101 Science–4 DIY ACTIVITY evaporation Evaporation is when a liquid turns into a gas. When water or another liquid is heated by the Sun or another heat source, it changes into tiny, invisible pieces called water vapor, which rise up into the air. The rate of evaporation increases when 1. temperature is high. 2. on a windy day. 3. when air is dry. 4. when exposed surface area is more. Condensation The process by which water vapour changes into water on cooling is called condensation. In nature, water vapour condense into water in many ways. Cloud Formation The heat of the sun causes water in seas, rivers, and lakes to evaporate and become water vapour. These water vapour ascend into the atmosphere. They condense back into small water droplets when they come into touch with chilly air. Clouds are created when these droplets combine. DIY ACTIVITY Evaporation is faster under in the presence of sunlight. Take two shallow dishes. Pour half a glass of water in each. At noon, keep one dish in a place that gets sunlight and the other in a room. In the evening, pour out the water from the dishes into two separate glasses of the same size. Compare the amount of water from the two dishes. Was the amount of water same in both the dishes? Why? Experiment showing condensation. Fill the glass three–quarters full with water Add the ice–cubes to the water until the water level is close to the top. Leves the glass until water droplets form on the outside of the glass. Explanation: The water droplets on the outside of the glass come from the air. As the air outside the glass. cools, the water vapour in the air condenses and water droplets are formed. EVAPORATION PRECIPITATION PERCOLATION CONDENSATION TRANSPIRATION
102 Science–4 Sedimentation and Decantation We clean water using sedimentation and decantation when it contains insoluble pollutants like sand and mud. In order for the pollutants to settle in the bottom of the container, water is left to stand for a few hours. Sedimentation is the term for this. After that, water is gently drained out without disturbing the pollutants that have gathered. It is known as decantation. Dew and frost You might have seen tiny droplets of water present on leaves and petals of flowers early in the morning. Actually, the nights are comparatively colder than the days. During the nights, water vapours in the air condense into tiny drops on the ground, on plants and also on window panes. These are called dew drops. hail, snow and sleet When it is very cold, raindrops freeze and become small balls of ice. They fall on the ground as hail. If water vapour are cooled suddenly they freeze into tiny white snowflakes. A mixture of rain and snow or hail is called sleet. Fog In winters air just above the land is cold. The water vapour close to the ground condense on dust particles or smoke to form dense cloud. This thick cloud of water droplets is called fog. When the weather is foggy, it becomes difficult to see things that are close by. PUrIFICatION OF water Nature does not always provide us with pure water. It may contain soluble pollutants, suspended particles, and pathogens. There are several ways to clean impure water. Boiling water is the quickest way to make it germ-free. Water bacteria are destroyed by boiling. Among the techniques for purifying water are filtration, decantation, and sedimentation. Sedimentation and decantation
103 Science–4 DIY ACTIVITY KEY WORDS Land breeze : wind that blows from the land to the sea during the night time. Sea breeze : wind that blows from the sea to the land during the day time. Condensation : the process by which water vapours change into water on cooling. Evaporation : the process by which water on the surface of water bodies change into water vapours. Filtration : the process of removing insoluble impurities from a liquid by passing it through a fflter. Filtration By passing impure water through a filter, such as a little piece of cloth or a specialised paper called filter paper, impure water is purified. Since the contaminants are still on the filter, the water is clear. By putting it through porous filters, water can also be cleaned. In water filters, these filters are employed. Chlorination This technique involves adding chlorine to water to destroy bacteria. Chlorination is the process of adding chlorine to water. Filtration Take some muddy water in a beaker. Filter it in the three different ways as shown below. Which one do you think is the most effective method? Why? Discuss in class. SUMMARY Weather is defined as the condition of air surrounding us at a particular time with respect to temperature, moisture and wind. The sun causes changes in weather as it heats the earth unevenly. The sun is also responsible for movement of wind and rain. Air is a mixture of gases. It has oxygen, nitrogen, carbon dioxide and water vapour. It also contains dust, smoke and germs.
