Question Bank 2020-21 Std – 6 Science

CHAPTER: 1

SOURCES OF FOOD

Q I. Answer the following questions: 1. Define the following:

a. food Ans. Food is any substance that we consume for nourishment, growth and development. b. staple food Ans. The food that is consumed most often by the people of a particular region is called the staple food. c. edible part of plant Ans. The parts of a plant that are safe to eat are called edible parts. d. ingredients Ans. Substances or components used to make a food item are called ingredients.

2. Give examples of the following: a. food items which we get from animals Ans. milk, eggs, meat,honey. b. food items which we get from plants

Ans. rice, cabbage, tomato,carrot.

c. spices which add flavour to our food Ans. clove, bay leaf, garlic, ginger.

d. carnivores Ans. lions, tigers, wolves,eagles.

e.herbivores. Ans. horses, elephants , cows , deer. e. omnivores. Ans. Human beings ,bears, crows, cockroaches. f. parasites. Ans. fleas, leeches, tapeworms, mosquitoes.

g. scavengers. Ans. vultures, crows, jackals, hyenas.

3. Differentiate between the following: a. scavengers and parasites. Ans.

scavengers parasites Animals that eat dead animals are called scavengers. Example: crow, vulture

Animals that live on or inside other animals for food are called parasites. Example: leech, tapeworm

b. carnivores and omnivores Ans.

carnivores omnivores Animals that eat only flesh of other animals are called carnivores. Example: lion, tiger

Animals that eat both plants and animals are called omnivores. Example: bear, crow

c. producers and consumers

Ans. producers consumers

Producers are capable of photosynthesis, a process by which they convert light energy into chemical energy. Example: green plants.

Consumers consume materials generated by the producers. Example: animals, man.

4. Write the edible parts of the following plants:

a. spinach – leaves b. ginger – stem c. rice – seeds d. carrot – root e. radish – root f. pumpkin – fruits g. tomato – fruits h. wheat – seeds

5. What is sprouting? Ans. Sprouting is the natural germination process by which seeds spring out.

CHAPTER: 2 COMPONENTS OF FOOD

Q I. Answer the following questions: 1. Define the following:

a. nutrients -the substances needed for growth and proper functioning of the body.

b. balanced diet-a diet that contains sufficient quantity of all nutrients that are required for proper growth and functioning of the body.

c. food pyramid- a diagrammatic representation of food classified into different groups that guides us to eat a balanced diet.

2. Name the different types of nutrients and their function. A.1. Carbohydrates-provides energy to the body. 2.Fats-a).provide almost double the energy as compared to carbohydrates. b).acts as insulation to prevent the loss of heat from the body. 3.Proteins-a). they are the main building materials of cells b).they provide our body with materials for cell growth. c).they also repair the damaged and worn out tissues. 4.Vitamins- a) they provide good health and proper growth. b)they help in various chemical reactions taking place inside our body. 5. Minerals-a) they help for the growth and development of the bones and teeth ,growth of cells and formation of red blood cells. b) they help in proper functioning of the circulatory system and nervous system.

3. Give two examples of food items for: a. carbohydrates- sugar, starch b. proteins-eggs,soyabeans

c. fats-ghee,butter d. vitamins and minerals-fruits ,vegetables. e. roughage-cabbage ,cucumber.

4. Name the following: a. water soluble vitamins – Vitamin B and C b. fat soluble vitamins – Vitamin A, D, E, K c. the richest source of plant protein – Soyabeans d. vitamin responsible for blood clotting – Vitamin K e. disease caused due to deficiency of Vitamin D – Rickets f. minerals responsible for causing anaemia – iron, Vitamin B12 g. two sources of phosphorus – beans, nuts h. two sources of Vitamin A – papaya,liver i. minerals responsible for strong bones and teeth – calcium,

phosphorus

5. Write down the disease caused by the deficiency of the following vitamins and minerals in our diet. 1. Vitamin A – night blindness 2. Vitamin B1 – beriberi 3. Vitamin B2 – skin disorders 4. Vitamin B12 – anaemia 5. Vitamin C – scurvy 6. Vitamin D – rickets 7. Vitamin E – Skin disorder 8. Vitamin K – haemorrhage 9. Calcium – rickets – soft bones 10. Iron – anaemia 11. Iodine – goitre 12. Sodium and potassium – muscle cramps

6. What is roughage? How is it useful? Ans. Roughage is a dietary fibre present in food that we eat. It is the part of food that is not digested by the human digestive system.

It helps the food to move through the digestive tract and in bowel movement which prevents constipation. it also provides bulk to the food and thus satisfies our appetite. 7. Write two sources for each of the following and their uses.

a. Vitamin D Ans. Vitamin D keeps the bone and teeth healthy and strong. Food sources – milk and butter b. Iron Ans. Iron forms haemoglobin which carries oxygen to all the cells of the body. Food source – meat, green leafy vegetables and dried dates c. Calcium Ans. Calcium is required for strong bones and teeth. Food source – milk, leafy vegetables and legumes d. Vitamin K Ans. Vitamin K is required for normal blood clotting. Food source – green leafy vegetables, wheat bran, cheese and egg yolk. e. Magnesium Ans. Magnesium is required for proper functioning of muscles and

nerves. Food source – green leafy vegetables, wholegrain, chicken and

fish

Q II. Fill in the blanks:

1. A lack of water causes dehydration. 2. The food pyramid helps us in planning a balanced diet. 3. Swelling and bleeding of gums is called scurvy. 4. Haemoglobin carries oxygen to all cells of the body. 5. Almost 90% of our blood is composed of water.

Chapter-3 Fibre to Fabric Multiple Choice Questions 1. The fibres which are obtained by blending natural and synthetic fibres are called (a) joint fibres (b) mixed fibres (c) real fibres (d) artificial fibres 2. Which of the following is used for making gunny bags? (a) Cotton (b) Jute (c) Wool (d) Polyster 3. In which of these states does the jute plant grow? (a) Punjab (b) West Bengal (c) Tamil Nadu (d) Kerala 4. The process of cultivating silkworm is called (a) sericulture (b) carding (c) drawing (d) spinning 5. Which of the following grows best in a black soil and warm climate? (a) Cotton (b) Flax (c) Jute (d) Coconut 6. Yarn is made from very thin strands called (a) fibres (b) looms (c) silver (d) weft 7. Which one of the following is not a natural fibre? (a) Cotton (b) Nylon (c) Flax (d) Wool Answers: Multiple Choice Questions 1. (b) 2. (b) 3. (b) 4. (a) 5. (a) 6. (a) 7. (b) Fill in the blanks (a) All clothes are made up of--------------- . (b) The fibres which are prepared from chemical substances in industry, are called------------- . (c) The cotton picked up from the plants still has its--------- in it.

Answers: Fill in the blanks. (a) fibres (b) artificial fibres/synthetic fibres (c) seed State whether ‘True’ or ‘False’ (a) Wool is a synthetic fibre. (b) The process of making yarn from fibres is called knitting. (c) Cotton fibre is a fibre which is obtained from the leaves of the cotton plant. (d) Yarn is made from fibres. Answers: State whether ‘True’ or ‘False’. (a) False (b) False (c) False (d) True Very Short Answer Type Questions 1. List the things which primitive people used to cover themselves? 2. Where do we get silk from? 3. Name the two types of natural fibres. 4. What is a fibre? 5. Name any 3 things that can be made from jute fibre. 6. What is weaving? 7. What type of soil is needed for the cultivation of cotton? 8. What is a cocoon? Answers: Very Short Answer Type Questions. 1. The leaves of trees, bark of trees and animals' skin were used by primitive people to cover their body. 2. We get silk from silkworm. Silk worms are reared on mulberry leaves. 3. Cotton, Silk 4. All clothes are made up of threads. Materials used for making clothes are known as fibres. Fibres are very thin, thread like strands from which fabrics (or cloth) are made. Cotton, nylon, wool., etc., are all fibres. 5. Gunny bags, ropes, curtains

6. The process of arranging two sets of yarn together to make a fabric is called weaving. 7. Black soil is needed for the cultivation of cotton. 8. A cocoon is the protective covering of a caterpillar. Short Answer Type Questions 1. Write any three characteristics of the cotton plant. 2. How are fibres classified? Give one example of each type. 3. What advantages does cotton have over synthetic cloth? 4. What are warp and weft yarns? Answers: Short Answer Type Questions 1. (i) Cotton requires little rainfall at the ripening of seeds. (ii) Cotton plants are usually grown at places having black soil. (iii) Cotton plant is bushy and 1–2.5 metres tall. 2. There are three types of fibres. (i) Natural fibres — Cotton (ii) Man-made or synthetic fibres — Nylon (iii) Mixed fibres — Terycot 3. Cotton cloth absorbs water efficiently and burns at a moderate speed. Synthetic fibres are not suitable for hot and humid weather as they do not absorb sweat whereas cotton clothes do. 4. In weaving cloth, the warp is the set of length wise yarns that are held on a frame or loom. The yarn that is inserted over and under the warp threads is called weft, woof, or filler.

