51 Science–4 LEARNING GOALS Afier completing this chapter, you will be able to know about: Teeth Care of teeth Digestion of food Good eating habits Microbes 6 Teeth, Digestion and Microbes LET’S WARM UP TEETH You must have witnessed a newborn infant without teeth. What does he look like? It’s adorable, isn’t it? Imagine yourself in the future without teeth. Your appearance would not be as adorable as a baby’s. Our smiles, which are white and glossy, make us appear wonderful. Without them, we cannot properly chew our food. To make food easier to swallow and digest, teeth break it up into smaller bits. They also assist us in speaking. Below is a list of items with pictures. Tick () in front of the tool we use to clean our teeth, make a happy face. Antiseptic Liquid Antiseptic Liquid Mouthwash Chewing Gum Ice Creame Tongue cleaner Self Direction
52 Science–4 Temporary and Permanent Teeth A newborn’s teeth are not visible at birth. Inside the gums of the infant are tooth buds. When he is about six months old, his teeth begin to erupt. The infant has twenty teeth by the time he is three years old. These baby teeth are referred to as milk teeth or temporary teeth. A child’s milk teeth begin to erupt and the following set of teeth begin to appear when he or she is between the ages of six and seven. Permanent teeth are the second set of teeth. Children have 28 teeth total. About eighteen years old is when four additional teeth begin to erupt. They’re referred to as wisdom teeth. A full set of teeth for an adult is thirty-two. In the lower jaw there are sixteen of them and sixteen in the upper jaw. Types of Teeth Your mouth has different-looking teeth all everywhere. They come in various forms. The purposes they serve determine their shape. Incisors For cutting the food, there are four teeth in each jaw that have a chisel-like structure. These teeth are known as incisors, or cutting teeth. Canines On either side of the incisors are two pointed teeth. Gripping and tearing the meal is their job. They are also known as tearing teeth or canines. Premolars Premolars are the flat teeth that are located next to the canines. There are four premolars in each jaw, totaling eight. During chewing, they have the job of tearing and crushing the meal. TEST YOUR UNDERSTANDING Complete the sentences. 1. Temporary teeth are also called _________________ teeth. 2. ffe second set of teeth is called _________________ teeth. 3. ffe number of teeth a child has _________________ . Application of Knowledge
53 Science–4 Pocket Fact Appearance of 20 teeth of a baby 6–12 months Central incisors appear 9–16 months Lateral incisors appear 13–19 months First molar teeth appears 16–23 months Canine appears 23–31 months Second molar appears Molars The largest tooth is the molar. They have a wide area for biting. Each jaw contains six molars, three on each side. They are used to pulverise and grind food. DIY ACTIVITY One jaw’s teeth have labels on them. The other jaw’s labelling should be finished, then finish off the table. Upper jaw Lower jaw Total Incisors Canines Molars Upper jaw Lower jaw Total Incisors Canines Premolars Molars
54 Science–4 Structure of a Healthy Tooth The root and the visible, white portion of the tooth, which are both elements of a tooth, are its two essential components. Soft gums encircle the teeth. To assist secure the tooth in the jaw bone, the root extends below the gum line. Enamel is the term for a tooth’s visible outer layer. The body’s toughest material is this one. Dentine, which is also incredibly hard, is located beneath the enamel. At the centre of the tooth, within the dentine, is the pulp. Both blood vessels and nerves are present. CARE OF TEETH Every time you chew, certain food fragments become lodged between the teeth. The bacteria feed on these food particles, particularly the sugar, and create plaque, which is a sticky layer. The enamel is harmed by the acid they create. A hole known as a cavity slowly forms. The pulp is then reached after the hole in the tooth becomes deeper and contacts the dentine. The soft pulp’s nerves start to hurt. You find it challenging to chew your food. A toothache, foul breath, cavities, bleeding gums, and indigestion are all symptoms of dental decay. In such a situation, we ought to see a doctor. An individual who cares for our teeth is a dentist. Our adult teeth must remain in place for our entire lives. In order to maintain healthy teeth, we must do so. • Twice daily tooth brushing is recommended. • Our tongues need to be thoroughly cleaned. • We ought to brush our teeth after each meal. • We shouldn’t consume excessive amounts of sweets or fizzy drinks. • Foods rich in calcium and the vitamins A, C, and D should be consumed. Foods that are healthy for teeth include milk, cheese, fruits, and cruciferous vegetables. Raw carrots and apples are recommended as being excellent for teeth. • We should visit the dentist at least once every six months. Tooth anatomy Pocket Fact Braces can correct a wide range of dental issues, including crooked, gapped, rotated or crowded teeth. Scan this QR code to know how braces correct the alignment of teeth.
55 Science–4 The Right Way of Brushing Teeth For brushing teeth, a soft toothbrush should be used. For a few minutes, we should softly wash our teeth. After that, rinse your mouth out at least 5–6 times with water. DIGESTION OF FOOD Our bodies utilise the food we consume to produce growth as well as energy for work. But the food we consume cannot be utilised in its current form. It must be reduced to a relatively straightforward, soluble form. Food can then be delivered to all areas of our body in this form after dissolving in the blood. Digestion is the process by which food is transformed into a simpler form. The digestive system is made up of the organs that help food get broken down. The Process of Digestion Food digestion starts in the mouth. brush the front of the teeth brush between the teeth brush the back of the teeth Correct brushing technique Digestive system
56 Science–4 GOOD EATING HABITS • Maintain a healthy diet. • Consume your food at a set time. • Chew your meal thoroughly. Don’t rush anything. • Playing is not recommended right after eating. • Avoid overeating. • Be sure to hydrate well and consume a lot of fresh produce. Eat your food at fflxed time. In the mouth The teeth break down the food we eat into tiny pieces. In the mouth, saliva and food combine. There is a liquid in the mouth called saliva. It’s a digestive fluid that kickstarts the breakdown of carbs. Carbohydrates are converted into simple sugars by it. In the stomach Food enters the food pipe when you swallow it. The stomach is entered through the food pipe. The stomach retains food for a few hours. Food is constantly churned in the stomach, becoming a fine paste. Acid is added to the food by the stomach. Any bacteria that might be in the food are destroyed by this acid. In the small intestine The meal moves into the small intestine from the stomach. A lengthy, coil-shaped tube, the small intestine. Digestional fluids from the liver and pancreas combine with the food in the small intestine. These digestive juices break down the lipids, proteins, and carbohydrates found in the diet. The small intestine is where food digestion is finished. The small intestine’s blood vessels receive beneficial compounds from the food that has been digested. These compounds are carried throughout the body by the blood. In the large intestine The big intestine is where the undigested food ends up. Most of the water in the food that is not digested is reabsorbed into the blood in the large intestine. Waste is all that is left at this point. Faeces are produced as a result of it leaving the body.Anus refers to the portion of the big intestine where faeces exit. Plants need water to grow. Water the plants regularly otherwise it will die. Green Tip
57 Science–4 MICROBES Microorganisms, sometimes known as microbes, are incredibly tiny living entities. They can only be seen under a microscope. There are microbes everywhere. They multiply quickly wherever there is warmth, moisture, food, and air. They may develop in the bodies of people and other animals, in or out of the water, and in or out of the soil. Certain microorganisms thrive in the circumstances our mouth and blood provide. While some microorganisms are beneficial to us, others are disease-causing. Germs are microscopic organisms that cause disease. Kinds of Microbes There are four different types of microbes: bacteria, viruses, protozoa, and fungi. Microscope bacteria viruses fungi protozoa Kinds of microbes Bacteria : Microbes with only one cell make up bacteria. They might be circular, spiral, or rod-shaped. Some bacteria are helpful because they, among other things, turn milk into curd, assist our bodies generate vitamins, and speed the decomposition of dead plants and animals. Diseases including tuberculosis, typhoid, and pneumonia can be brought on by harmful microorganisms. Viruses: Smaller than bacteria, viruses can only be observed under a strong microscope. Viruses are the root cause of conditions including the chicken pox, flu, polio, dengue, and the common cold. Protozoa: Protozoa are composed of a single cell as well. Protozoa are responsible for dysentery and malaria. Fungi : Fungi are microscopic organisms that thrive on rotting substances. They are capable of causing skin conditions including athlete’s foot and ringworm. Food items like bread, idli, dosa, and dhokla are made softer by a type of fungus called yeast.
