Solutions To Text Questions

Chapter 1: Nutrition in Plants Multiple Choice Questions Page No. 10 1. (d) 2. (b) 3. (c) 4. (b) 5. (c) Multiple Choice Questions Page No. 13 1. (b) 2. (c) 3. (b) 4. (c) 5. (c) SECTION A CLASS RESPONSE A. Oral Questions. 1. The process by which green plants make their own food (like glucose) from carbon dioxide and water by using sunlight in the presence of chlorophyll is called photosynthesis. 2. The leaves contain tiny, green coloured bodies called chloroplasts which contain a green pigment called chlorophyll, so, they are green in colour. 3. Non-green plants which obtain their nutrients from dead and decaying organic matter of plants and animals are called saprophytes. 4. Nutrition is the process of taking food by an organism and its digestion, absorption and utilisation by the body. 5. The mode of nutrition in which an organism cannot make its own food from the simple substances but obtains ready-made food made by green plants directly or indirectly is called heterotrophic mode of nutrition. B. Science Quiz. 1. Chlorophyll 2. Xylem 3. Phloem 4. Charles Reid Barnes WORKSHEET A. Tick (3) the correct options. 1. (d) 2. (d) 3. (b) 4. (a) B. Circle the odd ones. Give reasons for your choice. 1. Oxygen → It is produced during photosynthesis whereas others are required in photosynthesis. 2. Cuscuta → It is a parasite whereas others are autotrophs. 3. Lichens → It shows symbiotic association of algae and fungi whereas others are insectivorous plants. 4. Mistletoe → It is a parasitic plant whereas others are insectivorous plants. C. Fill in the blanks. 1. nitrogen 2. photosynthesis 3. guard 4. autotrophic Teacher’s Resource Pack SCIENCE-7 15 SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (a) 2. (c) 3. (c) B. Very Short Answer Questions. 1. Cuscuta and coral root/Indian pipe 2. Pitcher plant and venus flytrap/Utricularia/Drosera 3. Stomata 4. Cactus (fleshy stem) 5. Autotrophic and heterotrophic C. Short Answer Type-I Questions. 1. Organisms that cannot make their own food but obtain ready-made food made by plants directly or indirectly are called heterotrophs. Animals and non-green plants are heterotrophs. 2. Mistletoe has green leaves which make the food for plant but it receives water and minerals from the host plant on which it grows to synthesise its food. Thus, it is called partial parasite. 3. Some plants eat insects for fulfilling their nitrogen requirements for preparing proteins. 4. The mode of nutrition in which an organism makes its own food from simple substances like carbon dioxide, water and minerals present in the surroundings is called autotrophic nutrition. 5. The mode of nutrition in which the non-green plants obtain their nutrients from dead and decaying organic matter of plants and animals is called saprotrophic nutrition. D. Short Answer Type-II Questions. 1. We can decolourise a leaf by boiling it first in water and then in alcohol. This process is called bleaching. 2. The organisms which obtain the ready-made food from the body of a plant are called plant parasites. Cuscuta and mistletoe are plant parasites. 3. When an insect lands on the pitcher of the pitcher plant, the lid gets closed and the trapped insect gets entangled into the hair. The insect is digested by the digestive juices secreted by the pitcher. 4. The plants which live in or on the body of other plants and derive ready- made food from them are called parasitic plants. For example, Cuscuta and mistletoe. The plants which feed on insects for fulfilling their nitrogen requirements are called insectivorous plants. For example, Drosera, Utricularia, pitcher plant, venus flytrap. 5. (a) Lichens show symbiotic association or symbiosis. (b) We can learn to help others and to work and live together in harmony in the society. 16 Teacher’s Resource Pack SCIENCE-7 E. Long Answer Questions. 1. To show that sunlight is necessary for photosynthesis Things needed: A potted plant, a beaker, a Bunsen burner, alcohol, iodine solution, a dropper, boiling tube, test tube holder, watch glass, wire gauze and tripod stand Method : (i) Take a healthy potted plant and keep it in a dark room for 2-3 days to destarch the leaves. (ii) Cover one of its leaves partly with a strip of black paper and put the plant in sunlight for a few hours. (iii) Pluck this covered leaf and remove the black strip. (iv) Remove the chlorophyll from the leaf by boiling it first in water and then in alcohol. In this way, you get a decolourised leaf. Wash the leaf with water again. (v) Add a few drops of iodine solution over the colourless leaf and observe. Observation : You see that the part of the leaf covered with black paper does not turn blue-black on adding iodine solution while the uncovered parts turn blue-black. Discussion: The covered part of the leaf could not get sunlight, hence, no starch is formed in this part. Conclusion: This shows that sunlight is needed for making starch, i.e., sunlight is necessary for photosynthesis. 2. Rhizobium bacteria live in the root nodules of leguminous plants and provide them nitrogen in a soluble form. In return, the leguminous plants provide food and shelter to the Rhizobium bacteria. Both organisms have mutual relationship. Thus, they help each other in survival. 3. To show that carbon dioxide is necessary for photosynthesis Things needed : A wide-mouth glass bottle, a potted plant, potassium hydroxide solution, alcohol, water, a Bunsen burner, a rubber cork, a beaker, a dropper and iodine solution Method : (i) Take a potted plant having long and narrow leaves and place it in a completely dark room for 2-3 days to destarch the leaves. (ii) Take a glass bottle having a wide mouth and put some potassium hydroxide solution in it. Potassium hydroxide solution absorbs the carbon dioxide gas present in the glass bottle. (iii) Take a rubber cork which fits tightly to the mouth of the glass bottle and cut it into two halves. (iv) Insert one destarched leaf which is still attached to the plant into this glass bottle through the split cork. The upper half of the leaf

Teacher’s Resource Pack SCIENCE-7 17 should remain outside the glass bottle whereas the lower half of the leaf should be inserted in the glass bottle. (v) Keep the potted plant in the sunlight for 3 to 4 days. (vi) Pluck the leaf from the plant and take it out from the glass bottle. (vii) Remove the chlorophyll from the leaf by boiling it first in water and then in alcohol. In this way, a decolourised leaf is obtained. Wash the leaf with water again. (viii) Add a few drops of iodine over the colourless leaf and observe. Observation : You find that the lower half of the leaf (which was inside the glass bottle) does not turn blue-black on adding iodine solution. The upper half of the leaf (which was outside the glass bottle) turns blue- black. Discussion : The lower half of the leaf does not turn blue-black on adding iodine solution because starch is not formed in this part of the leaf. The lower half of the leaf was inside the glass bottle where there was no carbon dioxide. The upper half of the leaf turns blue-black on adding iodine solution because starch is present here, i.e., photosynthesis occurred here. Conclusion: This shows that carbon dioxide is necessary for photosynthesis. 4. The two types of heterotrophic nutrition in plants are saprotrophic nutrition and parasitic nutrition. (i) Saprotrophic nutrition: The mode of nutrition in which the non- green plants obtain their nutrients from dead and decaying organic matter of plants and animals is called saprotrophic nutrition. Plants which use saprotrophic mode of nutrition are called saprophytes. The roots of saprophytes contain organisms called fungi. The fungi secrete digestive juices on the dead and decaying matter and convert it into a liquid that is used as a nutrient by the non-green plants. E.g., fungi and bacteria (ii) Parasitic nutrition: The mode of nutrition in which some plants live in or on the body of other living organisms and derive their ready-made food from them is called parasitic nutrition. The plant which obtains the ready-made food is called a parasite and the organism from whose body the food is obtained is called the host. Eg. Cuscuta. F. HOTS (Higher Order Thinking Skills) Questions. 1. If plant leaves are devoid of stomata, then there will be no exchange of gases in the plants. They will not be able to make their food and give us oxygen. 2. No, only the green plants are autotrophic in nature. Non-green plants are heterotrophic in nature. 18 Teacher’s Resource Pack SCIENCE-7 3. If all the plants perish from the earth, the life will not exist on the earth. This is because all the organisms require oxygen for breathing and if plants will not be there then the process of photosynthesis will not occur and hence no oxygen will be released for breathing. 4. Photosynthesis maintains the balance between oxygen and carbon dioxide in atmosphere. During photosynthesis, plants take in carbon dioxide and release oxygen in the atmosphere. The living organisms breathe in oxygen from the atmosphere for respiration and release carbon dioxide. This carbon dioxide is again taken by plants for photosynthesis. So, the process of photosynthesis maintains a balance between oxygen and carbon dioxide. G. Application Based Questions. 1. Rohit will not get a positive starch test because keeping the plant in darkness, i.e., without sunlight, destarches the plant and thus, plant is unable to make starch. 2. Meeta possibly discovered a parasite and not an insectivorous plant because insectivorous plants are generally green in colour and can synthesise their food. On the other hand, parasites are generally non- green and depend on other green plants for readymade food. H. Practical Skill Based Question. We can obtain a decolourised leaf in following way— Take a leaf and boil it in water. Take out the leaf and boil it in alcohol. This will remove the chlorophyll from the leaf. Think And Answer. Page No. 17 Tick () the correct options. 1. (b) 2. (b) Chapter 2: Nutrition in Animals Think Page No. 24 The mucus secreted in the stomach protects its inner lining from the corrosive action of HCl. Multiple Choice Questions Page No. 20 1. (c) 2. (d) 3. (a) 4. (d) 5. (a) Multiple Choice Questions Page No. 27 1. (c) 2. (a) 3. (a) 4. (a) 5. (b) SECTION A CLASS RESPONSE A. Oral Questions. 1. The process by which the food is taken inside the body of an organism is called ingestion of food. Teacher’s Resource Pack SCIENCE-7 19 2. The process of breakdown of complex, insoluble food substances into simple, soluble food substances with the help of digestive juices prepared by the body is called digestion of food. 3. The process in which the simple, soluble digested food substances are absorbed into the blood is called absorption. 4. The process in which the undigested food is removed from the body is called egestion. 5. The pushing down of food by the walls of the oesophagus in a wave-like action is called peristalsis. B. Science Quiz. 1. Mastication 2. Enamel 3. Amylase 4. Liver 5. Small intestine WORKSHEET A. Tick (3) the correct options. 1. (c) 2. (a) 3. (c) 4. (c) B. Match the following. 1. (c) 2. (d) 3. (a) 4. (b) C. Fill in the blanks. 1. stomach 2. villi 3. 7.5 metres 4. egestion D. State whether the following statements are True (T) or False (F). 1. T 2. F 3. F 4. T SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (a) 2. (d) 3. (c) B. Very Short Answer Questions. 1. Bitter, sour, salty and sweet 2. Reticulum, omasum, rumen and abomasum 3. Canines 4. Ingestion, digestion, absorption, assimilation and egestion C. Short Answer Type-I Questions. 1. The undigested and unabsorbed food passes from the small intestine into the large intestine. The large intestine absorbs water and some salts from the undigested food material, due to this the undigested part of food becomes dry and almost semi-solid (faeces). It is passed out of the body through the anus. 2. The effects of tooth decay are as follows: (i) Holes or cavities in the teeth (ii) Foul smell (iii) Losing of teeth (iv) Toothache (v) Stomach disorders 20 Teacher’s Resource Pack SCIENCE-7 3. Animals that eat food quickly and later bring it back to their mouth for chewing are called ruminants. Cows, buffaloes, deer and goats are ruminants. 4. S.No. Milk (Temporary) teeth Permanent teeth (i) The temporary set of teeth The second set of teeth that grows when the child is in which grow again, after the age group of 6 months to 8 the milk teeth fall out are years are called milk teeth. called permanent teeth. (ii) These teeth are smaller and These remain till old age weaker and are 20 in number. and are 32 in number. (iii) They are replaced by new They cannot be replaced natural teeth. by new natural teeth D. Short Answer Type-II Questions. 1. The simple, soluble, absorbed food substances are transported to different parts of the body where they are utilised by the body for energy, growth and repair. This process is called assimilation. 2. (a) The carbohydrates breakdown into simple sugars called glucose. (b) The fats breakdown into fatty acids and glycerol. (c) The proteins breakdown into amino acids. 3. Teeth are of following four types on the basis of their structure and functions: (i) Incisors (cutting teeth): These are four flat and blade-like teeth present in the front part of each jaw. These teeth are used to bite and cut the food into small pieces. (ii) Canines (tearing teeth): These are present on either side of incisors. These are two in number in each jaw. They are sharp and pointed which help in tearing the food. (iii) Premolars (grinding teeth): There are two premolars next to each canine. They have broad and flat grinding surfaces. They grind food and break it into small pieces. (iv) Molars (grinding teeth): There are three molars present on either side of premolars. They also have broad and flat incisor canine premolar molar grinding surfaces and are used to crush and grind food. 4. (i) Tongue helps in mixing saliva with the food. (ii) It helps in pushing and swallowing the food into the food pipe. (iii) It has several taste buds which help in giving different tastes of food like—sour, salty, bitter, sweet. (iv) It enables us to speak. Teacher’s Resource Pack SCIENCE-7 21 5. Oesophagus contracts and expands to push the food down into the stomach. Digestion of food does not takes place in the oesophagus.