Long Answer Type Questions 1. What is a loom? For what purpose is it used? What is the difference between handloom and power loom? 2. How is weaving different from knitting? 0 Answers: Long Answer Type Questions. 1. A loom is a machine used to weave cloth from yarn. On a large scale, cotton fabrics are made by big machines that run on electricity. These machines are called power looms. The process of weaving done manually is called hand-loom. 2. Weaving is the process of converting yarn into cloth. The process of arranging two sets of yarn together to make a fabric is called weaving. Knitting is a method by which yarn is manipulated to create a textile or fabric. Knitting creates multiple loops of yarn, called stitches, in a line or tube. Knitting has multiple active stitches on the needle at one time. A single yarn is used in knitting. Knitting may be done by hand or by using a machine.

Chapter-5 Separation of Substances

Multiple choice questions: 1. A solid substance is dissolved in water. Which of the following methods is used for separating it? (a) distillation (b) evaporation (c) filtration (d) decantation 2. Iron is separated from the mixture by: (a) magnetic separation (b) sedimentation (c) winnowing (d) Sieving 3. The process of settling down of the particles of an insoluble solid in a liquid is called. (a) decantation (b) sedimentation (c) winnowing (d) sieving 4. Air is a: (a) pure substance (b) heterogeneous mixture (c) the compound of oxygen and nitrogen (d) homogeneous mixture 5. Oil and water can be separated through (a) filter paper (b) distillation (c) evaporation (d) separating funnel 6. Which of the following is a heterogeneous mixture? (a) a salt solution (b) a salt-pepper mixture (c) air (d) a fizzy drink 7. Which of the following is a homogeneous mixture? (a) mist (b) a sand-water mixture (c) an oil-water mixture (d) a nitrogen-oxygen mixture 8. Tiny pieces of stones are usually separated from pulses before cooking by the method called - (a) threshing (b) sieving (c) hand picking (d) winnowing

9. The process of changing vapour into its liquid is called (a) condensation (b) loading (b) winnowing (d) evaporation Answers: Multiple choice questions 1. (b) 2. (a) 3. (b) 4. (d) 5. (d) 6. (b) 7. (d) 8. (c) 9. (a) Fill in the blanks: 1. Materials which contain two or more substances in any proportion are called——————. 2.—————— mixtures are not uniform in appearance and composition. 3. Cereals like wheat and rice are sources of————-. 4. The process in which a liquid changes into vapour is called ——. 5.—————— is a process of separating the component of substances from a liquid mixture by selecting evaporation and condensation. Answers: Fill in the blanks 1 mixtures 2. Heterogeneous 3. carbohydrates 4. evaporation 5. Distillation State whether ‘True’ or ‘False’ 1. Rock salt is an impure substance. 2. Filtration is used to make fruit juice. 3. The saline water from oceans is rich in salt. Answers: 1. Rock salt is an impure substance. True 2. Filtration is used to make fruit juice. True 3. The saline water from oceans is rich in salt. True

Very Short Answer Questions 1. What is winnowing? 2. What is a saturated solution? 3. Name the processes by which water is separated from rice and pulses after washing them. 4. Which method is usually used to separate small pieces of stones from pulses at home? 5. Define pure substances. 6. Which substance is used for loading the clay particles suspended in muddy water? Answers: Very Short Answer Questions 1. The process of separating the wheat grain from the chaff is called winnowing. 2. A solution in which no more substance can be dissolved at a given temperature is called a saturated solution. 3. Sedimentation and Decantation 4. Hand-picking 5. Substances that contain only one kind of particles and cannot be separated by any processes are called pure substances. 6. Alum Short Answer Questions 1Define solubility of a substance. How does the solubility of a substance vary with temperature? 2(a) State one use of the method of winnowing. (b) Give one use of the ‘handpicking’ method of separating mixtures in daily life. 3 Why do you often need to separate mixtures into their components? Answers:

1.Solubility is the ability of a substance to dissolve in a given liquid. The solubility of a solid solute generally increases with the rise in temperature. This means that larger amount of a substance (sugar, salt, etc.) can be dissolved in a given amount of water on heating it (or raising its temperature). On the other hand, the solubility of a substance decreases on lowering the temperature (by cooling). This means that lesser amount of a substance (sugar, salt, etc.) will dissolve in a given amount of water on cooling it (or on lowering the temperature). 2.(a) Winnowing helps in the separation of husk from wheat grains. (b) Hand-picking helps in the removal of solid impurities from a mixture. For example, removal of stones from pulses and rice. 3.We often need to separate mixtures into their components as most substances that occur in nature may contain: (i) one or more useful substances (ii) one useful substance and one or more harmful or unwanted (undesirable) substances Chapter-6

Changes around us

Mark the correct answer in the following: 1. Spoiling of milk by microbes can be slowed down by

(a) cooling at low temperature in refrigerator (b) pasteurization (c) simple cooling (d) cooling with the help of freezing mixture 2. Iron sheets are prevented from rusting by the process of (a) galvanization (b) tinning (c) both (a) and (b) (d) none of these 3. In pasteurization (a) milk is heated to high temperature (b) milk is suddenly cooled (c) milk is heated to high temperature and then suddenly cooled (d) none of these 4. Which of the following is a desirable irreversible change? (a) Rusting of an iron nail (b) Burning of paper(c) Formation of curd from milk (d) Rainfall Answers: Multiple choice questions 1. (b) 2. (c) 3. (c) 4. (c) Fill in the blanks: 1. Weathering of rocks is an ________________ change. 2. Rusting of iron bars is a ________________ change. 3. Changes that lead to the formation of a new substance are known as ________________ changes. 4. Depositing layer of zinc over the surface of Iron is known as _____ . 5. Melting of wax near the wick of a candle is _________ but burning of wax in the wick of the candle is ____________. Answers: Fill in the blanks. 1. Irreversible 2. Chemical 3. Chemical 4. Galvanisation 5. Physical change ; Chemical change State whether ‘True’ or ‘False’ 1. The glowing of Electric bulb is a physical change 2. Formation of day and night is not a periodic change

3. Pasteurised milk can be stored for many days 4. Pressure or force can bring about a reversible as well as irreversible change . 5. When glucose is dissolved in water, the heat is absorbed and produces cooling effect Answers: State whether ‘True’ or ‘False’. 1. True 2. False 3. True 4. True 5. True Very Short Answer Questions 1. Name the process of depositing a thin layer of zinc over iron. 2.Mention the type of change in the following a. sneezing b. condensation of steam to water c. breaking of glassware d. magnetisation of steel bar Answers: Very Short Answer Questions 1. galvanisation 2. a. physical b. physical c. physical d. physical Short Answer Questions

1. Differentiate between reversible and irreversible changes A.Reversible changes- Changes in which the objects or materials can be obtained back in their original form. Example-a) Melting of chocolate b) Melting of solid wax into liquid wax and forming solid wax from liquid wax by cooling. Irreversible changes- Changes from which we cannot get objects or materials back in the original form . Example-a) Burning of paper which turns into ash b)Rusting of an iron nail.