58 Science–4 KEY WORDS SUMMARY In our lifespan, we have two sets of teeth: milk teeth and permanent teeth. There are 20 milk teeth and 32 permanent teeth. We have four different types of teeth: canines for biting and tearing, incisors for cutting, premolars and molars for grinding and chewing food. Crown and root are the two primary components of a tooth. Digestion is the process of converting food into simpler forms. In the mouth, the digestive process starts. Microbes, often known as microorganisms, are incredibly tiny living entities that can only be seen under a microscope. Microbes come in four different varieties: bacteria, viruses, protozoa, and fungi. EXERCISE TIME A. Tick () the correct answer. 1. ffis is the tooth’s outer coating. a. Plaque b. Crown c. Enamel d. Root 2. ffese teeth are used to bite the food. a. Canines b. Incisors c. Premolars c. None of these 3. Decay in the teeth is a. Vomiting. b. Fever. c. Bad breath. d. All of these 4. In the digestive system, this is not a component. a. Stomach b. Small intestine c. Nose d. none of these Milk teeth : children’s temporary set of teeth. Enamel : an outermost layer or coating of the tooth. Incisors : a tooth’s outermost covering or coating. Plaque : a yellow, gooey ffllm developed on the enamel’s surface. Microbes : tiny living things that can only be seen under a microscope.
59 Science–4 5. Which of these microorganisms contributes to the sofiness of bread and idli? a. Fungi b. Bacteria c. Protozoa d. None of these B. Write T for true statement and F for false statement. 1. A infant has a full set of thirty two teeth by the time it is three years old. 2. Enamel is a tooth’s external, visible layer. 3. ffe small intestine adds acid to the food. 4. Viral infections are what cause dysentery and malaria. 5. We should drink plenty of water. C. Fill in the blanks 1. Protozoa are also known as ____________________. 2. ____________________ is the fflrst stage of digestion. 3. Use ____________________ to clean the region between two teeth. 4. ffe chisel-shaped teeth present in the front of the jaws are called __________. 5. ffe ____________________ are also called wisdom teeth 6. ffe region where the crown meets the root is called ______________. D. Write short answers. 1. Name the four types of teeth. 2. Defflne digestion. 4. Discuss any three healthy eating habits. 3. What is the role of saliva in digestion? 5. Discuss the role of small intestine in the process of digestion. E. Answer these questions. 1. Explain the process of chewing. 2. How is plaque formed? Why does it harm the tooth? 3. What is the function of the stomach? 4. What are the functions of incisors, canines, premolars and molars? 5. What are microbes? Name two diseases caused by protozoa. 6. What benefflts do bacteria and fungi have for us? TIME TO THINK (HOTS) 1. Ayushi ate a very cold ice cream. Now her tooth is hurting. What do you think is the problem with her tooth? 2. What are the key steps and processes in the digestive system that lead to energy production?
60 Science–4 Observe the given picture and answer the following questions. 1. How many diffierent types of teeth do you see? ________________________________________________ 2. Write the correct number of the following teeth : Canines ________ Premolars ________ Incisors ________ Molars ________ TIME TO OBSERVE (Observational Skills) Make a chart of food items that are harmful to our teeth. TIME TO CREATE (Project Work/Creative Skills) We should brush our teeth twice a day, even at bedtime. Why? TIME TO DISCUSS (Collaborative Skills) Put a tick () if the child does a right thing. Cross () the other ones. 1. Ankush rinses his mouth afier eating. 2. Raman brushes his teeth without using a toothpaste. 3. Harjeet uses one toothbrush throughout the year. 4. Randeep eats too many sweets. 5. Rosy rinses her hands before and afier eating the food. 6. Geeta visits a dentist regularly. LIFE SKILLS Talk about the function, variety, and structure of teeth. Remind the students to brush their teeth. Describe the procedure for food digestion. Explain the many types of microbes. FOR THE TEACHER (Life Skills)
61 Science–4 LEARNING GOALS Afier completing this chapter, you will be able to know about: Safety at home Safety at school Safety on the playground Safety in the swimming pool Safety on the road Internet safety Safety signs First aid 7 Safety and First Aid LET’S WARM UP Write T for true and F for false statements. 1. Do not swim immediately afier your meal. _________ 2. Do not follow the rules of the game. _________ 3. Do not throw pens, pencils or rulers at others. _________ 4. Do not wear a seat belt while travelling in a vehicle. _________ Accident may happen any time anywhere, without giving any warning. Accidents cause harm to life and property. Accidents mostly occur because of our carelessness. Most accidents can be prevented if we are careful and follow simple rules of safety. SAFETY AT HOME In your house, there are many things that can cause accidents if you are careless. So, there are some safety rules that should be followed at home. Let us discuss them. Never leave your toys on the ground. When you’re done playing, put them back where they belong. You might trip over them if you don’t. Avoid playing with breakable goods like glass and tableware. You might suffer harm. Self Direction
62 Science–4 Do not climb up windows, tables, shelves, etc. Watch out for slick surfaces. Only take medication in an adult’s presence. Even touching some substances can be dangerous. Take caution. Do not experiment with electrical devices. Avoid using moist hands to interact with electrical lines or switches. A shock could occur. Avoid playing near hot pots, pans or gas stoves. Burns hurt badly. Never rest your weight on a balcony or terrace railing. Leakage of cooking gas is very dangerous, it can catch fire. If you smell leaking gas, you must do the following: Inform an adult immediately. Open all the windows and the doors for the gas to escape. Turn off the regulator of the gas cylinder. Do not touch any switch. Even a small spark is enough to catch fire. Do not light a matchstick. The gas in the room will catch fire. Contact the gas agency immediately. Pocket Fact Cooking gas has no smell of its own. Another gas with a smell is mixed with it so that if the cooking gas ever leaks, people will notice and accidents can be avoided. SAFETY RULES AT SCHOOL Some safety rules are prescribed to be followed in school. Accidents can be avoided if these safety rules are followed. Always follow the rules of discipline. Never push anyone or rundown the staircase. Never climb on desks and chairs. Do not make your class dirty. Do not use blade to sharpen your pencil. Do not play in the classrooms. Follow the rules of the game while playing. When we work we should use our safety gears or safety instructions for stopping any mis happening/accident Green Tip
63 Science–4 SAFETY RULES ON THE PLAYGROUND We should follow safety rules while playing. Playing on the swings, slides, and jungle gym requires caution. Never push anyone. Wait for your turn. Avoid approaching the moving swings too closely. Observe the game’s rules. Don’t hurt people with sports equipment. SAFETY iN THE SwiMMiNG POOL We should follow safety rules while swimming. If you’re learning to swim, use a swimming tube. Swim with an adult nearby at all times. SAFETY ON THE ROAD Here are some important road safety rules. Always walk on the footpath. If there is no footpath then always walk on the left. Cross the road on zebra crossing only. Obey the traffic rules. Never run to cross the road. Do not play on the road. Never cross a road behind a parked vehicle. During a Car or Bus Ride Safety rules while riding in a car or bus is crucial for their well-being. Here are some safety rules to convey to them: Stress on the importance of wearing seat belts at all times when sitting inside in a moving car. Make it a habit for everyone in the car. Always stand in a line when boarding or deboarding a bus. You must not remain standing while the bus is travelling. Keep your hands and head inside the vehicles at all times.
