet in our solar system and beyond is known to have a biosphere. The biosphere stretches to all parts of the Earth where life can be found. From top to bottom, the biosphere stretches for about 20 kilometers (12 miles). Almost all of life exists between a few hundred meters below the surface of the ocean to an altitude of about 5 kilometers. Life exists on and under the Earth’s surface, in water and in the air, so the biosphere continually interacts with all of the other Earth systems. Plants interact with the geosphere as their roots grow in soil and take in nutrients. Animals and bacteria living beneath Earth’s surface change the composition of soil.

Fungi decompose organic material and introduce nutrients back into the soil. Animals such as rabbits and wombats interact with the geosphere when they dig burrows. Bats living in caves is another example of biosphere and geosphere interactions. Plants in the biosphere interact with the atmosphere as they exchange gases during photosynthesis. Phytoplankton and other photosynthesizing marine organisms also interact with the atmosphere as they use the energy in sunlight to photosynthesize. They take in carbon dioxide and produce oxygen as a byproduct. Animals take in oxygen from air and release carbon dioxide when they exhale. Plants interact with the water cycle when they take in water through their roots and release water vapor into the air through their leaves. Plants and animals that live in rivers, lakes and oceans are constantly interacting with the water cycle. Discuss why the biosphere is also part of the geosphere, hydrosphere and atmosphere.

Activity 6.5

A Closer Look

Earth’s Biomes Climate describes the average weather conditions in an area over time. Climate is often described in terms of the amount of precipitation and the average temperature. Climate is different in different regions of the world. Tropical rainforests close to the equator receive high amounts of precipitation and warmth all year round. Other regions may experience different amounts of precipitation and temperatures from season to season. Some regions are cold and dry all year round.

tropical rainforest tropical grassland desert temperate forest temperate grassland boreal forest tundra polar ice

The climate of a region determines the types of organisms that survive there. Scientists classify the Earth’s land surface into biomes. A biome is a region that is characterized by its climate, vegetation and the organisms that can be found there. Organisms in each biome have adaptations that allow them to survive in their biome’s climate. Generally, Earth’s biomes occur in patterns, depending on distance from the equator. Biomes close to the equator include tropical rainforests and tropical grasslands. Further from the equator are deserts, temperate forests and temperate grasslands. Biomes far from the equator and close to the North Pole include boreal forests, tundra and polar ice.

Activity 6.6 17

Earth’s Cycles Earth’s spheres are continually interacting in many ways. These interactions enable the Earth to function as a complete system. Let’s take a look at some of Earth’s main cycles – the carbon dioxide-oxygen cycle, the water cycle, the carbon cycle, the nitrogen cycle and the rock cycle.

Animals take in oxygen and release carbon dioxide into the atmosphere.

Carbon Dioxide-Oxygen Cycle During photosynthesis, plants and other photosynthesizing organisms take in carbon dioxide from the air. The energy in sunlight, carbon dioxide and water are used to produce food in the form of sugar. Oxygen is produced as a by-product of photosynthesis and is released into the air.

Plants take in carbon dioxide to produce food through photosynthesis.

Amazing Fact!

Oxygen is produced as a by-product of photosynthesis and is released into the atmosphere.

Phytoplankton are microscopic photosynthesizing organisms found in salt and fresh water sources in the hydrosphere. They form the base of almost all marine ecosystems and play a vital role in the carbon dioxide-oxygen cycle.

Most organisms need oxygen to break down and release the chemical energy in food through a process called cellular respiration. The chemical energy is used to carry out life functions in the cells of the organism. Cellular respiration takes place in the cells of plants, animals, fungi and protists. During cellular respiration, carbon dioxide is produced as a by-product and is released into the air. By looking at the needs of organisms in the biosphere, we can see that carbon dioxide and oxygen move between organisms and the atmosphere in a cycle. This cycle is often referred to as the carbon dioxide-oxygen cycle.

Activity 6.7 19

The Water Cycle Although water is used by people and organisms in many ways, the amount of fresh water on Earth is the same today as it was millions of years ago. How is this so? Fresh water is constantly moving in a repeating pattern between the Earth’s hydrosphere, biosphere, geosphere and atmosphere in a process 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 and condenses into water droplets and tiny ice crystals. These droplets combine together and join with other particles to form clouds.

Go Online! Watch the water cycle in action in an animated video on the NGScience website. QuickCode: M5T5

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. People and many animals also release water vapor when they exhale.

As more water droplets combine, they get larger. When they are too large to remain in clouds, they eventually fall back to Earth as precipitation. Precipitation is any product of the condensation of atmospheric water vapor that is pulled by the gravitational force of the Earth from clouds to the surface of the Earth. Precipitation may be in the form of rain, snow, hail or sleet.

The water flows through streams and rivers and collects in groundwater, lakes and the ocean. When the air temperature increases, water held in ice, snow and glaciers begins to melt and moves into fresh water sources and the ocean.

Activities 6.8 – 6.9

Carbon Cycle Carbon is the foundation of all life on Earth. It is an element that forms part of the bodies of all organisms and is one of the most common elements on Earth. It is present in the geosphere where it is found underground, in soil and in rocks. It is part of the hydrosphere and atmosphere where it exists as carbon dioxide. However, carbon from these sources cannot be used by people, animals and other nonphotosynthetic organisms directly. So, how do these organisms get the carbon they need? The answer is the carbon cycle. The carbon cycle is the process by which carbon travels from the atmosphere to the biosphere and back into the atmosphere. During the carbon cycle, carbon is also stored in the Earth’s geosphere and hydrosphere. Plants, phytoplankton and other photosynthesizing organisms take in carbon dioxide from the atmosphere to produce and store carbonbased food in the form of sugars. atmospheric carbon dioxide

photosynthesis plant respiration

fossil fuels

organism decay

This carbon-rich food is passed to non-photosynthetic organisms when they feed on plants and other photosynthesizing organisms. During cellular respiration, energy is released from food and carbon dioxide is produced. Some carbon is stored in the body of the organism, and carbon dioxide is released back into the atmosphere. Carbon in the body of organisms does not enter and move through the carbon cycle. It is stored. The carbon in the trunk of a giant sequoia tree, for example, will be stored for as long as the tree is alive – which can be for thousands of years! When the tree dies, the carbon is recycled back into the atmosphere when the tree is decomposed by organisms such as bacteria and fungi. Decomposed organisms can also be stored deep underground as fossil fuels. The carbon in fossil fuels is released back into the atmosphere when people extract and burn the fuels.

atmospheric carbon dioxide

animal respiration

organism respiration

photosynthesizing plankton

Activity 6.10 23

Nitrogen Cycle Nitrogen is the most abundant element in our atmosphere. It makes up around 78% of the gases in air. Nitrogen is important to all forms of life. It makes up part of the genetic material in cells and is used to build proteins that perform a large range of cell functions. The nitrogen in the atmosphere cannot be used directly by most organisms. To take in nitrogen, it first must move into soil, change form and be taken in by plants. Decomposers then release nitrogen back into the atmosphere. This movement of nitrogen between the atmosphere and the soil in the geosphere is called the nitrogen cycle. Nitrogen enters the soil through decaying organisms and animal wastes.

Bacteria make nitrogen available to plants.

Essential to the nitrogen cycle are bacteria and decomposers such as fungi. Nitrogen that enters the soil from the atmosphere is changed by nitrogen-fixing decomposers into nitrogen compounds that can be used by plants. Plants take in these compounds through their roots to carry out cell processes. Animals get the nitrogen they need by consuming plants and other organisms that consume plants. Nitrogen is released back into the atmosphere by decomposers as they decompose dead organisms and their wastes.

Nitrogen is passed to animals when they consume plants and other organisms.

Bacteria convert nitrogen from the soil and release it back into the air.

Plant roots take in nitrogen.

Activity 6.11 25

Rock Cycle All of the rock in the geosphere can be classified into three main types – igneous rock, sedimentary rock and metamorphic rock. Each type of rock is formed by a different process in the geosphere. Beneath the Earth’s surface, rock in the geosphere exists as both solid rock and as molten rock called magma. Igneous rock forms when magma cools and returns to a solid state. This change of state can occur beneath the Earth’s surface. It also occurs when heat and pressure cause magma to flow onto the Earth’s surface as lava through volcanoes.

igneous rock

The continual weathering and erosion of rock on the Earth’s surface breaks down all types of rock into sediment. Over millions of years, layers of sediments form and press down on the lower layers. This pressure forms new rock called sedimentary rock. Rocks deep below the Earth’s surface are subject to immense heat and pressure. Over time, this heat and pressure cause the rock to change form. Rocks formed by this process are metamorphic rocks. Metamorphic rocks have different properties from the original rock they formed from. These processes, whereby rock is formed, broken down and made into new forms, is called the rock cycle. Which Earth systems interact during the rock cycle?

Activity 6.12

sedimentary rock

metamorphic rock

Science Words Use the words to complete the sentences. geosphere hydrosphere atmosphere biosphere biome

carbon dioxide-oxygen cycle water cycle carbon cycle nitrogen cycle rock cycle

1. The is the process by which nitrogen moves between the soil, organisms and the atmosphere. 2. The processes whereby rock is formed, broken down and made into . new forms is called the 3. A is a region that is characterized by its climate, vegetation and the organisms that can be found there. 4. The movement of gases between the atmosphere, photosythesizing organisms and animals is called the . 5. All organisms on Earth make up its 6. The

is the layer of gases surrounding the Earth.

7. All of the water on Earth makes up the

8. The is the movement of water between the hydrosphere and atmosphere. 9. The is the process by which carbon travels from the atmosphere to the biosphere and back into the atmosphere. 10. The

consists of all of the rock on Earth.

Review 1. Copy and complete the table. Earth’s Systems Sphere

Components

Geosphere Hydrosphere Atmosphere Biosphere 2. Draw a simple diagram to show the carbon-dioxide oxygen cycle. 3. True or false. Explain your answer. (a) Animals get the carbon they need when they breathe in carbon dioxide from the air. (b) Carbon enters the biosphere when plants photosynthesize. 4. How to plants get the nitrogen they need? 5. Define the Earth’s spheres and describe the relationships between them.

(a) (b) (c) (d)

The geosphere and the atmosphere. The biosphere and the atmosphere. The hydrosphere and the atmosphere. The hydrosphere and the biosphere.

In the Field

Biosphere 2 Earth is the only known place in the solar system and beyond to have a biosphere. However, Earth is actually home to a second biosphere built by humans – Biosphere 2. Biosphere 2 is a research facility built in the desert in Arizona, USA. It is a very large structure that resembles a giant greenhouse. The structure was built as a closed system which means there is no interaction or matter exchange with the outside environment. The purpose of Biosphere 2 was to demonstrate the viability of closed ecological systems to support and maintain human life in outer space.

Biosphere 2 contains seven different biomes including a rainforest, ocean, mangrove wetland, savannah grassland, desert, an agricultural area and human living quarters. In the 1990s, two missions were launched to see if humans could live sustainably inside Biosphere 2 with minimal assistance and interaction with the outside world. The first mission lasted two years with the researchers sealed inside the structure. They gathered data on how humans live and interact with the environment and the sustainability of such interactions. The mission also highlighted the complexity of Earth’s systems and spheres and how fragile they can be if not looked after.

Go Online! Take a look at the different ecosystems inside Biosphere 2 in a video on the NGScience website. QuickCode: D8L2

Space

How does the Earth, its moon and other objects in the solar system move and interact?

In this chapter you will ... • list the objects in our solar system and describe the ways in which they move. • list the different ways in which humans explore space and the ways in which the data collected is used. • represent data in graphical displays to reveal patterns of daily changes in length and direction of shadows, day and night, and the seasonal appearance of some stars in the night sky. • support an argument that the apparent brightness of the Sun and stars is due to their relative distances from the Earth.

How does the movement of the Earth affect life on its surface?

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

How does the distance of the Sun and other stars from the Earth affect their apparent brightness?