104 Science–4 The continuous movement of air from hot to cold regions and vice-versa is called air currents. These air currents are responsible for causing sea and land breeze. The earth is known as the blue planet due to abundance of water on its surface. The change of water into water vapour on heating is called evaporation. The change of water vapour into water on cooling is called condensation. Cloud formation, and frost, fog and hail, and snow and sleet are different ways in which water vapour condense into water in nature. The water we get in nature may not always be pure. While needs purification. Boiling, sedimentation and decantation, filtration and chlorination are some methods of water purification.. EXERCISE TIME A. Tick () the correct answer. 1. Which of the following gas is present in maximum amount in air? a. Oxygen b. Carbon dioxide c. Nitrogen d. Water vapour 2. ffle cool breeze which blows towards the land during the day is called a. Storm. b. Land breeze. c. Sea breeze. d. Fog 3. Dewdrops freeze into tiny crystals called a. Hail. b. Frost. c. Fog. d. Rain 4. Warm air a. Is heavier. b. Is lighter. c. Has no volume. d. Is harmful 5. Which of the following methods kills germs present in water? a. Boiling of water b. Chlorination c. Decantation d. Both (a) and (b) B. Write T for true statement and F for false statement. 1. Dew is not a form of water. 2. Chlorine gas can be passed through water to purify it. 3. Sea breeze blows from the land to the sea. 4. Filtration of water kills germs present in it. 5. Hail and frost can spoil crops.
105 Science–4 TIME TO THINK (HOTS) Jyoti feels boiling drinking water is better than sedimentation and decantation. Is she right? (Hint: Boiling destroys germs in water.) Observe the weather for 7 days and then make a chart on the different kinds of weather conditions that took place. Write your feelings about weather. TIME TO CREATE (Project Work/Creative Skills) C. Write short answers. 1. What does air contain? 2. What is humidity? 3. Why do clothes dry faster on sunny day? 4. What is fog? D. Answer these questions. 1. Why are mornings and evenings less warmer than noon? 2. What is the diffierence between wind and breeze? 3. What are the diffierent ways in which water vapour condense into water in nature? 4. Diffierentiate between chlorination and boiling. 5. What are the diffierent ways of purifying water? Rainwater-harvesting is a method used to collect, store and use rainwater for several purposes. Now, collect information about the other methods that are used to store and save water. Write them in your scrapbook. You may take the help of internet or your elders. LIFE SKILLS Ask the children to relate their experience of weather change. Discuss diffierent forms of condensation. Conduct experiments to show air currents, sedimentation and decantation and ffltration. FOR THE TEACHER Why are ventilation duct always made above the windows? TIME TO DISCUSS (Collaborative Skills) (Life Skills)
Activity Project: Earth and Natural Resources Protecting Our Environment: Understanding Pollution Aim: To educate students about the environment, various types of pollution, and how they can help to protect the environment. Materials Needed: 1. Large poster board or chart paper. 2. Markers, coloured pencils, or crayons. 3. Magazines, newspapers, or printed images related to the environment and pollution. 4. Glue and scissors 5. Reference materials (books, websites, or videos on pollution and environmental conservation) Research and Gathering Information Students work in small groups or pairs. Provide them with reference materials and ask them to research various types of pollution, such as air pollution, water pollution, and soil pollution. Encourage them to find information about the causes and effects of each type. Hands-On Activity Organize a hands-on activity, such as a litter cleanup in the schoolyard or a nearby park. This practical experience will reinforce the importance of keeping the environment clean and free from pollution. Protecting Our Environment: Understanding Pollution Creating a Weather Poster: Students work in small groups or pairs. Each group to create a poster about “Weather Detectives: Unlocking the Secrets of Weather, Air, and Water!” Class Discussion Lead a class discussion after the presentations. Ask questions to reinforce what the students have learned about weather, air, and water. Discuss how these elements affect their daily lives. Activity Time–5 APPROACH 106 Science–4
107 Science–4 LEARNING GOALS Afier completing this chapter, you will be able to know about: Matter Composition of matter ffree states of matter States of matter are interchangeable Usefulness of change of states Dissolving solids in water 12 States of Matter LET’S WARM UP Write ‘S’ for solid, ‘L’ for liquid and ‘G’ for gas for the following items. MATTER There are variety of things around us. Some of them are living and some are nonliving. Ball, balloon and sponge are some examples of non-living things, whereas butterfly and pigeon are some examples of living things. All these things have mass and occupy volume. Anything that has mass and occupies volume is called matter. Self Direction Unit VI: Matter and Force
