Grade VIScience

Exam Preparation Booklet

Chapter wise Important Questions & Solutions

Grade VI Science

Important Questions Chapter 1: Food - Where Does It Come From

Topic: Sources of Food Ingredients and Different Types of Food items

1. How do the states in the Northern and Southern regions of India differ from each other with respect to the types of food eaten in these states?

2. Describe any three food items of animal sources used in our diet.

3. Classify animals based on the type of food eaten by them. Give examples for each class.

4. India is a country with immense variety in the food consumed across different states. Justify the statement with examples.

5. What do you understand by the term ingredient? State the ingredients used in the preparation of dal-chawal.

6. How is honey obtained?

Topic: Edible Parts of Plants and Food Habits of Animals

7. What should be the characteristics of a material to be termed as edible?

8. Name any two edible flowers.

9. What are sprouts?

10. How are the eating habits of a butterfly and a crow different?

Chapter 2: Components of Food

Topic: Sources of Food Nutrients and Test for Nutrients

1. Pick the odd one out and give reasons for your answer. (i) Rice, wheat, sugarcane, maize, butter (ii) Fish, egg, cream, ghee, carrot (iii) Whole grains, vegetables, fruits, pulses, fish (iv) Cereals, pulses, vegetables, fruits, potato chips (v) Meat, fish, paneer, eggs, soyabean.

2. What are the major nutrients of a diet? If taken in equal amounts, which nutrient provides the maximum amount of energy?

3. What is the importance of mineral salts in our body? Give some examples of minerals that are essential for our body.

4. What is the process for detecting the presence of proteins in food items?

5. How is the presence of carbohydrates in a food item detected?

Topic: Balanced Diet, Malnutrition and Deficiency Diseases

6. Name the disease caused by the deficiency of: (i) Vitamin A (ii) Vitamin B

7. Why is milk considered as complete food?

8. A balanced diet should not have too much or too little of any nutrient. Why?

9. A person has stunted growth, and is very lean. His body is so thin and weak that he faces difficulty even while moving. What is the right diet to be given to such a person?

10. Given below is the diet chart of a child.

Breakfast Bread, jam

Lunch Chapati, potato curry, banana

Evening snack Sugarcane juice with lemon

Dinner Chapati with butter, spinach

vegetable, and salad

What are the components of a balanced diet that are missing in the given diet chart? What is the possible deficiency disease he may suffer from?

Chapter 3: Fibre to Fabric

Topic: Natural and Synthetic Fibres

1. Complete the following chart by classifying the fibres.

2. Select the natural fibres among the given fibres. Cotton, rayon, polyester, silk

Topic: Obtaining and Processing of Cotton and Jute Fibres

3. What are the conditions required for the cultivation of cotton?

4. Identify the fibre on the basis of the given properties.

Properties Fibre

It is cultivated in the rainy season and is commonly used for making gunny bags.

It is white in colour and is used for making blue denim cloth.

It is obtained from the fruit of a plant that is usually grown in places having black soil.

5. Identify the process shown in the given figure.

Topic: Obtaining Fabrics from Yarns

6. Fabrics are woven using _________. In this process, at least __________ sets of yarns are woven to obtain a fabric.

7. Write about the instrument that is used for making fabric from yarns by the process of weaving?

8. Explain the following terms: (i) Spinning (ii) Weaving

Topic: Advancements in the Clothing Industry

9. Name four unstitched pieces of fabrics that are still in use?

10. Write a short note on the advancements made in the field of clothing since the ancient times.

Chapter 4: Sorting Materials into Groups

Topic: Materials and Objects

1. Match the objects with the materials they are usually made from.

Objects Materials

(i) Shoes a Paper

(ii) Chairs b Leather

(iii) Note books c Glass

(iv) Window panes d Wood

2. Which group lists all the living things?

Group 1

Group 2

Group 3

Topic: Classification of Various Materials on the Basis of Their Appearance or Hardness

3. State whether True or False. (i) Different types of materials have different properties. (ii) Some materials are shiny in appearance while others are not.

4. It is easy to hammer an iron nail in a piece of wood but not in a piece of steel. Why?

5. Among the given objects, select those that are hard in nature. Paper, sponge, glass tumbler, keys, pen

Topic: Interaction of Various Substances with Water

6. A cloth bag containing salt fell into a bucket containing water. At first, it sinks to the bottom of the bucket. However, after sometime, the bag starts floating on the surface of the water. Explain.

7. Name two liquids that do not form a separate layer when mixed with water?

8. Between a tennis ball and a cricket ball, which one will sink in water and which one will not?

Topic: Classifying Materials as Transparent, Translucent and Opaque

9. Why do grocers keep toffees and chocolates in glass jars?

10. Rahul was studying in his room. He switched off all the lights in his room. He then turned on a flashlight near his study table. He kept an object ‘X’ in front of the flash light. He saw that it cast a faint circular shadow. However, another object ‘Y’ did not cast any shadow. What can be concluded about ‘X’ and ‘Y’?

Chapter 5: Separation of Substances

Topic: Need for Separating Substances

1. Write down three reasons why separation of substances is essential?

Topic: Handpicking, Sieving, Threshing, Winnowing and Magnetic Separation

2. A mixture contains two different solids, one having heavier particles and the other having lighter particles. Which separating technique can be used for separating the components of this mixture?

3. Hand picking can be used for separating the given balls on the basis of their colour.

4. Which of the given devices can be used to separate fine insoluble impurities from water?

Topic: Separating Mixtures by Sedimentation, Decantation, Filtration, Evaporation, and Condensation

5. Give one word for the following. (i) Squeezing out water from wet clothes in a washing machine (ii) Separation of cream from milk

6. What do X and Y indicate in the given figure?

7. Name the four steps by which a mixture of salt, sand, and iron filings can be separated.

8. How can the given mixtures be separated? (i) Kerosene and water (ii) Salt and water

Topic: Saturated and Unsaturated Solutions

9. A saturated sugar solution contains flour particles. Describe how the mixture can be separated into its components. No component of the mixture should be lost.

10. Reena prepares a saturated solution of sugar in water. She wants to dissolve more sugar. How can she do it?

Chapter 6: Changes Around Us

Topic: Reversible and Irreversible Changes

1. Rohit drew a flower on a drawing sheet using a pencil and then coloured it using water colours. He then cut the flower along its boundary. What are the reversible changes occurring in the given activity?

2. Explain the difference between reversible and irreversible changes with the help of examples.

3. Take about 50 mL of copper sulphate (blue vitriol) in a beaker. Place an iron nail in it. Observe the set up after an hour. What will you see? Classify the change that will occur in the beaker as physical or chemical. Give reasons for your answer.

4. The engine of a car derives energy from petrol to propel the car. What can you say about the reversibility of this process?