Movements of the Earth Rotation of the Earth If you observe the position of the Sun in the sky, you will notice that it rises in the east at dawn, is high in the sky at midday and sets in the west in the evening. This apparent movement is not due to the motion of the Sun, but the motion of the Earth. One way the Earth moves is by spinning on its axis. The Earth’s axis is an imaginary line that runs from the North Pole, through the Earth’s center, to the South Pole. One complete spin on its axis is called a rotation.

23.5o

The part of the Earth facing the Sun is in daytime. The part of the Earth facing away from the Sun is in night-time.

At the equator, the Earth’s spins at about 1,600 kilometers (1,000 miles) per hour. It takes the Earth 24 hours (one day) to complete one rotation. As the Earth rotates, part of the Earth is facing the Sun. This part of the Earth is lit up and experiences daytime. At the same time, the opposite side of the Earth is facing away from the Sun. This part of the Earth is in darkness and it is night-time. The rotation of the Earth also causes patterns in the different positions of the Sun in the sky. This results in predictable pattern changes in the length and direction of shadows. At sunrise, the Sun appears low in the sky. The shadows of the objects that block sunlight in the early morning are long. The shadows get shorter as the Sun rises in the sky. Shadows are at their shortest around midday when the Sun is directly above. Shadows get longer as the Sun moves lower and sets in the west.

Think Deeply Why are we not able to feel the motion of the Earth as it rotates about its axis?

Go Online! Watch the Earth’s rotation and the alternation of day and night in an animated video on the NGScience website. QuickCode: Y8H1

Activities 7.1 – 7.3 Objects cast longer shadows when the Sun is low in the sky and shorter shadows when the Sun is high in the sky.

Revolution of the Earth As the Earth rotates about its axis, it also revolves in a curved path, called an orbit, around the Sun. The Earth’s orbit is caused by the gravitational pull of the Sun. Earth orbits at a speed of about 107,000 kilometers (67,000 miles) per hour. One complete orbit of the Sun is called a revolution. It takes the Earth 365.24 days (1 year) to complete a revolution. The Earth’s axis about which it rotates is not straight up and down. It is tilted at an angle of 23.5o. This means that as the Earth orbits the Sun, one hemisphere is tilted towards the Sun and one hemisphere is tilted away from the Sun. It is a combination of the Earth’s revolution and its axial tilt that causes the change in seasons.

North Pole Spring in the Northern Hemisphere.

South Pole

North Pole

South Pole Summer in the Northern Hemisphere.

As the Earth orbits the Sun, the hemisphere tilted towards the Sun gets more direct sunlight than the hemisphere tilted away from the Sun. When the Northern Hemisphere is tilted towards the Sun, it gets more direct sunlight and experiences summer. At the same time, the Southern Hemisphere is tilted away from the Sun and gets less direct sunlight. It experiences winter.

Try This! As the Earth orbits the Sun, the number of daylight hours changes. Conduct your own research to find out the average number of daylight hours in each month in your area. Represent the data in a bar graph or line graph.

When the Southern Hemisphere is tilted towards the Sun, it is in summer, while the Northern Hemisphere is in winter.

Go Online!

During fall and spring, both hemispheres receive similar amounts of sunlight.

Observe how the Earth’s tilted axis causes changes in seasons in an animated video on the NGScience website. QuickCode: E3X5

What causes the change in seasons?

Activity 7.4 Winter in the Northern Hemisphere. North Pole

South Pole

North Pole

South Pole

Fall in the Northern Hemisphere.

Go Online! Watch the moon in motion in an animated video on the NGScience website. QuickCode: W9C5

Movements of the Moon At night, the moon is often visible as the largest and brightest object in the sky. It appears to be much larger than the stars around it. This is because the moon is much closer to the Earth than the stars. The small and sometimes faint stars you see in the night sky are much larger than the moon. They appear smaller and less bright because they are much further away. Just as the Sun’s gravity causes the Earth to orbit the Sun, the Earth’s gravity causes the moon to orbit the Earth. It takes the moon about 27.3 days to revolve once around the Earth. It also takes the moon about 27 days to rotate once on its axis. This means the side of the moon facing the Earth is always the same. The moon is not a source of light. We see the moon in the sky because it reflects the light from the Sun. If you observe the moon at different times of the month, you will notice it appears to change shape. The apparent changes in shape, called phases of the moon, are caused by different amounts of the moon reflecting the light from the Sun.

Try This! Form groups of three students. Assign each member of your group the role of the Sun, Earth and moon. Act out the different way the objects move. Swap roles.

Scientists have names for the moon at different times of the month based on the moon’s movement and the amount of light it is reflecting. During waxing phases of the moon, the lit up part of the moon we see increases in size until we see a full moon. During waning phases of the moon, the lit up part of the moon we see decreases in size until there is a new moon. We cannot see a new moon because the lit side of the moon is facing away from the Earth.

A Closer Look

Phases of the Moon First Quarter

Waxing Gibbous

Waxing Crescent

Full Moon

New Moon

Waning Gibbous

Waning Crescent

Third Quarter

Activity 7.5 39

The Sun

Think Deeply Why are we not able to see stars other than the Sun in the sky during the day?

Amazing Fact! The Sun is hot – really hot! The innermost layer of the Sun, its core, reaches temperatures of about 15,000,000oC (27,000,000,000oF). The surface of the Sun is about 6,000oC (10,800oF).

If you look into the night sky on a clear night, you are likely to see many stars. A star is a very large, hot ball of glowing gases that is held together by gravity. Stars give out large amounts of light and heat. The Sun is a star. It is the nearest star to Earth – about 150 million kilometers away. Scientists use this distance as a benchmark unit called an astronomical unit (AU). AU is used to measure other distances in the solar system. Our Sun may appear as the largest and brightest object in sky during the day, but compared to other stars, the Sun is medium-sized. The size of other stars we can see from Earth at night only appear small and less bright due to their great distance from the Earth. The further a star is from the Earth, the smaller and less bright it appears. The light and heat produced by the Sun is caused by nuclear reactions in its core. The immense amount of light and heat produced is enough to light up the Earth during the day and keep the planet warm enough for organisms to survive. Without the light and heat from the Sun, there would be no life on Earth.

Why does the Sun appear to be much larger and brighter than the stars we see at night?

Activity 7.6

A Closer Look

Structure of the Sun core radiative zone convection zone

photosphere

chromosphere

The Solar System A satellite is any object that orbits a central star or planet. In our solar system, the Sun is the central star. The satellites orbiting the Sun include the eight planets, their moons and other objects such as comets, asteroids and man-made objects. The largest satellites in our solar system are the eight planets. In order of their distance from the Sun, the four closest planets are Mercury, Venus, Earth and Mars. These planets are called the inner planets or terrestrial planets. They are made up mostly of rock and are similar in size to the Earth. Due to their close distance to the Sun, the inner planets are also much warmer than the planets further from the Sun.

Mars

Venus

Mercury

Earth

How are the other inner planets similar to Earth?

The outer planets are the four furthest planets from the Sun – Jupiter, Saturn, Uranus and Neptune. These planets are much larger than the inner planets and are not rocky. Jupiter and Saturn are made up mostly of gases such as hydrogen and helium and have dense atmospheres. They are called gas giants. Uranus and Neptune are made up of heavier substances referred to as ‘ices’ and are classified together as ice giants.

Neptune

Saturn

Uranus

Jupiter

In what ways are the inner planets different from the outer planets?

Mercury

The Inner Planets Think Deeply What characteristics of Mercury and Venus make them unsuitable to support life?

Venus

Mercury is the nearest planet to the Sun. It is also the smallest planet in the solar system with a diameter of 4,880 kilometers (3,032 miles). Mercury’s orbit around the Sun takes 87.97 Earth days, which is the shortest of all the planets in the solar system. Mercury has a rocky surface and no atmosphere. It has many craters formed by meteorites crashing into its surface. Venus is the second closest planet to the Sun. It has a diameter of 12,104 kilometers (7,521 miles) and completes an orbit of the Sun in 224.7 Earth days. Venus has a dense atmosphere that traps the heat from the Sun. This makes it the hottest planet in the solar system with temperatures of up to 471°C (880°F) during the day.

Earth is the third planet from the Sun. The Earth’s atmosphere makes the conditions on Earth suitable to support life. Ozone in the atmosphere helps to block harmful ultraviolet rays from reaching the surface. The Earth’s atmosphere also helps to regulate the temperature on its surface where water exists in three states – as the gas water vapor, liquid water and solid ice. Earth has a diameter of 12,742 kilometers (7,918 miles) making it the largest of the inner planets. Mars is the fourth planet from the Sun. It is often called the red planet due to its red, rocky surface. Mars has a diameter of 6,779 kilometers (4,212 miles) and completes an orbit of the Sun in 687 Earth days. Mars has a thin atmosphere made up mostly carbon dioxide. It has two moons – Phobos and Deimos. What characteristics do the inner planets share?

Activity 7.7 Mars

Earth

Go Online! On February 18, 2021, the NASA rover, Perseverance, landed on the surface of Mars. Its mission is to search for signs of ancient life and to collect rock samples to send back to Earth. On board Perseverance is a small robotic helicopter, Ingenuity. Its first successful flight on April 19, 2021, was the first powered flight on a planet other than Earth. Discover more about the adventures of Perseverance and Ingenuity on the NGScience website. QuickCode: G8Y5

Did You Know? Jupiter and Saturn are often called gas giants due to their composition of gases.

Jupiter

The Outer Planets Jupiter is the largest planet in the solar system with a diameter of 139,820 kilometers (86,880 miles). Its mass is more than two and a half times that of all the other planets in the solar system combined. It takes Jupiter and its 79 known moons 11.86 Earth years to complete a revolution of the Sun. Like the other outer planets, Jupiter does not have a well-defined solid surface. It is made up mostly of the gases hydrogen and helium. Saturn is the sixth planet from the Sun. It is often called the ringed planet due to its spectacular ring system. Saturn is the second largest planet in the solar system with a diameter of 116,460 kilometers (72,365 miles). Like Jupiter, Saturn is made up mostly of the gases hydrogen and helium. It takes Saturn 29.46 Earth years to complete a revolution of the Sun.

Saturn

Uranus

Uranus has a diameter of 50,724 kilometers (31,518 miles). It takes Uranus 84 Earth years to complete a revolution of the Sun. Uranus is made of water, methane and ammonia that surround a small rocky core. The atmosphere of Uranus consists of hydrogen and helium, along with methane which gives the planet its blue color. Uranus has 27 known moons. Neptune is the furthest planet from the Sun and has a similar atmosphere and composition to Uranus. It has a diameter of 49,244 kilometers (30,599 miles) and orbits the Sun once every 165 Earth years. Neptune has 14 known moons. How are the surfaces of the outer planets different from those of the inner planets?

Activities 7.8 – 7.9

Go Online! Learn more about the planets by taking a virtual trip through the solar system on the NGScience website. QuickCode: W1J4

Did You Know? Beyond Neptune, at a distance of 39.5 astronomical units from the Sun, lies Pluto. Prior to 2006, Pluto was classified as a planet. However, after looking at differences in its orbit and size, scientists reclassified Pluto as a dwarf planet.

Neptune

Other Bodies in the Solar System Did You Know? The Hale-Bopp comet was discovered separately by the astronomers Alan Hale and Thomas Bopp on July 23, 1995. In 1997, the Hale-Bopp comet became visible to the naked eye on Earth for a record 18 months. It will return to the inner solar system around the year 4385.

Besides the eight planets and their moons, there are many other objects in the solar system that are in orbit around the Sun. Comets are orbiting bodies comprised of frozen gases, rock, ice and dust. When a comet passes close to the Sun, heat causes it to release gases. This forms a tail of gases called a coma. The size of most comets ranges from around 700 meters to 20 kilometers.

Hale-Bopp comet

Think Deeply Halley’s Comet takes about 76 years to complete an orbit of the Sun. It was last seen by the naked eye from Earth in 1986. When will Halley’s Comet be visible to the naked eye from Earth in the future?