108 Science–4 DIY ACTIVITY MATTER hAs VoluME And MAss Volume An object’s volume is the area it takes up in space. The amount of room that water takes up in a tumbler is how much water there is. The stone’s volume is the area it takes up in space. Mass The amount of matter that makes up a thing is measured by its mass. The amount of wood in a table, for instance, determines its mass. Similar to that, this book’s mass equals how much paper it has. The unit of mass is the kilogramme (kg). Grammes and milligrammes are units of measurement for a very small mass. An electronic balance or a beam balance can be used to quantify mass. Matter makes up water and air. Let’s carry out the following tasks. Space occupied by an object is called volume ffe amount of matter an object contains is its mass. Air occupies space. Material required: One clear container filled with water, glass, tissue paper, ping pong ball Procedure: • Place the ping pong ball into the clear container filled with water. • Put the glass over the ping pong ball so that the ball sits inside the glass. • Push the glass down into the water, while it is still over the ball. The water level should rise around the glass and the ball should remain dry. • Remove the glass from the water. • Scrunch some paper into a ballput it into the glass. • Again place the glass, upside-down into the water and push down. The tissue paper should not get wet. Why? The paper remains dry because the glass which appears empty is actually filled with air. Due to this water could not enter the glass. This proves that air occupies space and therefore has volume.
109 Science–4 DIY ACTIVITY DIY ACTIVITY To prove : Air has mass. Take two balloons. Blow air into one. It enlarges in size. Tie the balloons at two ends of a scale. Tie a thread in the centre of the scale. The scale will tilt towards the side with the inflated balloon. The inflated balloon has air in it and thus occupies space. The scale tilted as the inflated balloon had more weight because of the air filled in the balloon. This proves air is matter, it occupies space and has weight. CoMPosITIon oF MATTER Molecules, which are incredibly small particles, make up all stuff. These molecules are really tiny. They are invisible to the human sight. several items contain several kinds of molecules. Every single molecule is continually moving. The space between the molecules is void. The intermolecular space is the name given to this void. ThREE sTATEs oF MATTER There are three different states of matter: solid, liquid, and gas. Water can be found in all three states in nature. Water exists in a liquid condition in rivers, ponds, and wells. Water can exist in two solid states: ice and snow. The peaks of the mountains are ice-covered. The gaseous condition of water is known as steam or water vapour. Air contains water vapour. Water turns into water vapour when it is heated. Water occupies space. We perform an activity to show’ that water occupies space. • Take an empty balloon and sketch its outline on a paper. • Now fill water in balloon and tight its mouth. Again we draw its outlines on a paper. Observation – We see that water filled balloon has large a shape. It is due to water filled in the balloon. Result: This shows that water occupies space. Evenly inflated balloons Flat balloon Filled balloon
110 Science–4 DIY ACTIVITY solids When matter is in the solid state, it has the following properties: • It has a definite shape. • It has a definite volume. • It has a definite mass. • Molecules are closely packed. Check out that crayon. It is shaped like a cylinder. It doesn’t alter in shape. It therefore has a distinct form. Additionally, the crayon takes up a specific amount of space. That indicates that the crayon has a distinct volume. It is manageable. If you move a solid from one place to another, it retains its shape and volume. This is the result of a solid’s tightly packed molecules, which prevents them from moving freely. liquids Water, oil and milk are liquids. Do they have a definite shape like a stone or a crayon? Let us find out. Pour the same amount of water into a variety of container shapes. Does water retain its shape when poured into various containers? Yes or No ice (solid) water (liquid) ffree states of matter crayon Molecules of a solid are closely packed. water vapour (gas) Pocket Fact When force is applied to some solids, like plasticine, rubber, etc., their shape can alter.
111 Science–4 Now, look at the picture given alongside. What happens when you pour water on the table? 1. Does it flow? Yes No 2. Does water have a definite shape? Yes No There is no fixed shape for a liquid. The container it is filled in assumes the shape of the object. Pouring a liquid on the ground causes it to flow. This is due to the fact that liquid molecules are not very closely packed. A liquid’s volume does not change when it is put into another container. A litre of milk, for instance, stays a litre whether it is put in a bottle or a sachet. It doesn’t alter in volume. Matter in the liquid state has the following properties: • It does not have a definite shape. • It has a definite volume. • It has a definite mass. • Molecules are not so closely packed. Gases Gases lack a defined volume but do have a defined mass. They don’t have a defined volume because they spread throughout the entire space. Gases spread in the entire available space. Molecules in gases are loosely packed. Pocket Fact ffe lightest state of substance is gaseous. Molecules in a liquid are less closely packed. TEST YOUR UNDERSTANDING Answers the following. 1. List two solids’ qualities. 2. Name two liquid properties.