64 Science–4 TEST YOUR UNDERSTANDING Give answer in one word. 1. What is the most common hazard in a kitchen? ______________ 2. What safety gear should you wear when riding a bicycle? ______________ 3. What safety device should you always wear when sitting in a car? ______________ 4. What is the initial care you provide in case of an injury or sudden illness? ______________ SAFETY SiGNS ON ROAD Safety signs use pictures, colours and shapes to warn us about danger. iNTERNET SAFETY Always ask a trusted adult for permission before using the internet. Let them know what you want to do online. Only visit websites that are safe and appropriate for your age. Use websites and apps that your parents or teacher have approved. Do not give any kind of personal information on the Internet. Do not accept online requests of strangers. Remember to balance your time between online activities and other activities like playing outside, reading, or spending time with family and friends. Don’t talk loudly or get up from your seat. Doing so may cause the bus or auto driver to become distracted. If the person operating the automobile or bus violates any traffic laws, speak out. while Riding a Bicycle Always wear a properly fitted bicycle helmet to protect your head in case of a fall or accident. Always stay alert while you ride bicycle. Ride on safe and designated bike paths or sidewalks whenever possible. Avoid busy roads and intersections. Keep both your hands on the handle bars. Application of Knowledge Stop No left turn No U turn Zebra crossing No horn No parking
65 Science–4 Different types of injuries need different types if first aid. Wash the small cuts and wounds with water. Apply an antiseptic lotion or cream. Wash the burnt area with cold water. Apply antiseptic cream on the affected area. If a person faints, make him/her lie down with the head lower than the body. This helps the blood to flow faster into the brain. FiRST AiD It is the immediate help given to a person who gets injured or falls sick. It can save a person’s life and prevent it from becoming worse. Keep calm until help arrives. Immediately try to find an adult person for help. Pocket Fact Do not apply ice pack on a burn, as it can cause frostbite and damage the skin. First aid box A first aid box usually has the following things: small pieces of clean cloth a small cotton roll a crepe bandage some adhesive bandage a pair of forceps (tweezers) a pair of scissors a pencil torch a thermometer a small roll of sterilized cotton pads a small soap Medicines in a first aid box an antiseptic lotion to clean wounds an antiseptic cream to apply on cuts and wounds an anti-burn cream DIY ACTIVITY Grab a shoebox. Glue a white sheet of paper over the entire thing before covering it. Create a plus sign with red sticky tape. With the assistance of your parents, gather the aforementioned goods and store them in the box.
66 Science–4 KEY WORDS First aid : an immediate help given to an injured person. Faint : feeling giddy or losing consciousness. Zebra crossing : the black and white zig-zag marking on a road meant for pedestrians to cross. Some insects like bees and wasps can sting us and these stings are very painful. Put some cold water or calamine on the affected area. It is good to be ready for any emergency and to know how to give first aid. It is still better to remember and follow safety rules to avoid accidents. Always remember ‘Prevention is better than cure’. SUMMARY Most accidents are the result of our negligence. You must abide by safety regulations whether you’re at home, on the road, in a car, at school, on a playground, or in a swimming pool. If we are cautious and adhere to specific safety guidelines, we can prevent the majority of incidents. Always obey the rules of the road. Sharp instruments should be handled with care. The first help given to the injured or sick person by another person is called first aid. A nose bleed, minor cuts, burns, fainting, bug bites, and other crises call for first assistance. A first aid box contains all the required things that are used in first aid. EXERCISE TIME A. Tick () the correct answer. 1. You should not a. Scatter your toys on the ffoor. b. Obey trafflc rules. c. Stay away from strangers. d. Wear seat belt in moving car
67 Science–4 2. If we smell leaking gas, we should a. close all the windows and the doors for gas to trap. b. turn offi the regulator of the gas cylinder. c. light a matchstick. d. none of hese 3. In case of an accident, we should a. call an adult or a doctor. b. stay calm and comfort the injured person. c. make the injured person lie down. d. all of these 4. We must keep this in our flrst aid kit. a. A pencil b. An antiseptic lotion c. A perfume d. Eraser. B. Match the following. 1. Electric shock (a) Apply burnol 2. Minor burn (b) Zebra crossing 3. Always cross the road (c) Wetlands 4. Accident (d) First aid 5. First help to the injured person (e) A sudden mishap C. Fill in the blanks using the words given in the help box. antiseptic lotion calamine seat belt zebra crossing 1. We should use ________________ to cross the road. 2. In case of an insect bite, apply ________________ on the skin to soothe it. 3. Always wear a ________________ while travelling in a car. 4. ________________ should always be applied on the burn. D. Write short answers. 1. Why shouldn’t we leave toys on the ffoor? 2. Why shouldn’t we play with breakable things? 3. Why should we not go too close to the moving swings? 4. Name two things that we must keep in our flrst aid kit.