2. Why is germination of a seed a chemical change? A. It is a chemical change because a seed has developed into a

complete plant which is permanent. When a seed germinates , it never turns back in the form of a seed and we get a totally different character from that of a seed.

3. Give one example of an exothermic change . A. An example of an exothermic change is combustion . (burning of a paper).

4. Pulling of a rubber string is a reversible change. Why? A.Pulling of a rubber string is a reversible change because when the rubber string is stretched and left ,it obtains back it's original form.

5. State the differences between physical and chemical changes.

A.Physical Changes-. Chemical Changes- 1.No new substance is formed. 1.New substances are formed. 2.Temporary. 2.Permanent 3.Can be reversed. 3.Cannot be reversed. 4.Energy is neither evolved nor 4.Energy is evolved or absorbed. absorbed in the form of heat and light. 5.Example- Melting of ice. 5.Example- Burning of wood.

CHAPTER-7

GETTING TO KNOW PLANTS

Q1 Write the scientific term of the following

i A leaf like protective covering enclosing a flower bud =sepals

ii A green swollen part at the base of a flower = thalamus

iii It contains the pollen grains = anther

iv The sticky part of the pistil which receives the pollen grains = stigma

v The stalk like structure of a stamen = filament

vi The small bead like structure found in the ovary = ovules

vii The female reproductive part of a flower = pistil

viii It connects the stigma to the ovary = style

ix A brightly coloured part of a flower = petals

x It develops into fruits after fertilisation = ovary

xi The flat green portion of a leaf = lamina

xii The stalk by which leaves are attached to stem = petiole

xiii The thick vein that runs in the middle of the lamina = midrib

xiv The arrangement of veins in a leaf = venation

xv The part of the stem between the two nodes = internodes

Q2. Define the following

HERBS- Herbs are the small plants which have soft and flexible stems.

LAMINA- Lamina is defined as the flat green portion of the leaf.

TRANSPIRATION – Transpiration is the process by which water is lost from the aerial parts of the plant in the form of vapour.

STOMATA—Stomata is defined as the small pores present on the surface of leaves.

POLLINATION—Pollination is defined as the transfer of pollen grains from the anther to the stigma of a flower.

Q3.Answer the following questions

1)Which part of the plant is known as food factories and why?

A – Leaves are the food factories of the plants because they prepare food by the process of photosynthesis.

2)What is chlorophyll? Write the role of chlorophyll in photosynthesis?

A)Chlorophyll is the green pigment present in leaves.

It traps solar energy from the sun and helps in photosynthesis.

3)Why do the leaves of some plants do not appear green?

A)The leaves of some plants do not appear green because the amount of chlorophyll present in them is less than the amount of coloured pigments.

4) What is the relationship between the type of root and the venation of the leaves?

A)Plants with tap roots have leaves of reticulate venation and plants with fibrous root have leaves of parallel venation.

Q4.Give two examples of each of the following

a. Taproots – hibiscus, neem.

b. Climbing roots—money plant, betel.

c. Trees-mango, neem.

d. Parallel venation- maize ,grass.

e. Reticulate venation— Tulsi, china rose.

Q7-Draw a neat labelled diagram of leaf.

Chapter – 10

Characteristics of living things

1. What are the characteristics of living things?

a. Living organisms have a cellular organization.

b. They show movements.

c. They grow and develop.

d. They respond to stimuli.

e. They have a definite life span.

2. Name the breathing organs of the following animals?

a. Frog and salamander: lungs and moist skin.

b. Earth worm : skin

c. Insect : Spiracles (small opening on the side of their bodies)

3. Define:

a. Excretion: The process of elimination of waste products from

the living organisms to maintain a constant environment in it is

called excretion.

b. Tropism : Movement of plants in the direction of stimuli is

known as tropism.

c. Nasticism : When someone touches the touch-me-not plants, its

leaves get folded. This movement is called nasticism.

QUESTION BANK Std -6

GENERAL SCIENCE

EXTRA QUESTIONS Chapter 11 Measurement and Motion A.Multiple Choice Questions: 1. Which of the following modes of transport is not based on the invention of the wheel? (a) Boat (b) Bicycle (c) Bus (d) Bullock cart 2. The unit you will use to measure the distance from Delhi to Patna is (a) centimetre (b) kilometre (c) millimetre (d) decimetre 3. To measure the length of a curved line, you will use: (a) thread (b) geometry scale (c) divider (d) both a and c 4. Which one of the following is the smallest unit of length? (a) mm (b) km (c) cm (d) m 5. Which is not an example of rotatory motion? (a) a planet moving around the sun (b) a boy on a giant wheel (c) a spinning top (d) the bob of a swinging pendulum 6. A ball rolling on a ground shows (a) periodic motion (b) rectilinear motion (c) rotational motion (d) both (b) and (c) 7. The motion of a pendulum is

(a) periodic (b) circular (c) curvilinear (d) rotatory 8. The motion of the arms of soldiers in a march past is (a) oscillatory (b) circular (c) periodic (d) non-periodic ANSWERS

1. (a) 2. (b) 3. (d) 4. (a) 5. (d) 6. (d) 7. (a) 8. (c) B. Fill in the blanks 1. Accurate measurement of any——— is very essential. 2. Motion in a————- is called rectilinear motion. 3. A body moving along a curve is said to be in———– motion. 4. The motion which repeats itself after regular interval of time is called————-. 5. Small and————- are called vibrations. ANSWERS

1. Accurate measurement of an object is very essential. 2. Motion in a straight line is called rectilinear motion. 3. A body moving along a curve is said to be in curvilinear motion. 4. The motion which repeats itself after regular interval of time is called periodic motion. 5. Small and rapid oscillations are called vibrations. C. State whether the following statements are ‘True’ or ‘False’ 1. The motion of the earth is periodic. 2. The motion of a train along the track is mostly rectilinear and at times curvilinear. 3. Handspan cannot be used to measure length accurately. 4. Mass is a unit of temperature 5. When a screw is tightened it exhibits only rotatory motion. 6. Movements of a bird in the sky can be said to have random motion. ANSWERS

1.True, 2. True, 3. True, 4. False, 5. True, 6. True D. Very Short Answer Questions 1. What is motion? 2. The distance between two bus stops is 35 m. Express this distance in (a) cm (b) km 3. What is the SI unit of the following? (a) length (b) mass (c) time (d) temperature 4. Why can footstep or a hand span not be used as a standard unit of length? 5. When is a body said to be at rest? 6. Name the two instruments which are used to measure very small lengths. 7. Name two things which can be used to measure the length of a curved line. 8. Define uniform motion and give one example. ANSWERS

1. The objects which change their positions with time (with respect to their surrounding) are said to be in motion. 2. Distance = 35 m We know, 1 km = 1000 m So, distance = 35/1000 = .035 km we know that: 1 m = 100 cm So, 35 m = 35 × 100 cm= 3500 cm 3. (a) length — metre(b) mass — kilogram(c) time — second. (d) temperature — Kelvin 4. Footstep or a hand span cannot be used as a standard unit of length as such units of measurements are not reliable; they vary from person to person, place to place and are affected by the local conditions. 5. The objects which cannot change their position (with respect to their surrounding) are said to be at rest. 6. Measuring tape and metre scale. 7. Thread and divider. 8. When a body travels an equal distance in equal intervals of time, it is said to be in uniform motion. For example, Planets move around the sun in uniform motion. F. Short Answer Questions 1. What is meant by rectilinear motion? Give two examples of rectilinear motion. 2. Define random motion. Give examples. 3. What is meant by periodic motion? 4. What two types of motion does the earth show? 5. What is an oscillatory motion? Give two examples. 6. How is a periodic motion different from non-periodic motion? 7. List the precautions to be observed while measuring the length using a scale. ANSWERS

1. Motion in a straight line is called rectilinear motion. In other words, when an object moves along a straight line path in a given time ,it is called rectilinear motion. Example-1) movement of a bullet fired from a gun . 2)A train moving on a straight track. 2. The translatory motion of a body which keeps on changing its direction in a disorderly manner is called random motion. Example-1)The motion of a cricket ball during a cricket game. 2) a football match . 3) flying bird in the sky. 3. The motion which repeats itself after regular intervals of time is called periodic motion. For example, the motion of a swing or a pendulum is periodic. 4. Circular and rotatory motion 5. When a body moves to and fro about a point, it is said to be in oscillatory motion. The oscillatory motion is a kind of periodic motion. Some examples of oscillatory motion are: • The motion of the heart muscles in a healthy person.