5. Classify the spoiling of food as a reversible or irreversible change.

Topic: Changes in the Properties of a Substance on Heating and Cooling

6. The iron blade of a tool used for digging has a ring. A wooden handle is fixed in this ring. How is this handle fixed? Is the produced change reversible? Why?

7. Ramesh took some water in a kettle and closed its lid. He then started heating it. He placed a pan above the spout of the kettle. After some time, he observed that water drops were falling from the pan. Explain why.

8. If we put a very hot glass in cold water, the glass cracks. Explain.

9. A metallic wire was tightly fixed on two poles, as shown in the given

figure. The wire was then heated using a burner. It was observed that the wire sags on being heated. Explain why.

10. Why is some space left between the successive rails on a railway track?

Chapter 7: Getting to Know Plants

Topic: Plants and its Different Types

1. Classify plants on the basis of the types of their stems and branches.

2. What are the different types of venations? How is a type of venation related to a type of roots?

3. Describe the plants having stems that cannot stand upright on their own.

Topic: Structure, Functions, Modifications of Root and Stem

4. How are water and minerals transported from roots to other plant parts?

5. Does the transport of materials in plants take place in one direction only? Justify your answer.

6. Answer the following questions. (i) What kind of root system does a maize plant have? (ii) What kind of venation forms a net-like pattern on both sides of the midrib? (iii) What are the bead-like structures present inside an ovary? (iv) What is the innermost part of a flower called? (v) What is the broad, green part of a leaf called?

7. Differentiate between tap root system and fibrous root system.

Topic: Structure and Functions of the Leaf and Flower

8. Define transpiration.

9. Answer the following questions. (i) What will happen when we boil a green leaf in a test tube containing spirit? (ii) What will happen when we add some iodine solution to the same leaf? (iii) What does the observation in (ii) indicate?

10. Write the edible part of the following plants. (i) Carrot (ii) Onion (iii) Spinach (iv) Potato (v) Lady’s finger

11. Name the structure that connects the leaf to the stem.

12. Give the difference between reticulate and parallel venation in plants. How is the type of leaf venation linked to type of roots in plants?

13. Why is leaf called the food factory of plants?

14. Draw a neat labelled diagram of the reproductive structure of a plant.

15. Which part of a flower is brightly-coloured? Name one plant in which this part is joined to other such parts?

Chapter 8: Body Movements

Topic: Locomotion in Humans

1. Which part of the skeleton protects the organs present in the lower portion of the body below the stomach?

2. Which part of the skeleton protects the brain?

3. What are the soft parts of the skeleton called?

4. Write a short note on ‘constituents of skeletal system’.

5. Which constituent of our skeletal system is present in upper portion of ear lobe?

6. What is the total number of bones in the rib cage? Are all these bones of the same type? Discuss.

7. How is the movement of muscles related to the movement of bones?

Topic: Locomotion in Animals

8. What are the different features found in birds that help them in flying?

9. Explain the gait or movement in an earthworm and a snail.

10. How does the streamline shape of the body enable fish to move inside water?

11. Describe the locomotion in snakes that helps them to move fast.

Chapter 9: The Living Organisms and Their Surroundings

Topic: The Living Organisms and Their Interactions

1. (i) Which term is used for describing the ability of an organism to produce offspring of its own kind? (ii) Define excretion.

2. What are the stages in the process of respiration?

3. Define stimuli. Give two examples of stimuli.

Topic: Habitat and Its Types

4. Describe various adaptations present in a fish that help it to survive in an aquatic habitat.

5. Pick the odd one out and give reasons for your answer. Sunlight, water, soil, air, microorganisms

6. State any one adaptation observed in the plants found in hilly areas. What is the significance of this adaptation?

7. Frogs can survive well both in water and on land. Explain how.

8. The abiotic factors of a region can determine the density of the biotic population of that region. Justify this statement with the help of a suitable example.

Chapter 10: Motion and Measurement of Distances

Topic: Measurement of Distance

1. What is a unit?

2. Why are standard units of measurement better than non-standard units of measurement?

3. Tanveer is 4 centimetres taller than Asif, but 3 centimetres shorter than Alam. If Alam’s height is 1.72 m, then what is Asif’s height in metre?

4. Convert the following (i) 2 mm into km (ii) 15 km in cm

Topic: Types of Motion and Speed

5. What is motion?

6. Give another example of an object that executes the same kind of motion as the wings of a butterfly.

7. Give one example each of the given motion. (i) Periodic motion (ii) Rectilinear motion

8. Write the type of motion associated with the given examples. (i) A ball rolling down an inclined plane (ii) Motion of the blades of a fan (iii) Membrane of a drum when beaten

9. What is a circular and rotational motion? Give one example each.

10. What is the similarity between motion of strings of a guitar and the membrane of a Tabla?

Chapter 11: Lights, Shadows and Reflection

Topic: Light and Shadows

1. Differentiate between transparent and translucent materials by giving examples.

2. What are shadows? How are they formed?

3. Why are we unable to see the sun during a total solar eclipse?

4. Draw a simple diagram to show the image formed by a pinhole camera. Write the characteristics of an image formed by such a camera.

5. How is the image formed in a pinhole camera different from a shadow?

6. Distinguish between luminous and non-luminous objects giving examples.

Topic: Reflection of Light

7. Give two examples from everyday life that prove that light travels in a straight line.

8. Why are looking glasses always made of plane mirrors?

9. Name two instruments based on the property of reflection of light.

10. Why is it impossible to see in the dark?

Chapter 12: Electricity and Circuits

Topic: Construction of Electric Cells, Electric Bulbs, and Electric Switches

1. Fill in the blanks. The number of terminals and filaments in an electric bulb are ______ and _______ respectively.

2. Why do manufacturers the mark negative and positive terminals of a cell?

3. What is the function of a switch in an electrical circuit?

Topic: Construction of a Torch

4. Ankit joined the two terminals of an electric cell directly and left it joined for some hours. He observed that the cell could not light up a torch bulb. Explain what happened to the cell.

5. Draw a diagram of a switch in the ON position by using a thermocol sheet, two drawing pins, a safety pin, and connecting wires.

6. The given figure shows two simple circuits. Circuit I consists of one cell, with its terminals labelled as M and N. Circuit II consists of two cells, with its terminals labelled as P, Q, S and T. The arrows over the wire segments indicate the directions of current in the two circuits.

Write the positive terminals of the three cells.

Topic: Conductors and Insulators

7. (i) Distinguish between conductors and insulators? (ii) How is electricity generated in an electric cell?

8. A student constructed a circuit using a bulb and an electric cell. He found that the bulb did not glow. What can be the possible reasons behind it?

9. Most electrical devices have cords which, when connected through a plug to a source of electricity, supply current to the device. These cords

are made of metal wires and have a plastic covering. Why do these cords have a plastic covering?