68 Science–4 E. Answer these questions. 1. What precautions should you take to avoid accidents at school? 2. What safety rules should we follow before crossing the road? 3. How will you help a person who has burnt his hand? 4. How will you help a person who has fainted? 5. How will you help a person who has been bitten by an insect? TIME TO THINK (HOTS) Why should we not wear synthetic clothes while playing with flrecrackers on Diwali? Conduct a live demonstration of basic first aid techniques using a mannequin or doll. Show them how to apply a band-aid, wrap a small wound with gauze on mannequin or doll. Explain that they should only practice these techniques under adult supervision. TIME TO CREATE (Project Work/Creative Skills) Observe the picture and answer the following questions. 1. What is happening in this picture? ___________________________ 2. Why is the person applying a bandage? ___________________________ TIME TO OBSERVE (Observational Skills) What do you think flrst aid means? TIME TO DISCUSS (Collaborative Skills) Visit an orphanage with your parents or teacher. Donate some flrst aid kits to the children who live there. Have a discussion on safety and flrst aid with them. Tell them how they can be safe at diffierent places and also give them some flrst aid tips. Also, learn from them things that you do not know. LIFE SKILLS To know more about safety please scan this QR code. WEBLINK (Social Skills)
69 Science–4 LEARNING GOALS Afier completing this chapter, you will be able to know about: Why do we need clothes? Sources of clothing Clothes worn in different seasons Clothes and work ffle clothes we wear Our national dress Care of clothes 8 Clothes We Wear LET’S WARM UP Colour the clothes and write the name of those we wear in summer. WHY DO WE NEED CLOTHES? Wearing clothes is essential for several reasons. First and foremost, clothes provide us with protection. They shield our bodies from the harsh elements like the sun, rain, wind, and cold. In hot weather, light and loose-fitting clothes help us stay cool, while in cold weather, warm and layered clothing keeps us snug and prevents us from getting too cold. (Creativity)
70 Science–4 SOURCES OF CLOTHING Clothes are made from various sources, and it’s fascinating to learn about where our clothing comes from. One of the primary sources of clothes is natural fibers. These fibers come from plants and animals. Natural Fibres Animals or plants are the sources of natural fibres. Plants are the source of our cotton, jute, hemp, and linen. We obtain wool from animals including camels, sheep, goats, and rabbits as well as silk from silkworms. Natural fabrics include little openings that allow air to enter and exit, making them more comfortable to wear. Thus, our skin is able to breathe, and sweat evaporates quickly. Synthetic Fibres Nature does not contain synthetic fibres like nylon, rayon, or polyester. They are also known as man-made fibres and are created artificially. These wrinkle-free, elastic, and waterproof textiles are manufactured from synthetic fibres. They dry up extremely fast. Nonporous describes synthetic fabrics. Can you tell the profession of these people by just looking at their clothes? ACTIVITY From ffibers to fabrics (Experiential Learning)
71 Science–4 CLOTHES WORN IN DIFFERENT SEASONS In the summer and winter months at school, you wear different uniforms. Ask your teacher what types of fibres each is composed of. In general, people dress to fit the weather. We dress in lightcolored cotton clothing during the summer. Cotton clothing absorbs perspiration, lets air circulate easily, and keeps our body cool. Less heat is absorbed by lighter colours. When it rains, we cover our dresses with waterproof clothing, such as raincoats, and footwear, such as gumboots, to stay dry. We dress warmly in dark-colored, heavy clothing made of leather, fur, or wool throughout the winter. They keep the cold off of us. Dark clothing reflects heat away from the body and keeps it warm. UNIFORMS Some people dress differently depending on their line of work. White coats are worn by nurses and doctors. A lawyer is dressed in a black coat, white trousers, and white shirt. In order to keep their clothing from getting dirty, factory workers cover their outfits with dungarees. Children in schools dress in a uniform so that their affiliation with a particular institution may be easily determined. A soldier’s outfit is made of durable fabric to prevent easy tearing. A waiter stands apart from the guests by donning a uniform. We should not use leather products which is a sign of animal abuse. Green Tip
72 Science–4 THE CLOTHES WE WEAR Depending on the temperature and traditions of the area, people in different places dress in various ways. A person living in Kerala will not wear the same as a person living in Punjab. Different countries’ citizens dress in various fashions. TEST YOUR UNDERSTANDING Answer in one word. 1. What natural ffiber is commonly used to make t-shirts and jeans? 2. What luxurious ffiber is produced by silkworms and used for ffine clothing and fabrics? 3. What type of uniform is common in the kitchen? Put the name of the state where each person is from beneath each image. ACTIVITY NATIONAL DRESS Some of our garments have evolved into national attire. The saree is the national clothing of India, while the kimono is the national garment of Japan. CARE OF CLOTHES In order for our clothes to last longer and look beautiful, we need to take care of them. • Regular wash and ironing are advised. Always dress neatly. saree (India) kimono (Japan) Application of Knowledge Holistic Learning
73 Science–4 • Silk and wool clothing can be dry-cleaned or should be washed with a mild soap. • If clothes are torn they should be mended. • Before storing and packing clothes they should be dried in the sun to kill germs. • Napthalene balls or dried neem leaves should be put between the folds of woollen clothes to protect them from moths, silverfish and other pests like rats and cockroaches. KEY WORDS Yarn : cotton thread. Cocoon : round sheath of silk thread. Tanning : changing skin into leather. Fibre : a ffilament obtained from plant and animal tissues that can be spun into cloth. Synthetic : artifficial material made by man. Pocket Fact Dry cleaning is a special way to clean clothes and fabrics that cannot be washed with water and soap. Instead of water, a special liquid called a solvent is used to clean the clothes. TEST YOUR UNDERSTANDING Sort the following into natural or synthetic fibres. 1. Cotton: _______________ 4. Linen: _______________ 2. Nylon: _______________ 5. Silk: _______________ 3. Polyester: _______________ 6. Wool: _______________
74 Science–4 SUMMARY Wearing clothes helps us look good and protects us from the heat, cold, and insect stings. People dress differently depending on the season, the event, their personal style, and their line of employment. Some of our garments have evolved into national attire. Clothing needs to be properly stored, cleaned, and ironed on a regular basis. EXERCISE TIME A. Tick () the correct answer. 1. Which of these clothes would you wear at home? a. Uniform b. Comfortable clothes c. Constumes d. None of these 2. Which of these ffibres are used to make clothes worn in summer? a. Solk and cotton b. Silk and wool c. nylon and Polyester d. Cotton and linen 3. ffle national dress of Japanese women is a. Saree. b. Kimono. c. Eans-top d. None of these B. Match the following column. Column A Column B 1. Cotton a. Man-made ffibres 2. Silk b. Sheep 3. Wool c. Silkworm 4. Nylon d. Plant ffibre C. Write T for true statement and F for false statement. 1. Nylon is a man-made ffibre. 2. Summer clothes are made of wool and flannel. 3. Dark colours reflect heat. 4. Uniforms also give us a sense of belongingness and pride. D. Write short answers. 1. Why do we wear clothes? 2. Why do sports teams have special uniforms?clothes from being dirty? 3. Why do students of different schools wear different clothes?
75 Science–4 4. What do Indian women wear as their national dress? 5. What is dry-cleaning? E. Answer these questions. 1. What is the difference between uniforms and casual clothes? 2. Why do we wear cotton clothes in summer? 3. Why are winter clothes made of fur, leather or flannel? 4. What are the ffibres? Name the three types of ffibres. 5. How can we take care of our clothes? TIME TO THINK (HOTS) Why do people of Kashmir wear phiran? Collect pictures of the different kinds of clothes people wear. Then paste them under the correct categories: summer, winter or rainy and make a chart. TIME TO CREATE (Project Work/Creative Skills) Discuss the different types of clothes that we wear on different occasions. TIME TO DISCUSS (Collaborative Skills) You must have seen individuals in need, begging, and tiny children standing by the side of the road wearing tattered clothing. fflese individuals lack appropriate clothing to hide their bodies. We can give them our gently used clothing that is no longer in fashion. Give some of the worn-out clothing that has accumulated in your closets to orphanages for disadvantaged kids. Encourage your friends to follow suit. During the winter, you can also give warm clothing and blankets. LIFE SKILLS Talk to the children about their choices of clothes. Discuss how the clothes depend on different factors like season, place where we live, our tradition, etc. FOR THE TEACHER To know more about different types of fibers. please scan this QR code. WEBLINK (Go Green, Life Skills)
Activity Project: Animals as Living Beings: Investigating the Life of Animals Aim: To help students understand that animals are living beings with characteristics like breathing, eating, moving, growing, having feelings and reproduction. Materials Needed: 1. Pictures or images of various animals 2. Drawing or coloring materials 3. Books or online resources about animal adaptations 4. Poster board or large paper 5. Glue, scissors, and markers Food Group Categories: Introduce the five main food groups (fruits, vegetables, grains, protein, dairy) and briefly explain what each group provides in terms of nutrition. Create the Digestive System Poster Use a large poster board or chart paper to create an eye-catching poster that depicts the digestive system. Draw or print images of the mouth, esophagus, stomach, small intestine, and large intestine. Teeth Section: Create a specific section on the poster dedicated to teeth. Draw or paste pictures of different types of teeth (incisors, canines, molars) and explain their functions. Safety Rules Handbook Provide each student with a blank sheet of paper or a small notebook. Instruct them to create a “Safety Rules Handbook” where they will compile important safety rules. Students can draw or paste pictures related to safety on each page. They can create their illustrations or use pictures from magazines or printed materials. Research and Illustrate Instruct each group to research and gather information about the clothing styles, materials, and purposes of clothing during their assigned time period. They can use books, online resources, or printed images from magazines. Activity Time–3 APPROACH 76 Science–4
(Creativity) 77 Science–4 LEARNING GOALS Afier completing this chapter, you will be able to know about: ffe sun Planets Stars Moons or satellites Difflerence between planets and stars How are planets and stars difflerent? Earth Festivals and seasons Our Universe: The Solar System 9 LET’S WARM UP Colour the picture and match them with their correct name. Rocket Sun Earth Solar System is a family of planets and other heavenly bodies that revolve around the bright central star called the Sun. The Sun, the Moon, stars and planets are heavenly bodies. Our Solar System consists of eight planets and their satellites, revolving around the Sun in fixed orbits. Sun’s gravity along with the movement of each planet keeps the planets in their orbits. Unit-IV : Our Universe
78 Science–4 THE SUN The Sun is a giant, fiery ball of burning gases in the center of our Solar System. It is incredibly hot and bright, and it provides us with light and warmth. The Sun is what makes our day and night as the Earth rotates, and it is the source of energy for all living things on our planet. Without the Sun, life on Earth would not be possible. PLANETS Planets are large celestial objects that orbit, or go around, the Sun. They are like Earth but can be very different in size, appearance, and characteristics. There are eight planets in our Solar System, and they include Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Planets do not produce their own light but instead shine by reflecting the light of the Sun. Sun Solar system The first four planets called inner planets. They have solid surfaces. The last four planets are called outer planets. These planets are mainly made up of gases. Below are some brief descriptions of the planets. Planet Description 1. Mercury It is the planet that is most near the sun. In the solar system, it is the smallest planet. It makes its orbit around the sun more quickly than any other planet. fie moon is absent from it. Pocket Fact fie ffrst alphabet of each of the words of this sentence will help you remember the planets in order : My Very Educated Mother Just Served Us Some Nuts.