Movement of the food in the oesophagus 6. (a) Teeth are involved in chewing of food. (b) Hydrochloric acid (HCl) present in the stomach helps in killing of bacteria. (c) Small intestine helps in absorption of food. (d) Large intestine helps in formation of faeces. E. Long Answer Questions. 1.

Digestion: The enzymes from the surrounding cytoplasm enter the food vacuole and breakdown the food into simple, soluble substances. Absorption: The digested food present in the food vacuole is absorbed directly into the cytoplasm. 2. The food that is swallowed goes into the first and largest chamber, the rumen. Here, it is partially digested and is called cud. It then goes to the second chamber or the reticulum from where it is returned to the mouth for further chewing. After thorough chewing and mixing with the saliva, the rechewed food is swallowed again. It now, bypasses the first two chambers and enters the third and the smallest chamber, the omasum. Here, it breaks down into smaller pieces. 22 Teacher’s Resource Pack SCIENCE-7 The food enters the fourth chamber or the abomasum. Here, a kind of gastric juice is secreted. It contains an enzyme and hydrochloric acid. The process of digestion completes here. The digested food now passes into the small intestine. Here, the absorption of the food takes place. The undigested food passes through the large intestine and is removed from the body. 3. (a) The various kind of teeth in our mouth and their functions are as follows: (i) Incisors (cutting teeth) : These are used to bite and cut the food into small pieces. (ii) Canines (tearing teeth) : These teeth help us in tearing the food. (iii) Premolars (grinding teeth) : These teeth are used to grind food and break it into small pieces. (iv) Molars (grinding teeth) : These teeth are used to crush and grind the food. (b) Teamwork We are inspired to work collectively as a team despite of our differences. F. HOTS (Higher Order Thinking Skills) Questions. 1. The substance ‘X’ is acid and it affects the tooth enamel. 2. Ruminants have compound stomach which enables them to digest cellulose. It is absent in human beings. 3. When chapati is chewed for some time, it mixes with the saliva which contains an enzyme, amylase. Amylase breaks down the starch present in the food into sugar, which makes its taste sweeter. 4. Pseudopodia or false feet are present in Amoeba which can be compared to the mouth of humans. 5. Yes, food vacuole in Amoeba is similar to the small intestine of human beings because the ingested food is digested completely and absorbed in food vacuoles. 6. Renin is an enzyme found in the stomach of infants. It converts soluble milk protein casein into paracasein. Thus, if an infant child vomits out milk, it is partially digested form of milk which looks like curd. G. Application Based Questions. 1. Our alimentary canal is a system in which food is always pushed down whether we are standing straight or hanging upside down. This is because the tongue pushes the chewed food in pharynx. It goes in oesophagus, where the walls of oesophagus start contracting and expanding to push down the food in stomach. Thus, it does not matter that in which position we are lying, the food is always pushed down. Teacher’s Resource Pack SCIENCE-7 23 2. Priya started coughing violently because on eating food hurriedly, the food particles enter the windpipe instead of entering the oesophagus. This causes choking of the windpipe that results in coughs or hiccups. Chapter 3: Fibre to Fabric Think Page No. 36 Natural silk is costly because it is obtained from silk moth . A small amount of silk is produced from a large number of cocoons. Multiple Choice Questions Page No. 35 1. (d) 2. (c) 3. (c) 4. (b) 5. (c) Multiple Choice Questions Page No. 37 1. (a) 2. (c) 3. (b) 4. (c) 5. (b) SECTION A CLASS RESPONSE A. Oral Questions. 1. Air gets trapped in the spaces between the wool fibres. Since, air is a bad conductor of heat, it does not allow the body heat to escape and keeps the body warm during winters. 2. The silky covering spun by the silkworm for its protection is called cocoon. It is made by silkworm to protect its development as pupa. 3. The rearing of silkworms for obtaining silk is called sericulture. 4. Throwing prevents the silk from splitting into individual fibres. B. Science Quiz. 1. (a) Animal fibres–wool, silk (b) Plant fibres –cotton, jute 2. Lohi, Marwari, Patanwadi, Nali/Bakharwal/Rampur bushair 3. Shearing 4. Lohi WORKSHEET A. Tick (3) the correct options. 1. (b) 2. (d) 3. (c) 4. (c) B. Circle the odd ones. Give reasons for your choice. 1. Reeling → Others are processes of obtaining wool whereas reeling is used in obtaining silk. 2. Tadpole → Others are the stages in life cycle of silkworm whereas tadpole is a baby frog. 3. Horse → All others give wool or fur, whereas horse does not give wool or fur. C. Fill in the blanks. 1. cocoon 2. shearing 3. mountain 4. Wool, silk 24 Teacher’s Resource Pack SCIENCE-7 D. State whether the following statements are True (T) or False (F). 1. T 2. F 3. T 4. F

SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (a) 2. (b) 3. (c) B. Very Short Answer Questions. 1. Sheep → Shearing → Scouring → Sorting → Combing → Dyeing → Spinning → Wool 2. Silk 3. The quality of wool is judged on the basis of thickness, length, shine, strength and fineness of fibres. 4. Sericulture C. Short Answer Type-I Questions. 1. Two individuals of desirable characteristics are selected as parents and then these are crossed (made to reproduce) to obtain new breed of animals having desirable characteristics of both the parents. This is called selective breeding. 2. The process of washing the fleece of sheep to remove dust, dirt, sweat, grease, etc., is called scouring. 3. (i) Wool has a high tensile strength and has high elasticity. (ii) It is lightweight and considerably resilient. (iii) It has the ability to retain shape. (iv) It can absorb large amount of water. 4. Silk is a fine, strong, soft and shining natural fibre obtained from silkworms. It is separated from the cocoons of silkworms that are reared on large scale. 5. Cocoons are boiled in hot water or treated in ovens to kill the larvae inside the cocoon. 6. We do not wait for the silk moth to hatch because if the larvae are not killed and allowed to grow, they will break the cocoons, thereby reducing the length of the silk fibres. 7. We need to boil the cocoons for extraction of silk because the hot water softens the silk gum, sericin so as to allow the unwinding of silk fibre as a single continuous thread. D. Short Answer Type-II Questions. 1. Shearing does not hurt the sheep because the uppermost layer of the skin of sheep is dead. Sheep are sheared in early summers so that they do not feel the heat. The hair of sheep grow again before the onset of winters and protect them from the cold weather.

Teacher’s Resource Pack SCIENCE-7 25 2. Wool is obtained from fur (hair) of sheep, goat, yak, etc., while silk is obtained from the cocoons of silk moth. 3. The fibres of the cocoon are reeled together to yield a stronger thread called raw silk. The damaged or waste cocoons are used to produce an inferior quality silk called spun silk. 4. Life cycle of a silkworm

(i) The female silk moth lays pale yellow eggs on the leaves of mulberry tree. (ii) The eggs hatch in two weeks to form caterpillars or silkworms. The silkworms feed on the mulberry leaves and grow bigger in size. During the larval stage, the silkworms shed their skin four times. (iii) Now, silkworms enter into pupa stage. Each silkworm begins spinning a cocoon. (iv) When the pupa (enclosed in cocoon) develops fully to form an adult silk moth, then the cocoon splits and a beautiful silk moth comes out. 5. Sericin is a water-soluble protective gum. The liquid silk secreted by the silkworm is coated with sericin which solidifies on contact with air and becomes silk fibre. It is softened by hot water. E. Long Answer Questions. 1. (a) The process of removing the hair from the body of a sheep is called shearing. (b) The process of separating the long fine quality fleece from the remaining inferior quality or broken pieces is called sorting of wool. (c) The process of removing the burrs from the fleece is called combing of wool. 2. The following steps are followed in the production of silk cloth from silk moth.

From silk moth to silk cloth 26 Teacher’s Resource Pack SCIENCE-7 3. Wool is obtained from the sheep by a long process which involves the following steps: (i) Shearing: The hair are removed from the body of sheep. It is done manually with a large razor or with an electrically-driven shearing machine. (ii) Scouring: The fleece of sheep is washed to remove dust, dirt, sweat, grease, etc. (iii) Sorting: The long fine quality of fleece is separated from the remaining inferior quality or broken pieces. (iv) Combing: The burrs are removed from the fleece. In this step, the fibres are straightened. (v) Dyeing: After combing, the fibres obtained are dyed in various colours. (vi) Spinning: The straightened fibres are spun or twisted together to make yarn which is either knitted or woven. 4. (a) Shearing is done in early summers so that the hair of sheep grow again before the onset of winters and protect them from the cold winters. (b) Kindness and care for the animals F. HOTS (Higher Order Thinking Skills) Questions. 1. Silk fibre on burning gives a smell of burning hair because it is an animal fibre and is made up of a protein. 2. Animal activists are against the silk production because in the process of obtaining silk, a large number of cocoons containing silkworms are boiled in hot water to loosen the silk thread. To obtain a little amount of silk, a large number of silkworms are killed. Think And Answer. Page No. 41 Tick () the correct options. 1. (b) 2. (c) Chapter 4: Heat and its Effects Think Page No. 44 During summers it is advised not to fill air into the cycle tyres very tightly because air expands on heating and therefore, the tyres may burst. Think Page No. 51 Two thin woollen blankets are warmer than a thick blanket because between the two blankets the air is trapped. It acts as a bad conductor of heat and prevents the flow of heat from both the sides. Think Page No. 51 In winter mornings, birds fluff out their feathers to keep their body warm.

