SCIENCE 5 TEXTBOOK – 2 Name: ___________________________________ Section: ________________ Roll No.: _________ School: __________________________________
Preface ClassKlap partners with schools, supporting them with learning materials and processes that are all crafted to work together as an interconnected system to drive learning. Our books strive to ensure inclusiveness in terms of gender and diversity in representation, catering to the heterogeneous Indian classroom. ClassKlap presents the Traveller series, designed specifically to meet the requirements of the new curriculum released in November 2016 by the Council for the Indian School Certificate Examinations (CISCE). Guiding principles: The 2016 CISCE curriculum states the following as its guiding principles for Science: Theme-based learning Relating science learning to the daily-life experiences of students Focus on skill/process development Providing opportunities for knowledge construction Infusion of environmental issues into the content Each of these principles resonates with the spirit in which the ClassKlap textbooks, workbooks and teacher companion books have been designed. The ClassKlap team of pedagogy experts has carried out an intensive mapping exercise to create a framework based on the CISCE curriculum document. Key features of ClassKlap Traveller series: Theme-based content that holistically addresses all the learning outcomes specified by CISCE curriculum Opportunities for experimentation, analysis and synthesis of ideas and concepts Exposure to locally relevant environmental problem solving Focus on science-specific vocabulary building Promotion of participatory and contextualised learning through the engagement of all relevant stakeholders in the learning process All in all, the Traveller Science books aim to enhance the learning of science, development of scientific temper and curiosity towards scientific activities along with the inculcation of healthy habits for environmental protection. – The Authors
Textbook Features • Use of simple, age-appropriate language • Activity-based approach to learning • Use of infographics and pictures to explain concepts and terms • Focus on subject-related vocabulary building I Think I Will Learn About • Introduces the concept/ • Lists the key learning subtopic in a manner as to outcomes of the lesson arouse curiosity and interest among students ? In-text Questions Pin-Up-Note • Oral discussion questions to check for learning and to • H ighlights the key points or gauge the understanding definitions level of the child Connect the Dots A Be Amazed • Fosters interdisciplinary • F ascinating facts and trivia thinking by connecting other related to the concept subjects to an aspect of the taught concept Inside the Lab A Note to Parent • Hands-on experience • E ngaging activities to be done provided for creating, at home along with parents to designing or implementing reinforce the concept something innovative and/or useful based on the concept learnt
Contents 7 Food Chains ��������������������������������������������������������������������������������������������������..2 8 Sound and Noise ������������������������������������������������������������������������������������������.�.8 Inside the Lab – B �������������������������������������������������������������������������������������������������16 Activity B1: Web of Life Activity B2: Making Music with Water 9 Work and Energy �������������������������������������������������������������������������������������������18 10 Light and Shadows ����������������������������������������������������������������������������������������25 11 Simple Machines �������������������������������������������������������������������������������������������35 12 Cleanliness and Hygiene �����������������������������������������������������������������������������47 Inside the Lab – C��������������������������������������������������������������������������������������������������55 Activity C1: Up, Up and Away! Activity C2: Be a Junior Engineer
7Lesson Food Chains I Will Learn About • producers. • consumers. • the food chain. • role of the food chain in maintaining the balance in nature. • causes of imbalance in nature. I Think Saleena was eating her lunch. She saw a squirrel on a tree near the window. She wondered where it gets its food from. Do you know how animals find their food? We know that plants and animals are living things. We have also learnt that living things need food to grow. Plants make their own food, while animals depend on plants and other animals for food. Some animals depend on dead animals and plants for food. Depending on food habits, living things are of two different types: producers and consumers. Let us learn about them in detail. Producers Living organisms that can produce their own food are called producers. All green plants are producers. Do you know how green plants make food? Leaves of plants are green in colour due to the presence of a pigment called chlorophyll. Chlorophyll helps plants to make food using sunlight, water and carbon dioxide. 2
Leaves take up carbon dioxide Light energy Oxygen from the air and roots absorb water from the soil. Plants Carbon prepare their own food with dioxide the help of sunlight, water and carbon dioxide. This process is called photosynthesis. Plants use this food for their growth and survival. Plants are then eaten by animals. Minerals Therefore, producers are the main source of food and energy for Water other organisms. Photosynthesis ? Who are the producers in nature? Consumers All living organisms that cannot prepare their own food and depend on plants or other animals for energy are called consumers. Some consumers eat only plants, some eat only animals and some eat both plants and animals. They can be grouped according to their eating habits. Let us learn about them. 1) Herbivores (‘herb’ means ‘plant’, and ‘vore’ means ‘eat’): These are animals that eat only plant parts as their food. For example, cow, rabbit, deer. 2) Carnivores (‘carni’ means ‘flesh’, and ‘vore’ means ‘eat’): Some animals like lion, tiger, crocodile, eagle and snake eat other animals for food. Carnivores feed on herbivores and eat other carnivores too. For example, lions can eat herbivores like the deer and other carnivores like foxes too. Be Amaze A d The largest land carnivore is the polar bear. It feeds mainly on seals. A polar bear Food Chains 3