10. Why are electrical wires made of aluminium and copper while they are covered with rubber and plastic?

Chapter 13: Fun with Magnets Topic: Magnet- An Introduction

1. What are natural magnets?

2. How are magnetic and non-magnetic materials classified?

Topic: Magnetic and Non-Magnetic Materials

3. Name two materials that can be converted into a permanent magnet.

Topic: Magnetic Poles

4. Mention two properties of a magnet.

5. Depending on the nature of the poles facing each other, two magnets attract or repel each other. In an experiment, magnets X and Y are used for testing magnetic attraction and repulsion. I. The North pole of magnet X is brought close to the North pole of magnet Y. II. The South pole of magnet X is brought close to the North pole of magnet Y. III. The North pole of magnet X is brought close to the South pole of magnet Y. IV. The South pole of magnet X is brought close to the South pole of magnet Y. In which two instances will magnets X and Y attract each other?

6. Suggest a method by which one can separate iron nails from mud without touching it.

Topic: Identifying Directions Using a Magnet

7. Explain how a bar magnet can be used for finding direction?

8 Which property of magnets helped travellers to find directions in old days?

Topic: Artificial Magnets

9. How can you make your own bar magnet by using another magnet?

10. The given figure shows a magnet and an iron piece that is to be magnetised. Draw the path of the magnet along which it should be

moved in order to magnetise the iron piece.

11. When magnetising an iron bar using the touch and stroke method, why is it important to ensure that the direction of stroking the bar magnet remains unchanged?

Topic: Demagnetization and Uses of Magnet

12. List three activities by which magnet loses its property.

13. Why is it not advisable to heat a magnet?

14. Suggest two ways of storing magnets such that they do not get demagnetised.

Chapter 14: Water

Topic: Sources of Water

1. The given figure represents various sources of water.

What can A and B represent in the given figure?

2.

Which type of water resource does X represent?

Topic: Need for Water Conservation

3. Answer the following questions. (i) Most of the usable water on earth is available to us in the form of _____________. (ii) Explain the need for conserving water.

4. Mention three practices that help in the conservation of water.

Topic: Rainwater Harvesting

5.

Explain the phenomenon shown in the figure.

6. Write the benefits of rainwater harvesting.

Topic: Water Cycle

7. (i) Draw a labelled diagram of the water cycle indicating the processes involved in it? (ii) Explain the formation of clouds?

8. If the temperature is below 0°C, then in which form does precipitation occur?

Topic: Consequences of Excess and Scarce Rainfall

9. What leads to droughts in a particular region?

10. What happens when a particular region receives excess rainfall?

Chapter 15: Air Around Us

Topic: Composition and Property of Air

1. Show the composition of air with the help of a pie diagram?

2. Which air constituents can be seen floating in the air when a beam of sunlight enters a dark room?

3. (i) Match the alternatives of Column A with their correct alternatives given in column B.

Column A Column B

Nitrogen Used in photosynthesis

Oxygen 1% of the total composition of air

Carbon dioxide Accounts for the humidity of air

Water vapour Makes 78% of the earth’s atmosphere

Other gases in air, water vapour, and dust particles

Necessary for combustion

(ii) Give the full forms of LPG and CNG.

4. Which component of air is also known as the ‘green-house’ gas?

5. What are the necessary conditions for combustion?

6. Answer the following questions. (i) Define rusting of iron. (ii) Suggest an experiment to show that rusting of iron requires both oxygen and water.

Topic: Uses of Air

7. How is a fire extinguisher useful in putting out a fire?

8. How do green plants help maintain the oxygen balance in the atmosphere?

9. How are plants and animals interdependent? Draw the oxygen-carbon dioxide cycle.

10. What role does air play in the reproduction of plants?

Topic: Air Pollution

11. What is smog?

12. Mention a way by which the air pollution caused by vehicles can be reduced.

13. Name the following. (i) Substances that contaminate air (ii) A thick layer in the atmosphere, made up of smoke and fog

14. Name two greenhouse gases.

15. Write two harmful effects of air pollution.

Chapter 16: Garbage In, Garbage Out

Topic: Wastes - Its Components and Vermicomposting

1. What is a landfill?

2. What steps should you take to minimize the use of plastics?

3. Give an example each of decomposable and non-decomposable waste?

4. What is composting?

5. List three ways in which we can recycle wastes of our rooms.

6. What is the need for proper disposal of wastes?

7. What is vermicomposting?

8. Give two changes that indicate that the rotting of garbage is complete.

9. What risk do plastic bags pose when they get into drains and sewer systems? How does burning of plastic bags pose a danger to the environment?

10.

What kind of garbage should be thrown in the two bins shown in the picture?

Grade VI Science

Solutions

Chapter 1: Food - Where Does It Come From

Topic: Sources of Food Ingredients and Different Types of Food items

1. In India, different types of food items are prepared in different states. For example, makki ki roti and sarson ka saag are commonly prepared in the North Indian states, whereas dosa and vada are common food items in South Indian states. The method of preparation of food, types of oils, the spices used etc. also varies from one region to another. For example, in Southern India, coconut oil is commonly used for cooking, whereas mustard oil is preferred in Northern India.

2. Three of the food items obtained from animals are as follows: (i) Milk: Milk is obtained from animals such as cows, goats, and buffaloes. (ii) Eggs: Eggs are obtained from hens, ducks, etc. (iii) Meat: Meat products are obtained from goat, sheep, pig, chicken, etc.

3. Animals can be classified into herbivores, carnivores, and omnivores on the basis of their eating habits. (i) Animals such as deer, butterflies, cows, giraffes, etc. eat only plants. Such animals are known as herbivores. (ii) Animals such as eagles and lions mostly eat other animals. Such animals are known as carnivores. (iii) Some animals such as chimpanzees and rats eat both plants and animals. Such animals are known as omnivores.

4. People living in different states in India have varied food habits. The method of preparation of food, types of oils, and the spices used are some of the reasons for this variety. For example, Makki ki Roti and Sarson ka Saag are easily available in the Northern states of India, whereas Dosa and Vada are common dishes of states of Southern India.

5. Ingredients are materials needed to prepare a dish or a mixture. Ingredients for dal are raw dal (pulses), water, oil, salt, spices, onions, tomato paste, etc. Ingredients needed to prepare boiled rice (chawal) are rice and water.

6. Honey is a sweet, yellow coloured, thick liquid produced by honey bees. Honey bees collect nectar (sweet juice) from flowers and convert it into honey. Bees produce excess honey and store it in their hives to sustain themselves during the winter season when there are no flowers. Humans collect honey from bee hives, and use it as a food item.

Topic: Edible Parts of Plants and Food Habits of Animals

7. Edible materials refer to materials which are fit to be eaten. Like leaves of a cabbage plant are edible. Some characteristics of a material for it to be termed as edible are as follows: (i) It should not be toxic. (ii) It should not lead to allergy in humans. (iii) It should not be excessively bitter or of bad taste. (iv) It should not be excessively hard, and should be chewable.