One of the most commonly found objects in space are asteroids. Asteroids are large rocks orbiting the Sun. They range in size from just a few meters up to hundreds of kilometers. Most asteroids orbit the Sun in an asteroid belt between the planets Mars and Jupiter.

asteroids

The largest asteroid observed in the asteroid belt is Ceres, which is also classified as a dwarf planet. It has a diameter of 940 kilometers (580 miles). Asteroids and comets often break up into smaller pieces and form meteoroids. Meteoroids have a size ranging from a grain of sand to one meter. If a meteoroid enters Earth’s atmosphere, it becomes known as a meteor. Most meteors burn up completely before reaching the Earth’s surface. The shooting stars we see at night are most likely meteors burning up in the Earth’s atmosphere. Occasionally, a meteor doesn’t burn up completely as it enters the atmosphere. A meteor that reaches the Earth’s surface is called a meteorite.

Ceres

Go Online! Discover more about comets, asteroids, meteoroids, meteors and meteorites on the NGScience website. QuickCode: V8H8

meteor

communication satellite

Like the planets and their moons, comets, asteroids and meteoroids are natural satellites. There are also many artificial satellites orbiting the Sun. An artificial satellite is a man-made object that is launched into space by people and enters the orbit of a body in space. Artificial satellites can orbit the Sun, Earth, other planets or moons. Communication satellites are artificial satellites that are used to receive and send data to and from the Earth. They can be used for weather forecasting, sending digital signals and can provide us with accurate information about locations on Earth. Some artificial satellites are used to observe and gather data about other objects in the solar system, such as planets, moons and the Sun. Space telescopes are man-made satellites in space. They enable astronomers to see things further away than most telescopes on Earth.

Activity 7.10

Hubble Space Telescope

One of the largest space telescopes is the Hubble Space Telescope. It was launched into low Earth orbit in 1990 and has allowed astronomers to gather high resolution images of deep space. People often go on missions aboard spacecrafts launched into space by powerful rockets. Some people spend extended periods of time in space living in space stations such as the International Space Station (ISS). The ISS is the largest man-made object in space. Discuss the ways in which people use artificial satellites in space.

Did You Know? The Hubble Space telescope is scheduled to be succeeded by the James Webb Space Telescope (JWST) in 2021. The JWST is a joint collaboration between the space agencies of the USA, Europe and Canada. The JWST is much larger than Hubble and will be used to observe much deeper into space.

Space Exploration Think Deeply One of the largest radio telescopes on Earth is the Five-hundred-meter Aperture Spherical Telescope (FAST), in China’s Guizhou province. As its name suggests, the telescope consists of a large dish with a diameter of 500 meters (547 yards). Among other tasks, the telescope is used to search for signs of life in distant galaxies. The telescope is surrounded by a five-kilometer (3 mi) ‘radio silence’ zone in which radio wave-emitting devices such as mobile cell phones are prohibited. Why do you think such devices are prohibited?

People have been exploring space for hundreds of years. Until the first rockets were sent into space in the 1950s, most space exploration was done from Earth using telescopes. Advances in science and technology have since allowed humans to develop more powerful telescopes and send many objects into space to collect data about the objects in space, their properties and the patterns in which they move. The first telescopes used to observe objects in space were light telescopes. They used a series of lenses to refract or reflect light to magnify distant objects so they appear closer and in finer detail. When viewing objects in space from Earth, light telescopes are subject to interference from the Earth’s atmosphere. Radio telescopes are telescopes that detect radio waves given off by distant objects. Groups of dishes are often used to focus the radio waves. Receivers and computers interpret and produce images from the data. Radio telescopes do not experience interference with the Earth’s atmosphere. The Atacama Large Millimeter/ submillimeter Array (ALMA) in the Atacama Desert of northern Chile is an observatory consisting of 66 radio telescopes.

A NASA Voyager space probe.

People also use space probes to explore space. A space probe is an object launched into space that has specialized instruments on board to study various objects in the solar system. A space probe usually has a mission objective and the instruments it carries are specifically designed to achieve the mission objective. Space probes include space telescopes, robots and unmanned spacecraft. Probes send the data they collect back to Earth for analysis and interpretation by scientists. The National Aeronautics and Space Administration (NASA) has sent probes into space to collect data on all eight planets in the solar system.

Amazing Fact! The Voyager program is an ongoing NASA mission which launched two space probes into space in 1977. The initial objective of the probes, called Voyager 1 and Voyager 2, was to pass by and collect data on Jupiter and Saturn. After successfully completing their objectives, they were sent deeper into space to collect data on Neptune and Uranus. Voyager 2 is the only spacecraft to have visited both Uranus and Neptune. Much of what we know about the outer planets is due to the valuable data sent back to Earth from deep space probes such as the Voyagers and others.

Go Online! Head to the NGScience website to learn about the many space missions NASA has undertaken and the data they have provided for scientists. QuickCode: W2V9

Activity 7.11 53

People also explore space by venturing into space in spacecrafts. Scientists that travel into space, called astronauts, are highly trained in operating spacecrafts and living in space. In space, astronauts collect data and do experiments that often cannot be done on Earth. They may have a specific mission goal, such as that of the Apollo 11, a NASA mission that aimed to land the first people on the Earth’s moon. A mission that was successful when Commander Neil Armstrong became the first person to step onto the lunar surface on July 21, 1969. The Space Shuttle was a partially reusable spacecraft designed and built by NASA to transport astronauts into space and back to Earth. The Space Shuttle Program ran from 1981 to 2011 in which time there were a total of 135 missions.

Think Deeply The Falcon 9 is a rocket launch system that carries spacecraft into space. After detaching from the spacecraft, the rocket is able to re-enter the Earth’s atmosphere and land vertically. What are the advantages of a reusable launch system such as Falcon 9?

A NASA space shuttle attached to rocket boosters.

Space exploration is also done on board orbital space stations. An orbital space station is a spacecraft capable of supporting human life whilst in orbit of the Earth. Space stations usually do not have propulsion or landing systems, but instead rely on the docking of other spacecraft for the delivery of supplies and transfer of crew. The International Space Station (ISS), is a large satellite that orbits the Earth. It’s the biggest man-made object in space. Since the year 2000, up to nine scientists have been on board the ISS at any one time. They are highly-trained to live and work in space. Whilst on board the space station, the scientists carry out investigations about living in space for long periods of time. The data collected on board the ISS is sent back to Earth and shared with many different countries.

International Space Station

What are the different ways humans explore space? What types of data are collected?

Activity 7.12

Beyond the Solar System Stars On a clear day, the Sun is the brightest object in the sky. It lights up the sky and all parts of the Earth’s surface. It allows as to see things around us. When the Sun sets, the sky becomes dark. The moon can provide some light when it reflects the light from the Sun, but generally people use artificial sources of light to see at night.

Go Online! Astronomers use names such as dwarfs, giants and supergiants to classify stars by their temperature, mass and luminosity. Discover more about the different types of stars on the NGScience website. QuickCode: B6Q1

If it’s a clear night, you may see stars in the sky. However, stars are faint and do not provide enough light to see the things around you. Our Sun is a star just like the stars you can see at night. So why is the Sun so much brighter and why are the stars at night so much dimmer? The reason is distance. Compared to the Sun, the stars we see at night are much further away. So, they appear smaller and less bright. Streetlights are a good way to observe how the distance of a source of light affects its brightness. When streetlights light up a street at night, the lights that are closer are brighter than the lights further up the street. The lights are identical and have the same brightness. The lights further down the street appear smaller and less bright due to their distance from you. Why are the stars in the night sky much smaller and dimmer than the Sun we see in the sky during the day?

AB 56

Activities 7.13 – 7.14

Constellations When observing the night sky long ago, people noticed that stars appeared in groups and formed patterns. These groups of stars are called constellations. Throughout history, people have used imaginary straight lines to connect the stars to create shapes. The constellation is then given a name based on the shape formed. Many constellations have been named after mythological creatures, animals and other objects. As the Earth rotates about its axis, the constellations appear to move from east to west. As the Earth revolves around the Sun, different constellations can be visible at different times of the year.

Did You Know? Constellations have long been used for navigation purposes at sea. The North Star, for example, is located directly above the Earth’s North Pole. By knowing the direction of north, sailors were able to determine the other cardinal points.

Activity 7.15

Go Online! Discover more about the different constellations that have been named and their movements in the night sky on the NGScience website. QuickCode: C7T5

A Closer Look

Our Closest and Brightest Stars When talking about distances between planets and other bodies in our solar system, scientists often use astronomical units (AU), which is the distance between the Earth and the Sun (150,000,000 kilometers). This is equivalent to the distance light travels in about 8 minutes. The distance between stars in space is so great that scientists use the term light years. A light year is the distance light travels in one year, which is about 9.46 trillion kilometers (5.88 trillion miles). The closest star to our Sun, Alpha Centauri C (also called Proxima Centauri), is about 268,770 AU away which is 4.25 light years. Alpha Centauri C is part of the three-star Alpha Centauri star system. The other two stars that make up the system, Alpha Centauri A (Rigil Kentaurus) and Alpha Centauri B (Toliman) are approximately 4.35 light years away. When viewed by the naked eye from Earth, Alpha Centauri A and B appear as one object. Together, they are the third brightest star in the night sky. Both stars are similar to our Sun. Alpha Centauri A is slightly more massive than the Sun and about 1.5 times brighter. Alpha Centauri B has about half the mass and brightness of the Sun.

Alpha Centuari A and B

Sirius

Different stars are visible from different parts of the Earth and change as the Earth rotates and revolves around the Sun. The Alpha Centauri star system is mostly visible from the Southern Hemisphere. It is visible in the southern parts of the Northern Hemisphere in the month of May. The second brightest star, Canopus is 310 light years from our Sun. Even at such a great distance, it appears bright in the night sky as it has eight times the mass of the Sun and is approximately 10,000 times brighter. The brightest star in the night sky, Sirius, is almost twice as bright as Canopus and is about 8.6 light years from our Sun. What determines the brightness of the stars we see in the night sky?

Galaxies Go Online! Journey into deep space and discover Earth’s place in the Milky Way in a video on the NGScience website. QuickCode: H6E1

Amazing Fact! Compared with other galaxies, our Milky Way is about medium-sized. One of the largest known galaxies, IC 1101, is thought to contain over 100 trillion stars.

All of the stars you can see in the sky belong to our galaxy. A galaxy is an enormous group of stars, planets, dust and gas clouds that are held together by gravity. Our solar system belongs to the Milky Way galaxy which scientists believe contains between 100 and 400 billion stars! Our galaxy is called the Milky Way as it appears as a band of light crossing the sky at night. The universe is home to billions of galaxies that all contain billions of stars. However, galaxies beyond on our own Milky Way are very faint in the night sky. Despite their extremely large size and the billions of stars contained within them, most galaxies cannot be seen with the naked eye at night. This is because they are such a great distance from the Earth.

The average distance between galaxies is one million light years! Scientists need to use large telescopes to collect the light from these galaxies in order to see them. Galaxies come in different shapes and sizes. Our own Milky Way is a spiral galaxy. Spiral galaxies are made up of a flat, rotating disk of stars, dust and gas. Most of the matter is concentrated in the center with arms extending out. Our solar system is located on one of the arms of the Milky Way galaxy.

Did You Know? The ‘milky’ appearance of the Milky Way is due to cosmic dust. Cosmic dust are tiny pieces of solid materials floating in space. Cosmic dust plays a role in the formation of new stars, planets and other objects such as comets.

Activity 7.16

Science Words Use the words to complete the sentences. rotation orbit revolution phases of the moon

comet asteroids inner planets outer planets

orbital space station constellation galaxy

1. One complete orbit of the Sun by the Earth is called a

2. A is an orbiting body comprised of frozen gases, rock, ice and dust. It often forms a tail when passing close to the Sun. 3. The four planets furthest from the Sun are the 4. The

are the four rocky planets closest to the Sun.

is a spacecraft capable of supporting human life whilst 5. An in orbit of the Earth. 6. A group of stars is called a

is an enormous group of stars, planets, dust and gas 7. A clouds that are held together by gravity. 8. 9. An

are large rocks orbiting the Sun. is the path the Earth takes as it revolves around the Sun.