3) O mnivores (‘omni’ means ‘all’, and ‘vore’ means ‘eat’): These animals eat both plants and animals as their food. For example, human, bear, squirrel and so on. 4) Scavengers: These are animals that feed on dead plants and animals. For example, vultures, crows and termites. If scavengers don’t eat dead animals, the surroundings will become very unclean and unpleasant. So, scavengers play an important role in keeping the environment clean by consuming dead animals. Some scavengers like termites feed on dead plants. Scavengers Vultures Crows Termites 5) Decomposers: Decomposers are the organisms Based on the type that feed on dead plants and animals and of food they eat, convert them into simpler forms or nutrients. consumers are grouped as These nutrients get mixed with the soil and can herbivores, carnivores, be used again by plants. Fungi and bacteria omnivores, scavengers and are some good examples of decomposers. decomposers. They are microorganisms that can only be seen under a microscope. Without decomposers and scavengers, ? Name any one decomposer. the world would be covered with dead plants and animals. If the decomposers did not do their job, the plants would not get the nutrients, and they will die. What would happen if we didn’t have plants? Animals would starve to death, as they depend on plants for their food. Do you see the connection here? Do you see how animals are dependent on other animals and plants for food? The food chain What does an eagle eat? It eats small animals such as snakes. What does a snake eat? It eats frogs, which in turn eat insects such as grasshoppers. Grasshoppers eat plants. Where do these plants get food from? They make food using sunlight, carbon dioxide, water and nutrients. In this way, plants and animals are linked to each other as they depend on each other for food. This is called a food chain. 4
A food chain always begins with producers or plants. The producers are consumed by herbivores, which are then eaten by carnivores. Smaller carnivores may also be eaten by bigger carnivores. Food chain Eagle (consumer – carnivore) Snake (consumer – carnivore) Mouse (consumer – omnivore) Grasshopper (consumer – herbivore) Grass (producer) Role of the food chain in maintaining the balance in nature The food chain maintains a natural balance on our Earth. An imbalance in the food chain can result in adverse effects on our life too. If any organism that forms a part of a food chain disappears, the entire food chain gets disturbed. For example, if the number of carnivores in an area decreases, the number of herbivores will increase. After a while, herbivores of that area will eat up all the plants very fast. Later, all the plants would have been eaten up by herbivores and no plant will be left. The number of herbivores will then start to reduce, as they will not get any plants to eat. In this way, some animals may disappear from the surface of the Earth. Many animals have disappeared from the Earth due to such imbalances in nature. Causes of imbalance in nature The main reason for this disturbance can be adverse climatic conditions like forest fires and floods. Human actions like clearing land, hunting and polluting our surroundings can also result in imbalances in nature. Let us now discuss the causes of imbalances in nature in detail. 1) Land clearing: Cutting down of forest area for the purpose of making buildings and farming is called land clearing. It causes many plants and animals to die Forest fire and thus disrupts the food chain. It Cutting trees leads to an increase in the amount of carbon dioxide in the air as the number of plants decrease. Food Chains 5
2) Forest fires also result in the clearing of huge portions of forest land and the death of many living organisms in the forest. Forest fire can be started by human beings or by natural causes such as lightning. 3) Lake/River clearing: In some places, people take over ponds, lakes and river banks, fill them up with soil and convert them into land areas for constructing houses or other buildings. Many people dump waste materials on the banks of water bodies, which gradually accumulate and fill up the water body. All these practices lead to a decrease in the number of water bodies and thereby the death of all aquatic animals that inhabit them. 4) Hunting: Many animal parts like horns and skin are used for making different products. Killing of animals for their body parts or for eating is called hunting. Animal skins are used to make leather items such as shoes and purses. Ivory is the hard white material obtained from the teeth of animals like the elephant and walrus. It is used to make Ivory products Leather items decorative items. 5) Pollution: The addition of harmful substances into the air, land and water bodies is called pollution. It is mostly caused by human activities like burning fuel in vehicles, dumping waste on land and in water bodies. It leads to the poisoning of land and water bodies with harmful chemicals. This can lead to the death of several animals. Polluted lake Smoke from cars We all know that the food chain is necessary to maintain a balance in the nature. We should try to keep our surroundings clean by reducing pollution and not dumping waste onto the land and into rivers. We should plant more trees and discourage people from buying products made from animal body parts. ? Name any one cause of imbalance in nature. 6
Connect the Dots English Fun Fill in the blanks by choosing the correct preposition given in the brackets. 1) A hen feeds ______ earthworms. (in, on) 2) Grasshoppers are food ______ many birds. (for, on) Social Studies Fun Like nature, we have producers and consumers in society as well. For example, a carpenter makes some furniture and someone buys it. Here, the carpenter is the producer, and the buyer is the consumer. A Note to Parent There are various channels like the BBC, National Geographic Channel and Discovery Channel that show the lives of plants and animals. Watch this famous video from Planet Earth (a TV series by BBC) showing the chase between a snake and an iguana for the food. https://www.youtube.com/watch?v=Rv9hn4IGofM There are many such videos. Watch them with your child to show them the world of plants and animals and their dependency on each other. Food Chains 7
8Lesson Sound and Noise I Will Learn About • sounds made by objects around us. • sounds made by living things around us. • warning sounds. • pleasant and unpleasant sounds. • noise pollution and its causes. • harmful effects of noise pollution. • ways to reduce noise in the surroundings. I Think It is 4 o’clock in the evening, and Raman heard the sound of a bell ringing. With a smile on his face, Raman rushes towards the door. How did Raman know what it was? We are familiar with many such sounds in our daily life. Have you ever thought about what these sounds are, or how they are produced? We often make and hear different types of sounds in our A sound is a everyday life. Both living and non-living things produce sounds. sensation that we Some sounds make us calm and happy, while other sounds hear. may be too loud or disturbing. Let us explore sounds made by various things around us. Sounds made by objects around us Every day, we come across many objects that make different types of sounds. 8