79 Science–4 2. Venus It is the second planet from the Sun and Earth’s closest planet and neighbour. Venus is the hottest planet. Its atmosphere is full of the green house gases, carbon dioxide and it is full of sulfuric acid. 3. Earth It is located third from the sun. Since water covers three-fourths of the earth’s surface, it is known as the “blue planet.” ffe only planet where life is known to exist is Earth. One moon is present. 4. Mars Its rocks and soil are red, and the night sky is red. It so also goes by the name “red planet.” Having two moons. 5. Jupiter ffe largest planet is that one. It is most recognised for having a large stormy red spot on its surface. For years, the storm has been raging. 67 moons orbit Jupiter. 6. Saturn ffe second-largest planet is this one. ffe rings surrounding it are what make it most famous. Ice, boulders, and dust make up these rings. 62 moons orbit Saturn. 7. Uranus From the sun, it is the eighth planet. ffe planet is the coolest. 27 moons are on it. 8. Neptune ffe sun is away from it the most of any planet. 14 moons are on it. STARS A star is a massive gas ball that emits heat and light energy. The diameters of stars vary. While some stars are significantly larger than the Sun, others are smaller. Because they are so extremely far away from Earth, stars appear to be quite little. In the sky, we can detect clusters of stars. Galaxy refers to a collection of stars. The universe contains countless billions of galaxies. Some star clusters appear to create particular patterns in the sky. They are referred to as constellations. MOONS OR SATELLITES The heavenly bodies known as moons or satellites orbit the planets. There is just one moon on Earth. Its size is greater than onefourth that of the earth. Other planets have moons, just like the earth. DIY ACTIVITY Make a model of the solar system on a sheet of cardboard or thermocol. You can make paper balls of difflerent sizes to represent planets. We should walk or use bicycle to get things from the store or do some work. Green Tip
80 Science–4 DIY ACTIVITY DIFFERENCE BETWEEN PLANETS AND STARS Compared to stars, planets are significantly smaller. As a source of light, stars are fixed in place and twinkle at night. There is no internal light on planets. Never do they sparkle. They just serve to reflect sunlight. Planets orbit the sun and are not fixed in place. This is what enables astronomers to determine if a celestial body is a planet or a star. Only gases make up stars. EARTH The only planet in the solar system has land, water, and air for supporting life is Earth. The atmosphere is a covering of air that encircles it. There is oxygen in the atmosphere. To survive, all living things require it. Additional gases including nitrogen, carbon dioxide, and water vapour are also present in the atmosphere. The earth is made up of one fourth land and three quarters water. Layers of the Earth Crust : The outer solid layer is called the crust. We live on the crust. Water and land are present here. Mantle : Below the crust is a thick layer of rocks and minerals called mantle. Core : The centre of earth is very hot and is called the core. It is made up of hot, molten material. Magma is molten rock that is located deep within the crust. Lava is the term for magma that has been driven through surface fractures. A volcano is an opening in the crust of the earth through which lava, ash, and hot gases spew during an eruption. By looking at an egg, we may comprehend the structure of the earth. Pick up a fully cooked egg. Make two parts of it. The crust is represented by the shell, the mantle is by the firm egg white, and the core is by the yellow portion.
81 Science–4 Movements of the Earth The rotation and revolution of the earth are two different types of motion. Let’s analyse these motions. Rotation Like a spinning top, the Earth revolves on its axis. Rotation is the term for this motion. One rotation of the Earth takes 24 hours to complete. The axis is a hypothetical line that passes through the Earth’s centre between the North and South Poles. Earth’s rotation on its axis is what causes day and night on the planet. The tilt of the Earth’s axis is 23.5°. As you totation is the term used to describe how the earth spins about its axis. One rotation of the planet takes a day, or 24 hours. Day and night are caused by the earth’s slanted axis during rotation. Half of it that faces the sun experiences daylight. The other half, which is in the shadow and has night, is dark. The day-lit portion of the earth rotates away. The night is in this part. The day comes to the other half as it travels towards the sun. Pocket Fact Venus rotates in a clockwise direction while all the other planets rotate in an anticlockwise direction. Pocket Fact Asteroids are pieces of large rocks. ffey are thought to be the remains of a planet. Rotation of the earth causes day and night TEST YOUR UNDERSTANDING Answer in one word. 1. ffe hottest planet of our solar system ____________________ 2. ffe ringed planet of our solar system ____________________ 3. ffe blue planet of our solar system ____________________ Self Direction
82 Science–4 DIY ACTIVITY Place a globe in a dark room. Pass a torch over the object. What have you noticed? It shows the rotation of the Earth. When we shine the torch on the globe in a dark room we see that the part facing the globe gets the light and the part facing away doesn’t recieve the light. When we rotate the globe we see that the other part of the globe recieves the light. This shows how day and night occur on earth if we take the globe as the earth and the torch as the sun. Revolution The earth does not remain in the same place as it rotates. It continuously moves around the sun in a definite orbit. The movement of earth around the sun in an orbit is called revolution. It takes 365¼ days for the earth to complete one revolution around the sun. Change of Seasons Seasons are brought on by the earth’s orbital rotation and tilt on its axis, respectively. Summer and greater sunlight are experienced in the hemisphere that is inclined towards the sun. Winter and less sunlight are experienced in the area that is slanted away. Both hemispheres enjoy autumn and spring in between these two seasons, which are neither hot nor cold. FESTIVALS AND SEASONS Numerous Indian holidays have connections to the sun, moon, stars, and seasons. The arrival of Holi heralds the start of spring. The Islamic calendar is based on the phases of the moon, hence Eid is reliant on the moon. Seasonal festivities like Pongal, Bihu, Lohri, and others are celebrated in many states. KEY WORDS Star : a huge ball of bright hot gases. Planet : a large round heavenly object in space moving around the sun. Satellites : natural or man-made bodies revolving around a planet. Solar system : the family of eight planets, along with their moons revolving around the sun. Solar year : the time taken by the earth to orbit around the sun once.