10. One complete spin of the Earth around its axis is called a 11. The is the apparent changes in the shape of the moon when viewed from Earth as its revolves around the Earth.

Review 1. Describe the movements of the Earth in space. 2. What causes the daily changes in length and direction of shadows? 3.

True or false. (a) The Earth rotates on its axis. (b) It takes the Sun one year to revolve around the Earth. (c) In our solar system, all of the planets and their moons orbit the Sun.

4. Copy and complete the table. Object

Natural Objects in Space Description

Sun planet comet asteroid 5. When does a meteoroid turn into a meteorite? 6. Why do space telescopes produce clearer images than light telescopes on the Earth’s surface? 7. Why do stars appear to move from east to west across the night sky? 8. Why are some stars only visible in the night sky at certain times of the year? 9. How does the apparent brightness of a star in the night sky relate to its distance from the Earth? 10. What is the Milky Way?

In the Field

Amateur Astronomer An astronomer is a scientist that observes objects in space such as stars, planets, moons, asteroids, comets and galaxies. Patterns in their observations allow them to model and predict the movement of objects in space. Astronomers may specialize to study certain aspects of space such as the solar system, constellations or the formation of distant galaxies. They use powerful light telescopes, radio telescopes and space telescopes to observe deep space. The data gathered by astronomers is often shared with the international community. In many cases, astronomers from different countries and space organizations collaborate in the building of observation equipment and work together to analyze the data they collect.

You don’t need to be an expert on space or know how to operate a radio telescope to be an astronomer. Most astronomers in the world are amateur astronomers. All you need to be an amateur astronomer is a clear night sky. You can use charts, smartphone applications or the Internet to help identify the objects you observe. You can observe the night sky using only your eyes. You can also take a closer look by using binoculars or a simple light telescope. So what are you waiting for? Get together with your friends or family and form your team of amateur astronomers!

Forces and Interactions

In this chapter you will ... • describe and distinguish motion, speed, velocity and acceleration. • describe the different ways in which forces can affect the motion of an object. • support an argument that the gravitational force exerted by Earth on objects is directed down. • describe Newton’s three laws of motion.

How can forces affect the motion of objects?

How can we describe and measure the motion of objects?

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

How does the Earth’s gravitational force affect the things on its surface?

Describing Motion What Is Motion? The things around us move in different ways. When something is moving, we say it is in motion. An object is in motion when it is continually changing position in relation to other objects. We can describe motion in different ways. You can describe the motion of a child on a swing as a back and forth motion. The people on a carousel move round and round. An airplane is in motion as it moves down a runway. It moves in a straight line, then up into the air.

The people on the carousel are in motion as they spin round and round.

Try This! In small groups, list some objects you see in motion from day to day. Take turns to describe the motion of the objects.

AB 68

Activity 8.1

Speed, Direction and Velocity When describing the motion of an object, we often talk about the speed and direction it is moving. Speed describes how fast or slow something is moving. It describes the distance an object travels in a certain time. To calculate the speed of an object, we need to divide the distance it travels by the time taken to cover that distance. speed =

distance time

Let’s calculate the speed of a cyclist that covers a distance of 28 kilometers in one hour. speed of cyclist =

28 km 1 hour

= 28 km/h We can say the speed of the cyclist was 28 kilometers per hour. A car covers a distance of 210 kilometers in three hours. Let’s find the speed the car was traveling. speed of car =

210 km 3 hours

= 70 km/h We can say the speed of the car was 70 kilometers per hour.

Most objects in motion are not traveling at a constant speed. During a race, a motorcycle speeds up as the race starts. It may reach a top speed of 150 kilometers per hour on the straight parts of the track and slow down to 50 kilometers per hour as it turns corners.

Try This! In small groups, use a trundle wheel to mark the start and finish line on a 100-meter running track. Take turns to run the length of the track and measure your average speed over 100 meters.

The speed of the motorcycle over the entire race is its average speed. Average speed is calculated by dividing the total distance covered by the total time taken to cover that distance. If the motorcycle race was 60 kilometers and the motorcycle completed the race in half an hour, we can say its average speed for the race was 120 kilometers per hour. What is average speed? How is it calculated?

Direction is the course or line from one object to another. The four cardinal directions of north, east, south and west are often used to describe motion. Denver is about 3,200 kilometers to the east of San Fransisco. An airplane completes the flight in four hours. To describe the motion of the airplane, we can say it travels at a speed of 800 kilometers per hour in an easterly directly.

When we use speed and direction to describe the motion of an object, we are describing its velocity. When we know the velocity of an object in motion at a certain position, we can predict where the object will be in the future if it maintains that velocity. We can also predict the time it will take for an object to arrive at a certain position. How does knowing an object’s velocity allow us to predict its motion?

Activities 8.2 – 8.3 71

Acceleration Imagine getting on your bike and pedaling slowly at a velocity of five kilometers per hour in an easterly direction. What happens when you press on the pedal as hard as you can? When you press the pedals with greater force, your speed increases and therefore your velocity changes. Any change in the velocity of an object is called acceleration. When you increase your velocity by going faster, the acceleration occurs in the direction of motion. When you use the brakes to slow down, your velocity decreases and the acceleration occurs in the opposite direction of motion.

Think Deeply Recall that velocity is the speed and direction of an object and acceleration is any change in velocity. Imagine you are cycling at a constant speed along a road. If you maintain the same speed as you turn a corner does acceleration occur? Explain your answer.

What occurs when an object accelerates in the opposite direction of motion?

Activity 8.4

Forces What Is a Force? Whenever an object has changed its position or is in motion, it is because one or more forces acted on or is acting on the object. Put simply, a force is a push or a pull. Forces can set things in motion. They change the speed or direction of an object in motion. Forces can also cause things to change shape. A push is when you press something away from you. You use a push when you kick a ball, setting it in motion. You use a push when you hit a tennis ball and change its velocity. A pull is when you tug something closer to you. You pull on a fishing rod when you wind in a fish. The gravitational force of the Earth pulls everything to its surface.

Activity 8.5 73

A force has magnitude and direction. Magnitude is the strength of a force. A large, strong force will move an object further and faster than a smaller, softer force. How a force affects the motion of an object also depends on the object’s mass. Larger, stronger forces are required to move objects of greater mass. The magnitude of the force required to move a wheelbarrow full of bricks is greater than the magnitude required to move an empty wheelbarrow. How does the magnitude of a force acting on an object affect its motion?

Activity 8.6

Balanced and Unbalanced Forces In a game of tug-of-war, one team pulls the rope in one direction and the other team pulls the rope in the opposite direction. What happens if both teams pull with the same force? What happens when one team pulls with a stronger force than the other team?

When both teams use the same amount of force in opposite directions, the forces cancel each other out. They are balanced forces. When the forces acting on an object are balanced, there is no change in motion. To win a game of tug-of-war, one team must pull with greater force. The forces acting on the rope are not equal. Forces that are not equal and do not cancel each other out are unbalanced forces. When there are unbalanced forces acting on an object, there is always a change in motion.

Look at the soccer ball on the ground. What forces are acting on the ball? Why is the ball not in motion? The forces acting on an object have both magnitude and direction. An object that is not in motion is said to be at rest. An object at rest typically has multiple forces acting on it, but they add up to give zero net force. A soccer ball on the ground is being pulled down by the force of gravity. At the same time, the ground is exerting a push force in an equal and opposite direction. The forces are balanced – there is zero net force – and the ball remains at rest.

Forces that do not sum up to zero can cause changes in an object’s speed or direction. When the footballer kicks the ball, he applies a force greater than the force of gravity. This creates an unbalanced force and sets the ball in motion. When there are unbalanced forces acting on an object, a change in motion occurs. Unbalanced forces can cause an object to: • start moving • speed up • slow down • change direction • stop moving

Activity 8.7

Contact Forces There are many different types of forces acting on the objects around you. Some forces occur when objects are touching. They are called contact forces. Applied forces and friction are examples of contact forces.

Applied Force An applied force occurs when a person or object applies force to another object when in contact with it. You use applied forces when you open and close a door, push a bike up a hill or twist the lid off a jam jar. A weightlifter uses applied force to lift a barbell. In order for the barbell to move, the lifter must apply a force greater than the force of gravity holding it on the floor.

In a baseball game, the pitcher is in contact with the ball and uses an applied force to pitch the ball to the batter. The batter uses an applied force when the ball is hit with the bat, causing it to accelerate in the direction in which the force was applied. In order to catch and stop the ball, a fielder will need to be in contact with the ball and apply a push force.

Activity 8.8

Friction You can use an applied force to push a shoebox across a wooden floor. The push will set the shoebox in motion. As the shoebox moves across the floor, it begins to slow down, then comes to a stop. What causes this to occur? When you slide a shoebox, you use a push force to set it in motion. The shoebox slows down and comes to a stop due to a contact force called friction. Friction is a force that opposes motion. It occurs when the surfaces of objects rub together. Rough surfaces produce more friction than smooth surfaces. A concrete sidewalk is rougher than a patch of ice. You are less likely to slip on the sidewalk as there is more friction between your shoes and the rough concrete surface. Friction is also greater when surfaces press harder together. A force of greater magnitude is required to slide a bookshelf full of books compared to an empty bookshelf. The bookshelf full of books has a greater mass and presses harder against the floor compared to the empty bookshelf.

Sometimes it is useful to reduce friction. A playground slide has a smooth surface to reduce friction. A snowboard has a smooth surface to help it move quickly over snow. As a force that opposes motion, we can increase friction to help things to slow down or stop. Grooves in rubber bicycle tires help to increase the friction between the bicycle and the road. Rubber brake pads on a bicycle increase friction when they press against the wheel rim. This allows the cyclist to slow down or stop moving.

What are some other examples whereby people change the amount of friction between objects?

A Closer Look

Air and Water Resistance Just as friction opposes the motion of solid surfaces that are in contact, a force also opposes motion when a solid object moves through a gas or a liquid. This force, called drag force, occurs when solid objects come into contact with the molecules in the liquid or gas. Drag that occurs when an object is moving through water is called water resistance. Like friction, water resistance is a force that opposes motion. It causes the object moving in the water to slow down and stop. To reduce the effect of water resistance, people design objects to be streamlined in water. Streamlined means it is shaped in a way to reduce drag. Boats are objects designed to be streamlined. The bottom of a boat, called the hull, is usually smooth. It is also pointed at the front which allows water to move past more easily. Being streamlined allows boats to move through water more easily and at a greater speed.

Drag that occurs when an object is moving through air is called air resistance. Just as boats are designed to be streamlined in water, vehicles such as airplanes, trains and cars are streamlined to reduce the drag force that occurs when they move through air. Sometimes, people design objects in a way that increases air resistance. When a skydiver leaps from an airplane, they are pulled down by the Earth’s gravity. Parachutes are designed to have large surface areas and use air resistance to slow the fall of skydivers, allowing them to land safely on the Earth’s surface.

Engineer It! A flood has blocked road access to a remote country town. Design and test a parachute system that can safely drop supplies from an airplane to the people in the town.

Activity 8.9 83

Non-contact Forces Try This! If you have a magnet, you can magnetize magnetic materials. Take a metal nail and stroke it in the same direction in a circular motion with a bar magnet. Repeat about 20 times. Test to see if the nail is able to attract magnetic objects.

Engineer It! Magnetic materials are always made of metal, but not all metals are magnetic. Design and build a device that is able to sort magnetic metals from non-magnetic metals. Gather a variety of metal objects to test your device.

Some forces can act on objects without direct contact. They are able to act at a distance and are called non-contact forces. Magnetic force, electric force and gravitational force are non-contact forces.