112 Science–4 DIY ACTIVITY When the mouth of a 1 litre bottle of gas is closed on a 2 litre bottle of the same gas, the gas spreads throughout the bottle and fills the full interior volume. Its volume increases from one to two litres. A gas will mix with the air if an open area is available for it to spread. As a result, a gas lacks a fixed volume. A gas has the following properties. • It does not have a definite volume. • It does not have a definite shape. • Molecules are very loosely packed. • It flows and spreads in the entire available space. • It has a definite mass. sTATEs oF MATTER ARE InTERChAnGEABlE A solid can become a liquid, and a liquid can become a gas, thanks to heat. When heated to a given temperature, a solid melts into a liquid. Wax and ice, for instance, both melt when heated. When heated, a liquid primarily transforms into a gas. When heated, water turns into water vapour. A gas generally transforms into a liquid when it cools. For instance, water vapour turns into liquid water when it is cooled. smoke • Take a steel tumbler and fill it with ice-cold water. • Do you find water droplets on the outer surface of the tumbler after sometime? There are water vapour in the air, which are not visible. When they come in contact with the cold surface of the tumbler, they change into water droplets. In a similar way, cold can cause a liquid to solidify into ice. Ice forms as water cools, for instance. States of matter are interchangeable.
113 Science–4 DIY ACTIVITY usEFulnEss oF ChAnGE oF sTATEs • Depending on the temperature, water can change to any one of its three states – solid (ice), liquid (water), or vapour (steam). Water in each of these states is useful to us. • Many metals such as iron, copper and aluminium can melt. So, they can be shaped into different things such as utensils and wires. dIssolVInG solIds In WATER Substances that dissolve in water are called soluble substances. For example, sugar and salt are soluble in water. Substances that do not dissolve in water are called insoluble substances. For example, chalk and sand are insoluble in water. When sugar is mixed with water, its molecules occupy the empty spaces present between the molecules of water. A solid that dissolves in a liquid is called a solute. A liquid in which a solute dissolves is called a solvent. The mixture we get when a solute dissolves in a solvent is called a solution. Sugar + Water = Sweet water (solute) (solvent) (solution) utensils wire Metals can be shaped into difflerent things. To show that there are empty spaces between the molecules of a liquid. Take a beaker. Fill it with water. Mark the water level on a paper strip pasted on the outer wall of the beaker. Add two teaspoons of sugar in the water and stir with the help of a clean glass rod. Note the water level in the beaker. The water level in the beaker remains the same. This shows that the volume of the solution remains almost even the same when we add a solute to a solvent. ffis indicates that sugar molecules ffill up the empty spaces between the molecules of water. ffey do not take up any extra space. ffis also shows that there are empty spaces between molecules of water.
114 Science–4 KEY WORDS SUMMARY Matter is everything that has mass and takes up space. A volume is the amount of space an object takes up. The quantity of matter is referred to as an object’s mass. In terms of the three states of matter, solid, liquid, and gas. Solids have a definite shape, volume and mass. Their molecules are closely packed. Although liquids lack a distinct shape, they do have a distinct mass and volume. They have less tightly packed molecules. Gases neither have a definite shape nor volume but have a definite mass. Their molecules are very loosely packed. A solution is created when a solute dissolves in a solvent. EXERCISE TIME A. Tick () the correct answer. 1. Which of the following states of matter can flow? a. Solid and liquid b. Liquid and gas c. Gas and solid d. Solid, liquid and gas 2. ffe process by which a liquid changes to its solid form is called a. evaporation. b. melting. c. freezing. d. solution 3. Which of the following substance is insoluble in water? a. Chalk b. Sugar c. Salt d. None of these Matter : anything that occupies space and has weight. Molecules : tiny particles that make up matter. Volume : the space occupied by a solid, liquid or gas. Solute : a solid that gets dissolved in a liquid. Solvent : a liquid in which a solid gets dissolved. Solution : the liquid that we get by dissolving solute in a solvent.