Teacher’s Resource Pack SCIENCE-7 27 Multiple Choice Questions Page No. 48 1. (c) 2. (c) 3. (b) 4. (c) 5. (d) Multiple Choice Questions Page No. 51 1. (a) 2. (a) 3. (b) 4. (c) 5. (b) SECTION A CLASS RESPONSE A. Oral Questions. 1. The degree of hotness or coldness of an object on some chosen scale is called its temperature. Thermometer is used to measure temperature. 2. (i) Conduction (ii) Convection (iii) Radiation 3. The materials which do not allow heat to pass through them quickly are called bad conductors of heat or insulators. 4. The range of Celsius scale is 0 °C – 100 °C. B. Science Quiz. 1. Radiation 2. Laboratory thermometer 3. Expansion of liquid on heating 4. Radiations of the Sun reaching us in the form of heat WORKSHEET A. Tick (3) the correct options. 1. (a) 2. (c) 3. (a) 4. (c) 5. (d) B. Circle the odd ones. Give reasons for your choice. 1. Wood → Wood is an insulator whereas others are good conductors of heat. 2. Iron → Iron is a conductor whereas others are insulators. 3. Bakelite handle → Bakelite is an insulator whereas others involve air trapped in two layers for insulation. C. Fill in the blanks. 1. clinical 2. metals 3. convection 4. smooth 5. 0 (zero) SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (b) 2. (b) 3. (b) B. Very Short Answer Questions. 1. – 10°C to 110°C 2. Heat can be conducted from one body to another only when they are (i) in contact with each other (ii) at different temperatures. 3. Through radiation 4. Heat is measured by thermometer. 28 Teacher’s Resource Pack SCIENCE-7 C. Short Answer Type-I Questions. 1. (i) Hold it horizontally so as to keep the level of mercury along the line of sight. (ii) Don’t hold the thermometer by the bulb. (iii) Wash the thermometer before and after use. 2. The flow of heat in a body from the hotter end to the colder end without any actual movement of the molecules of the materials is called conduction. For example, when we heat one end of a steel spoon on a Bunsen burner, the other end also becomes hot after some time. 3. Radiation is the process of transfer of heat from a hot body to a cold body without affecting the medium. For example, the heat from the Sun reaches us travelling through vacuum. i.e. the space between the Sun and the earth. 4. The cool air from the sea blowing towards the land is called sea breeze. Land absorbs heat faster than the sea. During the daytime, the land heats up more quickly than the sea water. Thus, the air above the land surface, being heated, expands and rises up. The cooler air above the sea surface blows towards the land to take its place. This sets up convection currents. 5. Mercury is used in thermometers because it is the only metal which is in liquid state at room temperature. It is shiny, visible and very sensitive to the slight changes in temperature. It does not stick to the glass. 6. Temperature in degree fahrenheit = 77 °F We know, C F – 32 = 5 9 5 × 77 – 160 C = 9 385 – 160 = 9 225 = = 25 °C 9 D. Short Answer Type-II Questions. 1. Similarities between laboratory and clinical thermometer : (i) Both are used to measure temperature and their constructions are almost the same. (ii) Both of them use mercury. Differences between laboratory and clinical thermometer: (i) There is a slight bend (kink) in the stem just above the bulb in case of clinical thermometer, whereas a kink is absent in laboratory thermometer. Teacher’s Resource Pack SCIENCE-7 29 (ii) Clinical thermometer is used to measure the temperature of human body, whereas laboratory thermometer is used for measuring temperature while performing experiments. 2. The materials which do not allow heat to pass through them quickly are called bad conductors of heat. Paper and wood are bad conductors of heat. 3.

4. (i) Radiation does not require a medium to travel whereas conduction and convection require medium to travel. (ii) Radiation is the faster mode of heat transfer as compared to conduction and convection. 5. (a) Nitika’s mother used a thermos flask because it keeps the soup hot for a long time. (b) Care, concern and love for the neighbours and elders E. Long Answer Questions. 1. A laboratory thermometer consists of a very fine capillary tube protected by a thick glass tube called stem of the thermometer. The lower end of the capillary tube is converted into a glass bulb filled with mercury and upper end of this tube is sealed. The stem is marked in °C or °F. The commonly used laboratory thermometers have a range from –10 °C to 110 °C. The precautions which are to be taken while reading a laboratory thermometer are– (i) Hold it horizontally so as to keep the level of mercury along the line of sight. (ii) Don’t hold the thermometer by the bulb while reading it. 2. (a) Metals are good conductors of heat. (b) Bakelite is an insulator so it does not allow the flow of heat from hot appliances into our hands, so we can hold it even when it is hot. 30 Teacher’s Resource Pack SCIENCE-7 (c) Air conditioned buildings have double-walled windows so that the air trapped between the two walls prevents the transfer of heat from both sides. (d) False ceilings keep the room warm during winters because air trapped between the two ceilings is poor conductor of heat and does not allow transfer of heat from either sides. (e) Asbestos sheets are preferred over iron sheets for roofing because asbestos is a non-conductor of heat. 3.

A thermos flask (a) Air is removed from the space between the two walls of the glass bottle to prevent the transfer of heat by conduction and convection. (b) The glass bottle is held inside the metal case with the help of cork because it is a bad conductor of heat. Thus, the transfer of heat into or out of the closed thermos flask is very less. F. HOTS (Higher Order Thinking Skills) Questions. 1. The clinical thermometer has a range of 35°C to 42°C because the human body temperature never goes beyond it. So, high temperatures cannot be measured by a clinical thermometer. 2. (a) Black shirt will be more comfortable in winters because dark colour has a tendency to absorb more heat and it will keep warm in winters. (b) White shirt will be more comfortable in summers because light colours reflect the light radiations absorb less heat and thus, keep us cool. 3. Mercury is a shiny liquid metal, highly sensitive to temperature. It can be easily seen in glass thermometers. Water is not easily seen in glass. It expands at very high temperature and can break the glass. That is why, water is not used instead of mercury in thermometers.

Teacher’s Resource Pack SCIENCE-7 31 4. The firefighting suits are always bright and shiny so that they reflect the heat around. In this way, the firefighter does not absorb heat. G. Application Based Questions. 1. In refrigerators, the freezers are always located at the top because this enables better cooling. 2. The rough surface of mud is an absorber of heat but not a good conductor of heat. Thatched roof being woody in nature is also a bad conductor of heat. That is why, mud houses with thatched roofs are cool in summers and warm in winters.

Chapter 5: Acids, Bases and Salts Multiple Choice Questions Page No. 62, 63 1. (a) 2. (d) 3. (a) 4. (b) 5. (c) Multiple Choice Questions Page No. 66 1. (c) 2. (c) 3. (b) 4. (b) 5. (b)

SECTION A CLASS RESPONSE A. Oral Questions. 1. The substances which are sour in taste are called acids. Examples of acids are hydrochloric acid and sulphuric acid. 2. Natural indicators – Litmus, turmeric Human-made indicators–Phenolphthalein, methyl orange B. Science Quiz. 1. Formic acid 2. Lactic acid WORKSHEET A. Tick (3) the correct options. 1. (b) 2. (a) 3. (c) 4. (b) B. Circle the odd ones. Give reasons for your choice. 1. Amla → Amla is bitter whereas others are sour in taste. 2. Lactic acid → Lactic acid is an organic acid whereas others are mineral acids. C. Fill in the blanks. 1. red 2. corrosive 3. synthetic/human-made 4. Basic 32 Teacher’s Resource Pack SCIENCE-7 SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (b) 2. (b) 3. (d) B. Very Short Answer Questions. 1. Acids – Sulphuric acid and nitric acid/hydrochloric acid Bases – Sodium hydroxide and potassium hydroxide/calcium hydroxide/ magnesium hydroxide 2. • The neutral litmus solution turns red when added to some acidic solution. • The neutral litmus solution turns blue when added to some basic solution. • The neutral litmus solution does not change its colour when added to some neutral solution. 3. Hydrochloric acid C. Short Answer Type-I Questions. 1. Curd, lemon juice and tamarind taste sour because they contain acids. 2. When we eat very spicy food, the stomach produces large amount of hydrochloric acid which leads to acidity in stomach. 3. Antacid tablet contains magnesium hydroxide (weak base) which neutralises the effect of excess acid produced in the stomach and gives relief. D. Short Answer Type-II Questions. 1. (a) Sulphuric acid – used in manufacturing of fertilisers/plastics/ textiles/paper (b) Hydrochloric acid – used in manufacture of chemicals/dyeing/ tanning of leather (c) Nitric acid – used in manufacture of fertilisers 2. Factory wastes may contain harmful acids. If these wastes are directly discharged into water bodies, the acids present in them would kill the fishes and aquatic organisms. Thus, before discharging the wastes, they should be neutralised by treatment with basic substances. 3. (a) Annie applied baking soda (a mild base) to neutralise the effect and give relief from pain caused by the sting. (b) From Annie we learn to be concerned and helpful. E. Long Answer Questions. 1. (a) Excessive use of fertilisers makes the soil acidic. (b) (i) Quicklime or slaked lime should be added to the soil when it is too acidic. (ii) Manure or compost should be added to the soil when it is too basic. Teacher’s Resource Pack SCIENCE-7 33 2. S.No. Parameters Acids Bases (i) Taste Sour Bitter (ii) Touch Not soapy Soapy or slippery (iii) Effect on litmus Turn blue litmus Turn red litmus paper indicator paper red paper blue (iv) Effect on yellow No effect Turn yellow turmeric paper turmeric paper indicator indicator red (v) Effect on colourless No effect Colourless phenolphthalein phenolphthalein indicator indicator turns pink (vi) Effect on pink china Pink china rose Pink china rose rose indicator indicator turns dark indicator turns pink (magenta) green (vii) Solubility in water Most of the acids Most of the are soluble in water. bases are insoluble in water. 3. (a) The acids that are found in plants and animals are called organic acids. (b) Tartaric acid, acetic acid/citric acid/lactic acid (c) Mineral acids are prepared from the minerals of the earth whereas organic acids are found in plants and animals. Mineral acids are also called human-made acids while organic acids are natural acids. F. HOTS (Higher Order Thinking Skills) Question. Acids are helpful in various ways in maintaining good health. HCl produced in our stomach kills the microorganisms in the food and disinfects it. Various organic acids found in food items like curd, lemons and amla are good for our health because they are rich sources of various vitamins and minerals. G. Application Based Questions. 1. We can identify them by performing litmus test. Dil. NaOH solution will change red litmus paper into blue and dil. HCl will turn blue litmus paper red. Water will not change the colour of any litmus paper showing its neutral nature. They can also be checked by a pH paper. 2. ‌ (a) Solution P is strongly acidic and solution R is strongly basic. (b) Solution P and R will react to show neutralisation reaction. 34 Teacher’s Resource Pack SCIENCE-7 H. Practical Skill Based Question. 1. (i) Acidic solutions turn blue litmus paper red. (ii) Basic solutions turn red litmus paper blue. (iii) Neutral solutions have no effect on litmus papers. 2. (i) Acidic solutions have no effect on turmeric indicator. (ii) Basic solutions turn yellow turmeric indicator red. (iii) Neutral substances have no effect on turmeric indicator. Chapter 6: Physical and Chemical Changes Think Page No. 80 People living in Mumbai will experience the problem of rusting more because Mumbai is a coastal area and its air contains a lot of water vapour (moisture). Multiple Choice Questions. Page No. 80 1. (b) 2. (b) 3. (d) 4. (a) 5. (c) SECTION A CLASS RESPONSE A. Oral Questions. 1. Cutting of paper is a physical change because no new substance is formed, only physical state, i.e., size of paper is changed. 2. A change in which one or more new substance(s) with entirely different chemical compositions and properties from the original substances are formed is called chemical change. For example, burning of fuels/crackers, cooking and digestion of food, change in the colour of cut fruits, vegetables. 3. (i) Galvanisation (coating iron with other metals) (ii) Coating the iron surface with paint or grease (iii) By converting iron into stainless steel or alloying B. Science Quiz. 1. Physical change 2. Presence of oxygen and water or water vapour (moisture) 3. Iron, carbon, manganese, chromium and nickel are the constituents of stainless steel. WORKSHEET A. Tick (3) the correct options. 1. (d) 2. (c) 3. (c) 4. (b) B. Circle the odd ones. Give reasons for your choice. 1. Photosynthesis in plants → Photosynthesis in plants is a chemical change whereas others are physical changes. 2. Grinding of a substance → Grinding of a substance is a physical change, whereas others are chemical changes. Teacher’s Resource Pack SCIENCE-7 35 3. Hammering of metals → Hammering of metals is a physical change wheras others are chemical changes. C. Fill in the blanks. 1. state 2. evaporation 3. weak 4. physical SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (a) 2. (d) 3. (c) B. Very Short Answer Questions. 1. (i) Stretching of rubber band (ii) Grinding of a substance (iii) Expansion or contraction of substances on heating and cooling (iv) Melting of wax (v) Formation of clouds 2. When magnesium oxide is dissolved in water, it forms magnesium

hydroxide [Mg(OH)2]. 3. Chemical change C. Short Answer Type-I Questions. 1. Iron objects like iron nails, grills, railings and pipes when kept in moist air for a few days, get covered with a brown powdery substance called rust. This process is called rusting of iron. 2. The two conditions necessary for the rusting of iron are– (i) Presence of air (oxygen) (ii) Presence of water or water vapour (moisture) 3. Melting of ice does not form any new substance. Ice and water both have the same chemical composition. Only change in physical state takes place during the process. Thus, the melting of ice is a physical change and not a chemical change. D. Short Answer Type-II Questions. 1. (i) Only physical properties (size, shape, colour and state) change during a physical change. (ii) No new substance is formed. (iii) Generally, a physical change is reversible. (iv) Generally, no overall energy change takes place. (v) Chemical composition of a substance remains the same during a physical change. 2. (i) During a chemical change, one or more new substances are formed. (ii) Chemical changes are permanent. Thus, a chemical change cannot be reversed by simple physical methods. (iii) During a chemical change, net change in energy takes place. A large amount of energy is either given out or absorbed in the form of heat or light. For eg. burning of fuel produces large amount of heat.