• A child on a swing. 6. The motion which repeats itself after regular intervals of time is called periodic motion. A motion, which repeats itself but not in a fixed interval of time is called a non-periodic motion. 7. In taking a measurement of length, we need to take the following precautions (care) to get the correct measurement of the length. (a) Placement of scale: The scale should be placed with the objects along its length. (b) Worn out ends of the ruler: Sometimes, due to repeated use the zero mark of a scale gets worn out and cannot be clearly seen. In some cases, the ends of the scale may get damaged or broken due to various reasons. In such cases, we should measure the length of the object starting from any other mark of the scale (say the 1 cm mark). We subtract the reading of this mark (1cm) from the reading of the other end. (c) The position of the eye: The correct position of the eye is also important for taking a measurement.

Chapter 12 Light,Shadows and Reflection Multiple Choice Questions 1. Which of these is not a source of light? (a) Sun (b) Fire (c) Star (d) Moon 2. Which of the following is not a translucent object? (a) Cellophane paper (b) Wall (c) Butter paper (d) Tissue paper

3. Which of the following is not an artificial source of light? (a) Candle (b) Electric (c) Sun (d) None of these 4. Which of the following are non-luminous bodies? (a)Stars (b) Incandescent lamps (c) Rock (d) None of these 5. Materials which allow light to pass through them are called (a) translucent (b) transparent (c) opaque (d) all of these 6. The object which does not allow light to pass through it is called (a) opaque (b) transparent (c) translucent (d) none of these 7. Which of the following material allows light to pass through it? (a) Copper (b) Wood (c) glass (d) Walls 8. Sunlight can pass through (a) bushy tree (b) rocks (c) water (d) walls ANSWERS 1. (d) 2. (b) 3. (c) 4. (c) 5. (b) 6. (a) 7. (c) 8. (c) Fill in the blanks : 1. The main source of light on earth is the———–. 2. All source of light is———– objects. 3. Substances that allow most of the light to pass through them are called—————- substances. 4. If we place an object in the path of light, a —————-is formed. 5. A very—————– beam of light is known as a ray of light. ANSWERS 1. The main source of light on earth is the sun. 2. All source of light is luminous objects. 3. Substances that allow most of the light to pass through them are called transparent substances. 4. If we place an object in the path of light, a shadow is formed. 5. A very narrow beam of light is known as a ray of light. State whether the following statements are ‘True’ or ‘False’

1. The image formed by a plane mirror is always of the same size as the object. 2. Non-luminous bodies reflect all the light that falls on them. 3. A solar eclipse occurs when the moon’s shadow falls on the earth. 4. Opaque objects allow all the light that falls on them to pass through them. 5. Light takes several years to travel from the earth. ANSWERS 1. True, 2. True, 3. True, 4. False, 5. False Very Short Answer Questions 1. What are luminous objects? Give two examples. 2. Name any two man-made luminous bodies. 3. Name three opaque materials. 4. Name two transparent objects. 5. What is light? 6. What is a shadow? 7. Define reflection. ANSWERS 1. The object that gives out its own light is called a luminous object . Examples- sun, stars 2. Bulb, tube light 3. Rock, wood, wall 4. Glass, water 5. Light is a form of energy which helps us to see. 6. A shadow is a dark space (shade) formed behind an opaque object when it blocks light from any source. 7. The bouncing back of light rays from the surface of an object is called reflection. Short Answer Questions 1. What is lateral inversion? 2. State any one observation from everyday life which shows that light travels in straight line. 3. Distinguish between a solar and a lunar eclipse. 4. Which of the following are the sources of light? The book, tube light, the moon, the sun, stars, planets, meteor, table, chair, electric bulb. 5. Distinguish between the natural source of light and artificial source of light. 6. What are the characteristics of a shadow? 7. What is the difference between an image and a shadow? ANSWERS 1. If we stand in front of a plane mirror, we see the image of our body in it. Though our image appears to be just as we are but there is a peculiar difference in it. In the image, the left-hand side pocket of our shirt will appear on the right-hand side. Our right eye will appear as the left eye in our image. Our right and the left hand will appear as the left and right hand respectively. It means that the side of the image is reversed, i.e., opposite to that of the object formed by a plane mirror which is called as lateral inversion. 2. Light travelling from the sun to the earth is an observation that shows light travels in a straight line. 3. When the earth comes between the moon and the sun, the earth’s shadow falls on the moon. This is called a lunar eclipse. When the moon comes between the sun and the earth, the moon’s shadow falls on the earth. This is called a solar eclipse. 4. Tube light, sun, stars, electric bulb.

5. The source of light which occur naturally is called the natural source of light.For example- the sun, stars and glow worms. Sources which are made by man artificially are called the man-made source of light. For example- electric bulb, tube light, kerosene oil, candle, CFL, fluorescent lamp. 6. The nature of shadow depends on the nature of the object which blocks the light. • The size of the shadow depends on the size of the source of light and object and also on the distance between the source of light and the object, the wall or the screen. • A transparent object does not stop light completely. Therefore, it casts a weak shadow. • A translucent object stops light only partially. Therefore, it casts a weak shadow. • An opaque object stops the light completely. Therefore, it casts a dark shadow. • The shadow is always formed in the opposite direction of the source of light. • The sharpness of the shadow depends on the size of the light source. • The shape of the shadow is usually similar to the outline of the objects which block the light. Hence, we can identify an object from the shadow. • When the source of light or the object moves, the shadow also shifts accordingly. 7. a)The shadow of an object is always black whereas the image is coloured. b)The shadow gives only the outline of the object whereas the image gives detail of the object. Long Answer Questions 1. Distinguish between a parallel, a convergent and a divergent beam of light. 2. Describe an experiment to demonstrate rectilinear propagation of light. 3. What is meant by (a) luminous objects and (b) non-luminous objects? Name any three luminous objects and three non-luminous objects. State whether the moon is a luminous object or a non-luminous object. ANSWERS 1. A beam of light is parallel when the rays of light are parallel to each other, i.e the distance between the rays remains the same. • A beam of light is convergent when the rays of light meet at a point. • A beam of light is divergent when the rays of light spread out from a point. The distance between the rays goes on increasing. 2. To show that light travels in a straight line Materials Required: A piece of rubber tube and a candle Procedure: Fix a lighted candle on a table, stretch a narrow rubber tube straight and look through it at the flame. Do you see light coming from the flame? The light from the flame is visible. Now coil the rubber tube and look through it at the flame. Do you see the light coming from the flame? The light coming from the flame is not seen. Conclusion: This experiment shows that light travels in straight line. 3. The object that gives out its own light is called a luminous object. Sun, stars and a burning candle are examples of luminous objects. Objects that do not give out their own light are called non-luminous objects. A pencil, clothes, paper and the wall are some common examples of non-luminous objects. Moon is a non-luminous object. It does not have the light of its own. It shines because of the light of the sun falling on it.