115 Science–4 4. In a liquid, molecules are a. Closely packed. b. Not so closely packed. c. Loosely packed. d. Scattered B. Write T for true statement and F for false statement. 1. Milk has ffixed mass and volume. 2. Molecules in a gas are less tightly packed than solids. 3. Camphor changes directly into solid state. 4. Salty water is an example of a solution. 5. Liquids take the shape of a container they are poured in. C. Fill in the blanks. 1. ffe space occupied by an object is its ______________ . (volume / mass) 2. Oxygen in the air is in ______________ state. (liquid / gaseous) 3. When you heat water, it changes into ______________ . (ice / water vapour) 4. ffe state of matter of oil is ______________ . (gaseous / liquid) 5. ffe solid form of water is ______________ . (ice / mass) D. Name the following. 1. Small particles that form a substance. _______________ 2. ffey have molecules for apart from each other. _______________ 3. ffis form of matter neither has a deffinite shape nor a deffinite volume. _________ 4. A solid that dissolves in a liquid. _______________ E. Write short answers. 1. What is matter? 2. Deffine volume. 3. How can you say that liquids have a ffixed volume? 4. What do you mean by soluble and insoluble substances? F. Answer these questions. 1. How can we say that air is matter? 2. What are molecules? What are their properties? 3. What are the difflerences between solids and liquids? 4. What are the properties of gases? 5. Explain how water can change from one state to another. 6. Give an example to prove that change of states of matter is useful. 7. Explain the terms – solute, solvent and solution with the help of examples.
116 Science–4 TIME TO THINK (HOTS) 1. Smoke from a ffire spreads throughout a room. Why? 2. An orange has a deffinite shape but orange juice does not. Why? Observe the given picture and answer the following questions : 1. Describe what’s happening in this picture. ______________________________________________ 2. What is coming out of the spout of the kettle? ______________________________________________ TIME TO OBSERVE (Observational Skills) Mini’s dupatta got wet in the rain. What could be the quickest way to dry her dupatta? TIME TO DISCUSS (Collaborative Skills) Circle the correct word to complete the passage given below. Sam’s mother came from her oce. She was tired/fresh some quickly took a glass of cold / hot water. He cut a lemon / apple and squeezed it to take out its pulp / juice. He added the lemon juice, two tablespoon of sugar / sand and a pinch of red chillies / salt in the glass. He stirred it to make lemonade. He served it to his mother. ffis shows that Sam is caring / selffish. LIFE SKILLS Explain the concept of molecules and the arrangement of molecules in three states of matter. Ask the students to do all the activities mentioned in the chapter. FOR THE TEACHER (Life Skills) To know more about states of matter please scan this QR code. WEBLINK
Self Direction 117 Science–4 LEARNING GOALS Afier completing this chapter, you will be able to know about: Force Types of force Work Simple machines Energy 13 Force, Work and Energy LET’S WARM UP fie use of force can have a variety of effects. Determine what happens affler applying force in the pictures given below. FORCE Push and pull are forces, as we already know. A push or a pull causes an object to move, change its speed, or change its direction. This is known as force. It resembles an invisible force with the ability to influence events. Things move, cease moving, or change how they move, depending on the application of force.
118 Science–4 Therefore, force can • move a body, • change the direction of a moving body, and • stop a moving body. Force can also change the shape or size of a body. TYPES OF FORCE There are different types of forces. Let us learn about a few of them. Muscular Force We use our muscles to do so many things like writing, lifting, pulling, and pushing. The force exerted by the muscles of our body is called muscular force. Use force to start the motion a ball. Use force to change the direction of a ball. Use force to stop the motion of a ball. Force can change the shape of an object. Types of forces Muscular force Gravitational Force The force which acts between two masses is called gravitational force. The force between the earth and any other objects having mass is called gravity. Gravitational force and gravity cannot push things. If there was no gravity, we would have been floating in the air. Gravitational force Pocket Fact When you stand, walk, or run, your muscles and bones work together to keep you balanced and not fall over. ffis is because of gravitational force too!