36 Teacher’s Resource Pack SCIENCE-7 (iv) During a chemical change, both the physical and chemical properties of a substance are changed. 3. Explosion of crackers is a chemical change because during burning of crackers new substances are formed and heat, light, sound and gases are produced. 4. Yes, the chemical properties of a substance get changed during a chemical change. This is because, in a chemical change, entirely new substance(s) with new chemical composition is/are formed. 5. (a) Burning of crackers is a chemical change. (b) No, burning crackers is not good for environment as it causes air pollution. (c) Friendship, religious harmony, concern and care for friends E. Long Answer Questions. 1. S. No. Parameters Physical change Chemical change (i) New No new substance One or more new substance is formed. substances are formed. (ii) Nature of It is a temporary It is a permanent change change. change. (iii) Reversibility It is easily It is generally reversible by irreversible. simple physical methods. (iv) Physical and Only the physical Both the physical and chemical properties of the chemical properties properties substance are of the substance are changed. changed. (v) Amount of Generally, there is Change in energy energy (in the no overall change takes place as a very form of heat in energy. large amount of or light) energy is absorbed or given out. 2. To prepare crystals of copper sulphate by the process of crystallisation Things needed: A beaker, dilute sulphuric acid, a tripod stand, a Bunsen burner, a china dish, a stirrer, a filter paper and copper sulphate powder Method: Take about 100 mL of water in a beaker and add a few drops of dilute sulphuric acid to it. Put the beaker on a tripod stand and heat it with the help of a Bunsen burner. When it starts boiling, add copper sulphate powder while stirring continuously. Continue adding copper sulphate powder till no more powder can be dissolved. Filter the obtained solution to remove insoluble impurities and collect the filtrate in china dish. Teacher’s Resource Pack SCIENCE-7 37 Preparing crystals of copper sulphate Allow the solution of copper sulphate to cool slowly. Leave the apparatus undisturbed for 24 hours. Observation: You observe blue crystals of copper sulphate in china dish. After 24 hours, separate the copper sulphate crystals from the solution by decantation and dry the crystals by keeping them between the filter papers. Conclusion: The pure large crystals of copper sulphate are obtained. F. HOTS (Higher Order Thinking Skills) Questions. 1. Burning of candle is a physical as well as a chemical change. The melting of wax is a physical change because no new substance is formed. Burning of wax changes carbon into carbon dioxide, thus it is a chemical change. 2. Rusting of iron objects is faster in coastal areas than in deserts because the air in coastal areas has lot of moisture or water vapour while the air of deserts is dry. And, presence of moisture is a necessary conditon for rusting to occur. 3. The change A and change B, both are chemical changes. 4. The ice cube crushed gently with heavy utensil or hammer will melt faster because it is broken in small pieces. G. Application Based Question. Colour of silver coin changed because silver gets oxidised into silver oxide. Copper changes its colour because chemical reaction occurs and it changes to green-coloured copper carbonate. (Copper and silver are highly reactive.)

Chapter 7: Weather, Climate and Adaptations of Animals to Climate Think Page No. 91 Yes, similar thing can happen to other animals also. To prevent the drastic climatic changes, we must preserve and protect our environment from the effects such as global warming, ozone holes, etc. 38 Teacher’s Resource Pack SCIENCE-7 Multiple Choice uestionsQ Page No. 89 1. (b) 2. (c) 3. (b) 4. (d) 5. (b) Multiple Choice Questions Page No. 93 1. (a) 2. (c) 3. (c) 4. (c) 5. (b) SECTION A CLASS RESPONSE A. Oral Questions. 1. The average weather pattern at a place, taken over a long period of time is called the climate of that place. 2. The factors which determine the climate of a place are as follows: (i) Distance from the equator (latitude) (ii) Altitude (iii) Distance from the sea (iv) Wind (v) Human activities 3. Polar bears, penguins, seals and reindeers, foxes, musk deer 4. The atmospheric conditions on a particular day, at a place with respect to temperature, humidity, rainfall, speed and direction of wind, etc., is called the weather at that place on that day. B. Science Quiz. 1. Temperature, humidity, rain, snow and wind are the different factors which determine the weather of a place. 2. Millimetres 3. Rain gauge WORKSHEET A. Tick (3) the correct options. 1. (c) 2. (c) 3. (b) 4. (c) B. Circle the odd ones. Give reasons for your choice. 1. Electricity → Others are elements of weather. 2. Polar bear → A polar bear is found in polar regions whereas others are found in tropical regions. 3. Tiger → A tiger lives in tropical regions whereas others live in polar regions. 4. Temperature → Temperature is a factor that determines weather whereas others are the factors determining climate. C. Fill in the blanks. 1. beak 2. hygrometer 3. blubber 4. streamlined D. State whether the following statements are true (T) or false (F). 1. T 2. T 3. F SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (b) 2. (d) 3. (d) 4. (b) Teacher’s Resource Pack SCIENCE-7 39 B. Very Short Answer Questions. 1. Maximum-minimum thermometer 2. Bharatpur in Rajasthan and Sultanpur in Haryana 3. The wild animals such as lions, tigers and leopards are called big cats. 4. A red-eyed frog C. Short Answer Type-I Questions. 1. (a) Very cold climate (b) Very hot and dry climate (c) Hot and humid climate 2. Birds migrate to warmer regions when winter sets in. They come back when winter is over. This is called migration. 3. The favourable characteristics (features and habits) which enable the living organisms to survive and breed in their surroundings (habitat) is called adaptation. 4. Elephants have large ears. When the temperature rises, the elephants flap their large ears and use them as fans to cool themselves in the hot and humid climate of tropical rainforests. 5. The long colourful beak helps the toucan to reach the fruits on branches which are too weak to support its weight or weight of any other animal. 6. Red-eyed frog has sticky pads on its feet which help it to climb easily on the tree trunk on which it lives. 7. Penguin, Seal, Arctic tern and Siberian crane live in polar regions. Lion- tailed macaque lives in tropical rainforests. D. Short Answer Type-II Questions. 1. (a) Blubber under the thick skin keeps the body warm in extreme cold climate. (b) Streamlined body helps them in swimming. (c) White-coloured body merges with the surroundings of ice and snow and black-coloured feathers absorb heat from the sun to keep their body warm during the day. 2. The daily weather report carries information about temperature, humidity and rainfall during the past 24 hours. It also gives the timings of sunrise, sunset, moonrise and moonset and predicts the weather for the day. 3. Relative humidity is the amount of water vapour present in the air. It is expressed as a percentage of the maximum amount of water vapour the air can hold at that temperature. It is measured with the help of hygrometer. 4. The regions far away from the equator are cooler because these regions do not get direct sun rays but get slanting sun rays. So, these regions are cooler than the equator. 40 Teacher’s Resource Pack SCIENCE-7 5. During summers, afternoons are hotter than mornings because the movement of the earth is such that the sun rays fall directly during afternoon whereas in the early morning sun rays are slanting. E. Long Answer Questions. 1. S.No. Weather Climate (i) Weather describes the Climate is the average atmospheric conditions on a weather pattern of a place particular day, at a place with taken over a long period of respect to the temperature, time. humidity, rainfall, speed and direction of wind. (ii) Weather is measured for a Climate is measured for a smaller region. larger region. (iii) Weather at a place changes Climatic changes are gradual suddenly. and not sudden. 2. The big and long pointed teeth of elephants are called tusks. Tusks are modified teeth of the elephant. Elephants use the tusks to tear off the bark of trees which they eat as food. They also use the tusks for fighting with their enemies and protecting themselves. 3. Adaptations in camel to survive in desert region are— (i) It has a hump where fat is stored. The camel utilises this fat as food in case of its scarcity. (ii) A large amount of water gets stored in its stomach. (iii) It sweats very little and also excretes very little water in urine. This helps to conserve water. (iv) It has large soles which help to walk on soft ground. (v) It has long legs which keep the body away from the heat of sand. (vi) Long eyelashes protect the eyes from sand. 4. (a) The following adaptations in polar bears help them to adapt in polar regions: (i) presence of outer thick layer of fur (ii) presence of a thick layer of fat blubber under the skin (iii) white-coloured fur helps them camouflage in snow and protect them from their enemies. (iv) short ears and tail prevent loss of body heat (v) long, curved and sharp claws help them to walk in ice. (vi) wide and large paws help in moving easily in snow. (vii) strong sense of smell helps to locate and catch prey. (b) We should also adapt (adjust) ourselves according to our circumstances. Teacher’s Resource Pack SCIENCE-7 41 F. HOTS (Higher Order Thinking Skills) Questions. 1. Small ears and tail are the adaptations of animals of polar regions to prevent heat loss from their body parts and conserve body heat. 2. Yes, the statement is correct. Expansion of cities and increasing urbanisation and industrialisation has led to deforestation. Due to this there is an increase in the amount of carbon dioxide which caused global warming. Chapter 8: Winds, Storms and Cyclones Think Page no. 105 The rotation of earth on its axis makes the trade winds and polar winds to blow in an easterly direction. If the earth stops rotating, it will change the direction of winds, ultimately changing the wind, the rainfall pattern and climatic changes on earth. Multiple Choice Questions Page no. 103 1. (d) 2. (b) 3. (b) 4. (d) 5. (c) Multiple Choice Questions Page no. 109 1. (a) 2. (d) 3. (b) 4. (c) 5. (c) SECTION A CLASS RESPONSE A. Oral Questions. 1. (a) The layer of air surrounding the earth is called atmosphere. (b) The pressure exerted by the air present in the atmosphere is called atmospheric pressure. 2. Reduced air pressure is accompanied with high speed winds. 3. Cyclones and thunderstorms 4. The air (in a region) becomes warm when heated. It expands and rises upwards creating a low pressure area behind. B. Science Quiz. 1. Wind currents are generated due to uneven heating of the earth. 2. Westerlies 3. Trade winds blow in the eastern direction. 4. Wind speed, wind direction, temperature and humidity contribute to the development of cyclones. WORKSHEET A. Tick (3) the correct options. 1. (c) 2. (b) 3. (b) 4. (c) 5. (a) B. Circle the odd ones. Give reasons for your choice. 1. Cyclone → Cyclone is a natural disaster whereas others are different types of winds.