83 Science–4 SUMMARY The solar system, which includes the sun and the eight planets, is a family. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune are the eight planets, listed in decreasing order of their distance from the sun. Since stars are the source of light, they are stationary and sparkle at night. The crust, mantle, and core make up the three layers of the earth. The earth’s axis is a hypothetical line that traverses its centre. Day and night are caused by the earth’s slanted axis as it rotates. Seasons are brought on by (1) the earth’s rotation in its orbit and (2) the tilt of the earth’s axis. Numerous Indian holidays have connections to the sun, moon, stars, and seasons. EXERCISE TIME A. Tick () the correct answer. 1. Which of the following describes how the Earth’s seasons are created? a. Earth’s tilted axis b. Revolution of the Earth c. Rotation of the Earth d. Both (b) and (c) 2. ffe name of the earth’s centre is a. Mantle b. Core c. Melting point d. Crust 3. Molten rock which is forced out through cracks in the earth’s surface is called a. Lava b. Magma c. Layer d. Volcano 4. Day and night are a result of the earth’s rotation, which is a. Migration b. Revolution c. Rotation d. Season 5. Which planet has maximum number of moons? a. Jupiter b. Uranus c. Neptune d. Saturn
84 Science–4 TIME TO THINK (HOTS) 1. Would it be possible for us to live on Mercury? 2. A star produces light and heat. 3. What would happen if Earth’s axis were not tilted? 4. Neptune is a very cold planet. B. Write ‘T’ for true and ‘F’ for false against following statements. 1. Stars have their own light. 2. ffe earth completes its revolution in 376 days. 3. ffe sun moves round the earth. 4. Earth is a planet. C. Name the following. 1. ffe planets that have solid surfaces ____________ 2. ffe planet, also referred to as the morning star ____________ 3. ffe movement of the Earth around the Sun ____________ 4. ffis festival marks the beginning of the spring season ____________ 5. Fixed paths of planets around the Sun ____________ D. Write short answers. 1. Name all the planets of solar system. 2. Deffine: (a) Orbit (b) Satellite 3. Why is Earth called the blue planet? 4. ffe equator divides the earth into two halves. Name them. 5. What is an equator? E. Answer these questions. 1. Difflerentiate between magma and lava. 2. Why does the Sun appear larger than other stars in the sky? 3. What are the three layers of the earth? Give a short description about each. 4. Difflerentiate between equator and axis. 5. What causes change of seasons? Explain.
(Go Green, Life Skills) 85 Science–4 TIME TO OBSERVE (Observational Skills) 1. Find the information about different seasons and make chart. 2. Find the information about Chandaryan-3 and make PowerPoint presentation. TIME TO CREATE (Project Work/Creative Skills) Discuss objects other than the planets that constitues the solar system. TIME TO DISCUSS (Collaborative Skills) We are shielded from the heat of the sun by the atmosphere, which acts as a blanket. ffis blanket is damaged by factory and vehicle emissions. As much as possible, we should strive to walk nearby distances to reduce car exhaust. Have you ever taken any action to preserve the environment? LIFE SKILLS Help the students understand the movements of the earth through activities and models. FOR THE TEACHER Observe the given picture and answer the following questions: 1. Can you identify any star constellations in the picture? _____________________________________ 2. Describe what they look like? _____________________________________ To know more about rotation and revolution of the Earth please scan this QR code. WEBLINK
More About Moon One-Fifth the Size of Earth: The Moon is much smaller than Earth, about one-fifth the size of our planet. No Atmosphere: Unlike Earth, the Moon has no atmosphere. This means there’s no air to breathe, and the sky always looks black. Extremely Cold and Hot: The Moon’s temperatures can be extreme. During the day, it can get scorching hot, but at night, it becomes incredibly cold. Moonquakes: Just like earthquakes on Earth, the Moon experiences “moonquakes.” These are caused by the gravitational pull of Earth and the cooling of the Moon. Mysterious Dark Side: The Moon always shows the same face to Earth. The side that’s always facing away from us is called the “dark side,” even though it’s not always dark. Space Junk: There are many pieces of space junk on the Moon, including items left by astronauts from the Apollo missions, like flags and footprints. Ages-Old Surface: The Moon’s surface is very old. Some parts of it are around 4.5 billion years old, nearly as old as the Moon itself! Lunar Maria: The dark, flat areas on the Moon are called “lunar maria” (singular: mare), and they were formed by ancient volcanic activity. Extreme Days and Nights: A day on the Moon (one sunrise to the next) is about 29.5 Earth days long, and a lunar night is just as long. That’s a very long day and night! Footprints Last: The footprints left by astronauts on the Moon’s surface will likely stay there for a very, very long time. Because there’s no wind or water to erase them, they might last for millions of years. The Moon is Moving Away: The Moon is slowly moving away from Earth at a rate of about 1.5 inches (3.8 centimeters) per year. Micro-Meteorite Impacts: The Moon’s surface is covered in tiny craters caused by micro-meteorite impacts. These are little pieces of space debris that hit the Moon. These fascinating facts reveal the Moon’s unique characteristics and add to the wonder of Earth’s nearest celestial neighbor. Reading Fun 86 Science–4 Science–4
Activity Project: Exploring Our Solar System Aim: To foster a deeper understanding of the Solar System and its celestial bodies through research and creative presentation. Materials Needed: 1. Poster boards or individual sheets of paper. 2. Markers, coloured pencils, crayons. 3. Access to books, websites, or educational resources about the Solar System. Research Assign each student or group of students a specific celestial body or aspect of the Solar System to research. This could include planets, moons, constellation, and the Sun. Solar System Tour Organize a “Solar System Tour” where students visit each presentation or display to learn about different aspects of the Solar System. Planet Posters Create a detailed poster for their assigned planet, moon, or celestial object. Include key information, illustrations, and fun facts. Spacecraft Models Build a small model of a spacecraft that has explored a celestial body. Include information about the mission and discoveries. Discussion Ask students to share their favourite discoveries and what they found most fascinating about the Solar System. APPROACH Activity Time–4 87 Science–4
88 Science–4 LEARNING GOALS Afier completing this chapter, you will be able to know about: Enviornment Air pollution Water pollution Soil pollution Noise pollution Preventing pollution Disposal of waste Reduce, reuse and recycle Environment and Pollution 10 LET’S WARM UP 1. Name some natural resources that are essential for our survival. __________________________________________________________________ __________________________________________________________________ 2. How can planting trees and taking care of green spaces benefft the environment? __________________________________________________________________ __________________________________________________________________ 3. What are some small actions you can take to protect the environment in your daily life? __________________________________________________________________ __________________________________________________________________ All living and non-living things around us form the environment. Everything that forms the surrounding of a living thing is called environment. Every living things has its own environment. For example the environment of a plant includes the water, air, sun, weather, soil and the creatures living in it. Self Direction Unit-V : Earth and Natural Resources
89 Science–4 Importance of envIronment We depend on the environment for our needs. It provides us food, water, air, clothing and other materials we use in our daily life. How do we damage our envIronment? Human beings are the most developed living things in nature, but their actions have disturbed its balance. Their increasing population has led to a great increase in their needs. It has also led to the production of more waste all around. These wastes are harmful for air, water and land on the earth. The addition of these harmful substances to our natural resources is called pollution. The harmful substances which cause pollution are called pollutants. aIr poLLutIon When the air we breathe becomes dirty or unhealthy is called air pollution. It happens when things like smoke, dust, chemicals, or tiny particles get into the air and make it not good to breathe. The pollutants can be manmade or natural. causes Factories and industrial plants release smoke, chemicals, and dust into the air when they make things. This can make the air dirty. Vehicles like cars, trucks, and buses produce smoke and harmful gases when they run. This pollution is called “vehicle emissions.” Sometimes, things like volcanic eruptions, wildfires, and dust storms can put pollutants into the air naturally. Pollutants produced by nuclear explosions and war explosives also affect air quality. Smoke from automobiles and factories cause air pollution. Smoke and ash released from volcanoes pollute air. Composting leaves is one of the smartest a great way to mulch, fertilize and improve your soil. Green Tip Pocket Fact An average human being needs about 14 kg of air everyday for breathing.