Chapter-13 Magnets

Multiple Choice Questions 1. Which of the following is preferred to make an electromagnet? (a) Steel (b) Soft iron (c) Stainless steel (d) Plastic 2. The poles of a magnet are located at its- (a) upper surface (b) middle point (c) ends

(d) lower surface 3. A magnet can attract an- (a) copper plate (b) iron ring (c) rubber band (d) glass rod 4. The magnetic compass is used by- (a) navigators (b) pilots (c) soldiers (d) all of these 5. The two ends of a bar magnet are called- (a) points (b) roads (c) poles (d) ends 6. A magnet loses its magnetic property by (a) using (b) storing (c) hammering (d) clearing 7. A freely suspended magnet points in which direction (a) north-south (b) east-west (c) only north (d) only south 8. Which of the following makes use of a magnet? (a) a shirt button (b) a plastic toy (c) a door stopper (d) a can opener ANSWERS

1. (b) 2. (c) 3. (b) 4. (d) 5. (c) 6. (c) 7. (a) 8. (c)

Very Short Answer Type Questions. 1. Name a natural material that possesses the properties of a magnet. 2. Name three methods of making magnets. 3. Name any three items in which magnets are used. 4. What name is given to the ends of a magnet where the attraction is strongest? 5. Which of the following materials are not attracted to a magnet? wood, nickel, copper, steel, aluminium,iron. 6. Name an instrument which is used to find directions. 7. Name the material that is used to make a permanent magnet. 8. What happens when the N-Pole of a magnet is brought near to the N-Pole of a suspended magnet? ANSWERS 1. Loadstone 2. The three methods of making magnets are:

(a) Single touch method (b) Double touch method (c) Electrical method 3. Compass, refrigerator doors, doors of wooden shelf 4. Poles 5. Wood, copper,aluminium 6. Magnetic compass 7.The material that is used to make a permanent magnet is from mixtures of iron, cobalt or nickel with other materials. 8.The poles repel each other. Fill in the blanks with suitable words. (a) The mineral called magnetite is mainly composed of oxides of————-. (b) Materials that are not———— by magnets are called non-magnetic materials. (c) An electromagnet is a———– magnet. (d) The pull exerted by a magnet or magnetic substance is called————-. ANSWERS (a) The mineral called magnetite is mainly composed of oxides of iron. (b) Materials that are not attracted by magnets are called non-magnetic materials. (c) An electromagnet is a permanent magnet. (d) The pull exerted by a magnet or magnetic substance is called magnetic pull. State whether the following statements are ‘True’ or ‘False’. (a) The unlike poles of magnets repel and the like poles attract each other. (b) The two poles of magnets can be easily separated. (c) A magnet is the strongest at the poles. (d) The heating of a magnet does not demagnetize it. (e) All metals are magnetic in nature. (f) Rubber is a magnetic substance. (g) Magnetic compass helps in knowing the direction. (h) The soft iron pieces used to store magnets are called Keepers. ANSWERS (a) False, (b)False, (c) True, (d) False (e) False, (f) False, (g) True, (h) True. Short Answer Type Questions 1. What are magnetic substances? 2. Write three uses of magnets? 3. What do you understand by the directive property of a magnet? State one of its advantages. 4. Differentiate between permanent and temporary magnets. 5. How does an electromagnet differ from a permanent magnet? 6. Differentiate between natural and artificial magnets. 7. What is the proper way of storing bar magnets when not in use? Draw a labelled sketch to show the arrangement? 8. How can self–demagnetisation of magnets be prevented?

ANSWERS 1. Materials that are attracted by a magnet are called magnetic materials. Examples of magnetic materials include iron, cobalt, nickel, steel, etc., and their alloys. 2. (i) Magnets are used in magnetic compass used to find directions. (ii) Magnets are used for the separation of magnetic material and non-magnetic materials. (iii) Magnets are used to hold objects like a sticker, refrigerator doors, pencil box lids, pins, etc.

3. A freely suspended magnet always rests pointing in the North-South direction. This property of a magnet is called its directive property. This property is used in the magnetic compass and is of help to sailors and navigators. 4. Permanent magnets retain their magnetic properties for very long periods of time. They are made from mixtures of iron, cobalt or nickel with other materials. Temporary magnets retain their magnetic properties only for a short period of time. They are usually made of iron, cobalt or nickel. 5. Permanent magnets retain their magnetic properties for very long periods of time. They are made from mixtures of iron, cobalt or nickel with other materials. Electromagnets are special types of magnets in which the magnetism is produced by a flow of electric current. 6. Magnets are the substances which have the property of attracting iron. Magnetic materials that occur freely in nature are called natural magnets. Magnets that are made in laboratories or factories are called artificial magnets. 7. Students do this activity in the class. 8. Self-demagnetisation of magnets are prevented by the following: (i) We should not drop a magnet on the floor. (ii) We should not heat a magnet. (iii) We should store the magnets properly (when not in use). (iv) We should never hit a magnet with a hammer. (v) Rough handling of magnets should be avoided. Long Answer Type Questions 1. Explain how magnets get demagnetized? 2. Describe the construction and working of a magnetic compass.

ANSWERS 1. The magnetic properties of a magnet can be destroyed by the following methods: • By heating the magnet strongly and keeping it in the east-west direction • By hammering the magnet strongly • By dropping the magnet repeatedly on a hard surface • By striking the magnet against a hard surface receptively • By self-demagnetization: when the two poles of a magnet are left free, the magnet loses its magnetism slowly; this is called self-demagnetisation. 2. A magnetic compass is a simple device used for finding direction. It consists of a magnetic needle that can turn freely about its centre. The needle is encased in a box with a transparent top. Directions are either printed on a card placed below the needle or marked on top of the box. Usually, the north pole of the needle is painted red or blue, or is in the shape of an arrowhead. When kept away from magnetic materials, the north pole of the needle points towards the geographical north. To find directions, the box is turned till the north mark on the card falls exactly below the north pole of the needle. In this position, the other directions are also indicated by the card.

Chapter 14 Electricity and Circuits Multiple-choice Questions: 1. Which of the following is not a conductor? (a) Copper (b) Mica (c) Silver (d) Iron 2. Which of the following is an insulator? (a) Silver (b) Aluminium (c) Copper (d) Plastic 3. Where do we get electricity from a (a) sun (b) metal (c) wire (d) battery 4. Electric current flows only when the circuit is (a) open (b) closed (c) incomplete

(d) broken 5. The energy provided by electricity is called (a) electrical energy (b) chemical energy (c) solar energy (d) all of these 6. The flow of electricity is known as electric (a) energy (b) power (c) generator (d) current 7. Which of these does not use electricity? (a) Gas stove (b) Computer (c) Television (d) Steam Iron 8. In an electric circuit, the bulb will glow when the circuit is (a) open (b) closed (c) both (a) and (b) (d) neither when open nor when closed

ANSWERS 1. (b) 2. (d) 3. (d) 4. (b) 5. (a) 6. (d) 7. (a) 8. (b) Fill in the blanks: 1. Electricity is the basic part of nature and is one of the most widely used forms of————-. 2. A large number of machines in shops and factories run on—————–. 3.————-is an electrical component used for lighting. 4. A switch is a device which controls the ON-OFF mechanism of any electric———–.

ANSWERS 1. Electricity is the basic part of nature and is one of the most widely used forms of energy. 2. A large number of machines in shops and factories run on electricity. 3. The bulb is an electrical component used for lighting. 4. A switch is a device which controls the ON-OFF mechanism of an electric circuit. State whether the following statements are ‘True’ or ‘False’ 1. Plastic is an insulator. 2. The electric circuit allows current to flow through. 3. The electric cell has one terminal only. 4. A bulb gives light when its filament glows. 5. A battery consists of two or more cells.

ANSWERS 1. True, 2. True, 3. False, 4. True, 5. True

Very Short Answer Questions 1. What is an electric circuit? 2. Name a device which is used to ‘open’ or ‘close’ a circuit. 3. What kind of cell is used in a wristwatch? 4. State whether the following are conductors or insulators. wood, distilled water, copper, plastic, aqueous solution, silver, brass, water. 5. What are conductors? Give three examples. 6. Name any four appliances that work on electricity.