119 Science–4 Frictional force: When two surface slide over each other, a force acts between them which slows down the motion of the two surfaces. This force is known as frictional force or simply friction. For example, a rolling ball stops after a while because of friction between the surface of the ball and the ground; a bicycle stops after applying brakes due to the frictional force between brakes and the wheel, etc. A rough surface offers greater friction than a smooth surface. Friction helps us to write and walk, but does not allow machines to move smoothly. Magnetic Force If you hold a magnet next to iron or steel things, like pins, you’ll see that the magnet pulls the pins with a strong attraction and they stick to the magnet. Make an effort to remove the magnet’s pins. They seem to be being drawn towards the magnet by some force. The magnet’s force is known as the magnetic force. Cranes employ extremely big magnets to raise weighty iron and steel things. Frictional force WORK We say that work has been done on an object when force is applied to it and the thing travels over a distance. Only when we push or pull on a body and the body moves is stated to be work completed. Even though force is used, Pushing Almirah with the wall no work is done. Moving a table, work is done. Magnetic Force Take a small empty glass bottle. Fill it with water. Put some iron nails and steel pins in the bottle. Close the lid of the bottle tightly. Now bring a magnet near it and see what happens. Do the iron nails move? ____________________ Do the steel pins move? ____________________ ACTIVITY Application of Knowledge
120 Science–4 in science work is not completed if a body is not moved from its initial position. We exert force, for instance, when we push against a wall. But the wall stays put. So no job is completed. However, the ball moves from its initial location when we kick it. Work is finished. SIMPLE MACHINES Simple tools like a screwdriver to fix a screw, a hammer to drive a nail, or a knife to cut vegetables are used frequently in daily life. These tools simplify our work. They are known as machines. These tools don’t have a lot of parts or attachments and are quite easy to use. Therefore, they are known as simple machines. Simple machines facilitate our job by lowering the required effort or by reversing the force applied. Simple machines come in six different varieties. Types of Simple Machines Lever A lever is a basic tool that can be used to lift objects, cut objects, and open containers. Examples of levers include scissors, bottle openers, and see-saws. Pulley A wheel and a rope are used to create a pulley. A load may be raised, lowered, or moved using it. It is used to lift weights in cranes, hoist flags, pull water from wells, and other things. Wheel and axle A wheel and axle configuration consists of a circular frame called the wheel rotating on a rod known as the axle. Wheel and axle examples include a doorknob, a screwdriver, and a steering wheel. Inclined plane An inclined plane is a slope. It makes it easier to lift something heavy. Instead of lifting something heavy straight up, you can push it up on inclined plane with less force. Bottle opener Scissors Wheel and axle Pulley
121 Science–4 Wedge A wedge is a simple machine which is used to cut or split things. It is made of two inclined planes joined back to back. A wedge has a sharp edge in front and blunt edge at the back. Examples of wedge are knife and axe. Screw A screw is an inclined plane wrapped around a cylinder. It usually has a flat end and a sharppointed end. A screw is used to hold things together or tighten things. ENERGY The ability to do work is called energy. The energy is required to do all kinds of work. All the appliances run on energy. Factories, trains, aeroplanes and all the vehicles on road need energy to function. All living things require energy to live. We get energy from the food that we eat. Machines get energy from fuels like petrol, diesel, coal and gas. Sources of Energy Energy sources are things that provide us with energy. Energy comes from a variety of sources. Solar Energy The sun is the main source of energy. The energy that we get from the sun is called solar energy. We get heat and light from the sun. Green plants trap this energy to make food. Example of wedge Example of wedge Solar cookerPlant getting solar energy Solar energy is clean. It creates no carbon emission or other heat-trapping green gases. It avoids the environmental damage associated with mining or drilling for fossil fuels. Green Tip Look at some machines working in your home. Find out how one form of energy is changed into another. ACTIVITY Application of Knowledge