42 Teacher’s Resource Pack SCIENCE-7 2. Rainfall → Rainfall is a normal phenomenon whereas others are violent wind currents. 3. Transpiration → Others are the conditions that contribute to the development of cyclones whereas transpiration is not. C. Fill in the blanks. 1. atmosphere 2. lighter 3. high, low 4. trade winds 5. cyclos SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (c) 2. (d) 3. (c) B. Very Short Answer Questions. 1. (i) First stage warning – cyclone alert / cyclone watch (ii) Second stage warning – cyclone warning 2. (i) unequal heating between the equator and poles of the earth (ii) unequal heating of land and water of oceans 3. (i) moisture (ii) an unstable air mass (iii) a lifting force C. Short Answer Type-I Questions. 1. The density of hot air is less in comparison to the cold air, i.e., the hot air is lighter, thus it rises upwards. 2. (i) It is difficult to ride a bicycle against the direction of wind. (ii) Rowing the sail boat in the direction of wind is easy. (iii) Bursting of bicycle tube by filling too much air. 3. It is difficult to ride a bicycle while moving against the wind because the blowing wind exerts a pressure in the opposite direction in which the bicycle is moving. 4. In some parts of India, it rains during winters. In winters, the wind blows from the land towards the oceans. Thus, during winters land cools down faster than water in oceans (retaining heat for much longer time). So, the temperature of water in the sea is higher than that of land. The air above water heats up and creates a low pressure area. The cooler wind from land rushes towards the ocean forming winter monsoon. 5. The air expands on heating, then the volume of air increases but the mass remains the same and the density of air decreases. In other words, hot air is lighter than cold air so it rises upwards. The region from where air rises creates low pressure area. Conversely, cold air is heavier than hot air. So, cold air sinks downwards. The region where the air sinks, high pressure area is created. Teacher’s Resource Pack SCIENCE-7 43 6. When we blow air in the space between the two balloons from our mouth and the balloons come closer to each other, we conclude that high speed winds are accompanied by reduced air pressure. D. Short Answer Type-II Questions. 1. In nature, due to certain situations, warm air rises at a place and air pressure at that place gets lowered. The cold air from the surrounding areas rushes in to fill its place. This sets up convection currents in air. 2. The wings of an aeroplane are designed in such a way that the air above them moves faster than the air below them. When the aeroplane runs on the runway in order to take off, the air above the wings moves faster, the air pressure becomes very small as compared to the pressure below. The resultant upwards push or lift makes the plane fly. 3. The violent stormy winds accompanying a cyclone result in great loss of property and damage of houses, electric poles, industries, schools, hospitals, vehicles, crops, etc. The fast-moving flood water of the sea brought in by cyclone destroys roads, railway tracks and crops, reduces soil fertility and drowns animals. The continuous heavy rain brought by cyclones worsens the flood situation, pollutes drinking water thus cause- water-borne diseases and causes severe breakdown in communication and transport systems. 4. It is safe to take shelter in a bus during a thunderstorm because if the lightning strikes the bus, its metal body can conduct lightning to the earth safely without causing any damage. 5. (a) (i) Communicate rapid warnings to the concerned government agencies to the ports, ships, to fishermen and general public living in the coastal areas through radio, T.V., newspapers, etc. (ii) Make necessary arrangements to shift the essential household goods, domestic animals, vehicles, etc., to safer places. (iii) Store enough drinking water, food, clothing, blankets and first- aid kits. (iv) Keep the phone numbers of all emergency services like police and hospital ready. (b) Cooperating and helping others and becoming a good citizen E. Long Answer Questions. 1. (a) The pressure exerted by the air present in the atmosphere is called air or atmospheric pressure. (b) The hot water present in the closed can forms steam. When cold water is poured over it, the steam inside it condenses and forms water. Since, there is no air pressure, the large air pressure outside the tin can crushes it inside. 2. (a) A cyclone is a huge revolving storm caused by very high speed winds blowing around a central area of low pressure zone over the ocean. 44 Teacher’s Resource Pack SCIENCE-7 (b) The formation of a cyclone is a very complex process. Factors like wind speed, wind direction, temperature and humidity contribute to the development of cyclones. (i) As the sun heats the surface of ocean water, the warm water, in turn heats the air above it. This causes a low pressure on a vast area of the ocean. Due to the low pressure, the moist air from the ocean surface begins to rise rapidly. This creates strong upward winds that rotate spirally. (ii) As the warm and moist air rises high up in the atmosphere, it gets cooled and the water vapour present in it condenses to form clouds by releasing heat. (iii) The heat released during condensation warms the air all around and this warm air rises higher into the atmosphere causing a low pressure. Therefore, more air rushes to the centre of the storm and this cycle is repeated. (iv) Repetition of this cycle ends with the formation of a very low pressure system with very high speed winds revolving around it. Thus, a huge revolving storm called cyclone is formed. 3. In summers, land near the equator of earth heats up faster than the water in the oceans. So most of the time, the temperature of land is higher than that of water in oceans. The air over the land gets heated and rises creating a low pressure area. This causes the cooler winds to blow from the oceans towards the land. The winds blowing from the oceans towards the land in summers are called summer monsoon winds. These monsoon winds carry a lot of water (in the form of water vapour) from the oceans and bring a large amount of rain on land. In India, the land gets heated much more than the water in the Arabian Sea and Bay of Bengal during the summers. The monsoon winds blowing from Arabian Sea and Bay of Bengal bring heavy rainfall in most parts of India. The summer monsoon is very important to the farmers in our country because most of the annual rainfall occurs at this time that helps in growing crops. F. HOTS (Higher Order Thinking Skills) Questions. 1. The news is incorrect because a cyclone cannot generate on land (deserts). It needs a constant supply of warm and moist air and this is possible only over a large ocean floors. 2. A cyclone cannot be observed on land because there is no supply of warm and moist air on the land as it is present over the large ocean surface. G. Application Based Questions. 1. On a windy day, the wind blowing in opposite direction opposes the rickshaw. So, it needs more efforts to pull the rickshaw which shows that air exerts pressure. Teacher’s Resource Pack SCIENCE-7 45 2. (a) Bus or car is the best place to take shelter during a thunderstorm because if the lightning strikes, the car’s metal body can conduct lightning to earth safely without harming us. (b) We should not sit under a single big tree during a thunderstorm because it is likely to be hit by lightning due to its closeness to the clouds. Chapter 9: Soil Multiple Choice Questions Page No. 117 1. (a) 2. (b) 3. (a) 4. (c) 5. (c) Multiple Choice Questions Page No. 122 1. (d) 2. (a) 3. (b) 4. (a) 5. (b) SECTION A CLASS RESPONSE A. Oral Questions. 1. The topmost layer of the earth’s crust consisting of the mixture of rock particles and humus is called soil. 2. The process by which huge rocks breakdown into small rock particles by the action of the sun’s heat, wind, rain, flowing water and other climatic conditions, is called weathering of rocks. 3. A vertical section through the soil showing its different layers is called the soil profile. 4. The process in which water passes down slowly through the soil is called percolation of water. B. Science Quiz. 1. Sandy soil, loamy soil and clayey soil 2. Weathering 3. A–horizon → topsoil B–horizon → subsoil C–horizon → substratum d–horizon → bedrock or parent rock 4. (a) Clay (b) Gravel WORKSHEET A. Tick (3) the correct options. 1. (a) 2. (c) 3. (b) 4. (a) 5. (d) B. Circle the odd ones. Give reasons for your choice. 1. Frogs → Frogs live on land and in water whereas others live in soil. 2. Pebble → Pebbles are particles of rock whereas others are types of soil particles. 46 Teacher’s Resource Pack SCIENCE-7 C. Fill in the blanks. 1. groundwater 2. clayey 3. Clayey 4. Sandy D. Match the following. 1. (b) 2. (d) 3. (a) 4. (c) SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (c) 2. (c) 3. (b) 4. (d) B. Very Short Answer Questions. 1. Loamy soil 2. (a) Clayey soil (b) Sandy soil 3. Clayey soil 4. Minerals, agriculture and reservoir of groundwater C. Short Answer Type-I Questions. 1. Humus is formed by the decomposition of dead remains of plants and animals by bacteria and other microorganisms present in the soil.

2. S.No. Clayey Soil Sandy Soil (i) It has very small particles. It has quite large particles. (ii) It has little air. It is well-aerated. Its particles are tightly Its particles have large spaces (iii) packed and it is less porous. and it is porous. It has high water-holding It has low water-holding (iv) capacity. capacity. (v) It is heavy. It is light. (vi) It is very sticky when wet. It is not sticky. 3. The volume of water (in mL) which passes down the soil per minute is called percolation rate. 4. Percentage of water absorbed by soil:  mass of waterabsorbedbythe soil  =  × 100%  mass of thesoiltaken   1000 − 80  =  ×100%  50   20  = ×100%  50  = 40% Thus, the percentage of water absorbed by the soil is 40 %. Teacher’s Resource Pack SCIENCE-7 47 D. Short Answer Type-II Questions. 1. Loamy soil is best for growing crops because of the following reasons : (i) It has adequate air spaces between its particles to hold air needed by the plant roots. (ii) It contains sufficient amount of humus to provide necessary nutrients for the growing plants. (iii) It can be ploughed easily. 2. The air present in the spaces between the soil particles is absorbed by the root hair of plants for respiration. Also, it provides oxygen to the animals living in the soil. 3. The properties of soil are as follows – (i) It contains air. (ii) It contains water (moisture). (iii) It allows water to percolate. (iv) It can absorb water. 4. Soil is an important natural resource because– (i) It supports growth of plants and trees by holding their roots firmly. (ii) It is a home for many organisms. (iii) It is essential for agriculture which depends completely on the fertility of the soil. Agriculture provides us our basic needs, i.e., food, shelter and clothing. (iv) Soil supplies water and mineral nutrients to the plants. Thus, soil is an inseparable part of our life. E. Long Answer Questions. 1. A vertical section through the soil showing the different layers of the soil is called the soil profile. Each layer differs in texture, colour, depth and chemical composition. These layers are referred to as horizons.

Soil profile 48 Teacher’s Resource Pack SCIENCE-7 2. Clayey soil mainly contains clay. It has very little amount of sand and silt in it. It is less porous because clay particles being much smaller are tightly packed together, leaving little space for air. So, clayey soil has little air. Being non porous it has a very good water-holding capacity. Clayey soil gets waterlogged easily during the rainy season. 3. To show that soil contains water (or moisture) Things needed: Dry garden soil, a glass beaker, a watch glass, a Bunsen burner and a tripod stand Method: Take some dry garden soil in the glass beaker and cover it with a watch glass. Heat the beaker by using a Bunsen Experiment to show that soil contains burner as shown in the Figure. water (or moisture) Observation and discussion : You observe tiny drops of water on the inner side of the watch glass. When soil is heated then water present in it evaporates forming water vapour (or steam). This hot water vapour rises, gets cooled and condenses on the cold inner surface of the watch glass to form tiny water droplets. Conclusion: Soil contains water (or moisture) present as a thin invisible film around its particles. 4. (a) Clayey-loamy soil has good water-retaining capacity, that is why, it is preferred for growing wheat. (b) Honesty, humanity and concern for the fellow human beings. F. HOTS (Higher Order Thinking Skills) Questions. 1. No, this cannot be called weathering because weathering is a natural process which occurs due to the agents like wind, sunlight, water and pressure of roots. It takes many years and is a gradual process. 2. Sand particles are non-sticky and big in size whereas clay has sticky and small-sized particles. Due to the sticky nature of clayey soil, it is used to make pots, toys and statues. G. Application Based Questions. 1. X—Clayey soil, Y—Sandy soil 2. Loamy soil Chapter 10: Respiration in Organisms Multiple Choice Questions Page No. 132 1. (a) 2. (c) 3. (b) 4. (d) 5. (d) Teacher’s Resource Pack SCIENCE-7 49 Multiple Choice Questions Page No. 135, 136 1. (a) 2. (b) 3. (d) 4. (d) 5. (c) SECTION A CLASS RESPONSE A. Oral Questions. 1. (i) External respiration (breathing) (ii) Internal respiration (cellular respiration) 2. The taking in of air, rich in oxygen, into the body is called inhalation. 3. The giving out of air, rich in carbon dioxide, outside the body is called exhalation. 4. (a) During exercise, breathing rate increases. (b) While sleeping, breathing rate decreases. B. Science Quiz. 1. Tracheae 2. Spiracles 3. (i) Stomata (ii) Lenticels 4. (a) gills (b) tracheae (c) moist skin (d) lungs (on land), moist skin (in water) WORKSHEET A. Tick (3) the correct options. 1. (c) 2. (c) 3. (d) 4. (d) B. Circle the odd ones. Give reasons for your choice. 1. Stomach → Stomach is a part of digestive system whereas others are parts of respiratory system. 2. Sulphuric acid → Sulphuric acid is an acid whereas others are produced during anaerobic respiration. 3. Earthworm → Earthworm breathes through its moist skin whereas others breathe through spiracles. 4. Oesophagus → Oesophagus is the organ of digestive system whereas others are organs of respiratory system. C. Fill in the blanks. 1. breathing rate 2. bronchi 3. aerobes 4. upwards, outwards SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (a) 2. (a) 3. (a) 4. (b) B. Very Short Answer Questions. 1. (a) cockroach (b) fish (c) earthworm/frogs (d) humans/frogs