8. Pumpkin, broccoli, cauliflower have edible flowers.

9. Sprouts are the small, white structures which grow out of seeds when they are soaked for two days.

10. Since butterfly feeds only on the nectar of plants, it is a herbivore. Crow feeds on plants and animals both. Therefore, it is an omnivore.

Chapter 2: Components of Food Topic: Sources of Food Nutrients and Test for Nutrients

1. (i) Butter: It does not contain carbohydrates. (ii) Carrot: It is not a source of fats. (iii) Fish: It does not yield dietary fibres. (iv) Potato chips: It is not a part of a balanced diet. (v) Soybean: It is not an animal source of protein.

2. Five major nutrients are present in the food that we eat. These are carbohydrates, proteins, fats, vitamins, and minerals. Additionally, our food also contains water and fibre, which are required by our body. If taken in equal amounts, fats provide the maximum amount of energy.

3. Minerals are one of the five major nutrients required by our body. They are essential for the proper growth and functioning of the body. The deficiency of minerals in the body can lead to diseases such as anaemia, goitre, etc. Iron, iodine, calcium, and phosphorus are some of the essential minerals required by our body.

4. In order to test for the presence of proteins in a food item, a small piece of powdered or mashed food item is taken in a test tube. About 10−12 drops of water is added to the test tube following which two to three drops of copper sulphate solution is added. Finally, ten drops of caustic soda solution is added to the test tube. A change in the colour of the solution to a violet colour indicates the presence of proteins in the food item.

5. For testing the presence of carbohydrates in food, a small quantity of food matter is taken into a test tube after which a few drops of iodine are added to the test tube. If the food contains carbohydrates, the food changes colour to blue-black. This change in colour confirms the presence of carbohydrates.

Topic: Balanced Diet, Malnutrition and Deficiency Diseases

6. (i) Night blindness (ii) Beri-beri

7. Milk is a rich source of many essential nutrients including fats, proteins, vitamin A, vitamin D, phosphorus, calcium, etc. Therefore, drinking a glass of milk twice a day helps in preventing many deficiency diseases. Thus, milk is considered as complete food.

8. A diet that contains all the nutrients in correct proportions is called a balanced diet. Proper quality (i.e., having all the nutrients) and quantity of food is very important for

proper health, growth, and functioning of our body. If a diet has too much of nutrients, it can lead to problems such as obesity, hypertension, vomiting, etc. On the other hand, a diet containing too little of nutrients can lead to deficiency diseases such as anaemia. Thus, a balanced diet should not have too much or too little of any nutrient. It should include all the required nutrients in balanced proportions.

9. A person suffering from protein energy malnutrition shows stunted growth. He may have a very thin and weak body. Such a person should be given a diet including: Protein rich food (i) Pulses, beans, soyabean and peas obtained from plant products. (ii) Meat, fish, paneer, milk and eggs obtained from animal sources. Carbohydrate rich food: − Sweet potato, potato, sugarcane, papaya, melon, mango, maize, bajra, rice, wheat etc.

10. The diet chart given in the question lacks food containing proteins and calcium. Therefore, the child may suffer from the following: (i) Kwashiorkor (protein deficiency disease) (ii) Bone and teeth defects (calcium deficiency)

Chapter 3: Fibre to Fabric

Topic: Natural and Synthetic Fibres

1. a. Natural b. Synthetic c. Plant d. Animal

2. Cotton and silk are natural fibres.

Topic: Obtaining and Processing of Cotton and Jute Fibres

3. The conditions required for the cultivation of cotton are: (i) Presence of black soil (ii) Warm climate

4.

Properties Fibre

It is cultivated in the rainy season and is commonly used for making gunny bags.

Jute

It is white in colour and is used for making blue denim cloth.

Cotton

It is obtained from the fruit of a plant that is usually grown in places having black soil.

Cotton

5.

The given figure shows the process of spinning. In this process, yarn is made from fibres.

Topic: Obtaining Fabrics from Yarns

6. Fabrics are woven using looms. In this process, at least two sets of yarns are woven to obtain a fabric.

7. Weaving is carried out using looms. These looms can be powered-operated

(powerlooms) or hand-operated (handlooms). A handloom and powerloom are shown in the given figures.

8. (i) The process of making yarn from fibres is called spinning. In this process, fibres from a mass of cotton or wool are drawn out and twisted. This brings the fibres together and yarn is formed. Charkha, takli, etc. are some devices used for spinning. (ii) Weaving is the process of arranging two sets of yarns together to form a fabric. Weaving is done on looms that are either hand operated or power operated.

Topic: Advancements in the Clothing Industry

9. Saree, dhoti, lungi, and turban are unstitched pieces of fabric that are still used in India.

10. (i) Early human beings used tree leaves, barks, and animal skin as garments. (ii) As humans became more civilised, they started to weave and make mats and baskets using dry grass and twigs. (iii) In ancient India, people used to wear fabrics made of cotton that was cultivated along the banks of river Ganga. Today, India is one of the largest producers of cotton. (iv) With scientific progress and the invention of the sewing needle, stitched clothes gained popularity.

Chapter 4: Sorting Materials into Groups

Topic: Materials and Objects

1.

Objects Materials

(i) Shoes b Leather

(ii) Chairs d Wood

(iii) Note books a Paper

(iv) Window panes c Glass

2. Group 3 has all living things.

Topic: Classification of Various Materials on the Basis of Their Appearance or Hardness

3. (i) True (ii) True

4. Wood is much softer than steel. Hence, an iron nail can be easily hammered in wood.

5. Glass tumbler, keys and pen are difficult to compress. Thus, these objects can be classified as hard objects.

Topic: Interaction of Various Substances with Water

6. Salt is soluble in water. Initially, the bag containing salt settles at the bottom of the bucket as it is denser than water. After sometime, water moves inside the cloth bag and dissolves the salt present in it. When the salt becomes completely dissolved, the bag becomes lighter and starts floating on the surface of the water.

7. Milk, lemon juice, alcohol and vinegar are some of the liquids that do not form a separate layer when added to water.

8. The tennis ball will float on water because of the air present inside it. On the other hand, leather is an important component of cricket ball, which is quite heavy. Therefore, the cricket ball will sink in water.

Topic: Classifying Materials as Transparent, Translucent and Opaque

9. Grocers keep toffees and chocolates in glass jars as glass is a transparent substance. Hence, these are easily visible to the customers.

10. ‘X’ is a translucent object while ‘Y’ is a transparent object.