122 Science–4 Animals and human beings use this food to get energy. A solar cooker uses solar energy to cook food. Similarly, a solar heater uses the solar energy to heat water. Wind energy Wind possesses a lot of energy. When wind blows, it moves the blades of a windmill and generates electricity. Thus, wind is a source of energy. Windmills Flowing water is used to produce electricity Solar heater Water energy Falling or flowing water has a lot of energy. This energy is used to generate electricity. Thus, water is a source of energy. Geothermal energy Extreme heat emanates from the centre of the earth. Geothermal energy is the name for the heat energy that comes from this region of the earth. Electricity is also created using this energy. Different Forms of Energy • Heat energy is needed to cook our food and heat our homes in winter. It can also be used to generate electricity. • Light energy makes us able to see objects around us. Plants use the light energy of the sun to make their food. Heat Energy Lght Energy We can save energy by turning off lights when we leave a room or by not leaving the TV on when we’re not watching. It’s like being an energy-saving superhero! Green Tip
123 Science–4 • Electrical energy is used by us to light up houses, streets, offices, etc. We also use it to run household appliances such as refrigerators, fans and computers. • Sound is also a form of energy. When an object vibrates, it produces sound in the air. • Sound travels in the air and reaches our ears, so we can hear it. • An atom is the smallest particle of matter. When an atom breaks down, it gives out energy called atomic energy. This energy is used to produce electricity in power plants. SUMMARY Force can move a body, change the direction of a moving body and stop a moving body. It can also change the shape and size of a body. Muscular force, gravitational force, frictional force and magnetic force are the different types of forces. Work is done only when an object is moved through a distance using force. KEY WORDS Force : a push or a pull that makes a body move or stop moving. Work : when force is applied on a body to make it move through a distance. Gravity : the force of attraction exerted by earth. Energy : the capacity to do work. Machine : a device that makes our work easier. Electrical Energy Sound Energy TEST YOUR UNDERSTANDING Write ‘T’ for true and ‘F’ for false statements. a. Crane is an example of a wheel and axle. b. Work is said to be done while holding a book in your hand. c. Plants use chemical energy to prepare their food. d. A knife is an example of an inclined plane. e. Screws are used to hold objects together. Holistic Learning
124 Science–4 EXERCISE TIME A. Tick () the correct answer. 1. In which of the following situations is work done? a. Pushing a tree b. Holding a bag c. Pushing a wall d. Lifiing a bag 2. Which of the following activity uses force? a. ffrowing a balloon b. Squeezing a tube c. Catching a balloon d. All of these 3. Which of the following type of energy is stored in fuels? a. Chemical b. Heat c. Mechanical d. Light 4. Which of the following force is responsible to make a moving object stop on its own? a. Muscular b. Frictional c. Gravitational d. Both (a) and (b) 5. Which of the following activity uses force? a. Catching a balloon b. ffrowing a balloon c. Squeezing a tube d. All of these B. Write T for true statement and F for false statement. 1. ffe Sun is the main source of energy to the Earth. 2. Frictional force always acts in the direction of a moving object. 3. Cranes use mechanical force to lifi things. 4. A wedge is made up of three inclined planes. ________ 5. Friction increases the speed of a moving object. C. Write short answers. 1. Defflne : a. Work b. Energy c. Force 2. Name the diffierent forms of energy. 3. What is magnetic force? Simple tools which we use in our daily life to make work easier are called simple machines. Lever, pulley, wheel and axle, inclined plane, wedge and screw are six types of simple machines. Energy is the capacity to do work. Heat energy, light energy, electrical energy, etc. are different forms of energy. The different sources of energy are the sun, the earth, water, wind, atoms and fuel.