50 Teacher’s Resource Pack SCIENCE-7 2. The number of times a person breathes in a minute is called the breathing rate. The breathing rate of an adult human being at rest is 15-18 times a minute. 3. Respiration is the process of taking in oxygen, using it for the release of energy by breakdown of food, and removing the waste products– carbon dioxide and water. 4. During exhalation, ribs move downwards and inwards while the diaphragm relaxes and moves upward to its original position. 5. Anaerobic respiration C. Short Answer Type-I Questions. 1. We should breathe only through the nose because the hair and mucus present on the inner lining of nostrils trap unwanted particles and germs and prevent their entry into the nasal passage. 2. S.No. Parameters Breathing Cellular respiration (i) Process It is a physical process in It is a biochemical which exchange of gases process in which the (oxygen and carbon dioxide) breakdown of food takes place. No chemical takes place. reaction takes place. (ii) Energy Energy is not released. Energy is released. (iii) Occurrence It occurs outside the cells. It occurs inside the cells. (iv) Enzymes Enzymes are not involved. Enzymes are involved at certain stages of respiration. 3. During inhalation (i) the ribs are pushed upwards and outwards. (ii) the diaphragm contracts and moves downwards. 4. The taking in of air, rich in oxygen, into the body is called inhalation. The giving out of air, rich in carbon dioxide, outside the body is called exhalation. 5. The breathing becomes faster during exercise because when we do heavy exercise, we need extra energy. We breathe fast and take deep breaths. As a result, more oxygen is inhaled and supplied to our cells. It speeds up the breakdown of food and more energy is released to fulfil our requirement. D. Short Answer Type-II Questions. 1. The oxygen of the air diffuses in from the thin walls of alveolus into blood capillaries. The oxygen combines with haemoglobin in the blood to form oxyhaemoglobin which is carried to all the cells of the Teacher’s Resource Pack SCIENCE-7 51 body. Similarly, carbon dioxide produced by breakdown of food during respiration enters the blood and reaches alveolus in the lungs through diffusion. 2. S.No. Parameters Aerobic respiration Anaerobic respiration (i) Presence of It takes place in the It takes place in the oxygen presence of oxygen. absence of oxygen. (ii) Breakdown Complete breakdown Incomplete breakdown of food of food (glucose) takes of food (glucose) takes place. place. (iii) End products The end products are The end products are carbon dioxide and carbon dioxide and water. alcohol. (iv) Amount A large amount of A very small amount of energy energy is released. of energy is released. released (v) Occurrence It takes place in living It takes place in yeast organisms. and in some form of bacteria. 3. The roots of the plants have tiny hair called root hair. The root hair are in contact with the air present in the soil particles. Oxygen from the air in soil particles diffuses into root hair and reaches all the cells of the plant, where it is used for respiration. Carbon dioxide produced during respiration goes out through the root hair by diffusion. 4. Photosynthesis is the process of synthesising food by utilisation of carbon dioxide and releasing of oxygen whereas respiration is the process of taking in oxygen for the breakdown of food and releasing carbon dioxide and water. E. Long Answer Questions. 1.

The exchange of gases takes place in alveoli present in the lungs.

52 Teacher’s Resource Pack SCIENCE-7 2. (a) Insects — Insects breathe through spiracles. From spiracles, oxygen goes into tracheae, diffuses into the body tissues and reaches every cell. Oxygen is used for the breakdown of food to produce energy and carbon dioxide. This carbon dioxide from the cells goes into the tracheae and moves out of the body through spiracles. (b) Earthworms — Earthworms breathe through their moist skin. The oxygen enters the body through the skin by diffusion. After respiration, the carbon dioxide diffuses out through the skin. (c) Frogs — Frogs live both on land and in water. On land, frogs breathe through lungs. In water, they breathe through their moist skin. (d) Fish — The fish breathes by taking water through its mouth and sending it over to the gills which are found in both sides of its head. The blood vessels present in the gills absorb the dissolved oxygen from the water and send it to all parts of the body. The carbon dioxide from different parts of the body comes back into the gills by the blood and is then expelled into the surrounding water. 3.

4. (a) Nitika felt pain due to a muscle cramp which happened because of anaerobic respiration in muscle cells in which lactic acid is formed. Glucose in the muscle cells Lactic acid + Energy (food) anaerobic respiration (b) Kind, concerned, compassionate and helping nature 5. (a) Figure (a) shows inhalation and figure (b) shows exhalation. (b) During inhalation, the intercostal muscles contract, the ribs are pushed upwards and outwards. The diaphragm contracts and moves downwards. It increases the space in the chest cavity. Thus, the air rushes into the lungs. The lungs get filled up with air and expand. During exhalation, the intercostal muscles relax, the ribs move downwards and inwards. The diaphragm relaxes and moves upward to its original position. It decreases the space in the chest cavity and the air rushes out of the lungs. The lungs get emptied and contract. Teacher’s Resource Pack SCIENCE-7 53 F. HOTS (Higher Order Thinking Skills) Questions. 1. We will not be able to breathe if our diaphragm shows no movement. 2. Frog is an amphibian, i.e., it lives both on land and in water. That is why, it requires a dual mode of breathing. Therefore, it breathes through lungs on land and moist skin in water. 3. An athlete breathes faster and deeper than usual after finishing the race because he needs to inhale more oxygen, which in turn speeds up the breakdown of food and releases more energy. 4. Sneezing prevents the entry of unwanted foreign particles from inhaled air and thus, a dust-free clean and germ-free air enters into the body. G. Application Based Questions. 1. It is not advisable to sleep under the trees at night because during the

night, in plants only respiration takes place and they release CO2 in the air.

Since, photosynthesis takes place only during the day, the CO2 produced at night remains unconsumed. This may lead to insufficient oxygen and suffocation for the person sleeping under the tree. 2. We should breathe only through the nose because the hair and mucus present on the inner lining of nostrils trap unwanted dust, other particles and germs and prevent their entry into the nasal passage.

Chapter 11: Transportation in Animals and Plants Think Page No. 146 It is because our pulse rate increases in case of fever. Multiple Choice Questions Page No. 146 1. (b) 2. (c) 3. (c) 4. (a) 5. (c) Multiple Choice Questions Page No. 151 1. (b) 2. (c) 3. (a) 4. (d) 5. (c)

SECTION A CLASS RESPONSE A. Oral Questions. 1. 72-80 beats/minute 2. Waste materials produced in our body are toxic and may cause health hazards, thus it is necessary to excrete waste materials from the body. 3. Plants need a transport system to transport water and minerals absorbed by the roots up to the leaves and food prepared by the leaves to all parts of the plant. 4. The upward movement of water and minerals in a plant through xylem is called ascent of sap. 54 Teacher’s Resource Pack SCIENCE-7 B. Science Quiz. 1. (a) Amoeba - body surface (b) Earthworm – nephridia (c) Cockroach – malpighian tubules (d) Vertebrates – kidneys 2. Vascular system 3. Excretion 4. Arteries WORSHEET A. Tick (3) the correct options. 1. (c) 2. (d) 3. (d) 4. (b) B. Circle the odd ones. Give reasons for your choice. 1. Capillaries → Capillaries are blood vessels whereas others are components of blood. 2. Oxygen → Oxygen is a component of fresh air whereas others are excretory products. 3. Liver → Liver is an organ of digestive system whereas others are organs of excretory system. 4. Pancreas → Pancreas is a digestive gland whereas others are organs involved in excretion of wastes. C. Fill in the blanks. 1. Platelets 2. heart rate 3. stethoscope 4. nephrons SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (a) 2. (b) 3. (b) B. Very Short Answer Questions. 1. Septum prevents the mixing of oxygenated blood with the deoxygenated blood in heart. 2. (a) undigested food (b) carbon dioxide (c) excess water, urea, some salts and other metabolic wastes in the form of sweat. 3. Xylem and phloem 4. Human heart is roughly equal to the size of our fist, about 12 cm in length and 9 cm in breadth. C. Short Answer Type-I Questions. 1. The heart beats faster during and after a physical exercise so as to supply more oxygen because at such times the body cells need more oxygen to release more energy through respiration. 2. The process of removal of waste products produced in the cells of the living organisms is called excretion. 3. The process of cleaning the blood of a person (with kidney failure) by separating the toxic waste or excretory products using a dialysis machine is called dialysis. A person who suffers from kidney failure is put on dialysis to remove the waste products from the blood. Teacher’s Resource Pack SCIENCE-7 55 4. Blood is a red-coloured fluid which flows in the blood vessels to every part of the body. The components of blood are – (i) Fluid component – blood plasma (ii) Solid component – blood cells (WBCs, RBCs and platelets) 5. (a) Left atrium (b) Right ventricle (c) Left ventricle (d) Right atrium D. Short Answer Type-II Questions. 1. (a) Arteries have thick and elastic muscular walls because the blood flow is rapid and at high pressure in the arteries. (b) Arteries are not easily seen because they lie quite deep under the skin. (c) Veins have thin and less elastic muscular walls because the blood flow is slow and at low pressure in veins. 2. Transpiration helps in transportation of water and minerals by producing a ‘suction pull’ which pulls the water from roots to great heights in the tall trees. 3. S.No. Parameters Arteries Veins (i) Direction of Carry blood from the Carry blood from blood flow heart to various body different body parts parts to the heart (ii) Nature of Carry oxygen-rich Carry carbon dioxide- blood blood (except rich blood (except pulmonary artery) pulmonary vein) (iii) Flow of Blood flows at a Blood flows at a blood high speed and high low speed and low pressure. pressure. (iv) Walls Walls are thick and Walls are thin and less elastic. elastic. (v) Valves Valves are absent. Valves are present. (vi) Position in Arteries are deeply Veins are not deeply the body seated. seated. 4. The functions performed by sweating in human beings are — (i) Sweating helps in removing excess water, some salts and urea as liquid waste from the body. (ii) Sweating helps in keeping the body cool during summers. E. Long Answer Questions. 1. To show that xylem conducts water in plants Things needed: A conical flask, red dye (safranin or eosin), a small plant, a blade and a microscope 56 Teacher’s Resource Pack SCIENCE-7 Method: Dissolve a red-coloured dye (either eosin or safranin) in a conical flask. Put a plant which has a soft stem in the conical flask containing red-coloured water. Leave the setup for about half an hour. Now, take out the plant and cut a thin section of its stem. Observe the section under a low power microscope. Observation:The portion of the vascular tissue which contains xylem is stained red. Conclusion: Xylem conducts water through the stem. 2. To show that phloem transports food prepared by the leaves Things needed: A potted plant and a razor blade Method: Take a potted plant with a thick stem. Carefully remove the bark of the stem with the help of a razor blade. This is known as girdling of stem. The girdling of stem removes the phloem tissues of the stem. Leave the plant in sunlight for few days and observe the girdled part carefully. Observation: The part of the stem above the girdle shows swelling, while the lower portion dries up. Reason: Girdling of stem removes the phloem tissues of the stem. As a result, the food prepared by the leaves could not be translocated below the girdled part of the stem. Therefore, the food gets collected above the girdled part, resulting in swollen stem. The portion below the girdled stem dries up due to the lack of food. Conclusion: Phloem transports the food prepared by the leaves to the different parts of the plant. 3. (a) When both the kidneys of a person stop working, the waste products start accumulating in the blood and the person may die in a week or so. (b) Love, concern and care for parents F. HOTS (Higher Order Thinking Skills) Questions. 1. If the blood does not have enough platelets, then blood clotting will get affected. 2. The heart is divided into two equal halves to segregate the oxygenated blood from the deoxygenated blood and avoid their mixing. 3. Xylem can only conduct water from the soil and transport it to all parts of the plant in upward direction. Phloem translocates the food from leaves to all parts of the plant for utilisation as well as storage. It supplies food to the aerial parts as well as the roots in both directions. 4. The main function of WBCs is to fight against germs that enter our body and protect us from diseases. That is why, they are often called soldiers of the body.