Magnetic Force Place an iron nail on a table. Slowly move a magnet towards the nail. What do you notice? A magnet is an object with magnetic force. Magnetic force occurs in an object due to the motion of electrically-charged particles. As you observed when you moved the magnet near the iron nail, magnetic force can act at a distance. It is a non-contact force. It can act through solids, liquids and gases. Magnetic force can attract objects made of certain metals such as iron and nickel. Magnetic force cannot attract objects made of plastic, wood, rubber or glass.

A magnet has two poles – a North pole and a South pole. It is at each pole that the magnetic force is the strongest. When the like poles of two magnets are brought together, they push or repel each other. When unlike poles are brought together, they pull or attract each other.

Like poles repel each other. Unlike poles attract each other.

Many objects make use of magnetic force. Some doors use magnets to keep them closed. Magnets are used to stick notes and photographs to refrigerators. They are used in electric motors, loudspeakers and can also be used for medical imaging and storing data on computer disks. When a magnet is hanging freely, it will come to rest with the South pole pointing in the direction of north and the North pole pointing in the direction of south. A compass is a device that uses this property to find the direction of north. A maglev (magnetic levitation) train has magnets that repel it from the track. This reduces friction and allows the train to travel at fast speeds.

maglev train

Activity 8.10 85

Electric Force

Think Deeply How are the interactions that occur between magnets similar to those between charged objects?

All matter is made up of tiny particles which can have a positive charge or a negative charge. Electric forces are created when there are unbalanced electrical charges inside an object. An object that has more positive particles is positively charged. An object that has more negative particles is negatively charged. When two objects with the same charge are close to one another, they repel each other. When two objects with different charges are close to one another, they attract each other.

Objects with opposite charges attract each other. Objects with like charges repel each other.

Take a balloon and rub it through your hair. Slowly pull the balloon away from your head. What do you observe? Rubbing the balloon through your hair created two opposite static charges. The charges attract one another and make your hair stand up. Notice that your hair and the balloon do not need to be touching to affect each other. Electrical forces are non-contact forces and can act at a distance.

Gravitational Force Why does a ball fall to the ground when you drop it? Why do skydivers fall to the surface of the Earth when they leap from an airplane? For an object to be in motion, like a skydiver falling to the Earth’s surface, one or more unbalanced forces must act on it. All objects have an invisible force that pulls on other objects. This force is called gravitational force, or gravity. A skydiver falls to the surface of the Earth due to the pull of the Earth’s gravity. The strength of an object’s gravitational force depends on it mass. The gravitational force of objects with a small mass, such as a tennis ball, is too weak to observe. Compared to a tennis ball, the Earth has a much greater mass. The strong gravitational force of the Earth keeps everything on the Earth’s surface. The Sun’s gravity attracts the Earth and other planets in the solar system. It keeps the planets and other objects in the solar system in orbit around the Sun.

The Earth’s gravity pulls the skydiver to its surface.

Try This! Attach a string to a small toy. Hold the unattached end of the string. Describe the forces acting on the toy. Are the forces balanced or unbalanced? Let go of the string. Describe the motion of the toy and the forces acting on it. Explain the forces acting on the toy when it is at rest on the floor.

Gravitational force also depends on distance. The closer objects are to each other, the greater the gravitational force.

Activities 8.11 – 8.13 87

A Closer Look

Mass vs Weight In everyday language, we often use the terms mass and weight to describe how heavy something is. But in science, mass and weight have different meanings. Mass is a measure of how much matter is in an object. Weight is a measure of the force of gravity pulling an object. On Earth, everything is pulled by the gravitational force of the Earth. So, both the mass and weight of an object does not change. The gravity on the Earth’s moon is about one-sixth that of the Earth. This means you would weigh one-sixth as much when on the surface of the moon. An object in deep space, where there is no observable gravity acting on it, would have the same mass as it does on Earth but would have no weight at all. The gravity of the Earth’s moon is one-sixth that of the Earth. An astronaut with a weight of 60 kg on Earth would weigh 10 kg on the moon.

AB 88

Activity 8.14

Laws of Motion Sir Isaac Newton is considered one of the most important scientists in history. He made many discoveries and provided detailed explanations for the many scientific theories he proposed. Newton’s work provided explanations about the force of gravity and the movement of the moon around the Earth and the planets around the Sun.

Go Online! Learn more about Sir Isaac Newton and his many theories and discoveries on the NGScience website. QuickCode: Y3J1

Did You Know? The unit of measurement for force is newtons (N), named after Sir Isaac Newton. On Earth a one-kilogram mass exerts a force of 9.8 newtons. Use this to calculate your weight in newtons.

Sir Isaac Newton

Much of our understanding of force and motion comes from Newton’s laws of motion – three laws that describe the relationship between the motion of objects and the forces acting on them.

First Law of Motion Newton’s first law of motion says that an object at rest will remain at rest until an unbalanced force acts upon it. Similarly, an object that is already moving will continue moving until an unbalanced force acts upon it. The tendency of objects to resist change in their velocity is called inertia. Let’s look at the inertia of a bowling ball. When the bowling ball is on the rack, it is at rest. There are no unbalanced forces acting on it. When you take the ball and bowl it down the lane, you apply a push force to the ball and set it in motion. The inertia of the bowling ball keeps it moving at almost the same speed in the same direction down the lane until it hits the pins. The pins exert a force on the bowling ball and change its speed and direction. We use the words ‘almost the same speed’ because on Earth, the forces of gravity and friction slow the motion of the bowling ball slightly.

You can feel the effects of inertia as a passenger in a moving car. Inside the car, you are moving at the same velocity as the car. If the car stops quickly, you continue to move forward until your seatbelt applies a force to stop your motion. In space, objects that overcome the gravity of the planets and the Sun keep moving and will continue to do so unless an unbalanced force acts on them. The NASA space probe Voyager 1 was launched into space in 1977 and has been in motion ever since. It is currently more than 2.2 billion kilometers (1.36 billion miles) from Earth and is moving at a speed of about 56,000 kilometers (35,000 mi) per hour. Voyager 1 will continue to move at this speed unless an outside force changes its velocity.

Try This! Place a piece of cardboard or playing card over a cup. Place a coin on the cardboard. Use your finger and thumb to quickly flick away the card. Use your knowledge of Newton’s first law of motion to describe what you observed.

Second Law of Motion Try This! In small groups, take turns in applying forces of different magnitude and direction to a tennis ball at rest. Predict the motion of the ball before each force is applied.

Think Deeply Make a prediction. When a rock is thrown into a river, how will the magnitude of the force and mass of the rock relate to the size of the splash and waves that form when the rock collides with the water?

Newton’s second law of motion describes how objects change velocity when unbalanced forces act upon them. It allows us to predict the motion of objects. It states that when an unbalanced force acts on an object, its change in velocity depends on its mass and the magnitude and direction of the unbalanced force acting upon it. A pebble on the bank of a river is at rest. The net forces acting on the pebble sum up to zero. When you pick up the pebble and throw it into the river, you set it motion. The velocity of the pebble – the speed and direction in which it is moving – depends on its mass and the magnitude of the force you applied to it. If you throw a small pebble, it will move at a greater speed and distance than if you were to throw a large rock. Similarly, if you throw a small pebble with a greater force, it will travel further than if you were to throw it with a smaller force. In order for the motion of a large rock to match that of a small pebble, a force of greater magnitude is required.

Third Law of Motion Newton’s third law of motion states that for every action, there is an equal and opposite reaction. This means forces always act in equal but opposite pairs. Let’s look at Newton’s third law using the example of a diver on a diving board. When standing on the diving board, the force of gravity pulls the diver down. This is an action force. At the same time, the diving board is pushing the diver up. This is a reaction force. When the diver jumps and pushes down on the diving board, the board pushes the diver up with an equal and opposite force. In athletics, sprinters use special blocks to secure their feet before the race begins. When the race begins, the sprinters exert an action force onto the blocks behind them. The blocks exert a reaction force in the forward direction and propel the sprinter forward.

Go Online! Watch the laws of motion in an animated video on the NGScience website. QuickCode: J7R3

Activity 8.15 93

Science Words Use the words to complete the sentences. motion speed average speed direction velocity acceleration

force contact force applied force friction water resistance streamlined

air resistance non-contact force magnetic force electric force gravitational force inertia

1. A force that can act at a distance is called a

2. occurs in an object due to the motion of electrically-charged particles. is the tendency of objects to continue at their 3. current velocity. 4. A

object is shaped in a way to reduce drag.

is drag that occurs when objects move through water.

is drag that occurs when objects move through air.

7. The distance an object travels in a certain time is its 8. A

is a push or a pull.

9. Any change in the velocity of an object is called 10. A force that occurs when objects are touching is a

. .

11. is a force that opposes motion when the surfaces of objects rub together. 12.

is the course or line from one object to another.

13.

The speed and direction of an object is its

is the total distance covered and the total time taken to 14. cover that distance. 15. A force created when there are unbalanced electrical charges inside an . object is called an 16. An object is in 17.

when it is in the process of changing position.

is an invisible force that pulls on other objects.

occurs when a person or object applies force to another 18. An object when in contact with it.

Review 1. How can you calculate the average speed of an object? 2. What is the difference between velocity and acceleration? 3. Provide an example of: (a) balanced forces acting on an object. (b) unbalanced forces acting on an object. 4. List five ways forces can affect the motion of an object. 5. Provide an example where people intentionally increase friction. 6. Provide an example where people intentionally decrease friction. 7. Why do people make objects that are streamlined? 8. What is the difference between mass and weight? 9. Why do the people on a bus move forward when it stops abruptly? 10. Use Newton’s third law of motion to describe how a rocket is launched into space.

Matter and Materials

In this chapter you will ... • make observations and take measurements to identify materials based on their properties. • describe the properties of the three states of matter. • develop a model to describe that matter is made up of particles too small to be seen. • provide evidence that when matter changes state, the total weight of matter is conserved. • conduct an investigation to determine whether the mixing of two or more substances results in new substances.

What are the properties of the three states of matter?

How can we change the state of matter?

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

Properties of Materials Try This! What are some objects you use from day to day? How are the properties of the materials they are made of suited to the use of the objects?

The objects around us are made of different materials. Common materials include metal, wood, glass, plastic, fabric and rubber. Different materials have different properties. When we make objects, we need to understand the properties of the materials used to make them to ensure the object is useful and safe. Look at the objects below. What materials are they made of? What properties of the materials make them suitable for how the objects are used?

Transparency Materials can be different in their transparency. Transparency is the property of allowing light to pass through. Look at the objects below. The glass bowl is transparent. Transparent materials allow almost all light to pass through. That is why you can clearly see the salad in the bowl. You can see that there are apples in the plastic bags, but you cannot see them clearly. The plastic bags are translucent – they allow some light to pass through.

Think Deeply What are some objects that are intentionally made of transparent materials? What materials are they made of? What are some objects that are intentionally made of opaque materials? What materials are they made of?

You can’t see what is in the metal mixing bowl as it is opaque. Opaque materials do not allow light to pass through.

translucent plastic bags

opaque metal bowl transparent glass bowl

Activity 9.1 99

Electrical Conductivity Think Deeply Study an electrical appliance in your home. Identify the materials that are electrical conductors and insulators. What other materials are used in its construction? How are the properties of the materials suited to the use of the appliance?

Did You Know? Water contains dissolved substances that make it a good conductor of electricity. You should never use electrical appliances near water or with wet hands.

Materials that allow electricity to flow easily through them are called electrical conductors. Metals are generally good conductors of electricity. For this reason metals such as copper are used in electrical wires and circuits. The particles that make up metals contain free charges that are able to flow and conduct electricity. Materials that do not allow electricity to flow easily through them are called electrical insulators. Wood, ceramics and plastic are examples of materials that are electrical insulators. Electrical devices and appliances often use a combination of electrical conductors and insulators to control the flow of electricity and protect people. For example, an electrical plug has metal prongs surrounded by a plastic handle. This allows people to plug in appliances safely without getting an electrical shock.