A clock makes a ‘tick-tock’ sound. An alarm clock makes a loud sound that wakes us up. Gadgets in the kitchen, such as An alarm clock Pressure cooker whistles the pressure cooker, microwave oven, tea kettle, fan, and mixer and grinder, make a variety of sounds. For example, the pressure cooker whistles when the steam escapes from it; the continuous moving of the fan makes a certain sound and so on. You must have heard different types of doorbells making a variety of pleasant sounds. Doors make a banging sound. The hinges in doors may also make a creaking sound when the door is opened or closed. These are some of the sounds made by non-living things. Let us now learn about various sounds made by living things around us. Sounds made by living things around us The plants and animals around us make different kinds of sounds. You must have heard the rustling of leaves. Fallen, dry leaves crackle when we walk on them. You must also have heard the chirping of birds, barking of dogs, or perhaps the roar of a Chirping of birds Barking of a dog lion in a nature park. Animals give alarm calls as warnings of danger or information about the location of food through such sounds. Sometimes, a male animal makes a special sound to attract the female.d Be Amaze A A few animals can make and hear sounds that humans cannot make or hear. For example, we cannot make or hear the sounds that bats make. Sound and Noise 9
Human beings also make a variety of sounds. We talk, shout, sing, laugh, cry and so on. We make sounds by clapping our hands or stamping our feet. We also make sounds while coughing or sneezing. You must have visited a crowded market. You must have heard a lot of sounds there, such as people talking to each other, sellers shouting and so on. Sometimes, we also hear announcements made using loudspeakers. Warning sounds How do we get to know that an ambulance or a fire brigade is nearby? They have a special sound to alert people. Such sounds are warning signals. They alert people about any danger. A few examples of warning signals are as follows: A siren of a police van: A police van siren makes Police van with a flashing siren a loud sound and alerts people of some danger. It also warns people on the road to let police vehicles pass through urgently in case of an emergency. Ambulance siren: When an ambulance is carrying Ambulance with a siren a patient, its siren makes a loud sound. This helps the ambulance to pass through the traffic on the road easily. This way the patient can get medical help urgently. We must always make way for ambulances. Fire alarm: It makes a loud sound to warn people if there is a fire inside a building. If people hear such alarms, they should immediately exit the building. Fire engine siren: When a fire engine is on its way to Fire alarm put out a fire, it makes a loud sound. This alerts the people on the road to allow the fire engine to go quickly so that the people trapped in a fire can get help at the earliest. ? When does a fire alarm make a loud sound? Fire engine siren Pleasant and unpleasant sounds Do we hear the same sounds everywhere in our surroundings? 10
Try this! 1) Form groups of five students each. 2) Carry a pencil and paper to record all the sounds you can hear. 3) Go outside your classrooms. 4) Walk around all the places in your school. 5) Also, notice the roadside sounds entering your school. 6) Now, discuss your findings with other groups. What did you find? You heard different types of sounds. How are they different? Some of them are soft, some are loud. Some are short sounds, and others are long. Pleasant sounds: Soft sounds like the chirping of birds, playing the flute are pleasant to our ears. They make us feel happy and comfortable. We all love music. The sound of musical instruments gives us pleasure and relief. Can you recognise the sound of a tabla, a violin or a guitar? Yes, we can easily recognise them as they make different sounds. Let us find out how different musical instruments make different sounds. Some instruments make a sound when struck by an object. For example, a drum or a xylophone. Some other instruments make sounds when their strings are made to vibrate. For example, a guitar or a violin. Drum Xylophone Violin Guitar Instruments such as a flute or a trumpet produce sounds when a column of air inside them vibrates. ? Give an example of a Flute Trumpet pleasant sound. Sound and Noise 11
Unpleasant sounds: A loud sound is unpleasant to our ears. For example, sounds of loudspeakers, horns of vehicles, drilling and so on. Airplanes also make a loud sound while taking off and landing. Horns of vehicles Drilling Noise pollution and its causes So far, we have learnt that sounds are not always pleasant. They are sometimes so loud that they cause discomfort to our ears. Such unwanted loud sounds are called noises. Sometimes, noise is so loud that it can be harmful to our ears. For example, sound from engines, traffic, blaring speakers, and firecrackers and so on. A lot of loud noise in a particular area causes noise pollution. A loud sound that causes discomfort to our ears is called noise. A lot of loud noise causes noise pollution. Noise pollution Noise pollution is caused due to: 1 playing music 2 unnecessary honking 3 sounds of machines systems or televisions of horns in traffic in factories and loudly electrical appliances at home 12
4 sounds made by 5 bursting firecrackers 6 shouting or speaking aeroplanes while during festivals too loudly taking off and landing Harmful effects of noise pollution Due to noise pollution, we may suffer from problems such as headache, loss of sleep, hearing loss, increase in stress, dizziness, tiredness and so on. Headache Loss of sleep Hearing loss Increase in stress Dizziness Tiredness Sound and Noise 13
Ways to reduce noise in the surroundings • While playing guitars or drums, close the windows and doors of your house so that others do not get disturbed. • Do not play loud music on your computer or music system. • Do not slam car doors or the doors of your house. • Keep the volume of your television or radio under reasonable limits. • Speak softly on the telephone. • Get electrical appliances checked regularly to reduce the noise caused by them. • If you have a garden in front of or around your house, plant trees and bushes there. They absorb sound. Connect the Dots English Fun Phonics is a method of reading by correlating sounds with symbols in an alphabet writing system. Solve this phonic crossword puzzle. Words: SAIL, RAIN, PAINT, TRAIN PAIL, SNAIL, TAIL, NAIL TN PL S L R N NL T L 14
Social Studies Fun City Country Tokyo Japan Here is the list of the top five noisiest cities in the Delhi India world. Three of them are Indian cities! Cairo Egypt Kolkata India Mumbai India A Note to Parent Discuss with your child how sounds help during an emergency. Tell him/her about the importance of sirens and alarms during a fire. Sound and Noise 15
B Inside the Lab Make sure you do these activities only with the help of your teacher or an adult. Activity B1: Web of Life Let us create a food chain using picture cards of animals. You will need: scissors, gum, chart papers, pictures of different plants/plant parts like grass, vegetables, fruits, cereals, pulses and pictures of animals. (Example: earthworm, grasshopper, rabbit, deer, elephant, wolf, lion, tiger, eagle, frog, fish, snake, hen, crow, crane, duck, squirrel, cow, cat, dog, mouse and human being.) You need to: 1) U se a pair of scissors to cut the chart paper into equal-sized pieces. (The teacher should help the student while cutting.) 2) P aste the pictures of plants and animals on the chart paper pieces to make picture cards. Your game cards are ready. 16