ANSWERS 1. An electric circuit is a path through which the current flows. 2. The electric switch 3. Button cell 4. Conductors –copper, silver, brass, aqueous solution,water. Insulators – wood, distilled water, plastic. 5. The materials that allow electric current to pass through them are called conductors. For example- silver, copper, iron. 6. Television, Microwave, Steam iron, Hairdryers. Short Answer Questions 1. Why is a complete path required for the current to flow? 2. What is the purpose of using an electric switch? Name some electrical gadgets (electrical appliances) which have switches built into them. 3. What is the switch? Explain the working of a switch with the help of diagrams. 4. Why do electricians wear rubber hand gloves while working with electricity? 5. What does each of the following do in an electric circuit? (a) bulb (b) cell (c) wires (d) switch 6. What are the advantages of a dry cell?

ANSWERS 1. A complete path is required for the current to flow because electricity cannot flow in an open circuit. 2. A switch is a device that controls the ON-OFF mechanism of an electric circuit. Some electrical gadgets (electrical appliances) which have switches built into them are an electric lamp, table fan, washing machine, juicers, etc. 3. A switch is a device which controls the ON-OFF mechanism of an electric circuit. When the switch is OFF no current flows and the circuit is said to be open. When the switch is ON, the circuit is said to be closed and allows the current to flow. 4. Electricians wear rubber hand gloves while working with electricity because rubber is a bad conductor of electricity. 5. (a) bulb—When current flows through the filament in the bulb , it heats up and starts glowing as a result the lights up. (b) cell—The cells are the source of electric current in an electric circuit. (c) wires—Wires carry current in an electric circuit. (d) switch—A switch is a device that controls the ON-OFF mechanism of an electric circuit. 6. Dry cells have the following advantages: (i) Dry cells can be easily transported from one place to another. (ii) Dry cells are very light in weight and small in size. (iii) Dry cells can be easily stored in houses.

Long Answer Questions 1. What happens when the switch is in the (a) ‘On’ position (b) ‘Off’ position 2. Distinguish between conductors and insulators, giving examples of each. 3. What preventive measures should we follow to avoid an electric shock? 4. How does an electric torch work?

ANSWERS 1. (a) ‘On’ position – When the switch is ON, the circuit is said to be closed and allows the current to flow. (b) ‘Off’ position – When the switch is OFF no current flows and the circuit is said to be open. 2. The materials that allow electric current to pass through them are called conductors. For Example- iron, copper, silver. The materials that do not allow electric current to pass through them are called insulators. For example-rubber, plastic, glass. 3. Electricity is called a good servant but a bad master. Thus, the following safety measures are to be taken while using electric appliances. (i) While repairing electrical appliances check that it is not connected to the mains. (ii) Wear rubber gloves and rubber slippers while handling electrical appliances. (iii) Do not touch switches or any other electrical appliance with wet hands. 4. The inside of a torch has two or three cells placed in such a way that the positive end of one touches the negative end of the other cell. The cells are in series. The cells are the source of electric current. They are connected through a switch to a small bulb. The negative terminal of the cell presses against the spring at the bases of the torch. The positive terminal of the cell presses against the metal tip at the base of the bulb. There are three metal strips, metal strip A is a part of the switch, metal strip B connected with the metal case of the bulb, metal strip C connected with the spring While metal strips B and C are fixed, metal strip A can be pressed and made to slide. When the switch is pushed to the ‘on’ position, the metal strip A is pushed forward so that it touches B and C and the circuit is completed which makes the bulb to glow. When the switch is pushed to the ‘off’ position, the contact between metal strip A and B is broken and the circuit is incomplete. Now, the current does not flow through the circuit and the bulb does not glow.

Chapter 16 Air Multiple Choice Questions 1. The largest amount of gas in the air is (a) nitrogen (b) carbon dioxide (c) argon (d) oxygen 2.The gas released by the green plants during photosynthesis is (a) nitrogen (b) oxygen (c) carbon dioxide (d) helium 3.Air is considered to be (a) a compound (b) a solvent (c) mixture (d) an element

4. The component of air which is utilised by the plants in respiration is (a) carbon dioxide (b) oxygen (c) nitrogen (d) water vapour 5. The envelope of air around earth’s crust is called (a) wind (b) atmosphere (c) carbon dioxide (d) wind 6.Water is found in the air in the form of (a) water vapour (b) carbon (c) dust (d) smoke 7.The air in industrial cities has usually higher amount of one of the following components than normal air (a) Oxygen (b) Carbon dioxide (c) Nitrogen (d) Argon ANSWERS 1. (a) 2 (b) 3(c) 4 (b) 5 (b) 6 (a) 7 (b) Fill in the blanks 1. There is always some water vapour in the————- around us. 2. The layer of atmosphere extends up to—————kilometres. 3. Air is a———— of several gases. 4. The————— we live in is surrounded by a blanket of air. 5. The air surrounding the earth is called as————. ANSWERS 1. There is always some water vapour in the air around us. 2. The layer of atmosphere extends up to 300 kilometres. 3. Air is a mixture of several gases. 4. The earth we live in is surrounded by a blanket of air. 5. The air surrounding the earth is called as the atmosphere. State whether the following statements are ‘True’ or ‘False’ 1. Air has a fixed percentage of water vapour. 2. Dust and smoke present in the air cause respiratory disease. 3. Nitrogen is the most reactive gas of the air. 4. Plants do not need oxygen. 5. Plants require nitrogen for photosynthesis. ANSWERS

1. False, 2. True, 3. False, 4. False, 5. False. Very Short Answer Questions 1. Name the gas used to fill the packets of potato chips? 2. Name various components of air. 3. What is the amount of nitrogen in the air? 4. Which of the two is present in a lesser amount in air – oxygen or nitrogen? 5. Which gas in the atmosphere is essential for respiration? ANSWERS 1. Nitrogen 2. Nitrogen,Oxygen, carbon dioxide, noblegases,hydrogen, smoke particles, dust particles and water vapour. 3. 78% 4. Oxygen 5. Oxygen Short Answer Questions 1. What is the wind? State three uses of wind. 2. Give four uses of air in our day to day life. 3. What is air? Write about the composition of air. 4 .Why is polluted air harmful to us? 5.Why do divers and mountaineers carry oxygen cylinders with them? 6. How do plants and animals help each other in the exchange of gases in the atmosphere? 7.What are sources of oxygen and carbon dioxide in the air? ANSWERS 1. Fast moving air is called the wind. The three uses of the wind are: (i) It helps in the movement of yachts (sailing boats), parachutes, gliders and aeroplanes. (ii)It helps birds, bats and insects in flying. (iii)It helps in the dispersal of seeds and pollen of flowers of several plants. 2. (i) Air helps birds, bats and insects in flying. (ii) Air plays an important role in the water cycle as it carries water vapour in it. (iii) It helps in the drying of clothes. (iv) Air helps in the dispersal of seeds and pollen of flowers of several plants. 3. Air is a colourless, odourless and tasteless gas. It consists of the following: • Oxygen 21% • Nitrogen 78% • Carbon dioxide 0.03% • Noble gases 0.97% • Smoke particles variable • Dust Particles • Water vapour

4. Some air pollutants are poisonous. Inhaling them can increase the chances of health problems. People with heart and lung disease, older, adults and children are at greater risk of getting affected by air pollution. 5. The layer of atmosphere extends up to 300 kilometres above the earth’s surface. However, it gets thinner as we go higher and higher above the surface of the earth. Therefore, it becomes difficult to breathe at high altitudes. That is why mountaineers carry oxygen cylinders while trekking at high altitudes. Divers carry oxygen cylinders with them as they cannot use the oxygen dissolved in water for breathing. 6. Carbon dioxide is required by green plants to manufacture their food in the presence of water and sunlight through the process of photosynthesis. During this process, oxygen is released which is taken in by animals during the process of respiration. 7. During the process of burning carbon dioxide is formed. All organic materials when they burn/consume oxygen they produce mainly carbon dioxide. Respiration is also the source of carbon dioxide. Photosynthesis is the source of oxygen as green plants give out oxygen during photosynthesis. Long Answer Questions 1. Why is it considered unhealthy to breathe in through the mouth? 2. Explain oxygen and carbon dioxide cycle in the atmosphere. ANSWERS 1. It is unhealthy to breathe in through the mouth because the air that goes in through the mouth does not get filtered whereas when the air is taken in through the nose the nasal hairs trap the dust particles and filter the air. 2. The oxygen of the atmosphere does not get consumed. Though oxygen is being used by all living organisms, its amount in the atmosphere remains nearly constant. It is because of the oxygen and carbon dioxide cycle that continuously operates in the atmosphere. Humans and other animals exhale carbon dioxide. Plants take in carbon dioxide and give out oxygen during photosynthesis. Humans and other animals inhale oxygen and the process goes on continuously. So, the balance of carbon dioxide and oxygen in the atmosphere is maintained. Me