Activity 9.2

Electrical wires contain electrical conducting copper surrounded by electrical insulating plastic.

100

Heat Conductivity Materials that allow thermal energy to flow easily through them are called heat conductors. Heat is the movement of thermal energy. If you stir a hot soup on a stove with a metal spoon, the thermal energy of the soup moves through the metal spoon to you hand. The spoon soon feels warm. Most metals are good heat conductors. Materials that do not allow thermal energy to flow through easily are called heat insulators. If you stir the hot soup using a wooden spoon, thermal energy would not flow easily through the wooden spoon and it would not feel as warm. Wood, ceramics and some plastics are examples of heat insulators. A fry pan is made of both heat conducting and heat insulating materials. The base of the fry pan is metal. The thermal energy from the stove can easily pass through the base of the fry pan to cook your food. The handle of the fry pan is made of plastic which insulates your hands from the hot metal part of the fry pan.

Amazing Fact! To land on the surface of planets with an atmosphere, a spacecraft relies on air resistance to slow it down. This produces a great amount of heat which can damage the spacecraft. To overcome this, some spacecraft are fitted with a protective shield made of ceramic or other heat insulator. The shield absorbs and dissipates heat away from the spacecraft.

Try This! Discuss some situations where knowing about the heat conductivity of an object is important.

1 01

Amazing Fact! Graphene is a transparent material made of a single layer of carbon atoms arranged in a honeycomblike pattern. It is the world’s strongest material and also the most conductive in terms of heat and electricity.

Strength, Hardness and Flexibility People sometimes think that strength and hardness are the same property. Although hard objects can be strong and strong objects can be hard, they are different properties. Strength is the ability of a material to retain its structure when forces are applied to it. There are two main types of strength – compressive strength and tensile strength. Compressive strength is a measure of how much a material can be pressed together before breaking. Materials such as steel, rocks, glass, concrete and some ceramics have high compressive strength. Tensile strength is a material’s ability to withstand being pulled apart without stretching or breaking. Steel, bamboo and carbon fiber have high tensile strength.

1 02

Hardness is the ability of a material to withstand being scratched or indented. To determine the hardness of a material, you can scratch it with other materials of known hardness or measure the amount of force required to indent it. Generally, harder materials are more difficult to cut than softer materials. Diamond, steel, granite and concrete are hard materials. Flexibility is how much a material can be bent or stretched without breaking. Rubber, plastics and fabrics are often made to be flexible. What are some examples where strong, hard or flexible materials are used to make objects?

Activities 9.3 – 9.4

103

Density and Buoyancy Engineer It! Get together with your friends and design a floating ‘barge’ that can support objects denser than water. Challenge other groups to see which barge can support the most weight.

Look at the brick and the sponge. They take up a similar amount of space – they have similar volumes. However, the brick is much heavier than the sponge – it has a greater mass than the sponge. The amount of mass that fits into a given volume is called density. The brick is more dense than the sponge. Density is measured in grams per cubic centimeter (g/cm3). When we know the volume and mass of an object, we can calculate its density by dividing its mass by its volume. Different types of matter have different densities.

104

Matter

Density

State

Helium

0.000178 g/cm3

gas

Air

0.001293 g/cm3

gas

Ice

0.920 g/cm3

solid

Water

1 g/cm3

liquid

Gold

19.3 g/cm3

solid

Objects that are less dense than the liquid or gas they are placed in, will float. Helium is less dense than air. That is why helium balloons float in the air. Ice is less dense than water. This is why ice blocks in your cold drink and icebergs in the ocean float. Metals are much more dense than water. However, many boats and ships are constructed from metal and are able to float on water. They are able to float because of buoyancy. Buoyancy is the upward force exerted by a liquid or gas on an object immersed within it. The size of the force is equal to the weight of the liquid or gas that the object displaces. Consider the bottom part, or hull, of a ship. Its walls are made of metal, but most of the space inside the hull is air. When the ship enters the water, its hull displaces, or pushes away, a large volume of water. The water applies an upward force to the hull. The magnitude of the force is equal to the weight of the displaced water. The weight of the water displaced is greater than the weight of the ship and so it floats.

Think Deeply What will happen to a helium balloon that is released outside and rises in the sky?

Amazing Fact! The world record for the least dense solid is aerographene with a density of just 0.00016 g/cm³. It is a man-made material that was discovered in a laboratory by scientists in China in 2003. Apart from an amazingly low density, it is also an excellent heat insulator. Scientists and engineers are looking at ways we can use this material in our everyday lives.

How is the density of matter related to its buoyancy?

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What Is Matter? Inflate a balloon by blowing air into it. Notice that the balloon gets bigger. The amount of space the balloon takes up – its volume – increases. The air in the balloon, the balloon and even you are matter. Matter is anything that has mass and volume.

Think Deeply Do objects of greater volume always have greater mass than objects of smaller volume? Explain your answer.

Mass is the amount of matter an object has. Mass is measured using a scale or balance and is commonly measured in kilograms, grams, ounces or pounds. Volume is how much space the matter takes up. The foam ball and the baseball are both made of matter. Volume is commonly measured in cubic units, milliliters or liters. Observe the foam ball and the baseball on the balance. Notice that the foam ball takes up more space than the baseball – it has a greater volume. However, the baseball has a greater density and greater mass.

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Matter is made up of tiny particles, called atoms. They are the basic unit of all matter. Atoms are so small they can only be seen with special highpowered microscopes. Matter typically exists in three forms or states – solids, liquids or gases. The state matter is in depends on the arrangement of its atoms.

States of Matter The objects around you, such as your desk, chair, books and pencils are solid matter. Solids are matter that have a fixed shape and volume. The particles that make up solid matter are tightly packed together. This gives solid matter its rigid shape.

The particles in solid matter are packed tightly together.

The shape and volume of a solid does not change when it is placed in different containers. If you take a solid and move it between different containers, its shape and volume does not change.

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Water, fruit juice and cooking oil are examples of matter in a liquid state. Like solids, liquids have a fixed volume. This means the amount of space taken up by a liquid always stays the same. Like solids, liquids cannot be compressed. Compared to a solid, the particles that make up a liquid are less tightly packed together. They are free to slide past each other. This property allows liquids to flow and change shape. A liquid will spread out to take the shape of the container it is in. When you pour some milk from a carton or bottle into a glass, the shape of the milk changes, but the volume of the milk remains the same.

The particles in liquids are more spread out than those in solids. They are able to slide past each other.

How is the arrangement of the particles in liquid matter different from that in solid matter?

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Gases are matter that can change in both shape and volume. You can’t always see gases, but they are all around you. The air you breathe is a gas. The water vapor released from a boiling kettle is also a gas. If you take a balloon filled with air and squeeze it gently, you will notice that the shape of the balloon changes. When you let the air out of a balloon, the gas particles spread out in all directions. The gas takes the shape and fills the space of the container it is in. The particles that make up a gas are able to move about freely. This property allows gases to change in both shape and volume.

The particles in gases are much more spread out than in solids or liquids, and move about freely.

Gases can be compressed. When a gas is compressed, its volume decreases. We compress air to fill a scuba tank. Inside the scuba tank, the compressed air takes up much less space than the air around you. Compare and contrast the properties of solids, liquids and gases.

Activities 9.5 – 9.6 The air in a scuba tank is compressed.

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Changes in Matter Physical Changes Take a sheet of scrap paper and fold it in half. By folding the paper, you have changed its shape. You have made a physical change to matter. A physical change is a change to matter in which no new matter is made. When a physical change is made to matter, the amount of matter does not change. If you take a block of chocolate and break it into pieces, the chocolate will have a different shape and appearance, but the amount of chocolate does not change. Physical change can also take place when matter is heated or cooled. If you heat the pieces of chocolate in a saucepan, they will melt into a liquid. If you turn off the heat and allow the chocolate to cool, it will form a solid again. When the chocolate changed from a solid to a liquid and back to a solid again, the amount of matter remained unchanged. Many physical changes, including those that involve a change in state, are reversible. This means the matter can be changed back to its state or condition before the physical change occurred.

Activity 9.7

Breaking chocolate into pieces and melting chocolate are physical changes.

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The Changing States of Water Most matter changes state when it is heated or cooled. Some matter requires large increases or decreases in temperature before it changes state. Gold is a solid at room temperature. It needs to be heated to over 1,000oC (1,832oF) before it begins to melt. Other matter can change state more easily. On Earth, water exists in three states – as solid ice, liquid water and as the gas water vapor. Let’s take a look at the temperature changes that must take place for water to change from one state to another. At room temperature, water is in a liquid state. When water is cooled to 0oC (32oF), it begins to change into solid ice. This process is called freezing and the temperature at which this occurs is called its freezing point. So, the freezing point of water is 0oC.

Try This! Is the freezing point of fresh water the same as the freezing point of salt water? Plan and conduct an investigation to find out.

Activity 9.8 Water will freeze at 0oC.

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Think Deeply Many years ago, people used steam engines to power trains. In a steam engine, water is heated by burning coal to produce steam. The steam then drives the engine. Why are steam engines not used much today?

At temperatures below 0oC, ice will remain in its solid state. If ice is heated, it can change from a solid to a liquid. The process in which matter changes from a solid to a liquid is called melting. The temperature at which this begins to occur is called the melting point. The melting point of matter is the same as its freezing point. So ice has a melting point, 0oC (32oF). When water is heated it changes from a liquid into the gas water vapor. This process, called evaporation, occurs more rapidly the more water is heated. At 100oC (212oF), water begins to boil. Boiling is the process by which a liquid rapidly changes into a gas. When water boils, it changes into an invisible gas called steam. The temperature of a boiling liquid does not increase, even when more heat is added.

Activity 9.9

Steam is an invisible gas. The mist you see rising from boiling water consists of many tiny water droplets that form as water vapor condenses.

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Have you ever noticed water droplets form on the side of a cold glass of water? The droplets of water form when water vapor in the air cools as it comes in contact with the cold glass. This process of changing from a gas to a liquid is called condensation. Condensation can occur at any temperature.

A Closer Look

Freezing, Melting, Boiling and Condensation

At 0oC, liquid water freezes and becomes solid ice.

At 0oC, solid ice melts and becomes liquid water.

When water vapor cools, it condenses into liquid water.

At 100oC, liquid water boils and becomes gaseous steam.

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Chemical Changes A chemical change occurs when two or more substances combine and a new substance is formed. Consider an iron nail that is left outside. Over time, the oxygen from air combines and reacts with the iron to form a new substance – rust. Rust forming on an iron nail is an example of a chemical change. Chemical changes are usually not reversible unless further chemical changes are made. Chemical changes occur at different rates. Some changes can occur very rapidly, like the explosion of fireworks. Others occur slowly, like the slow burning of a wooden log. Chemical changes like the weathering of rocks can occur over millions of years.

Go Online! Go online and watch a video on the different chemical changes to matter. QuickCode: V8K8

In what ways is a chemical change different from a physical change?

Rusting metal is a chemical change.

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We can identify when a chemical change is taking place or has taken place in the past by looking for evidence of a chemical change. Such evidence can include a change in color like the presence of red rust on iron or tarnish on silverware. Many chemical changes give off heat and light like the burning of a flammable gas or wood. Chemical changes can also be accompanied by a change in scent. A pizza will give off a pleasant smell as it cooks. If the pizza is overcooked, it burns and releases an unpleasant smell. Chemical changes can also cause bubbling or fizzing. Placing aluminum foil in a strong acid will cause it to fizz, bubble and become warmer as hydrogen gas is created.

Did You Know? A chemical change is also called a chemical reaction. A chemical reaction has two parts. The matter before the chemical change occurred is called the reactant. The new matter produced as a result of the chemical reaction is called the product.

Think Deeply What changes in matter occur when a chef makes a pizza, cooks it in a wood-fired pizza oven then serves the pizza to a customer?

Unlike physical changes, chemical changes are irreversible. Once the chemical properties of matter are changed, it cannot return to its original state.