3) F ind out how many different combinations of food chains you can form using them. For example, grass, grasshopper, frog, snake and eagle will form one chain, while plant, rabbit and wolf will be another chain. 4) D o it as a group activity with your friends. Activity B2: Making Music with Water Jal Tarang is one of the oldest musical instruments. It uses different sizes of bowls filled with different amounts of water and a metal spoon. You will need: six glasses, water and a metal spoon. (Note: Handle the glasses carefully while filling them, draining them and tapping them with the spoon) You need to: 1) Fill all the glasses with water. 1 2 3 4 5 67 2) Tap them with a metal spoon. 3) Listen to the pleasant sound produced. 4) N ow, drain half of the water from all the glasses. 5) Tap them with the metal spoon again. 6) Observe the sound variation. 7) P ut different amounts of water in each glass. (Use small amounts of water to avoid wastage and spilling.) 8) Tap them with the spoon again. 9) Listen to the sound again. Inside the Lab – B 17
9Lesson Work and Energy I Will Learn About • work. • energy. • forms of energy. • sources of energy – renewable and non- renewable. • importance of solar energy. I Think We have learnt about energy-giving food. Do you know what work and energy mean? Where do non-living things like fans, cars, washing machines, solar cookers and so on get their energy from? Work When we apply a force on an object by pushing or pulling it to move, stop or reshape it, we do work. For example, when we pick a box from the ground, the box moves from its original position. The force that we applied on the box made it move. So, we did work. 18
When we hit a ball using a bat, the force we apply makes the ball move from one position to another. So, we can say that work is done. In our daily lives, we do many activities and say that we have done work. But in science, work is not done in every activity. Work is done only when it involves displacement of an object. When we push or pull any object, we move it from its original position to a new position. So, work is said to be done in such cases. The pictures given below are a few examples of work done in our day-to-day life: Work done in our day-to-day life Measuring work can sometimes be tricky. For work to be done, the position of the object should change from one point to another. For example, work is done when we move a trolley bag from one position to another. Sometimes, we may apply a lot of force to move When a force applied something. But if things do not move upon applying causes displacement of force, it means that no work is done. For example, if you an object, then work is push the wall with all your energy but the wall does not said to be done. move, no work is done. This is because the wall did not change its position. Work not being done Work and Energy 19
Try this! A few pictures are given below. Tick () the pictures where work is done and cross (×) the pictures where work is not done. Leaf falling Car moving Girl sitting with books on her head Holding a heavy load Pushing heavy boxes from one corner of the room to another Energy We learnt that we need force to do work. To apply force, we need energy. Energy is the ability to do work. Energy is required to do all kinds of work. We get energy for doing work from the food we eat. We need different amounts of energy to do different kinds of work. For example, • we need more energy to swim or climb than to walk slowly on ground. • we need more energy to climb up the stairs than to walk a few steps on plain ground. Can you think of more examples of work, from your daily Energy is the ability to do life, that require more energy? work. 20
Forms of energy We find energy in different forms. Let us discuss some of them. 1) Light: It is the form of energy we can see. 2) Heat : Rub your palms 10–15 times. Now, quickly touch your eyes with your palms. What do you feel? We can feel warmth. This form of energy is heat. Burning of fuels such as coal or cooking gas produces heat energy. The Sun is the natural source of heat on the Earth. 3) Sound: Sound energy is produced due to vibrations of objects. It can travel through air or water to reach our ears. Then, we can hear. For example, when a doorbell rings, vibrations are produced inside the bell. This produces sound that travels through the air to reach our ears and then we can hear the doorbell. 4) Wind: Try blowing on a notebook from the side. What happens to the pages of the notebook? Think about what you do when you want to blow a balloon. The wind energy makes the pages move and the balloon blow. This is the energy present in moving air or wind. 5) Electricity: Look at the electric bulbs and fans in your classroom. Where do they get the energy to work? They use electricity or electrical energy. 6) Mechanical energy: The energy that an object has due to its movement or position is called mechanical energy. For example, the water stored in a dam has energy due to its position. When it falls down, it has energy due to its movement. We need energy in one form or the other. We need energy: • for our body to do work. Dam • to light up bulbs, tube lights and so on. • to use phones, televisions, computers and so on. • to cook food. • to cool or heat homes and offices using fans, heaters and coolers. • to run vehicles. ? Name a form of energy that we can see. Work and Energy 21
Be Amazed A Have you seen lightning during the rainy season? It is the natural form of electricity. It is very powerful. It can burn everything on its way. During lightning, we should avoid standing under a tree. Lightning Sources of energy – renewable and non-renewable We get energy from different sources. 1) The Sun is the main source of energy on the Earth. We get this energy in the form of heat and light. Plants use this energy to make their food and store it in different parts. Some energy is used for the growth of the plant. When we eat plant parts, we get the energy stored in the plant. 2) Wind is another natural source of energy. The energy obtained from wind is converted to electrical energy using windmills. The energy of the wind makes the blades of the windmills spin. The movement of the blades helps the generators to generate electricity. 3) Water is also an important source of energy. The energy Windmills of moving water is used to generate electricity that is called hydroelectricity. To make electricity, water stored in dams is used to turn turbines that help the generators to generate electricity. Reservoir Powerhouse Long-distance Dam Generator power lines Turbine River 22