Chapter 5: Separation of Substances

Topic: Need for Separating Substances

1. Separation of substances is essential for (i) removing impurities or harmful components from useful substances (ii) separating two different but useful components (iii) removing used up components

Topic: Handpicking, Sieving, Threshing, Winnowing and Magnetic Separation

2. The method of winnowing can be used for separating the components of the given mixture.

3. Handpicking

4. The sieve shown in figure (A) i.e., the one having smaller holes can be used to separate fine insoluble impurities from water.

Topic: Separating Mixtures by Sedimentation, Decantation, Filtration, Evaporation, and Condensation

5. (i) Churning/centrifugation (ii) Filtration

6. X indicates evaporation. Y indicates condensation.

7. The components of the given mixture can be separated by the following steps: (i) Magnetic separation - Separates iron filings from the mixture (ii) Filtration - Separates sand from the mixture (iii) Evaporation - Separates salt from water (iv) Condensation - Recovers evaporated water

8. (i) Separating funnel/Decantation (ii) Evaporation

Topic: Saturated and Unsaturated Solutions

9. The given mixture contains flour in a sugar solution. As flour is insoluble in water, it can be separated by filtration. Water along with the dissolved sugar will pass through the filter paper, while the bigger flour particles will remain on the paper. The mixture of sugar and water can be separated by evaporation, followed by condensation. The sugar will remain in the container containing the mixture after the evaporation is complete. The water vapours can be collected and cooled to re-obtain

water.

10. Reena can dissolve more sugar in the solution by heating the solution.

Chapter 6: Changes Around Us

Topic: Natural and Synthetic Fibres

1. Drawing a flower on a drawing sheet is a reversible change. A reversible change is one in which a substance that is undergoing the change can be recovered in its original form. In the given case, the drawing on the sheet can be erased easily.

2.

Reversible Changes Irreversible Changes

(i) Changes that can be reversed to re-obtain the original substance or substances are called reversible changes.

(i) A change is called irreversible if the substance or substances undergoing the change cannot be re-obtained.

(ii) For example, the melting of ice is a reversible change. This is because the water formed on melting can be converted back into ice by cooling.

(ii) For example, the curdling of milk is an irreversible change. This is because once milk is curdled, it cannot be re-obtained.

3. After an hour, we will notice that the colour of the solution in the beaker has changed from blue to green. This is due to the formation of iron (II) sulphate. The iron nail on the other hand will have a brown deposit of copper over it. The change occurring in the beaker is a chemical change due to the formation of two new substances − iron (II) sulphate and copper.

4. The combustion of petrol to propel a car is an irreversible process. The burnt petrol gives energy and gases. Petrol cannot be re-obtained from these products of combustion.

5. Irreversible changes are the changes that cannot be reversed. The spoiling of food is an irreversible change.

Topic: Changes in the Properties of a Substance on Heating and Cooling

6. To fix the handle, the ring is heated. On heating, the ring becomes slightly larger in size, i.e., it expands. Then, the handle is fitted in the ring. The produced change is reversible. This is because the ring regains its original size (contracts) once it cools down.

7. The water drops falling from the pan are formed by the process of condensation. When the kettle containing water is heated, water vapours are formed. When these vapours come in contact with the cool surface of the pan, they lose energy and change into liquid.

8. The outer surface of the glass comes in direct contact with the cold water and contracts. The inner surface, which is not in direct contact with the cold water, does not contract as quickly. Therefore, the glass breaks because of unequal contraction.

9. When a substance is heated, it expands in size. Hence, the metallic wire expands on heating. As it is fixed at both ends, it sags down in the middle of expanding.

10. Small gaps known as expansion gaps are left between the rails on the railway tracks. This is done to ensure that when the metallic rails expand during the daytime, they do not damage each other.

Chapter 7: Getting to Know Plants

Topic: Plants and its Different Types

1.

On the basis of the types of stems and branches, plants can be classified as follows: (i) Herbs: These are plants with green and tender stems. They are usually short and may not have many branches. (ii) Shrubs: These are plants with hard but not very thick stems. The stem branches out near the base. (iii) Trees: These are tall plants with hard and thick stems, having branches in the upper part, much above the ground.

2. (i) There are mainly two types of roots in plants. They are: a. Tap roots: These roots consist of a main root, which grows vertically downwards. This main root gives rise to many small branches. For example, these roots can be observed in the young plantlets of gram. b. Fibrous root: These roots arise in clusters from the base of the stem. They do not have a main root. These roots can be observed in grasses. (ii) Venation can be of two types. a. Parallel venation: In this type of venation, the veins are parallel to each other. It is commonly found in grasses. b. Reticulate venation: In this type of venation, the veins are arranged in the form of a net-like structure around the midrib. It can be easily observed in the leaves of rose plants. Plants with tap roots will always have leaves with reticulate venation, while plants with fibrous roots will always have leaves with parallel venation.

3. Plants with weak stems that cannot stand upright on their own are described as follows: (i) Creepers: These are plants with weak stems that cannot stand upright and spread on the ground. (ii) Climbers: These are plants that take support of neighbouring structures and wrap around them to climb up.

Topic: Structure, Functions, Modifications of Root and Stem

4. Water and minerals are transported to different plant parts through xylem, the narrow tube present inside the root, stem and leaves of plants.

5. The transport of materials in plants does not take place in one direction only. Water and minerals are transported from roots to the aerial parts of plants. Food is manufactured in the leaves, though it can be transported in any direction, depending upon the requirement.

6. Solution (i) Fibrous root system (ii) Reticulate venation (iii) Ovules (iv) Pistil (v) Lamina

7. Tap root system (i) It does not have any primary root. A tuft of roots arise from the base of the stem. (ii) It develops many secondary roots on its sides. E.g. All dicot plants have tap root system. Fibrous root system (i) It has a main root or primary root, which grows straight down. (ii) These roots spread out in all directions. E.g. All monocot plants have fibrous root system.

Topic: Structure and Functions of the Leaf and Flower

8. The process by which water evaporates through the leaves of plants is called transpiration.

9. (i) All the green colour of the leaf will come out into the spirit. (ii) The leaf will turn blue-black in colour. (iii) The observation in (ii) indicates the presence of starch in the leaf. It is the food material formed inside the leaf as a result of photosynthesis.

10. (i) Carrot Root (ii) Onion Leaf (iii) Spinach Leaf (iv) Potato Stem (tuber) (v) Lady’s finger Fruit

11. Petiole is the structure that connects the leaf to the stem.

12. Venation refers to the pattern in which the veins are distributed in the lamina of the leaves. Venation is of two types, reticulate and parallel. In reticulate venation, the veins form a network of veins on either side of the midrib. In parallel venation, the veins are arranged parallel to each other. It is generally seen that plants with reticulate roots have a tap root system while plants with parallel venation have a fibrous root system.

13. Leaf prepares food for plants by the process of photosynthesis. This process takes place in the presence of sunlight and a green-coloured substance called chlorophyll. This

process also utilises carbon dioxide and water for synthesising glucose. All these processes take place inside the leaf. Hence, leaf is called the food factory of plants.