Activities 9.10 – 9.12

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Fruit salad is mixture of different kinds of fruits.

Mixtures and Solutions Mixing salt and fresh water creates a solution of salt water.

What Is a Mixture? Look at the bowl of fruit salad. It contains different kinds of matter. It contains different kinds of berries. The fruit salad is an example of a mixture. A mixture is two or more kinds of matter that are mixed together. The different kinds of matter in a mixture retain their individual chemical properties, but the mixture may have new properties. It may be different in color, taste or have different melting and boiling points. Take a teaspoon of table salt and stir it into a glass of warm water. After a while, you will not be able to see the salt in the water. The salt dissolves in the water forming a solution of salt water. A solution is a mixture in which the matter has blended completely and remain evenly mixed.

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Air is a solution. It is a mixture of nitrogen, oxygen, carbon dioxide and other gases. People often mix different kinds of metals together or with other substances to produce a new metal with specific properties. They may be made to be lighter or stronger. These mixtures of metals are a type of solution called alloys. Aluminum alloys contain mostly aluminum along with other metals, such as steel. They are often used when an object needs to be lightweight. Stainless steel is a metal solution made of iron and other metals. This makes it more resistant to the chemical change of rusting.

stainless steel

Activity 9.13

Did You Know? To make most alloys, different types of metals are melted and mixed together. When the solution cools, it changes back to a solid state, and the metal has new properties.

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sieve

Separating Mixtures We can use our knowledge of the properties of matter to separate the parts of a mixture in different ways. Such properties include size, density, magnetism, evaporation and boiling point. Sifting is a process that can be used to separate a mixture of solids made up of large and small particles. To separate a mixture by sifting, we use a sieve. A sieve is a tool with a meshed bottom. By sifting a mixture of solids through the mesh, the larger solids remain in the sieve and the smaller solids pass through the holes in the mesh thereby separating the solids. Sifting is often used to separate water and food when cooking. A strainer is a type of sieve often used to separate foods like pasta and rice from the water in which it was cooked.

A strainer is a sieve used to separate a mixture of water and pasta.

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Activity 9.14

A mixture of magnetic and non-magnetic solids can be separated using a magnet. A junkyard has a mixture of all kinds of solid matter. The metal in a junkyard has value as it can be sold to refiners where it is reused or recycled. To separate magnetic metals from the other solids in a junkyard, a powerful electromagnet is used. We can separate mixtures of liquids and solids by allowing the mixture to settle, then decanting the mixture. Decanting can be used to separate mixtures of matter that have different densities. In a mixture of sand and water, the sand is denser than water. When allowed to settle, the sand will sink to the bottom. The water can then by poured out, leaving only the sand.

Activity 9.15

Try This! Make a mixture of paper clips and sand or gravel. Use a bar magnet to separate the mixture. Can you think of another way to separate the mixture? Which way is more efficient?

Think Deeply When gold panning, a mixture of river bed rocks, bits of gold, soil and sand is placed in a pan. Water is then used to wash away the top layers leaving only gold in the pan. Why is gold the last thing left in the pan?

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When fine-grained solids are mixed with a liquid, we can separate the mixture using filtration. Take a mixture of water and fine-grained sand. To separate the mixture, we can pour it into a funnel containing filter paper. The filter paper allows the water to pass through, but not the sand. The sand left in the filter paper is called the residue. The water that passed through the filter paper is called the filtrate.

Activity 9.16

Mixture of water and sand.

Funnel and filter paper

Sand particles (residue)

Filtration is used to separate fine grains of coffee from water.

Water (filtrate)

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Separation methods, such as filtration and sifting, are not useful in separating solutions. One way we can separate the matter in a solution is by evaporation. Take a solution of sugar and water. By heating the solution in a beaker, the water evaporates into the gas water vapor. The sugar is left in the beaker. Unless the separation of a solution by evaporation includes the condensation and collection of the water vapor, the liquid part of the solution is lost.

Think Deeply Take a mixture of sand in a salt water solution. How can you use a combination of separation techniques to separate the sand and salt into different containers?

Evaporation is how salt is separated from water during the water cycle. The water vapor rises as it evaporates and condenses in clouds before falling back to Earth as precipitation.

Activity 9.17

water vapor

water and sugar solution

Did You Know? Evaporation is one method of farming salt for people to use. The sun and wind dries up salty sea water in shallow pools. Large salt crystals remain and are gathered by salt farmers. This method of farming salt has been used for hundreds of years!

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A Closer Look

Distillation One way that matter in a solution can be separated is through the process of distillation. Distillation separates the matter in a solution using boiling and condensation. Let’s look at how distillation can separate a solution of salt water.

thermometer

Go Online! Go online and watch a video on the different methods of distillation. QuickCode: F7L8

distilling flask

water vapor salt water solution

water out Bunsen burner

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Salt water is a solution of water and salt. The boiling point of water is lower than that of salt. When a salt water solution is heated in a flask, the water will boil, change into a gas and leave the flask through a tube. The salt, which has not reached its boiling point, remains in the flask. The water vapor then cools and condenses in a condenser and changes back to liquid water. How is the process of distillation different from evaporation alone? Distillation is used to separate the aromatic essential oils from plant and flower matter.

condenser

Engineer It! Separating a solution one flask at a time is not practical on a large scale. Design a desalination plant that continuously distills water from the ocean to provide a nearby town with fresh water.

cool water in

distillate of fresh water

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Science Words Use the words to complete the sentences. transparency electrical conductors electrical insulators heat conductors heat insulators strength

hardness flexibility density buoyancy mass volume

physical change steam chemical change mixture solution

1. is the ability of a material to withstand being scratched or indented. 2. is the ability of a material to retain its structure when forces are applied to it. 3. The upward force exerted by a liquid or gas on an object immersed within it is called . 4.

allow thermal energy to easily flow through them.

do not allow thermal energy to easily flow through them.

6. A

is two or more kinds of matter that are mixed together.

7. A is a mixture in which the matter has blended completely and remain evenly mixed. 8. A occurs when two or more substances combine and a new substance is formed. 9. When water boils, it changes into an invisible gas called 10. A

is a change in matter whereby no new matter is made.

11. The amount of matter an object has is its space matter takes up is its .

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. The amount of

12.

is the amount of mass that fits into a given volume.

13. How much a material can be bent or stretched without breaking is its . 14.

is the amount of light that can pass through a material.

15.

allow electricity to flow easily through them.

16.

do not allow electricity to flow easily through them.

Review 1. Provide an example of an object that has the properties below. (a) translucent and flexible (b) hard and strong (c) electrical conductor (d) heat conductor 2. Why does ice float in water? 3. Describe the arrangement of particles in solids, liquids and gases. 4. Which state of matter can be compressed? 5. Provide an example of a physical change and a chemical change. 6. What is the freezing point of water? 7. What is the boiling point of water? 8. How could you separate a mixture of sand and gravel? 9. List two ways you could separate a solution of salt water.

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Energy

In this chapter you will ... • list and describe different forms of energy. • describe the ways in which thermal energy moves within an object or between objects. • provide evidence that energy can be transferred from place to place by heat. • describe the ways in which heat moves through conduction, convection and radiation.

What are some different forms of energy? How do we use different forms of energy?

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What is thermal energy? How does thermal energy move between objects?

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

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The city of Hong Kong during the day.

What Is Energy? Energy is all around us. We cannot see energy, but we can see the things that energy does. Energy makes things move. It powers the machines we use. It can make things get hotter or produce sound. Energy is used to light up our homes and cities and power the vehicles we use. All organisms need energy to grow, reproduce and carry out life processes. Plants use the light energy from the Sun to make food in the form of sugar. This energy is passed to animals and people when they eat plants and other animals. Scientists define energy as the ability to do work or cause change. The work or change caused by energy can be measured and observed.

The city of Hong Kong at night.

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Discuss the different ways energy affects your daily life.

Forms of Energy Energy cannot be made and cannot be destroyed. It exists in many forms and can be transformed from one form to another. Let’s take a brief look at some forms of energy. Kinetic energy is the energy of movement. A car speeding along a motorway has kinetic energy. The faster the car moves, the more kinetic energy it has. An object does not have to be moving to have energy. An object can have energy due to its position or structure. This energy is called potential energy. A roller coaster car at rest at the top of a track has potential energy. The potential energy is converted to kinetic energy when the car speeds down the track. All matter is made up of tiny particles. The movement of these particles is called thermal energy. All objects have thermal energy. The faster the particles in matter move, the more thermal energy it has.

Try This! Gravitational potential energy is the energy stored in an object due to its height above the Earth’s surface. Discuss some situations where an object loses kinetic energy and gains potential energy and vice versa.

The greater the speed of the car, the greater its kinetic energy.

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Plants use light energy to make food. The energy is passed to animals when they eat plants.

Think Deeply Why is chemical energy a form of potential energy?

Chemical energy is energy that is stored. It is a type of potential energy. Energy is released when chemical reactions take 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. 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. Electrical energy is generated by the movement of charged particles – electric current. Electrical energy is very useful to people as it allows energy to be moved from place to place or be converted into other forms of energy. Electric current travels in transmission lines from power stations to our cities and homes.

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Light energy is a form of energy that travels in magnetic and electric fields. Visible light is the only form of energy that we can see. The light from the Sun is our most important source of light energy. Sound energy is caused when something vibrates. The vibrations travel in waves. We hear sounds when sound waves reach our ears. In this chapter, we are going to take a closer look at two types of energy – thermal energy and light.

A battery-powered flashlight converts chemical energy into electrical and light energy enabling the boy to see at night.

Activity 10.1

The violin bow causes the strings to vibrate which produces sound waves that travel out in all directions.

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Thermal Energy What Is Thermal Energy? All matter is made up of tiny particles. Whether matter is in a solid, liquid or gas, these particles are always in motion. How much these particles move is called thermal energy.

Try This! In small groups, place a glass of water in sunlight and use a thermometer to measure how its thermal energy changes throughout the day.

The more thermal energy matter has, the higher its temperature. Temperature is how hot or cold matter is. It is a measure of the average kinetic energy of the particles in matter. The faster the particles mover, the greater the temperature. When matter gains thermal energy, the particles that make up the matter move faster. Its thermal energy increases and its temperature also increases. When matter loses thermal energy, the particles that make up the matter move slower. Its thermal energy decreases and its temperature decreases.

The particles in the hot coffee have more kinetic energy than the particles in the cold soda. The coffee has more thermal energy.

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So how does matter gain thermal energy? The movement of thermal energy is called heat. Heat occurs whenever there is difference in temperature. Let’s look at an example of the heat that occurs when a hot object comes in contact with a cold object. In both objects, the particles are moving – they have kinetic energy. When the objects are touching, their particles collide with each other. As they collide, the hot object passes energy to the cold object. The hot object gets cooler and the cold object gets warmer. Heat will continue to move in this way until the temperature of both objects is equal. When you place a cold metal spoon into a hot cup of tea, energy moves from the hot tea to the spoon. The tea loses thermal energy and gets cooler. The spoon gains thermal energy and gets hotter. The metal spoon will continue to gain thermal energy from the hot tea until the temperature of the tea and the spoon are equal.

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How does heat move through the metal rod in the photograph above? Just as heat moves from hot to cold between objects, it also moves in this way within objects. Let’s look at an example of placing a metal rod over a fire. The heat from the fire will cause the particles at the tip of the rod to gain thermal energy and its temperature increases. These particles then collide with the particles adjacent to them. In this way, heat in transferred from the hot region to the cold region of the metal rod.

Activity 10.2

The arrow shows the direction of energy flow within the rod.

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What is the difference between temperature and thermal energy?