4) Fuels: We run vehicles and machines using fuels like petrol, coal and gas. These fuels, found in the ground, are some of the sources of energy. A large amount of heat is produced when we burn them. This energy is then used by the vehicles or machines to run. Energy sources like the Sun, wind and water are long lasting. We can use them again and again. Such sources of energy are called renewable Fuel energy sources. The energy that we obtain from them is called renewable ? Name any one renewable energy. energy source. Some of the sources of energy such as petrol, diesel and kerosene are limited. They may get over someday. Such sources are called non-renewable sources. The energy obtained from these sources is called non-renewable energy. We must use non-renewable energy sources wisely and carefully. Importance of solar energy All forms of energy are useful to us in one way or the other. We cannot imagine our life without solar energy. Let us learn how solar energy plays an important role in our daily life. 1) Due to light, we are able to see different things and colours around us. 2) P lants use light energy to make food. We get this energy when we directly or indirectly eat plants. 3) S olar energy is a renewable source of energy available to everyone for free. 4) H eat energy from the Sun helps in maintaining the temperature on the surface of the Earth. 5) S unlight is a natural disinfectant that helps in keeping the nature clean. It is useful for killing germs. 6) The heat energy from the Sun also helps in enabling water cycle. Work and Energy 23
Connect the Dots English Fun Underline the prepositions in the given sentences: 1) We get energy from the running water. 2) We get heat and light from the Sun. 3) Energy is present in moving air. Social Studies Fun The top five countries in the world that use wind energy to generate electricity are given below. Name the continents they are situated in. 1) China: ____________________________________________________________________ 2) United States of America: __________________________________________________ 3) Germany: _________________________________________________________________ 4) Spain: _____________________________________________________________________ 5) India: _____________________________________________________________________ A Note to Parent Try out the different activities given in the lesson with your child at home. Help them to understand the concept of work being done/not done using these activities. 24
10Lesson Light and Shadows I Will Learn About • transparent, translucent and opaque objects. • formation of shadows. • changes in shadows according to the position of the Sun. • formation of day and night. • eclipses. I Think Look at the picture. The boy in the picture is Ronak. He likes to make various shapes on the walls in front of light. How is he doing it? Have you ever tried it? When we stand out in the Sun, we can see a dark area on the ground at our feet. It looks similar to us. It moves as we move. Do you know what it is? It is called a shadow. Shadows are formed when any object blocks the light. Some objects form dark shadows whereas some do not form a shadow at all. We know that depending on how well an object allows light to pass through it, there are three types of objects – transparent, translucent and opaque. Let us recall them. Transparent, translucent and opaque objects Transparent objects allow light to completely pass through them. Translucent objects allow only some amount of light to pass through them. Opaque objects completely block light from passing through them. Let us look at some objects and try to classify them as transparent, translucent or opaque. 25
Try this! You will need: clear coloured plastic bottles, construction paper, non-coloured plastic sheet, tissue paper, wax paper, aluminium foil, cardboard, flashlight or torch and a pen. You need to: (Perform this activity with the help of your teacher.) • Go to a dark room to do this activity. • Light your torch. • Direct your torch light towards all objects one by one. • Observe the amount of light passing through each object. • Tick mark in the table below for the type of object. Object Transparent Translucent Opaque Clear coloured plastic bottles Construction paper Non-coloured plastic sheet Tissue paper Wax paper Aluminium foil Cardboard Transparent materials like plastic sheets allow light to pass straight through them. Translucent materials allow a little light to pass through them. Translucent materials include tissue paper, wax paper, and ? Name any one object that allows light to pass through it completely. plastic bottles. Opaque materials include construction paper, cardboard and aluminium foil. Opaque materials do not allow light to pass through them. Formation of shadows Did you notice the dark patch behind the opaque objects in the previous activity? It is the shadow of that object. 26
Take a look around and see what kind of things form shadows. You will notice that buildings, trees, vehicles, chairs and almost everything has a shadow. The easiest example is our body. Shadow formed by a tree Shadow of the human body Let us perform an activity to understand how shadows are formed. Try this! You will need: a torch and an opaque object such as a book, a duster or a toy. You need to: Place the opaque object between the torch and a surface which will act as a screen. What do you see? We can see that a shadow is formed on the screen or wall. How did it form? We know that light travels in a straight line. When an object blocks the path of light, a shadow is formed. Opaque objects create clear cut dark shadows as A shadow is a dark patch they block out the light completely. formed when an object blocks the path of light. Translucent objects allow only some light to pass What type of objects form through them. They can form shadows but dark shadows? the shadows are not so dark. ? Transparent objects allow light to completely pass through them. They do not block the light. So, they do not form shadows at all. Have you ever noticed that your shadow follows wherever you go? It is because your body continuously blocks the Sun’s rays from falling on the ground. Therefore, when you move, the shadow also moves along with you. At night you do not see any shadow because it is dark. However, after sunset you can see shadows if the streetlight or your house lights are switched on. Light and Shadows 27
So, the conditions required for the formation of shadows are: 1) a source of light 2) an opaque or translucent object 3) a surface like a screen or wall where shadow can to be formed. Try this! 1) Perform the previous activity again. a) What is the colour of the shadow? Is it the same as the object? No. A shadow of an opaque object is always black in colour. b) Where does the shadow fall? Is it behind the torch? Or is it behind the object? It is behind the object. Thus, we can say that a shadow is always formed at the opposite side of the source of light. 2) Now, turn off the torch. Are you able to see the shadow? No. Hence, we can say that a shadow cannot be formed in the absence of a source of light. 3) Now, turn on the torch again. Move the object towards the torch and then away from the torch. What do you see? The shadow becomes bigger when the object is moved towards the source of light. It becomes smaller when we move the object away from the source of light. Hence, we can conclude that the size of the shadow depends upon the distance between the source of light and the object, and the distance between the object and the screen. ? Give any one condition required for the formation of shadow. 28