Chapter 17 Garbage In Garbage Out

Multiple Choice Questions 1. Which of the following can be recycled? (a) Leather shoes

(b) Animal waste (c) Waste paper (d) Kitchen waste 2. Which wastes can be recycled? (a) Plastic (b) Onion Peel (c) Eggshell (d) Banana peel 3. Dried leaves and plant wastes are best disposed off by (a) burning (b) composting (c) using as fuel (d) throwing in ponds 4. Which of the following is used for vermicomposting? (a) Redworms (b) Earthworms (c) Blue worms (d) Tapeworms 5. The colour of dustbins in which biodegradable garbage is collected as (a) black (b) green (c) yellow (d) blue 6. By recycling used paper we can save (a) metals (b) paper (c) trees (d) glass ANSWERS 1. (c) 2. (a) 3. (b) 4. (a) 5. (b) 6. (c) Very Short Answer Type Questions 1. What are landfills? 2. What type of worms are used for vermicomposting? 3. Define the term ‘wastes’ 4. Name any three materials which do not rot even after years. 5. Name three waste materials which can be recycled. 6. What is meant by recycling? ANSWERS 1. Landfills are large low lying open areas for disposal of non -biodegradable garbage. 2. Red Worms

3. Wastes refer to substances that pollute the environment. 4. Plastic, metals, glass 5. fresh paper, plastic, glass 6. Recycling means that we should collect discarded items made of plastics, paper, glass and metals and send them to the respective industries for making fresh paper, plastic, glass and metal objects. Fill in the blanks with suitable words. 1. Biodegradable waste materials are also known as———. 2. ————–do not have teeth. 3. Plastics have become an integral part of our————. 4. Consuming food packed in such————— could be harmful to our health. 5. The compost made by using —————–is called vermicompost. ANSWERS 1. Biodegradable waste materials are also known as organic waste materials. 2. Redworms do not have teeth. 3. Plastics have become an integral part of our life. 4. Consuming food packed in such plastic bags could be harmful to our health. 5. The compost made by using red worms is called vermicompost. State whether the following statements are ‘True’ or ‘False’ 1. We should not recycle aluminium products. 2. Many wastes are non-biodegradable. 3. We should try to minimise the use of the non-biodegradable substances. 4. Plastics are biodegradable materials. 5. Wood and cow dung are biodegradable wastes. ANSWERS 1. False 2. True 3. True 4. False 5. True. Short Answer Type Questions 1. What are red worms? 2. What might happen if the garbage is not removed from our homes and our surroundings? 3. What is meant by biodegradable waste materials and non-biodegradable waste materials? Give two examples of each type. 4. State one difference between composting and vermicomposting. 5. Why are polyethene bags a great problem for us? 6. Why should you carry your own bag for shopping? ANSWERS 1. Redworms are worms that are helpful in the process of vermicomposting. 2. If the garbage is not removed from our homes and our surroundings it can spread a lot of diseases such as typhoid, malaria and various infectious diseases. Mosquitoes and other insects live in places where there are piles of garbage and ultimately spread various diseases in the area. 3. Materials that can be decomposed by the action of microorganisms (decomposers such as bacteria and fungi) into simpler and harmless substances so that it cannot harm the environment are called biodegradable waste material. All the garbage from plants (such as fruit and vegetable peels, leftover food, leaves, paper, cotton, jute, etc.) and from animals (such as cow dung) are biodegradable waste material.

Materials that cannot be decomposed by the action of microorganisms into harmless substances are called non-biodegradable waste materials. The garbage which consists of plastics, glass and metal objects is non-biodegradable. 4. Composting is the method in which biodegradable wastes such as vegetable peels, waste food, leaves, etc., can be recycled and converted into manure by burying them in compost pits. The method of making compost from kitchen wastes (or kitchen garbage) by using red worms is called vermicomposting. The compost made by using red worms is called vermicompost. 5. Plastic bags thrown on roads and other places go into drains and the sewer system. As a result, drains get clogged and dirty water spills on roads. During heavy rains, it might even create a flood-like situation and spread many diseases as well. 6. We should carry our own bag for shopping as it minimises the use of plastic bags and is cost effective.

EXERCISE Q/A FOR SECOND TERM CHAPTER-11 TOPIC MEASURMENT 1. Define Measurement A. Measurement is the process of comparing an unknown quantity with a known fixed quantity. 2. Define rest and motion A. When an object does not change its position with respect to a stationary object with time is said to be at rest. 3. Arrange the following in their increasing value 10mm, 100m 0.5km, 20cm A (a) 100m 1m=1000mm So.100m=100* 100mm =10000mm. (b) 0.5km 1km=10000000mm 0.5 km=50000mm (c)20cm 1cm=10mm So, 20cm=20*10mm =200mm Thus the increasing value is 10mm.20cm, 100m, 0,5km. 4. Convert

(i) 22.4cm into mm 1cm=10mm So, 22.4cm=22.4*10mm =224mm (ii) 568cm into m 1cm=1/100m So, 568cm=1/100*568m =5.68m (iii) 18cm into km 1cm=1/100000km So, 18cm=1/1000000*18 =0.00018km (iv) 83000km into m 1km=1000m So, 8300km=8300*1000m =8300000m 5. While measuring the length of pencil the reading of the scale at one end is 5.5cm and that the other end 17.2cm .What is the length of the pencil? A. The length of the pencil is 17.2 - 5.5cm=11.7cm 6. Why is estimation necessary in daily life? A. Estimation skills will help us in every sphere of our life we need to correctly measure things so that we can make life easier for us 7. Why non-standard units cannot be used for accurate measurements? A. Measurements made with non -standard units gave inconsistent results. It leads to confusion and conflict. 8. Differentiate between translational motion and rotational motion. A.

TRANSLATIONAL MOTION ROTATIONAL MOTION

1. When all parts an object move the same distance in a given time the object is said to have translational motion

2. E.g. A train moving on a straight track, a train moving along curved track.

1.When all points on a moving object move about a fixed point or axis of rotation it is said to have rotational motion 2.E.g. Rotation of the Earth, motion of the blades of a fan.

CHAPTER-12 TOPIC: LIGHT, SHADOW AND REFLECTION 1. Why is it not safe to see the sun directly? A. One must not look at the sun without protection because the eye lens is a converging lens which will converge the rays of the sun to a point on the retina burning that part of it. This will cause a permanent damage which cannot be rectified. 2. What is shadow? How is it formed? A. A dark region behind an object where light is not able to reach is known as a shadow. Shadow is formed when an opaque object comes in the path of light. 3. What are transparent ,translucent and opaque objects.

A. The objects which allow most of the light to pass through them are called transparent objects. E.g. - glass, clean

water.

The objects that allow some light to pass through them are called translucent objects. E.g.-butter paper, thin plastic sheets. The objects which do not allow light to pass through them are called opaque object –E.g. Concrete wall, human body.

4. Differentiate between image & shadow

A.

IMAGE SHADOW

1.Image is coloured 2.It gives detail and outline of an object.

1.Shadow of an object is always black 2.It gives only the outline of the object.