90 Science–4 effects • When the air is polluted can cause asthma, lung diseases and throat irritation. • Air pollution can harm plants and trees. It can damage them. • Animals can also get sick from air pollution. Birds and insects can be affected by polluted air. • Smog (a mixture of smoke and fog) can make it difficult to see and breathe, and it’s not healthy.. acid rain Acid rain is like regular rain, but it’s not good for the environment. Harmful gases like nitrogen, carbon and sulphur are released from vehicles and factories due to burning of fuel. These gases rise up and combine with moisture. They form acids. When it rains, these acids combine with raindrops and fall on the earth. This is called acid rain. Acid rain can hurt plants, trees, and even buildings. It can make fish and other aquatic animals sick or even die. water poLLutIon The mixing of harmful wastes in water bodies is called water pollution. causes Sewage water, water mixed with chemicals and hot water from factories pollute the water bodies. People throw garbage, flowers, plastic waste, etc. in rivers and lakes. They wash clothes and vehicles and bathe animals. Smog Acid rain damages crops Garbage pollutes water Chemical wastes from factories cause water pollution Pocket Fact While solar, wind, and water energy do not harm the environment, fuels like coal, wood, petrol, diesel, and kerosene contribute to air pollution.
91 Science–4 Chemical fertilizers and insecticides used in crop fields get mixed with rainwater and flow into rivers and lakes. These pollute water. effects • Polluted water can harm fish, plants, and other aquatic organisms. It can decrease the oxygen levels in water, making it difficult for aquatic life to survive. • Polluted water is full of bacteria, If we drink it, we may fall sick. • Many harmful germs grow in polluted water. They cause diseases such as typhoid, diarrhoea and dysentery. Land poLLutIon Land pollution is the addition of harmful substances to the soil. causes Land pollution is caused by waste from various sources. Domestic waste is a very big problem. Solid waste from the industries pollutes the soil. Chemicals used as fertilizers and insecticides too cause land pollution. effects • Insects and animals gather around piles of dirt on land and spread germs and diseases. • Chemicals in pesticides and fertilizers are harmful to the useful bacteria living in soil. When these bacteria die, the quality of the soil is reduced. • Harmful chemicals are absorbed by plants and when human beings eat such plants, they become ill. TEST YOUR UNDERSTANDING 1. Pollution from cars and factories is an example of __________ pollution. 2. _________________ and ________________ get mixed to form smog. 3. Drinking polluted water can cause diseases like ________ and ________ . 4. Chemical fertilizers and _________________ used in crop ffelds get mixed with rainwater and fflow into rivers and lakes. Land pollution We should prefer water purification plants to recycle waste water, instead of dumpting of waste sewage water in river. Also stop throwing trash in river as it pollutes the water and the aquatic animals suffers a lot. Green Tip Application of Knowledge
92 Science–4 DIY ACTIVITY Take two pots and fill each pot half with soil. Mark them A and B. Put plant waste in pot A and things like polythene bags, empty glass bottles and broken plastic toys in pot B. Put the pots aside. Observe them after 3−4 weeks. Plant waste in pot A has been decomposed. The plant waste has been converted into manure by the action of microbes. The nutrients released in the process could be used by the plants again. So, they are called biodegradable. In pot B, the polythene bags, empty glasses, bottles and broken toy parts did not undergo any such change. The microbes could not ‘act’ on them and convert them into manure. So, they are called non-biodegradable. noISe poLLutIon Unwanted and unpleasant sound to our ears is known as noise. Noise is produced by bursting crackers, loudspeakers, vehicles on the road and heavy machines in factories. Noise also causes environmental pollution. effects • People living in noisy areas have poor hearing capacity. • It can also cause loss of memory. BIodegradaBLe and non-BIodegradaBLe waSteS Waste materials which decompose or rot after some time and get mixed with the soil are called biodegradable wastes. Peels of fruits and vegetables, leaves and things made of wood and paper usually decompose. Non-biodegradable wastes are the wastes that do not rot or decompose even after long period of time. Waste materials like plastic, glass, metal and rubber do not decompose. Plastic is the most harmful no-biodegrable waste Biodegradable waste Non-biodegradable waste
93 Science–4 preventIng poLLutIon We cannot clean the earth’s pollution in one or two days. There are many ways by which we can reduce air, water, land and noise pollution. • Do not allow trash or water to accumulate close to your home. Put the trash in the right areas for disposal. • Chemicals, oils, paints, and medications shouldn’t be flushed down the toilet or down the drain. • Before discharging dirty water into lakes, rivers, or the ocean, dirty water from houses and factories should be treated to remove pollutants. • Compressed natural gas (CNG) and liquefied petroleum gas (LPG) should be used as vehicle fuel. As a result, air pollution is reduced. • Chemical pesticides and fertilisers shouldn’t be used in excess by farmers. • When possible, use public transportation, carpool, bicycle or walk instead of driving alone. • Plastic bags shouldn’t be used because they don’t rot and can clog drains. Utilise jute or cotton bags. • We should plant more trees. This helps in purifying air. • Noisy machines should be run in sound-proof rooms in factories. • In factories, noisy equipment should be used in soundproof spaces. • The big chimneys in factories should have filters. dISpoSaL of waSte Waste that is biodegradable and nonbiodegradable need to be treated differently. Therefore, the rubbish collection companies sort them first. Biodegradable wastes are dumped in large pits called landfills. Here landfills they are covered with a layer of moist soil and allowed to rot. Waste that can be recycled, such as plastic, metal, and glass, is transferred to recycling facilities. These are melted down here and used to create new goods. Incinerators are used to burn non-biodegradable garbage that cannot be recycled. Landffll
94 Science–4 reduce, reuSe and recYcLe Decomposition of wastes is challenging. The three R’s can help us protect the environment. Reduce, reuse, and recycling are known as the three R’s. reduce Reduce the amount of resources you use. Avoid purchasing items you do not require. Avoid being drawn to bulky packing materials. When shopping, use your own bag rather than requesting a polythene bag from the store owner. reuse Purchase items that can be utilised repeatedly over a long period of time. Stay clear from items that must be thrown away after each usage. recycle Recycling is the process of turning trash into useful materials. Old newspapers, empty glass bottles, plastics, and tins are just a few of the trash that can be recycled and used to make new items. worLd envIronment daY People all over the world are gradually becoming aware of their duty to preserve the environment. In 1972, the United Nations General Assembly decided to dedicate a day to raise environmental awareness and to encourage actions to protect the environment. The United Nation has declared 5th June as World Environment Day (WED). Find out the slogan for World Environment Day of this year. KEY WORDS Environment : all living beings and non-living things that occur naturally on the Earth. Land pollution : mixing of harmful substances in the soil. Pollution : an undesirable change in water, soil and air that brings down the quality of the environment. Soil erosion : the loss of fertile top soil due to rain or wind. Water pollution : the addition of household, agricultural and industrial wastes in the water.