14.

15. Petals are the brightly-coloured parts of a flower. Datura plant, which has bell-shaped flowers, has joined petals.

Chapter 8: Body Movements

Topic: Locomotion in Humans

1. The pelvic bone present in the region below the stomach protects the organs present in the lower portion of body.

2. The skull encloses the brain and protects it. The skull is made up of several bones joined through a fixed joint.

3. Cartilage

4. The skeletal system mainly consists of bones. Bones are hard structures. There are 206 bones in our body. The bony skeleton provides shape to our body. The skeletal system also consists of structures called cartilages. Cartilages are parts of the human skeletal system, but they are not as hard as bones. These can be easily bent. For example, the upper portion of the ear above the ear lobe is made up of cartilage.

5. Cartilage is present in the upper part of the ear which is not as hard as the bone and can be bent.

6. 24 ribs (12 pairs) and one sternum bone constitute our rib cage. All the ribs present in the rib cage are not of the same type. Out of the 24 ribs, 8 pairs are true ribs, 2 pairs are false ribs and 2 pairs are floating ribs. True ribs start from the backbone and join the chest bone to form a cage-like structure called the rib cage. Like true ribs, false ribs and floating ribs also start from the backbone. However, they do not reach the chest bone.

7. Muscles work in pairs to pull a bone. If one muscle contracts, then its partner (the other muscle of the pair) relaxes. This pulls the bone towards the contracted muscle. When the relaxed muscles contract and the contracted muscles relax, muscles are pulled back to their original positions.

Topic: Locomotion in Animals

8. Birds can fly because: (i) They have hollow and light bones (ii) Their body is streamlined (iii) Their forelimbs are modified into wings (v) They have strong shoulder bones (vi) Their breast bones are modified to hold the muscles of flight

9. Earthworm is a limbless animal. Bones or a skeleton system is absent in earthworms. Its body is divided into many segments and the body appears to be composed of several rings that are joined from their ends. These rings contain the muscles that help them to move in the soil. While moving, the earthworm keeps its hind part fixed to the ground and extends its front part. After this, it releases the front part and moves the hind part forward. The repeated muscle expansions and contractions help the earthworm to move forward in the soil. The snail moves with the help of a thick muscular foot. The muscles present in the foot help it to move forward and it drags its shell along while moving.

10. Streamline shape is a type of body shape in which the middle portion of the body is broad and there are two tapering ends. Fish have a streamlined body shape. This shape allows them to move easily in water. When a fish swims in water, the muscles that cover its skeleton cause the front part of the body to curve towards one side. On the other hand, the tail (having fins) curves towards the opposite side. Then, immediately the body and the tail curve towards the other side. This causes a jerk, thereby pushing the body to move forward. Many such jerks in succession help the fish move forward.

11. The body of a snake curves to form many loops. Each of these loops presses hard against the ground and causes the body of the snake to be pushed forward. Since the snake has a long body, it forms many such loops. Thus, it is able to move very fast.

Chapter 9: The Living Organisms and Their Surroundings Topic: The Living Organisms and Their Interactions 1. (i) Reproduction

(ii) Excretion is the process by which living things get rid of wastes from their bodies.

2. The process of respiration has two stages: (a) External respiration, which involves taking in oxygen and giving out carbon dioxide (b) Internal respiration, which involves the oxidation of food in each cell and the release of energy

3. The changes in our surroundings that make us respond to them are called stimuli. For example: bright light, touching hot objects, etc.

Topic: Habitat and Its Types

4. Fishes are adapted for an aquatic habitat. Their body is streamlined and is covered with slippery scales that help water to pass around their body. The fins and tail of the fishes help them to maintain their balance and to change direction while swimming. Fish have a pair of gills that help them to take up the dissolved oxygen from water for breathing.

5. Microorganisms: Microorganisms are biotic components of a habitat, while sunlight, water, soil and air are abiotic components.

6. Mountain trees such as Pinus, spruce etc. are conical in shape with needle-like leaves. This adaptation allows snow and rainwater to slide off easily.

7. Frogs can survive well both in water and on land because of the presence of the following features:

● They have strong hind legs, which help them leap and catch their prey. ● They have webbed feet, which help them swim easily in water. ● While on land, they breathe through their skin, on the other hand, when they

are in water, they use their gills for breathing.

8. The abiotic factors of a region can determine the density of the biotic population of that region. For example, deserts have low biotic population because of their hot and

humid climatic conditions. Heat and humidity are two of the abiotic factors in deserts. Adverse abiotic factors make the survival of biotic components difficult.

Chapter 10: Motion and Measurement of Distances

Topic: Measurement of Distance

1. A unit is a fixed quantity against which unknown quantities can be measured.

2. Unlike non-standard units of measurement, standard units of measurement do not change from place to place or vary from person to person. Hence, standard units of measurement are better than non-standard units of measurement.

3. Alam’s height = 1.72 m 1 m = 100 cm Therefore, Alam’s height in centimetres = (1.72 × 100) cm = 172 cm Tanveer is 3 centimetres shorter than Alam. Hence, Tanveer’s height = (172 − 3) cm = 169 cm Tanveer is 4 centimetres taller than Asif. Hence, Asif’s height = (169 − 4) cm = 165 cm

Therefore, Asif’s height in metres

4. (i) 1 km = 1000 m = 1000000 mm

1 mm =

2 mm = km = 0.000002 km (ii) 1 km = 1000 m = 100000 cm 15 km = 15 × 100000 = 1500000 cm

Topic: Types of Motion and Speed

5. When an object changes its position with time, the object is said to be in motion.

6. (i) The kind of motion executed by the wings of a butterfly is vibratory motion. (ii) Strings of a guitar in motion are also the example of vibratory motion.

7. (i) Periodic motion: The motion of the bob of a simple pendulum is periodic. (ii) Rectilinear motion: The motion of a car on a highway is rectilinear.

8. (i) A rolling ball possesses rectilinear as well as rotational motion. (ii) The blades of a fan possess circular motion.

(iii) Membrane of a drum possesses periodic motion.

9. A circular motion is one in which the object moves in a circular path. Example: A toy moving in a circular track. A rotational motion is one in which an object moves on its own axis. Example: Wheel of bicycle undergoes in rotational motion.

10. Both the strings of a guitar and the membrane of a Tabla execute vibratory motions.

Chapter 11: Lights, Shadows and Reflection

Topic: Light and Shadows

1. Transparent substances are those through which things can be seen. Glass, water, and air are examples of transparent substances. Translucent substances are those through which objects can be seen but not clearly. For example, oiled paper allows partial visibility.

2. Shadow is the dark region formed behind an opaque or translucent object. It is formed due to an obstruction of light provided by such objects.