Teacher’s Resource Pack SCIENCE-7 57 G. Practical Skill Based Question. The portion of the plant below the girdled stem dries because phloem gets removed due to girdling. The lower part of the plant does not get food prepared by the leaves and thus, dries up. This proves that food is translocated by the phloem. Chapter 12: Reproduction in Plants Multiple Choice Questions Page No. 163 1. (b) 2. (d) 3. (c) 4. (c) 5. (b) Multiple Choice Questions Page No. 166, 167 1. (c) 2. (b) 3. (b) 4. (c) 5. (d) SECTION A CLASS RESPONSE A. Oral Questions. 1. The production of new individuals from their parents is known as reproduction. 2. (a) Male gametes → pollen grains (stamens) (b) Female gametes → ovary (carpel/pistil) 3. Pollen grains 4. The fusion of male and female gametes to produce zygote is called fertilisation. B. Science Quiz. 1. Stamen 2. Carpel 3. Dispersal by an explosive mechanism, wind, water and animals 4. Pea, castor/balsam/geranium WORKSHEET A. Tick (3) the correct options. 1. (b) 2. (d) 3. (d) 4. (a) B. Fill in the blanks. 1. asexual 2. sporangiophore 3. wind 4. seed SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (d) 2. (b) 3. (a) B. Very Short Answer Questions. 1. Potato and onion 2. (i) Self-pollination (ii) Cross-pollination 3. Sexual and Asexual reproduction 4. Mustard, tomato C. Short Answer Type-I Questions. 1. The transfer of pollen grains from the anther to the stigma of a flower is called pollination.

58 Teacher’s Resource Pack SCIENCE-7 2. (a) Rose, jasmine (b) grass and wheat (c) Vallisneria and Hydrilla 3. Fruits of coconut, seeds of lotus and water lily are dispersed by water. 4. Pea, balsam D. Short Answer Type-II Questions. 1. Self pollination Cross pollination The pollen grains from the anther The pollen grains of a flower of of a flower are transferred to one plant are transferred to the the stigma of the same flower or stigma of a flower of another another flower of the same plant. plant of the same kind. 2. Seed dispersal is essential for plants because it provides following benefits to the plants: (i) It prevents overcrowding of plants in an area. (ii) It prevents the competition for water, minerals and sunlight among the same kind of plants. (iii) It helps the plants to grow in new areas or new places. 3. The process in which a seed begins to grow into a seedling (baby plant), when suitable conditions are available is called germination of seeds. The conditions necessary for germination of seeds are water, air and warmth or sunlight. 4. Seeds and fruits dispersed by wind have the following special features: (i) They are small and lightweight. Thus, they are easily blown away by the wind. (ii) They have wings or hair around them. E. Long Answer Questions. 1. When a pollen grain falls on the stigma of a flower, it grows as a thin pollen tube which moves downwards. This pollen tube penetrates the stigma, passes through the style and enters into the ovule. The male gamete moves down to the ovule through the pollen tube. The tip of the pollen tube bursts open and male gamete comes out of the pollen tube. The male gamete fuses with the female gamete present in the ovule to form a fertilised egg called zygote. This fusion of male gamete with the female gamete to produce zygote is called fertilisation.

Teacher’s Resource Pack SCIENCE-7 59 Fertilisation in a flower 2. Differences between sexual and asexual reproduction S.No. Parameters Sexual reproduction Asexual reproduction (i) Involvement Both parents, the male Only one parent is of parent and female are involved. involved. (ii) Involvement Gametes are involved. No gametes are of gametes involved. (iii) Production Plants are obtained from Plants are obtained of seeds existing parents through without the seeds. production of seeds. (iv) Similarity to Newborn plants are not Newborn plants the parent identical to the parent are identical to the plant plant. parent plant. Example grass, wheat, corn, apple, Spriogyra, mosses, pea, Hydrilla fern, potato, onion, ginger 3. Certain seeds and fruits are dispersed to far off places by certain animals. They can be carried away by various means. For example, • Some fruits develop hooks on their surfaces by which they get attached to the fur of animals and are carried away to distant places before they get rubbed off from their bodies and fall to the ground. Eg— The fruits of gokhru, Xanthium and Urena are dispersed by animals due to their hooked surfaces. • Sometimes, animals eat seeds along with the fruits. These seeds remain undigested and pass out with faeces at some other distant places. 4. (a) The greenish-black patches found on bread are called bread mould. They reproduce through spores. (b) Hygiene and kindness F. HOTS (Higher Order Thinking Skills) Questions. 1. If all the seeds of a plant fall at same place, below the same plant, there will be overcrowding of plants. This will cause a struggle for space, water and nutrients for the seeds to grow into a plant. Thus, probability of healthy growing plants will be reduced. 60 Teacher’s Resource Pack SCIENCE-7 2. Flowers are generally colourful and fragrant to attract the pollinators like insects and other animals. If flowers are not fragrant and colourful, pollination will probably occur only by wind or water and thus, fruits will be formed. 3. Insect-pollinated flowers are more attractive than wind-pollinated flowers because insect-pollinated flowers need to attract insects by their good fragrance and bright colours. Whereas wind blows itself and carries mature pollen grains with it. 4. Methods of artificial vegetative reproduction are so commonly used nowadays because they are simple, less expensive and quick method of multiplying a plant. Plants grown this way require less time to mature and bear more fruits than those grown from the seeds. CROSSWORD PUZZLE ACROSS DOWN 1. TUBER 3. STAMEN 2. PISTIL 4. RHIZOME 5. BULB Chapter 13: Time and Motion Multiple Choice Questions Page No. 177, 178 1. (b) 2. (b) 3. (a) 4. (b) 5. (c) Multiple Choice Questions Page No. 179, 180 1. (a) 2. (b) 3. (a) 4. (a) 5. (d) SECTION A CLASS RESPONSE A. Oral Questions. 1. Sunrise and sunset 2. Kilometre/hour 3. Odometer is an instrument which shows the distance travelled by the vehicle in kilometres. B. Science Quiz. 1. Straight line 2. A body is said to be in uniform motion when it is moving at a constant speed along a straight line path. 3. Distance travelled and time taken WORKSHEET A. Tick (3) the correct options. 1. (a) 2. (b) 3. (c) 4. (d) B. Fill in the blanks. 1. time period 2. speed 3. dependent 4. non-uniform

Teacher’s Resource Pack SCIENCE-7 61 SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (d) 2. (a) 3. (b) B. Very Short Answer Questions. distance travelled 1. Speed = 2. Metre per second (m/s) time taken 3. Distance-time graph 4. Stopwatch C. Short Answer Type-I Questions. 1. A small metal ball (bob) suspended by a long thread from a rigid support, such that the bob is free to swing back and forth is called a simple pendulum. 2. Time taken from extreme to mean position is 0.25s. So, time taken for 1 oscillation will be 1 minute 40 seconds. Time period is the time taken to complete one oscillation, so time period is 1 minute 60 seconds. 3. (a) Straight line represents uniform motion or constant speed. (b) Curved line represents non-uniform motion or changing speed. D. Short Answer Type-II Questions. 1. Here, speed = 3 m/s time taken = 20 minutes (we know, 1 minute = 60 s) = 20 × 60 = 1200 seconds distance travelled We know, Speed = time taken or distance travelled = speed × time taken = 3 m/s × 1200 s = 3600 m = 3.6 km (we know, 1 km = 1000 m) Thus, the distance between Monica’s house and her school is 3.6 km. 2. (i) Here, in the first case Speed = 20 km/h Time taken = 15 minutes 15 1 = = h (we know, 1 hour = 60 minutes) 60 4 We know, Speed = distance travelled time taken or distance travelled = speed × time taken 1 = 20 km/h × h 4 \ distance travelled = 5 km (ii) In the second case Speed = 60 km/h Time taken = 15 minutes 15 1 = = h (we know, 1 hour = 60 minutes) 60 4 62 Teacher’s Resource Pack SCIENCE-7 We know, Speed = distance travelled time taken \ distance travelled = speed × time taken 1 = 60 km/h × h 4 = 15 km \ Total distance covered = 5 + 15 km = 20 km Thus, the total distance covered by car is 20 km. 3. Distance travelled = 300 km Time taken = 5 hours Speed = distance travelled time taken 300 km \ Speed of the train = = 60 km/h 5 hour Thus, the speed of the train is 60 km/h. 4. (a) Principle of periodic motion (b) We should be punctual in our life because it makes our life more systematic and comfortable. Punctuality brings discipline in our life and avoids causing inconvenience to others also. 5. (a) Uniform motion (b) Non-uniform motion (c) No motion E. Long Answer Questions. 1. (a) The length of the string from the point of suspension to the centre of the bob is called the length of the pendulum. (b) The one complete to-and-fro motion of the bob about its mean position is called an oscillation of the pendulum. (c) The maximum displacement of the bob from its mean position on either side is called the amplitude of the pendulum. (d) The time taken by the bob of a pendulum to complete one oscillation is called the time period of the pendulum. 2. (a) (b)

Distance-time graph for an object moving Distance-time graph for a stationary at constant (or uniform) speed object (i.e., when the object is at rest)

Teacher’s Resource Pack SCIENCE-7 63 F. HOTS (Higher Order Thinking Skills) Questions. 1. (a) aeroplane – km/h (b) tortoise – m/s (c) ant – cm/s (d) horse – km/h 2. Car A moves faster–graph shows car A travels more distance in less time. G. Application Based Question. (a)

(b) The distance covered by the car at 6:15 pm is 75 km. Chapter 14: Electric Current and its Effects Think Page No. 190 We use copper wires for making connections in a circuit because copper is a good conductor of electricity. Multiple Choice Questions Page No. 190 1. (b) 2. (b) 3. (c) 4. (c) 5. (a) Multiple Choice Questions Page No. 193, 194 1. (a) 2. (a) 3. (c) 4. (a) SECTION A CLASS RESPONSE A. Oral Questions. 1. The path along which the electric current can flow is called an electric circuit. 2. The three effects produced by an electric current are— (i) Heating effect (ii) Magnetic effect (iii) Chemical effect 3. A fluorescent tube does not generate heat because it does not work on the principle of heating effect of electric current and have filaments. It works on the concept of fluorescence. 4. A fuse wire should have a low melting point and low resistivity. 5. The strength of the electromagnet (or solenoid) increases with increase in the number of turns. B. Science Quiz. 1. The current flows from positive terminal to negative terminal in a closed circuit. 64 Teacher’s Resource Pack SCIENCE-7 2. Hans Christian Oersted, a Danish scientist. 3. Electric bell, mixer grinder/fans/washing machines/cranes 4. Nichrome wire (an alloy of iron, nickel, chromium and magnesium). 5. Tungsten WORKSHEET A. Tick (3) the correct options. 1. (a) 2. (c) 3. (b) 4. (b) 5. (c) B. Match the following. 1. (b) 2. (d) 3. (e) 4. (a) 5. (c) C. Fill in the blanks. 1. open 2. short circuit 3. electromagnet SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (a) 2. (c) 3. (a) B. Very Short Answer Questions. 1. Wood, plastic, wool and rubber 2. (a) Tungsten metal (b) Nichrome alloy 3. Electric room heater, electric iron, electric toaster and electric oven/ electric kettle/water heater (geyser)/immersion rod C. Short Answer Type-I Questions. 1. The property of a material by virtue of which it opposes the flow of an electric current through it is called its resistance. 2. A magnet produced by passing an electric current through a coil of insulated wire wound around soft iron rod is called electromagnet. 3. Greater the magnitude of electric current passed through a given wire, greater will be the heat produced in it. D. Short Answer Type-II Questions. 1. (a) Resistance – (b) Electric cell – (c) Battery – (d) Electric bulb – (on), (off) (e) Switch in ‘ON’ position – (f) Wire – 2. A sudden flow of very large current due to direct contact of a live and a neutral wire is called short-circuit. Short-circuit is caused due to defective or damaged wiring. 3. Electromagnets are used in— (i) motors that drive fans, mixers, washing machines, etc. Teacher’s Resource Pack SCIENCE-7 65 (ii) cranes to lift heavy loads like big machines, steel girders and scrap iron objects for loading and unloading purposes. (iii) electric bells, telegraphs, telephone instruments, loudspeakers, etc. (iv) used by doctors to remove tiny iron particles from the eyes of a person 4. (a) Overloading of the electric circuit (b) We learn to be alert all the time and doing right thing at the right time and showing the presence of mind and reacting quickly. E. Long Answer Questions. 1. The cylindrical coil of wire is called a solenoid. The strength of a solenoid can be increased by (i) increasing the number of turns of the wire. (ii) increasing the magnitude of the electric current passing through the coil. 2. (a) Advantages of an electromagnet over a permanent magnet are – (i) The magnetism of an electromagnet can be switched ‘ON’ or ‘OFF’ as desired. This is not possible with a permanent magnet. (ii) The strength of an electromagnet can be increased as required. Electromagnet can be made very strong by increasing the number of turns and the amount of current passing through the coil. On the other hand, a permanent magnet cannot be made so strong. An electromagnet is used in an electric bell as it works on the magnetic effect of current. (b)