Changes in shadows according to the position of the Sun We know that the Sun is the main source of light. Depending on its position, length of shadows changes. Due to the position of the Sun in the sky in the mornings and evenings, our shadows are longer. At noon the Sun is overhead. Have you observed that your shadow is very short at noon? Shadows during different times of a day Morning Noon Evening In the night and in the absence of artificial light, our shadows disappear altogether. Why do we have shadows of different length throughout the day? This happens because of the changes in the distance between us and the Sun throughout the day. Note: We should never look at the Sun with naked eyes. It will hurt our eyes. Be Amaze A d Norway is called the Land of the Midnight Sun because the sun never sets entirely. This phenomenon occurs between late May and late July. During this time the Sun continues to shine through the local midnight hour. Midnight Sun at Norway Formation of day and night on Earth We have days and nights on Earth. Light and Shadows 29
Day and night formation occurs due to the opaque nature of the Earth, and its movements. We know that the Earth is a planet. It moves around the Sun in a fixed path called the orbit. The Earth shows two types of movements. 1) Revolution: The movement of the Earth around the The movement Sun in its orbit is called a revolution. It takes 365 days of earth around the sun and six hours, or one year, for the Earth to make in its orbit is called the one full revolution around the Sun. revolution of the earth. Earth takes 365 days and 2) Rotation: While revolving around the Sun, the Earth six hours to complete one also spins on its axis. The Earth’s axis is an imaginary revolution. line passing through the centre of the Earth and the north and south poles. The spinning of the Earth on North pole its axis is called rotation. The rotation of the Earth is similar to the spinning of a top. The Earth takes 24 hours to complete one rotation. The Earth’s rotation is very important as it causes the formation of day and night. The movement South pole of the earth on its axis is called rotation of the earth. Rotation of Earth The Earth takes 24 hours to complete one rotation. ? What is an orbit? Let us perform an activity to understand how day and night are formed. Try this! You will need: a globe, a marker, a table and a torch. You need to: 1) Use the marker to mark the location where you live on the globe. 2) Darken the room. 3) Place the globe on a table. It represents our Earth. 4) Take a torch to represent the Sun. 30
5) Light the torch pointing towards globe where your location is marked. 6) Spin the globe slowly. What do you see? The portion of the globe The Sun that faces the torch gets light. But, as the globe is an Formation of day and night The Earth opaque object, the light does not pass through it. So, the opposite side remains in darkness. The portion of the globe facing the torch light represents day. The opposite side of the globe, away from the torch light represents night. Note down the countries having night when your country is having day. While turning the globe slowly, you will notice that Formation of day and night certain portions of the globe will start to go from darkness to light. Similarly some parts of the globe will start going from light to dark. In the same way, days and nights occur due to the rotation of the Earth. Eclipses Have you ever heard about eclipses? An eclipse There are two types of takes place due to the formation of a shadow. When eclipses – solar eclipse a heavenly body moves into the shadow of another and lunar eclipse. heavenly body, an eclipse occurs. We get to see two different types of eclipses: solar eclipse and lunar eclipse. Eclipses occur when the Sun, Moon and Earth are in a straight line. Solar Eclipse: A solar eclipse occurs when the Moon comes in between the Sun and the Earth causing the shadow of Moon to fall on certain portions of the Earth. The solar eclipse is not seen from every place on the Earth. It can be seen only from those locations where the shadow of the Moon falls on the Earth. From these locations, it appears as if the Sun has gone dark. Light and Shadows 31
Moon Sun Earth Solar eclipse Phases of the solar eclipse Solar eclipse can be either partial or total. In partial eclipse, the Sun is partially hidden by the Moon. In a total eclipse, the Sun is completely hidden by the Moon. Note: We should never look at the Sun directly specially during a solar eclipse. Even though it appears dark, the harmful rays of the Sun can still damage our eyes. The Solar eclipse occurs solar eclipse when the Moon comes in can be seen between the Sun and the only through Earth. Solar eclipse can specially either be partial or total. Special glasses to view designed a solar eclipse glasses. 32
Lunar Eclipse: A lunar eclipse occurs when the Earth comes in between the Moon and the Sun. The shadow of the Earth falls on the Moon causing the Moon to disappear for some time. Moon Sun Earth Lunar eclipse Lunar eclipse occurs when the Earth comes in Lunar eclipses can be seen by a much larger area of between the Sun and the the Earth than solar eclipses. They can also be viewed Moon. Lunar eclipse can without special equipment to protect the eyes. Like solar either be partial or total. eclipses, lunar eclipses are also of two types – partial and total. In a partial lunar eclipse, the Moon is partially hidden by the Earth, whereas during a total lunar eclipse, the Moon is completely hidden by the Earth. ? During a lunar eclipse, whose shadow falls on the moon? Connect the Dots Social Studies Fun All four giant planets (Jupiter, Saturn, Uranus and Neptune) experience eclipses, as they all have a considerable number of moons and the Sun appears relatively small from these planets. Light and Shadows 33
English Fun Write a poem about your shadow. My shadow I have a shadow that follows me everywhere, ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ A Note to Parent Discuss with your child how eclipses occur. Share experiences of any eclipse you have seen. Show them clippings of eclipses in the newspaper or on television. Encourage him/her to observe the eclipses that may occur in the area you live in. Take all necessary precautions before viewing eclipse. 34