125 Science–4 TIME TO THINK (HOTS) What will happen if: 1. there is no friction on earth. 2. there is no gravity on earth. 3. there is no Sun. Make a poster showing ways to conserve energy at home, in offices or at school. Write slogans emphasizing the need to save energy. TIME TO CREATE (Project Work/Creative Skills) ffink about games you like to play, like swinging on a swing or bouncing a ball. How do forces and energy play a role in these activities? TIME TO DISCUSS (Collaborative Skills) Machines are made for our help. So we should use them. But we should not completely become dependent on them as they may stop working anytime. LIFE SKILLS Take the children to a playground or a park. Ask them to observe examples of force used and work done. Display some simple appliances in the class while teaching simple machines like a sharpener, scissors, screw, etc. Discuss the various sources and forms of energy. FOR THE TEACHER 4. What is the use of light energy? 5. What are the six basic types of simple machines? 6. What is a screw? D. Answer these questions. 1. How is friction helpful? 2. Write a short note on energy. 3. Write a brief note on solar energy. 4. Explain any two simple machines. 5. Diffierentiate between an inclined plane and a wedge. (Life Skills)
Activity Project: Matter and Force Exploring the States of Matter Aim: To help students understand the relationship between matter and force through hands-on activities. Materials Needed: 1. Small toy cars or marbles. 2. Wooden ramps or inclined surfaces. 3. A variety of small objects (e.g., books, blocks, coins). 4. String or thread. 5. Ice cubes. 6. Water. 7. Empty plastic bottles with caps. 8. Balloons. 9. Small containers. Balloon-Powered Cars Provide students with small toy cars and balloons. Attach a straw to the car using tape, and thread a string through the straw. Blow up the balloon and attach it to the back of the car. Release the air from the balloon, and observe how the car moves forward. Discuss how the force of the air escaping from the balloon propels the car forward. Exploring the States of Matter Making Balloon Gas Partially fill an empty plastic bottle with warm water. Stretch the opening of a balloon over the bottle’s neck, making sure it’s airtight. Place the bottle in the fridge for a few minutes. Remove the bottle from the fridge and observe the balloon. Discuss how the gas inside the bottle has cooled down and turned into a liquid, causing the balloon to deflate. Activity Time–6 APPROACH 126 Science–4
TEST PAPER–1 Based on Chapter 1 – 6 A. Choose the correct answer. 1. Which of the following is required by green plants for photosynethsis? (a) Oxygen (b) Nitrogen (c) Carbon dioxide 2. Which one of the following plant is used to make brooms and baskets? (a) Bamboo (b) Tape grass (c) Ryegrass 3. Squirrels and monkeys are (a) Herbivore (b) Omnivore (c) Carnivore 4. A baby fish is known as (a) fry (b) larva (c) tadpole 5. Sugar is rich in (a) proteins (b) fats (c) carbohydrates B. Fill in the blanks. 1. The pigment called ............................ gives leaves their green colour. 2. During digestion, saliva in the mouth changes ............................ into ............................ . 3. Overcooking may destroy the ............................ present in the food. 4. The hard layer of our teeth is called ............................ . 5. Stagnant water breeds ............................. C. Give two examples of each of the following: a. Insectivorous plants ............................ ............................ b. Fixed aquatic plants ............................ ............................ c. Scavengers ............................ ............................ d. Arboreal animals ............................ ............................ e. Amphibians ............................ ............................ D. What are they called: a. Animals that eat both plants and animals. b. Animals that live both on land as wall as in water. c. Plants which grow in marshy areas. d. Animals that fly in the air. E. Answer the following questions. 1. What is hibernation? Name an animal which hibernates. 2. Why do we call a leaf “a food factory”? 3. What is food making process in plants called? 4 Give any two adaptations of under water plants. 5. Give two uses of grass plants. 6. What do carnivorous plants eat? 127 Science–4
TEST PAPER–2 Based on Chapter 7 – 13 A. Choose the correct answer. 1. The earth completes one revolution in (a) 28 days (b) 365¼ days (c) 24 hours 2. 1 Litre is equal to (a) 10 milliliters (b) 100 milliliters (c) 1000 milliliters 3. The number of planets in our solar system is (a) 36 (b) 8 (c) 5 4. The substances present in the soil which help the plants to grow are called (a) particles (b) nutrients (c) manures. B. Answer these questions in single word . a. Body building nutrients .......................... . b. The immediate help given to victims of accidents .......................... . c. Cutting teeth are also called .......................... . d. One of the methods of food preservation .......................... . e. An antiseptic cream to be applied on a burn .......................... . f. The larva of a butterfly is called a .......................... . C. Give the reason. 1. Plant cannot make food at night .................................................... 2. Teeth must be brushed at least twice a day. .................................................... 4. Children need a lot of proteins. .................................................... 5. We should avoid too much of sweets. .................................................... D. Tick () the correct words given in the brackets: 1. A food chain always begins with (plants / animals). 2. (Algae / Fungi) are green plants. 3. Tadpoles have (lungs/ gills ) for breathing. 4. The hump of camel stores (fats / proteins). 5. Incisors are (front teeth/ back teeth). E. Answer the following questions. 1. Name three simple machines. 2. What is meant by force of friction? 3. What is a push or pull-called? 4. Which is the biggest planet in the solar system? 5. What is the top layer of the earth called? 6 What are the causes of changes in seasons? 128 Science–4