5. How is the image formed by a plane mirror different from the image formed by a pinhole camera?

IMAGE FORMED BY A PLANE MIRROR IMAGE FORME BY APIN HOLE CAMERA

1.It is Virtual 2.It is erect 3.It is of the same size of the object

1.It is real 2It is inverted 3.It may be any size

CHAPTER-13 TOPIC MAGNETS 1. What will happen if a bar magnet is cut into half? A. There will be no change in the properties of a magnet rather each will have its two poles as it exist in pairs. 2. What is a magnetic compass? A. A device containing suspended magnetic needle used to find directions is called magnetic compass. 3. Give some examples of magnetic and non-magnetic materials. A. Examples of magnetic materials *iron *nickel *cobalt Examples of non-magnetic materials *rubber *wood *Plastic *gold *Silver 4. List the various shapes of magnets that you can find. A. The various shapes of magnets are: round, rectangular, horseshoe, right angled, disc shaped. 5.Write two uses of magnets. A. Uses of magnets are- * Compass needles are made of magnets *Used in Maglev trains 6. What are magnetic and non-magnetic materials? A. Magnetic materials –The materials that are easily attracted by a magnet Non -magnetic materials -The materials that are not attracted by a magnet. 7. How will you magnetize an iron piece and test that it is magnetized? A. To magnetize an iron piece and test that it magnetized *An iron piece is put on a firm surface *A magnet is held in one hand stroked on the iron in a loop from one end to the other end of the rod *This is repeated several times. Then we can test the iron rod by bringing it close to some paper clips .We observe that it attracts the paper clips. This proves that it is magnetized. 10. Magnets are used in maglev trains. Explain. A. Maglev stands for magnetic levitation.It is based on the fact that like poles repel to levitate or raise a train so that it is not touching the rails .This reduces friction and noise and it also allows train to run at very high speed

CH-14 TOPIC: ELECTRICITY AND CIRCUITS 1. Give the function of the following- (i) Electrical switch- it is a device that closes or opens a cirucuit thereby allowing or preventing the flow of current. (ii) Conductors -they allow electricity to pass through them so that they can be used in various electrical appliances.

(iii) Insulators -they do not allow electricity to pass through them so they help in safe handling of electrical gadgets. 3. When is a bulb said to be fused and why? A.When too much electricity flows through the bulb the filament gets heated up due to very high temperature and melts, the bulb gets fused as circuit is broken and no current flows. 6. Rubber or plastic is used for covering electrical wires. Why? A. Rubber or plastic are insulators so for safety the electrical wires are covered with rubber or plastic coverings. 7. What is the direction of electric current? A. The direction of electric current in an electric circuit is from positive terminal (+ve) to negative terminal (-ve) 8. What do you understand by a closed electrical circuit? A. The electric circuit in which the current flows from one terminal of the cell to another terminal is known as a closed circuit. 9. List a few uses of electricity A. Few uses of electricity are- *It is used to light up our homes ,offices and streets. *It is used to run devices like toasters ,geysers and electric iron. 12. What is MCB? What is the purpose of using it in a circuit? A.MCB is a Miniature Circuit Breaker .When the current in the circuit exceeds the safe limit it cause over heating of the wire .MCB is used to break the circuit and prevent damage to electrical appliances.

CH-16 TOPIC : AIR 1. In which layer of the atmosphere does the formation of cloud take place? A. The formation of clouds takes place in the troposphere. 2. How do the following organisms fulfil their oxygen requirements? (ii) SMALL ORGANISMS FOUND IN THE SOIL –The organisms take air rich in oxygen trapped in between the soil particles and fill their oxygen requirement. 3. How is air used to generate electricity? A. The wind rotates the wind mill which is used for the generation of electricity 4. Give reasons (i)Water vapour are not found in the layers above the troposphere. (ii)Earthworms come out on a rainy day. A. (i) Temperature and pressure drops as one goes up higher in the atmosphere.Rising water vapour cannot go higher than this layer because it changes into ice and is trapped there, so , water vapour is not found in the layers above troposphere. (ii)Air is trapped in the spaces between the soil particles .On a rainy day it is displaced when water enters these spaces between the soil particles and forms bubbles. 5. Nitrogen makes 78% of air but cannot be used by organisms .How is it made available to the organisms? A. Nitrogen is not used by animals including human beings directly .It is first converted by micro-organisms into nitrate which is then used by plants. Animals including humans get nitrogen through plants. 6. How is the balance between oxygen and carbon dioxide maintained in nature? A. It is maintained because of the process of photosynthesis and respiration. Plants release oxygen during the process of photosynthesis. They use oxygen for respiration. Animals including humans use oxygen for respiration and in return release carbon dioxide which plants uses to prepare food and release oxygen . This is how carbon dioxide and oxygen balance is maintained in nature. 8. List the major uses of air .Which musical instruments are played with the help of air? A. Uses of air (i)Oxygen present in the air is essential for the process of respiration (ii)Carbon dioxide present in the air is required for the process of photosynthesis. (iii)The wind rotates the windmill which is used for drawing water for running the flour mills (iv) Wind helps in the movement of kites parachutes and boats. The musical instruments such as guitar, flute and mouth organ are played with the help of air.

CH-17 TOPIC: GARBAGE IN AND GARBAGE OUT

1. Why is humus considered good for growing plants? A. Humus is considered good for growing plants because (i) It increases the ability of the soil to hold water and nutrients. (ii)It helps to keep the soil cool in summer and warm in winter. (iii) It is rich in carbon and nitrogen and is excellent for growing plants. (iv) It aids in preventing soil erosion by keeping the soil intact. 2. What is the name of the earthworm used in vermicompositing? How does it convert biodegradable soil waste into manure? A. The name of the earthworm used in vermicorpositing is Eisenia foetida. Earthworms eat plant waste cow dung or farm waste material. They pass the material through their body and in the process convert it into vermicrompost. This is how they consume garbage and convert it into valuable manure. 3. Why is incineration not a good practice of getting rid of garbage? A. Incineration is not a good practice of getting rid of garbage because the burning of dry leaves and other wastes results in increased level of carbon dioxide and carbon monoxide in the air. These gases cause respiratory problems especially among children and elders. Incineration can harm the environment if not properly managed. 4. Distinguish between biodegradable and non-biodegradable wasters. A.

BIODEGRADABLE WASTE NON-BIODEGRADABLE WASTE

i. The substance which can be broken down by micro-organisms like bacteria and fungi are called biodegrade waste.

i. The substance which cannot be broken down by micro-organisms like bacteria and fungi are called non-biodegrade waste.

5. What is a landfill? A.A landfill is a low -lying open area for the disposal of non-biodegradable garbage.Garbage is dumped into the landfill ,then it is covered with soil. Landfilling can harm the environment if not properly managed. 6. Why is an earthworm called a farmer's friend? A. Earthworm are called farmer's friend because of the multitude of service they provide that improves the soil fertility by converting the biodegradable waste into manure or compost. 7. Name the types of electrical wastes that are generated by humans. A. Monitors, television, computer, telephones fax, DVD/VCR/player, CD player, radios refrigerator, washing machine, dryers, air condition, vacuum cleaners ,toasters . 8. Why is plastic viewed as a menace? A. Plastic is a menace to humans, animals and environment because of the following reasons. (i) Plastic waste is accumulated in landfill accounts for a lot soil pollution over the year since It is non-biodegradable. (iii) Plastic also finds its way to drains and sewage pipes and clogs them. (iv)Animals sometimes feed on plastic bags and choke to death. (v) Sometimes little children suffocate while playing with plastic bags and toys 9. What are the 3R’s that should be followed? Explain. A. The 3R are Reduce, Reuse and Recycle (i) First R stands for Reduce -We should reduce the amount of waste we create. Throwing garbage puts pressure on the environment . We should buy only the right quantity of want we really need and choose products with less packaging. (ii) Second R stands for Reuse -We should reuse the waster as much as possible .Computer furniture clothing and many other items can be reused. for e.g.-setting the printer to print on both sides of paper, repairing broken appliances and shoes. (iii) Third R stands for Recycle- We should recycle the waste as much as possible for E.g. Plastic bottles can be recycled to make new things. Other things that can be recycled are glass, steel ,paper and cardboard.