Temperature vs Thermal Energy Temperature is a measure of the average kinetic energy of the particles in a given object. It is different from thermal energy – which is a measure of the total kinetic energy of an object’s particles. Consider a nail that has been heated until it glows white-hot. Its temperature is around 1,000ºC. The particles inside the nail are moving back and forth with high kinetic energy. Now consider a large steel beam that supports a bridge. On a winter morning, the temperature of the bridge is just 5ºC – much colder than the metal nail. However the metal beam contains more thermal energy than the nail as it contains far more particles. Similarly, a boiling pot of water has less kinetic energy than the water under an ice-covered lake.

The hot metal nail has a higher temperature, but less thermal energy than the cold steel beam.

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Transfer of Thermal Energy Thermal energy moves in three main ways – conduction, convection and radiation. Think again how heat moved in the metal rod placed on a fire. The thermal energy moved from the hot part of the rod to the cooler part of the rod. This movement of heat within an object is called conduction. Conduction also occurs when objects are touching. If you were to hold the cool end of the rod, before too long it would feel warm as thermal energy moves by conduction to your hand. Heat transfer from a hot cup to your hands and cooking a piece of fish in a pan are also examples of conduction. Heat is transferred from the pan to the salmon by conduction.

Heat passes from the cup of hot chocolate to the girl’s hand by conduction.

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Liquids and gases are similar in that they have no fixed shape. They are fluids. Thermal energy can be transferred from one region of a fluid to another due to movements within the fluid. This movement of thermal energy, called convection, is caused by hot parts of the fluid rising and the cooler parts of the fluid sinking. Think about the water in a kettle as it is heated. The water touching the heating element is heated by conduction. The water becomes warm and rises. As it does so, the cooler water sinks and a current is created within the water. The current causes the thermal energy to spread through the water in the kettle.

Go Online! Convection currents cause the heat in air to spread out in a hot air balloon. How does this result in the balloon lifting off the ground? Discuss with your classmates, then head to the NGScience website to find out. QuickCode: B6H1

The heating of air in a hot air balloon is also an example of convection.

Activity 10.3

A convection current forms as warm water rises and cool water sinks.

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For thermal energy to move by conduction and convection it must travel through matter. Between the Sun and the Earth is empty space. How does the heat from the Sun warm the Earth and other planets in the solar system? The answer is radiation. Radiation is the transfer of energy through electromagnetic waves. The warmth you feel when you place your hand near an electric heater or a campfire are examples of heat in the form of radiation. Radiant heat from the campfire warms the boy’s hands.

Describe the three main ways thermal energy is transferred within and between objects.

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Thermal Conductivity What materials is the pot below made of? Why were the materials chosen? When an object is heated, thermal energy moves from hot to cold. This occurs as the particles within the object collide. In order for heat to move from one region to another, it must pass through all of the particles in between. The time it takes for this to occur is different in different materials and different states of matter. The ability of a material or matter to transfer thermal energy is called thermal conductivity.

Think Deeply A vacuum is empty space that contains no matter. A vacuum flask is an insulating container consisting of two solid layers separated by partially-evacuated air which creates a near-vacuum. Why does this make a vacuum flask a good heat insulator?

Some materials allow heat to pass through them more easily than others. Materials that allow heat to pass through them easily are called good conductors of heat. The metal used to make the pot is a good conductor of heat. It allows heat to flow easily from the hotplate to the food.

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Materials that do not allow heat to pass through them easily are called poor conductors of heat, or heat insulators. The plastic handle on the pot is a poor conductor of heat. Heat cannot flow through the plastic easily, so it does not get as hot as the metal.

Go Online! Learn more about thermal conductors and insulators in a video on the NGScience website. QuickCode: M8N8

Wool and fabrics such as fleece are good heat insulators. They are often used to produce clothing to keep people warm. Generally, matter in a solid state are better conductors of heat than matter in a liquid state. This is because the particles in solids are more tightly packed together than the particles in liquids. Similarly, liquids are generally better conductors of heat than gases. What are some other objects people use that are useful due to their heat conductivity?

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Light What Is Light? Light is a form of energy that is made of vibrating magnetic and electric fields which travel out from its source as light waves. Light waves vibrate perpendicular to one another and also perpendicular to the direction the light wave is traveling. Light waves are transverse waves.

wavelength

magnetic wave electric wave

Wavelength is the distance between two similar points in the repeating pattern of a wave. We are able to see light when the wavelengths of the light waves are in a certain range. This light is called visible light. Light waves with wavelengths shorter or longer than visible light cannot be seen with our eyes.

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How Light Travels Think Deeply Jupiter is approximately 756 million kilometers from the Sun. Calculate how long light energy from the Sun takes to reach Jupiter. Compare your answer with your classmates.

Like thermal energy, light can travel through solids, liquids, gases and in a vacuum. In the vacuum of space, light travels at almost 300,000 km/s (186,000 mi/s). It takes the light from the Sun – our main source of light, about eight minutes to reach the Earth. Light travels slightly slower in air and slower still in liquids and solids. Light waves travel out from their source in straight lines called rays. Rays do not bend or curve, but can act in different ways when they hit an object.

8 minutes

Activity 10.4

Reflection When you hold a tennis ball out and release it, it falls in a straight line until it hits the floor. It then bounces up in the direction in which it was dropped. The angle at which the ball bounces off is equal to the angle at which it hit the ground. Reflection of light works in a similar way. Reflection is the change in direction of waves.

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When describing reflection of light, we call the incoming rays incident rays. We call the rays that bounce off the surface reflected rays. Light reflects so that the angle of reflection is equal to the angle of incidence. Objects that have rough surfaces reflect incoming light in different directions. The light is scattered. Objects with smooth surfaces, such as a mirror, reflect light rays in a regular way. The light rays reflect together in the same way as they arrived. This manner of reflection forms an image. Smooth surfaces such water on a still lake can also form images in the same way as a mirror.

Activities 10.5 – 10.6

incident rays

reflected rays

Light reflects evenly on smooth surfaces.

Light reflects unevenly on rough surfaces.

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Refraction and Dispersion When waves pass through one medium into another medium of different density, 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 amount of light that is refracted depends on the difference in density between the two mediums. The greater the difference in densities between two mediums, the more light bends as it passes through them. Look at the pencil in the glass of water below. The change in density as light moves from the air to the water bends the light waves and causes the pencil to appear broken. Light is refracted as it moves from the air to the water.

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. 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.

Spectacles refract light to make objects look clearer for people with impaired vision.

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A Closer Look

Light and Shadows A shadow is a dark area that forms when an object blocks light. You have learned that different materials can have different properties in terms of transparency. Objects that are transparent allow almost all light to pass through them. They do not block light and no shadow is formed.

Think Deeply How are shadows formed on a cloudy day different from those formed on a clear, sunny day? What causes this difference?

Translucent and opaque objects block light. When light hits translucent and opaque objects, a shadow forms. As translucent objects allow some light to pass through them, they generally form lighter shadows than opaque objects. If you stand in sunlight on a clear day, you’ll notice that your body blocks some of the light from the Sun and a shadow forms on the ground. How does your shadow change throughout the day? At sunrise, sunlight hits your body at a low angle and the shadow that forms is at its longest. As the Sun rises, the angle at which sunlight hits you increases and the shadow gets shorter. It will be its shortest when the Sun is directly above you – at around midday. It then gets longer as the Sun begins to set and will be at its longest again at sunset. The distance between the light source and the object blocking the light also affects the shadow that forms. The closer the light source is to the object, the larger the shadow.

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Visible Light 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. The color of light we see depends on the wavelength and frequency of the light waves. Look at the visible light spectrum below. We see light waves with short wavelengths and high frequencies as violets and blues. We see light waves with longer wavelengths and lower frequencies as reds and oranges.

high frequency

low frequency

The light from the Sun is called white light. Sunlight appears white, but it is actually a mixture of all of the colors in the visible light spectrum. 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. The spreading of white light into its component colors is called dispersion.

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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. We see an apple as green when it reflects green light and absorbs the other colors. The green light is reflected into our eyes. Light receptors in our eyes send messages to the brain and we perceive the apple as green.

Similarly, we see an apple as red when it reflects red light and absorbs the other colors. The brain perceives the reflected light as red.

Did You Know? 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. Lighter or white objects reflect most of the light waves that hit them. They tend to be cooler than dark objects.

Try This! In small groups, describe how light is absorbed and reflected when light hits different objects in your classroom.

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Think Deeply What do you think you will see when you use a blue filter and flashlight to shine blue light on a blue sheet of paper in a dark room? What do you think you will see when you shine the same blue light onto a red sheet of paper? Explain your answer, then plan and conduct an investigation to find out.

Try This! Use cellophane of different colors to observe the things around you. Describe how the cellophane changes the appearance of the objects you see.

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. 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. Some stage lights and traffic lights use white light that passes through filters of different colors. Light consists of three primary colors – red, green and blue. By mixing different amounts of each primary color, we are able to produce all of the colors in the visible light spectrum. Televisions, computer monitors and smartphones make use of this property of light to produce the full range of colors you see when using them. If you were to look at a television screen with a powerful magnifying glass, you’d see that the color image is made of only red, green and blue pixels. Computer graphics software allows users to precisely mix different amounts of primary colors to produce a full range of colors.

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Light and Our Eyes We see things when light enters our eyes from a source of light or when an object reflects light. Light enters our eyes through the cornea, which is like a clear round window at the front of the eye. It bends the light before it passes through the pupil – a dark circular opening into the eye. The size of the pupil is controlled by the iris. If the light is bright, the iris will make the pupil smaller to reduce the amount of light entering. Similarly, the iris will make the pupil larger when it’s dark to allow more light in. Once the light passes through the pupil, it goes 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 optic nerve. retina sclera

iris pupil lens cornea

Anatomy of the human eye.

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Light We Cannot See The color of light is determined by its wavelength. Short wavelengths give us blue and purple light, while longer wavelengths give us red and orange light. 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. 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. 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.

radio waves

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infrared

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 can detect infrared rays. They are used to produce images that show the temperature of objects.

pit organ

Pit vipers such as rattlesnakes are snakes with a unique sense organ called a pit organ. The pit organ is able to detect infrared rays which enables them to ‘see’ in the dark. They can sense heat from meters away and use it to accurately catch prey at night. Radio waves are light waves with very large wavelengths. We can use these waves to send and receive messages. rattlesnake

ultraviolet

x-rays

gamma rays

visible light

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Science Words Use the words to complete the sentences. energy thermal energy temperature heat conduction convection 1.

radiation thermal conductivity good conductors of heat poor conductors of heat light reflection

incident rays reflected rays refraction shadow frequency dispersion

is the change in direction of waves.

2. The change in speed and direction of light waves is called

3. The spreading of light into its component colors is called

4. is a form of energy that is made of vibrating magnetic and electric fields. 5. The ability of a material to transfer thermal energy is called

allow heat to pass through them easily.

do not allow heat to pass through them easily.

8. in matter.

is a measure of the average kinetic energy of the particles

is the movement of thermal energy.

10. is the movement of thermal energy caused by the rising and sinking of a fluid due to differences in temperature. 11.

is the transfer of energy through electromagnetic waves.

12. The movement of heat within an object is called

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13. The kinetic energy in the particles that make up matter is called . 14.

is the ability to do work or cause change.

15. is the measure of how quickly a wave repeats in a given amount of time. 16. A

is a dark area that forms when an object blocks light.

17. When light is reflected, the rays that hit a surface are called . The rays that bounce off the surface are called

Review 1. Describe and provide an example of each form of energy. (a) kinetic energy (b) potential energy (c) thermal energy (d) chemical energy (e) electrical energy (f) light (g) sound 2. Describe how heat moves when a metal rod is placed above a flame. 3. Which has more thermal energy, a cup of water at 50oC or the water in a lake at 5oC. Explain your answer. 4. Describe and provide an example of each type of heat transfer. (a) conduction (b) convection (c) radiation

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5. Draw a simple diagram to show the incident and reflected rays when light is reflected on a rough surface. 6. Explain why the spoon in the photograph below appears broken.

7. In terms of reflection and absorption, describe why we see a ripe lemon as yellow. 8. Use a Venn diagram to compare and contrast ultraviolet light and infrared light.

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