95 Science–4 SUMMARY There is harmony between living and non-living entities in nature. Among the most common air contaminants are gases, smoke, fumes, and dust. Garbage, sewage, agricultural waste, and chemicals all pollute water. Waste from a variety of sources contributes to land pollution. Noise pollution is caused by loudspeakers, loud music and horns and hooters. Waste materials are of two types — biodegradable and non-biodegradable wastes. We should practice three R’s — reduce, reuse and recycle to save our environment. EXERCISE TIME A. Tick () the correct answer. 1. What type of pollution occurs when the air is fflled with harmful substances? a. Land pollution b. Water pollution c. Noise pollution d. Air pollution 2. How does water pollution happen? a. When you plant more trees. b. When you use less plastic. c. When trash and harmful things get into rivers, lakes, or oceans. d. None of these 3. What can you do to help reduce air pollution? a. Leave lights and electronics on all day. b. Use public transportation, carpool, or walk instead of driving alone. c. Waste water. d. flrow trash in the river. 4. Which of these should be avoided to reduce pollution? a. Planting trees b. Using cloth bags c. Using plastic bags d. Burning crackers B. Fill in the blanks. 1. Air pollution happens when there are too many __________ and harmful substances in the air we breathe. 2. ____________ pollution occurs when garbage, trash, or chemicals get into rivers, lakes, or oceans. 3. Soil pollution can harm the __________ and make it hard for plants to grow. 4. To reduce pollution, we can use __________ energy sources .
96 Science–4 C. Write short answers. 1. What is pollution? 2. What is water pollution, and what can cause it? 3. Suggest any one method to prevent land pollution 4. What are some eects of noise pollution? D. Answer these questions. 1. Name some common types of pollution. 2. What is plastic pollution, and how does it harm our oceans and marine life? 3. What is acid rain? What are its harmful eects? 4. How have the actions of human beings disturbed the balance in nature? 5. What is the dierence between biodegradable and non-biodegradable wastes? 6. What role can individuals, communities, and governments play in ffghting pollution and protecting the environment? 7. How do the three R’s work? Clarify them. TIME TO THINK (HOTS) 1. Why should we not waste paper? 2. Why should we not use plastic bags? Observe the picture carefully and ansewer the following questions: 1. Can you identify the type of pollution depicted in the picture? ______________________________________ 2. How it can be harmful for us? ______________________________________ TIME TO OBSERVE (Observational Skills) Divide the class into small groups, with each group assigned a specific type of pollution to research. Types of pollution can include air pollution, water pollution, noise pollution, and littering. Each group create an awareness poster related to the type of pollution they researched. TIME TO CREATE (Project Work/Creative Skills)
97 Science–4 You and your friends disagree on whether to recycle at school. How can you have a constructive conversation to resolve this confflict and make a decision that beneffts the environment? LIFE SKILLS Discuss the causes of air, water, land and noise pollution. Make children understand how dierent kinds of pollution aect human beings. Tell them the importance of preventing pollution and of three R’s. FOR THE TEACHER Should Van Mahotsava be celebrated for only a week in a year? Or would it be better to celebrate it every day? Why? TIME TO DISCUSS (Collaborative Skills) To know more about pollution prevention, please scan this QR code. WEBLINK (Go Green)
98 Science–4 LEARNING GOALS Afier completing this chapter, you will be able to know about: Weather Air Water Puriffcation of water 11 Weather and Water LET’S WARM UP Look at the symbols shown below and predict the type of weather they represent. weather The air quality around us, including its temperature, wind speed, and likelihood of rain, is referred to as the weather. Daily and hourly variations in the weather are common. The sun is the cause of the weather variations. How? Winds blow due of the sun’s heat. It is also in charge of cloud movement. When the sun is shining brilliantly, its rays strike Earth directly, making the day hot. However, the sun’s rays are slanted in the morning and the evening. the Sun Causes Changes in weather We are aware that the sun is the planet’s primary energy source for heat and light. As the sun heats the planet unevenly, it alters the weather. This is due to the continual rotation of the earth around the sun. The axis of the earth is also slanted slightly. _____________ _____________ _____________
99 Science–4 DIY ACTIVITY As a result, part of the earth is always close to the sun while the other part is always a little bit farther away. The region of the planet closest to the sun receives more sunlight and experiences longer, warmer days. Consequently, summer is in full swing here on earth. The days are shorter and cooler in the area that is farther away. In this area, it is winter. The earth revolves around the sun, changing the seasons. The sun has a big impact on the direction of the wind. The air warms up as a result of the sun’s heat. This heated air rises and expands. The space is filled with heavier and cooler cool air. The action continues, and winds begin to blow. The wind’s direction is significantly influenced by the sun. The heat of the sun causes the air to warm up. This heated air expands and rises. Air that is denser and cooler is pumped into the area. While the action is still going on, winds start to blow. How Sunlight Warms the Earth Take two empty pans A and B of the same size. Fill both the pans with equal amount of sand. Keep pan A in the sun and pan B in the shade for two hours. Note the temperature of the sand in each pan. Are both temperatures the same? No. Sand in pan A will have a higher temperature than sand in pan B. Why? Pan A receives direct sunlight, but pan B does not. Pan A thus receives more heat than pan B. aIr We are aware that there is air everywhere around us. Although we cannot see it, when it blows, we can feel its presence. Breeze is the name for air that is moving slowly and is known as the wind. Storms are winds that move quickly. Air is a mixture of gases. It contains two main gases— oxygen and nitrogen. It has other gases like carbon dioxide and water vapour. It also contains smoke, dust and germs. 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. Pan A Pan bA
100 Science–4 water About 70% of the surface of the Earth is covered with water. It is found in rivers, lakes, oceans and under the ground. It is also found in glaciers and icebergs. It is also present in the atmosphere in the form of water vapours. Only about 3% of water is fit for drinking. Water is also present in air. Water changes form on heating and cooling. Let us study about two important processes by which one state of water changes into another state. Sea Breeze During the day, the land surface gets heated much faster than the sea. As the land gets heated, the air above the land also gets heated up. Warm air rises upwards. The cool air above the sea then rushes towards the land to take the place of the rising warm air. Thus a cool breeze blows towards the land during the day. This is called sea breeze. Land Breeze At night, the land cools down faster than the sea. The warm air above the sea rises up. Cool air from the land rushes towards the sea to take its place. This movement of air from the land to the sea is called land breeze. TEST YOUR UNDERSTANDING Fill in the blanks. 1. Movement of __________ (air/water) causes wind. 2. __________ (Warm/Cold) air rises up. 3. ffle Earth is __________ (vertical/tilted) at the axis. 4. Land cools __________ (faster/slower) than water. 5. Sea breeze blows during the __________. (day/night) Application of Knowledge