3. We are unable to see the sun during a total solar eclipse because the moon—which is an opaque object—comes between the sun and the earth, thereby creating a shadow on the earth’s surface. This shadow is large enough to prevent the view of the sun.

4.

Image formation in a pinhole camera Characteristics of an image formed by a pinhole camera: (i) It is inverted, and smaller in size than the object. (ii) It can be projected on a screen, and therefore, is a real image. (iii) It becomes clearer as the size of the pinhole decreases.

5. Image formed in a pinhole

camera Shadow

(i) The image is of the same colour as that of the object.

The shadow is always black, irrespective of the colour of the object.

(ii) The image formed is inverted. The shadow is not inverted.

6. Luminous objects are those objects which emit light of their own. e.g. sun, candle, torch Non-luminous objects are those objects which do not emit light of their own. e.g. the moon, planets

Topic: Reflection of Light

7. Two examples from everyday life that prove that light travels in straight lines are as follows: (i) The shadow of an opaque object is formed when light is thrown on it.

(ii) If mirrors are removed from a periscope, we are unable to see objects on the other side.

8. Image formed by a plane mirror has exactly the same size and shape as that of the object. Therefore, looking glasses are made of plane mirrors.

9. Kaleidoscope and periscope are two instruments based on the property of reflection of light

10. It is impossible to see in the dark because light is absent. Hence, no reflection takes place and no light from the objects enters into the eye.

Chapter 12: Electricity and Circuits

Topic: Construction of Electric Cells, Electric Bulbs, and Electric Switches

1 The number of terminals and filaments in an electric bulb are two and one respectively.

2. The negative and positive terminals of a cell must be marked to enable us to connect it to a circuitin the proper way. Many appliances work only when current flows in a particular direction. Therefore, we must make sure that the cell is connected properly.

3. In an electric circuit, a switch is used for breaking the circuit.

Topic: Construction of a Torch

4. When the two terminals of the electric cell are connected directly, the chemicals inside the electriccell get used up very fast until all the chemical energy inside it gets used up. After the cell’s energy gets used up, it can no longer be used in a torch bulb.

5.

The diagram is given as

6. The direction of current determines the polarity of a cell. Current always flows externally from the positive terminal to the negative terminal of a cell. It can be observed that the direction of current in circuit I is anti-clockwise. Hence, terminals M and N must be negative and positive respectively. The direction of current in circuit II is clockwise. Hence, terminals P and T must be positive and negative respectively.

Hence, the terminals labelled as N, P and S are the respective positive terminals of the three cells.

Topic: Conductors and Insulators

7. (i)

Conductor Insulator

a. They allow current to pass through them.

They do not allow current to pass through them.

b. In order to conduct electricity, conductors are used.

In order to protect from electric shocks, insulators are used.

(ii) In an electric cell, electricity is produced because of the chemical reactions taking place within the cell. Inside a cell, chemical energy gets converted into electric energy.

8. The possible reasons behind the fact that the bulb did not glow are as follows: (i) The student might have connected the terminals of the bulb and the cell incorrectly. (ii)The bulb might have been fused. (iii) The cell might have been used up.

9. An uncovered cord carries the risk of electric shock in case someone touches it. Hence, these cords are covered with some insulating material for protection.

10. Electrical wires are made of aluminium and copper since they are good conductors of electricity, thereby allowing current to pass through them. These wires are covered by insulators such as rubber and plastics so that no one gets an electric shock by touching the electric wires.

Chapter 13: Fun with Magnets

Topic: Magnet- An Introduction

1. Substances such as lodestone, which occur naturally and possess the property of attracting magnetic substances, are called natural magnets.

2. Magnetic materials are those materials that get attracted towards a magnet. Example: Iron, cobalt, nickel, etc. Non-magnetic materials are those materials that do not get attracted towards a magnet. Example: Rubber, plastic, wood, etc.

Topic: Magnetic and Non-Magnetic Materials

3. Soft iron and nickel can be converted into permanent magnets.

Topic: Magnetic Poles

4. Two properties of a magnet: (i) A magnet attracts magnetic materials such as iron, nickel, etc. This is called the attractive property of magnets. (ii) When suspended freely in air, a magnet always points in the north−south direction. This is called the directive property of magnets.

5. A magnet has two poles − North Pole (N) and South Pole (S). Like poles repel and unlike poles attract each other. In instances II and III, unlike poles of magnets X and Y are brought close to each other. Hence, the phenomenon of magnetic attraction will be observed in these two instances.

6. One can use a magnet for separating iron nails from mud without touching it. On bringing a strong magnet close to the mud, the nails will get attracted towards the magnet and stick to it, thereby causing the separation.

Topic: Identifying Directions Using a Magnet

7. When a bar magnet is suspended freely, it always comes to rest along the north−south direction. By observing the position of the suspended magnet, the direction guide of a place can be drawn. To find directions using a bar magnet, one should suspend it freely in a horizontal plane. When the magnet comes to rest, one has to stand beside it, facing the north pole of the magnet and spreading one’s hands on both sides.

In this position, the right hand represents the east direction and the left hand represents the west direction. The direction in which one faces is the north and the opposite direction is the south.

8. A freely suspended bar magnet always comes to rest in North−South direction. This property of a magnet helped travellers to find directions in old days.

Topic: Artificial Magnets

9. Touch-and-stroke method is used for magnetising a piece of iron bar. In this method, one of the poles of a bar magnet is moved, without lifting, from one end to the other of the iron bar. Upon reaching the other end, the magnet is lifted and the entire process is repeated.

When the process is repeated 40 − 50 times, the iron bar becomes a permanent bar magnet.

10. The path along which the magnet should be moved is shown in the given figure.

11. If a bar magnet is stroked in one direction, then the North Pole is created on one side, while the South Pole is created on the other side. If the direction of stroking the bar magnet is reversed, then the nature of poles will get reversed. Hence, it is important to ensure that the direction of stroking the bar magnet remains unchanged.

Topic: Demagnetization and Uses of Magnet

12. A magnet loses its magnetism if it is (i) heated

(ii) hammered (iii) dropped from some height

13. A magnet loses its magnetic property on heating. Therefore, it is advisable not to heat a magnet.

14. (i) Two bar magnets may be placed on either side of a wooden block, while two pieces of soft iron on the other two sides, for safe storage. (ii) A horseshoe magnet should be stored with a piece of iron across its poles.

Chapter 14: Water

Topic: Sources of Water

1. In the given figure, A can represent saline water, whereas B can represent rivers.

2. X represents saline sources of water such as oceans. It constitutes 97 % of the total water available on earth.

Topic: Need for Water Conservation

3. (i) Most of the usable water on earth is available to us in the form of groundwater. (ii) Water is essential for the sustenance of both plants and animals. The amount of usable water on earth is limited, so it needs to be conserved.