11Lesson Simple Machines I Will Learn About • need for simple machines in daily life. • types of simple machines, their parts and uses. I Think Have you ever played on a see-saw with your friend? How does it lift you up and bring you down easily? You must have seen a tractor, a crane, a wheelbarrow, a cycle, a see-saw or a screwdriver. These are all machines. What is a machine? Why do we use them? Let us find out. Need for simple machines in daily life We need to do different kinds of work in our day-to-day life. We need to lift, move or cut different things. We have learnt that to do any work, we need to apply force. A machine is a tool that makes our work easier. It helps us to do more work with less effort or force. You must have seen people loading or unloading heavy loads from a truck. How do they do it? They use a sloping surface for it, so that they can roll the load on it. Using a slope to unload 35
Have you seen anyone hitting a nail into a wall? What do they use? A hammer. Have you seen people drawing water from a well? They use a wheel and rope to pull it out easily. Sloping surfaces, nails, hammers and wheels and ropes are Using a hammer to a few of the simple devices that we use to make our work put in a nail easy. These are called simple machines. Simple machines are devices that can change the quantity, direction or point of action of a force that we apply. Let us see a few examples to understand this. When we use a wheel and rope to draw water from a well, in which direction do we apply the force? We pull the rope downward, so the direction of the force is downward. But, in which direction does the bucket carrying water move? It moves upward. What do we understand from this? The wheel and rope change the direction of the force that we apply. Let us examine another example. Can you lift any of your classmates? It may be difficult. Now, think about the two of you playing on a see-saw. By applying a force downward, you can lift him or her easily. The see-saw increases the strength and changes the direction of the force that you apply. We use a variety of simple machines in our day-to-day lives to make different kinds of work easier. Common tools like knives, tweezers, scissors, ice tongs, screwdrivers, ramps, door handles – all these are different types of simple machines. Let us learn about simple machines and how they make our work easier. Types of simple machines, their parts and uses The inclined plane, wedge, screw, pulley, There are six types of simple machines – the inclined wheel and axle and lever plane, the wedge, the screw, the pulley, the wheel are simple machines that and axle and the lever. help us in many ways. Let us now understand how these simple machines Load work and make things easier. Inclined plane 1) Inclined plane: An inclined plane is a flat surface Inclined plane with a slope. We can use this simple machine to move an object to a lower or higher level. We would need less energy and force to move objects through an inclined plane. Let us understand how inclined planes work with an activity. 36
Try this! You will need: a wooden plank, rice/beans in a plastic bag, rubber band, measuring tape and a stack of books. You need to: 1) Place 1 kg of rice in a paper bag. 2) Seal the mouth of the bag with a rubber band. 3) Take a rope and tie it to the rice Pulling a rice bag Pulling a rice bag with bag. the help of an inclined 4) Pull the bag of rice using the rope to plane the top of the stack of books. 5) Notice the amount of effort put in by you in order to lift the bag from the ground to the top of the stack of books. 6) Place the wooden plank inclined against the stack of books. 7) Pull the same load using the rope over the inclined plane from the ground to the stack of books. 8) Notice the amount of force applied by you in this case. You must have noticed that the effort required to pull the bag of rice from the ground to the top of the stack of books was much less when you used the inclined plane. Thus, the inclined plane makes our work easier. Uses of inclined plane: The staircase is an inclined plane that we use to climb. The ramps in hospitals help the patients in stretchers and wheelchairs to move up and down. 2) Wedge: A wedge is a kind of inclined Staircase Ramp plane with pointed edges that are used to do work like tightening, securing, holding or splitting things. Let us understand how wedges work with an activity. Wedge Cutting wood using a wedge(axe) Simple Machines 37
Try this! You will need: a knife, an apple, a fork, a plate You need to: (Perform this activity only in the presence of your teachers or parents.) 1) Place the apple on the plate. Cutting an apple using a knife 2) Take the fork and try to cut the apple into two equal halves. 3) Now, try to cut the apple using a knife. You will notice that cutting the apple with the knife was much easier than with the fork. A knife is a simple machine. The edge of the knife acts as a wedge that has a sharp end. This cuts the apple into halves easily. Uses of wedge: An axe helps us in cutting wood. Knives are used in the kitchen to cut various fruits and vegetables. 3) Screw: A screw is a modified inclined plane. In a Knife Axe screw, an inclined plane is twisted (swirled) around a rod like a road around a hill. Twisted roads A screw is a modified inclined plane Screws are useful for putting things together tightly. For example, a screw is used to connect two wooden or metal blocks. Screws are used in objects such as light bulbs. We also observe the different types of screws in our house such as milk caps, toothpaste lids and more. Try this! You will need: 2 small plastic bottles, 1 with a screw top cap and 1 with a push cap top, water (to fill the bottles) 38
You need to: 1) Fill the bottles with water so that they are half full. 2) Push the top onto one bottle and screw the top onto the other. 3) Go outside. Holding the cap of each bottle, try to drop the bottles. 4) Make sure that your clothes don’t get wet during this activity. Did you notice which bottle stayed shut and which bottle open? You would have noticed that the bottle with the screw cap stays intact. Whereas the bottle with the push cap drops off leaving the cap in your hand. Uses of screw: We use so many screws in Screw inside Screw used in Screw jacks wooden furniture to fix different parts of a bottle cap furniture used to lift furniture together. A bottle cap is also a type of screw that helps in keeping caps cars tight. Big screws called screw jacks are used to lift cars. Axle Wheel 4) Wheel and axle: The wheel and axle Wheel and axle Bicycle wheel is a kind of lever that moves objects with axle across distances. The axle is a rod that goes through the wheel. This lets the wheel turn. The wheels of a car or bicycle are wheels and axles that allow a car or bicycle to move easily despite it being a heavy object. Roller skates, gears in clocks and watches are also examples of wheels and axles. Have you ever played with a small toy car? Did you notice that they have wheels joined by axles? Uses of wheel and axle: The wheel and axle is used in door knobs. The knob that turns is the wheel, and the inner rod that is attached to the knob is the axle. By Door knob Steering wheel turning the knob (wheel), the inner rod (axle) moves, thus opening the door. Door knobs help us to close and open doors easily. The steering wheels of cars help us to change the direction of the car. 5) P ulley: A pulley is a wheel with a rope around it. Pulleys make Crane using a pulley lifting objects easier. For example, cranes use pulleys to lift heavy vehicles and building materials. Simple Machines 39