4. Three practices that help in the conservation of water are: (i) Clothes should be washed in washing machines only when the machine is filled to its maximum loading capacity. (ii) Taps must be closed while washing utensils, brushing teeth, shaving etc. (iii) Trees should be planted in the monsoon season when temperatures are lower and rainfall is sufficient.

Topic: Rainwater Harvesting

5. The given figure depicts rainwater harvesting. In this system, rainwater is collected in a storage tank, through pipes. This water usually contains soil and other insoluble impurities, and requires filtration. Rainwater can also be harvested by allowing water to go into the ground directly from roadside drains.

6. Rainwater harvesting is an environment-friendly process that has the following benefits: (i) It increases the level of the water table. In this process, water is either stored in tanks or it is allowed to seep under the ground. (ii) It helps in conservation of water. The stored water can be used for various domestic purposes.

Topic: Water Cycle

7. (i)

(ii) The process of condensation leads to the formation of clouds. Surface water evaporates and rises above the Earth’s surface. As the water vapour moves up, it cools down gradually. After reaching higher up in the atmosphere the water vapour present in the air condenses and forms tiny drops of water. Several of these water droplets combine together and form clouds.

8. When the temperature is below 0°C, the precipitation occurs in the form of snow.

Topic: Consequences of Excess and Scarce Rainfall

9. Soil continuously loses ground water. When it does not rain for a long period of time, the soil becomes dry. Subsequently, the level of the water table also goes down. This causes ponds, rivers, wells, and other water bodies to dry up. This leads to a situation of drought in the region.

10. Excess rainfall often leads to floods. Floods cause large-scale destruction of crops, forests and infrastructure. Villages and cities get submerged by water, and people get dislocated from their homes.

Chapter 15: Air Around Us

Topic: Composition and Property of Air

1. The gases present in the air are mainly nitrogen, oxygen, and

carbon dioxide.

Given pie diagram shows the broad composition of air.

2. Smoke, dust and water vapour can be seen floating in the air when a beam of sunlight enters a dark room. This is because these air constituents reflect light.

3. (i)

Column A Column B

Nitrogen Makes 78% of the earth’s atmosphere

Oxygen Necessary for combustion

Carbon dioxide Used in photosynthesis

Water vapour Accounts for the humidity of air

Other gases in air, water vapour, and dust particles

1% of the total composition of air

(ii) The full forms of LPG and CNG are liquefied petroleum gas and compressed natural gas, respectively.

4. Carbon dioxide is also known as the ‘green-house’ gas.

5. The necessary conditions of combustion are a combustible substance and a supporter of combustion, such as oxygen.

Combustion is a natural phenomenon in which a combustible substance burns out to give vapours and gases. Combustion is not possible without an oxidising agent such as oxygen or fluorine.

6. (i) Rusting of iron is a process of formation of iron oxide (reddish-brown colour) from iron. (ii) Experimental verification of condition required for rusting Three test tubes, three iron nails, anhydrous calcium chloride, wax, and water are taken. Some anhydrous calcium chloride is taken in a test tube. A layer of cotton and few iron nails are kept inside. The second test tube is filled half with boiled water to remove dissolved air. Some iron rails are dipped in it and a layer of wax is put on the layer of water. In the third test tube, tap water is taken and few iron nails are dipped in it. All the three test tubes are corked and kept undisturbed for a few days. After a few days, we will observe that the nails in the first and second test tube have not rusted, but the nail in the third test tube has rusted. It can therefore be concluded that both oxygen and water are required for rusting to take place.

Topic: Uses of Air

7. A layer of dry chemical extinguisher is sprayed over the burning object using a fire extinguisher. This cuts off the air supply and the fire is gradually put out.

8. Oxygen is used by living organisms during the process of respiration. This gas is also essential for the burning of objects. Green trees and plants produce oxygen. They consume carbon dioxide and release oxygen when they produce food by the process called photosynthesis. Thus, while oxygen is used up during combustion and respiration, it is returned to the environment during photosynthesis.

9. Plants and animals both respire and in doing so, consume oxygen and produce carbon dioxide. During the daytime, plants consume carbon dioxide to produce oxygen. This

oxygen is again available for consumption. This shows that plants and animals are interdependent. The oxygen-carbon dioxide cycle is shown in the given figure.

10. Air helps in the dispersal of seeds and pollen of flowers, thus helping them in reproduction.

Topic: Air Pollution

11. Smog is made up of smoke and fog. The smoke containing oxides of nitrogen combine with other air pollutants and fog to form smog.

12. The pollution caused by vehicles can be reduced by using cleaner fuels such as CNG.

13. (i) Air pollutants (ii) Smog

14. Carbon dioxide and water vapour

15. Harmful effects of air pollution: (i) Air pollutants cause respiratory problems such as asthma, cough and cold. (ii) The presence of pollutants such as CFCs destroys the ozone layer. (iii) Pollutants such as sulphur dioxide, sulphur trioxide and nitrogen dioxide combine with the water vapours present in the atmosphere to form acid droplets. These droplets fall on earth and cause acid rain. Acid rain has a harmful effect on both the living and the non-living. (Note: Any two will do.)

Chapter 16: Garbage In, Garbage Out

Topic: Wastes - Its Components and Vermicomposting

1. The area where garbage from a city is collected and dumped is called a landfill. This area is later converted into a park or a playground.

2. To minimize the use of plastics, (i) Cloth or paper bags instead of plastic bags should be used. (ii) If a plastic bag is being used, the same bag should be used over and over again. (iii) Eatables should be stored in glass bottles instead of plastic bottles.

3. Example of decomposable waste: Vegetable peels Example of non-decomposable waste: Aluminium wrappers

4. The process of rotting and converting of plant, animal and kitchen wastes into manure is called composting.

5. Three ways in which we can recycle wastes of our rooms are as follows: (i) Mats can be made from old clothes. (ii) Baskets can be made out of old polythene bags. (iii) Colourful hats, photo frames, and greeting cards can be made from waste paper.

6. Open-lying wastes can prove to be a major health hazard. Hence, wastes should be disposed off properly.

7. Vermicomposting is the method of making compost from degradable garbage using earthworms is called vermicomposting. During this process, decomposable waste materials such as plant and kitchen wastes are put in a pit. It is ensured that sufficient air and moisture is available for the wastes in the pit. Redworms are then put into the pit. These redworms convert the waste materials into compost after a period of 3-4 weeks.

8. The two changes that indicate that the rotting of garbage is complete are: (i) The garbage turns into black colour. (ii) There is no foul smell that comes out from the garbage.

9. Plastic bags, on getting into drains and sewer system, choke them up resulting in spilling of dirty water on the roads. Burning of plastic bags produces harmful gases, which can cause health problems.

10. Materials such as plastics, metals, glass etc. which can be reused, should be dumped into the blue bin.

Materials such as kitchen wastes, plant wastes, animal wastes etc. which cannot be reused should be dumped into the green bin.