The rope fits on the groove of the wheel. One part of the rope is attached to the load. When you pull the rope, the wheel turns and the load moves. Pulleys let us move loads up, down or sideways. Pulleys are good for moving objects that are hard to move. It also makes the work of moving heavy loads a lot easier. Pulley Wheel Axle Load Grooved rim Effort Pulley Parts of pulley Try this! You will need: a rope and bottle of water You need to: 1) Tie a rope on a bottle of water. 2) Try to lift the bottle off the ground by pulling the rope, and note the amount of effort required. 3) Now, pass the free end of the rope over a doorknob. 4) Try to lift the water bottle by pulling the rope downwards from the doorknob. It feels easier to pull the rope down to lift the object than it does to push the object up with your hands. A pulley also functions in a similar way. Uses of pulley: A pulley is used to draw water from wells. A crane is used to lift heavy objects, which is also one of the uses of the pulley. ? Which simple machines make use of wheels? 6) L ever: A lever is a bar, rod or platform that can move about a Pulley used to fixed point. The fixed point is called a fulcrum. A fulcrum is a point draw water where the lever touches the support. 40
A lever makes it easier to move a large load with little effort. For example, a see-saw. Look at the picture below. It consists of the following: The simple lever Effort Fulcrum Load Load: the object you are lifting Fulcrum: the point at which the lever moves or is attached Effort: the force applied to make the object move We use levers in many of our day-to-day activities. Let us do an activity to illustrate this. Try this! You will need: a small plastic container like a medicine cup, a rock, a small ball (such as a golf ball or a rubber ball), a ruler and glue. You need to: 1) Glue the base of the plastic cup to one end of the ruler. 2) Once it is dry, lean the centre of the ruler against the rock so that the cup faces up. 3) Put a ball in the cup. 4) Press the other end of the ruler. 5) This will cause the other end to flip up and the ball to fly out. 6) If you press harder, the ball should fly out faster. The ruler placed on the rock acts like a lever. Effort is applied by you at one end of the ruler to lift the load (ball) at the other end. The fulcrum is where the rock is placed. Thus, levers can be used to lift various things. The lever is classified into three categories, depending on the position of the load, fulcrum and effort. Class 1 levers: In this type of lever, the fulcrum is in between the effort and the load. For example, see-saw, scissors. Simple Machines 41
Load Load Effort fulcrum Effort Fulcrum See-saw Fulcrum Class 1 lever Load Effort applied Scissors Try this! You will need: scissors, a piece of paper You need to: 1) Take a paper. 2) Cut the paper using the scissors. 3) Observe the scissors carefully while you cut the paper. You will notice that effort is applied by your fingers at one end of the scissor. The load or paper is placed at the other end. The fulcrum lies in between the load and the effort. Class 2 levers: In this type of lever, the load is between the fulcrum and the effort. For example, a wheelbarrow, a bottle opener, a lemon squeezer and a nutcracker. Load Load Effort Effort Effort Fulcrum Load Fulcrum Fulcrum Lemon squeezer Class 2 lever A wheelbarrow 42
Try this! You will need: a lemon squeezer and a lemon. You need to: (Do this in the presence of your teacher or parent.) 1) Hold the lemon squeezer in your right hand. 2) Using your left hand, place the lemon in the lemon squeezer. 3) Now, press the two handles towards each other. You will see that the effort applied by your hand is at one end of the lemon juicer. The fulcrum lies at the other end where ? What class of lever does a the upper and lower parts of the lemon lemon squeezer belong to? squeezer are joined. The load or lemon is placed in between the effort and fulcrum. Class 3 levers: A class 3 lever has the effort in between the fulcrum and the load. For example, fishing rod, tongs. Load Load Effort Effort Fulcrum Fulcrum Class 3 lever A pair of tongs Have you seen your mother cook chapatis? She uses tongs to hold the chapati while placing it on the burner. The fulcrum lies at the end of the tongs where the upper and lower portions of the tongs meet. The load or chapati is at the other end. We press the middle portion of the tongs to lift the chapati. The effort is in the middle of fulcrum and load. Uses of lever: We use scissors to cut many things in our houses. Nut crackers are used to crack open many hard nuts like walnuts. Tweezers are used to pick up small objects that are difficult to be picked up by hands. Bottle openers are used to open bottle caps. Wheelbarrows are helpful everyday tools because they allow one to transport loads that are too bulky or heavy to carry with one’s arms. Simple Machines 43
Simple machines are the basic parts of complex machines. Hand drill A machine can, therefore, be composed of two or more Fishing rod of these simple machines. A hand drill, for example, is a combination of a wheel and axle and a screw. Similarly, a fishing rod is an example of a combination of a pulley and lever. The load is at the point where fish is caught in the hook. The effort is in the middle of the load and the fulcrum. The fulcrum lies near where the pulley is attached to the rod. The pulley is used to release and roll the fishing line back once a fish is caught. Be Amaze A d Do you know that our body parts also work as simple machines? Let us find out how. Our teeth help us to Our knee and shoulder cut with the edges; joints act like wheel they act like a and axle. wedge. Shoulder Teeth Our bones and muscles act like levers. Effort The joints where the bones meet become fulcrums. Muscles provide the effort. The Load load is anything that we lift, push or pull. Fulcrum Bones and muscles act like levers 44
Connect the Dots Maths Fun A man lifts a 12 kg weight using his hands. He can lift 20 times more using a simple machine. How much can he lift using the simple machine? Weight lifted by the man using his hands = ___________ kg Thus, the weight lifted by the man with help of a simple machine = 20 × __________ = ______________ kg Social Studies Fun Axes and simple stone wedges, which human beings have used since ancient times, are a type of simple machines. They probably were the oldest tools made out of stone by human beings. A stone axe Stone wedges A Note to Parent Help your child to list down eight tools used in day-to-day life at home and also categorise them into the six simple machine types. Also, explain to them how the simple machines help us in our work . Simple Machines 45
S. No. Machine Types of simple machines Uses at home or office 1) Hammer Lever Used to hit nails into walls or wood 2) 3) 4) 5) 6) 7) 8) 46
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