An electric bell 66 Teacher’s Resource Pack SCIENCE-7 3. The overheating of electrical wiring in any circuit due to the flow of large current through it is called overloading of the electrical circuit. Fuse wire is necessary in a circuit because in case of overheating or overloading, current stops flowing in the circuit and it remains safe. An electric fuse has a low melting point so when the current exceeds in the circuit, the fuse wire gets heated, melts and breaks the circuit immediately, keeping the devices safe. F. HOTS (Higher Order Thinking Skills) Questions. 1. Copper wire cannot be used for making an electric fuse because it does not have a low melting point which is an essential requirement for making a fuse. 2. A freely suspended coil will act as a magnet when a current is passed through it. It will deflect responding towards the earth’s magnetic field and align itself in north-south direction. G. Application Based Question. The bulb in the given circuit will not glow because both the wires are connected to the negative terminal and the current flows from positive to the negative terminal. The circuit with the required change is given below–

H. Practical Skill Based Question. 1. Fig. (i) is a stronger magnet because the number of turns of the coil are more around the iron rod. 2. Iron is a stronger magnetic substance than the steel. Chapter 15: Light Multiple Choice Questions Page No. 203 1. (c) 2. (a) 3. (c) 4. (b) 5. (c) Multiple Choice Questions Page No. 208 1. (a) 2. (c) 3. (b) 4. (c) 5. (b) SECTION A CLASS RESPONSE A. Oral Questions. 1. Light coming from the Sun and the light coming from a torch 2. Concave mirror and convex mirror Teacher’s Resource Pack SCIENCE-7 67 3. Lens 4. The image which cannot be obtained on a screen is called a virtual image. B. Science Quiz. 1. Concave mirror 2. Red 3. Real image WORKSHEET A. Tick (3) the correct options. 1. (d) 2. (d) 3. (c) 4. (a) B. State whether the following statements are true (T) or false (F). 1. F 2. T 3. F C. Fill in the blanks. 1. Convex 2. focal length 3. spectrum 4. dispersion SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (b) 2. (c) 3. (c) B. Very Short Answer Questions. 1. An image of a boy in the plane mirror 2. Concave mirrors are used (i) as shaving mirrors. (ii) as reflectors in torches and headlights of vehicles, such as cars, buses, etc. (iii) by dentists to see an enlarged image of teeth. (iv) by doctors to examine body parts such as eyes, ears, nose and throat. 3. The band of seven colours formed on a white screen when white light passes through a prism (or any transparent medium) is called spectrum of white light. 4. Bulging surface of a spoon always forms an erect image of the face. C. Short Answer Type-I Questions. 1. S.No. Parameters Convex lens Concave lens (i) Structure A convex lens is A concave lens is thicker in the middle thinner in the middle and thinner at the and thicker at the edges. edges. (ii) Action It is a converging lens. It is a diverging lens. (iii) Focus It has a real focus. It has a virtual focus. (iv) Image The image formed The image formed is may be real/virtual, always virtual, erect enlarged/small/equal and smaller than the to size of the object. size of the object.

68 Teacher’s Resource Pack SCIENCE-7 2. S.No. Convex mirror Concave mirror (i) A spherical mirror whose A spherical mirror whose reflecting surface is curved reflecting surface is curved outwards. inwards. (ii) Reflection of light takes Reflection of light takes place place at bulging out surface. at bent-in-surface. (iii) Principal focus is virtual and Principal focus is real and lies lies behind the mirror. in front of the mirror. (iv) It always forms a virtual, It always forms a real, inverted erect and diminished image. and highly diminished image. 3. The principal focus (F) of a concave lens is the point on the principal axis at which parallel rays of light after passing through the lens meet or appear to meet. 4. (a) Convex lens (b) Concave lens D. Short Answer Type-II Questions. 1. The image formed by a plane mirror is (i) of the same size and shape as the object. (ii) virtual and erect. (iii) laterally inverted with respect to the object. (iv) at the same distance from the mirror as the object. 2. Light enables us to see the objects around us. When light after reflection enters our eyes, we are able to see the objects. When light falls on the surface of an object, the object sends the light back. This process of sending back of light rays which fall on the surface of an object is called reflection of light. 3. The image which can be obtained on a screen is called a real image. A real image is always inverted. It is formed on the same side of the mirror where the object is placed. The image which cannot be obtained on a screen is called a virtual image. It is always erect or upright. It is always formed behind the mirror. 4. Newton with the help of Newton’s disc demonstrated that all seven colours combine together to make white light. 5. (a) Concave lens (b) Love and concern for the grandparents E. Long Answer Questions. 1.

Teacher’s Resource Pack SCIENCE-7 69 (a) F and F′ are the principal focus of convex lens. (b) O is the optical centre of the convex lens. (c) Distance between O and F or the distance between O and F′ is the focal length of convex lens. 2. (a) The phenomenon of splitting of white light into its component colours on passing through a transparent medium like glass prism is called dispersion of light. (b)

A glass prism splits the white light into seven colours. (c) Rainbow formation after the rain 3. We can distinguish between a plane mirror, a concave mirror and a convex mirror by looking at the images formed by them. (i) When the image is erect, of the same size as that of an object and it does not change its size and nature on moving the mirror closer or away from the face, the mirror is a plane mirror. (ii) When the image is erect, magnified and becomes inverted on moving the mirror away from the face, the mirror is a concave mirror. (iii) When the image is erect, diminished and it remains erect on moving the mirror away from the face, the mirror is a convex mirror. F. HOTS (Higher Order Thinking Skills) Questions. 1. The rear-view mirrors have a warning because the image in the rear- view mirror is smaller than the object so as to cover a larger area in view and thus, appears closer. Actually the images formed are closer than what they appear. Convex mirrors are used in rear-view mirrors. 2. Distance between person and plane mirror = 3m Distance between plane mirror and person’s image = 3m ∴ Distance between person and person’s image = 3 + 3 = 6m 3. Convex lens 4. A, O, T, V, W, X are the alphabets which form their similar images in a plane mirror. This is because these are symmetrical alphabets and the formed image does not appear to be laterally inverted.

70 Teacher’s Resource Pack SCIENCE-7 Chapter 16: Water : A Precious Natural Resource Think! Page No. 224 By preventing water pollution we are actually conserving it because only a fraction of fresh water is available for use by human beings and animals. It is an important natural resource. To increase its availability and overcome its shortage it is essential to save, conserve and prevent it from pollution. Multiple Choice Questions Page No. 222 1. (b) 2. (d) 3. (b) 4. (c) 5. (a) SECTION A CLASS RESPONSE A. Oral Questions. 1. The earth appears blue from space because 71% of the earth’s surface is covered with water. 2. About 97.5% of water available on the earth surface is present in the seas and oceans. This water is salty or saline and therefore, is unfit for human consumption. 3. World Water Day is celebrated on 22nd March. It is celebrated all over the world to attract everyone’s attention towards the importance of conserving water. B. Science Quiz. 1. The rainfall recharges the water table and raises it. 2. Drip irrigation is a modern method of irrigation which can help in conservation of water. 3. Infiltration WORKSHEET A. Tick (3) the correct options. 1. (b) 2. (a) 3. (d) 4. (c) B. Fill in the blanks. 1. solid 2. infiltration 3. deforestation 4. Bawri SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (d) 2. (d) 3. (d) B. Very Short Answer Questions. 1. (a) Ice/snow (b) Steam/water vapour 2. The upper limit of groundwater is called water table. 3. The minimum amount of water recommended by the United Nations for various basic needs is 50 litres per person per day. Teacher’s Resource Pack SCIENCE-7 71 C. Short Answer Type-I Questions. 1. (a) During heavy rainfall, water table rises. (b) During drought, water table falls. 2. The process of collecting rainwater from roofs and street corners and storing it for later use is called rainwater harvesting. 3. Drip irrigation is a technique of watering plants by making use of a system of narrow pipes or tubes with small holes which deliver water drop by drop directly around the roots avoiding the wastage of water. D. Short Answer Type–II Questions. 1. The natural sources of water contain many impurities. Following steps are involved to remove these impurities to make it suitable for drinking— (i) sedimentation (ii) filtration (iii) aeration (iv) chlorination 2. Wastage of water at home can be minimised in the following ways: (i) Avoid brushing teeth, washing hands or cleaning utensils with running water tap. (ii) Collect rainwater in drums and use it to water plants. (iii) Use a bucket and mug instead of using shower for a bath. (iv) Get leaking pipelines and leaking water taps repaired. (v) Mop the floor instead of washing with running water. (vi) Clean your vehicle with wet cloth instead of washing with running water. (vii) Do not throw the unused water left in the bottles, use it for watering plants or cleaning vehicles. 3. Various ways for proper management of water are: (i) Rainwater harvesting (ii) Prevention of wastage of water (iii) Reuse of water (iv) Revival of bawris (v) Drip irrigation (vi) Construction of dams 4. (a) Saving water is important for us because the supply of clean and fresh water is depleting at an alarming rate in some regions and we may suffer from moderate to severe water crisis in the coming years. (b) We should be aware of the problems caused by the scarcity of water. We should be concerned for the society and needs of people. We should also understand the importance of conservation of water and minimise its wastage. E. Long Answer Questions. 1. Following are the factors which deplete water table at a place— (i) Increase in population: Human population is increasing day by day. To meet the needs of an ever-increasing population, more houses, offices, schools, shops and roads are being built. These 72 Teacher’s Resource Pack SCIENCE-7 construction activities require huge supply of water. Borings made at the construction sites withdraw more and more groundwater which leads to the depletion of water table. (ii) Increase in industries: The number of industries is also increasing continuously so more water is used by industries leading to depletion of water table. (iii) Increase in agricultural activities: The demand for agricultural food crops has also increased due to increase in the population. A majority of farmers depend on rainwater to grow crops. But due to unpredictable rainfall, they depend on irrigation methods. At many places, the canal system may suffer from the lack of water due to erratic rainfall. Nowadays, farmers use large quantities of groundwater by digging deep tube wells to cultivate crops. This results in depletion of water table. (iv) Deforestation: Cutting down a large number of trees at a place is called deforestation. This leads to failure of soil to hold moisture. The water just runs off on the ground surface. (v) Decrease the effective area for seepage of water — Increasing population has caused high demand for construction. This has decreased the open areas like parks, playgrounds and other open spaces. The cemented floor does not allow the water to seep in the ground easily. This results in depletion of the water table. (vi) Scanty rainfall — Insufficient rainfall is called scanty rainfall , due to which less water seeps into the ground. This results in the depletion of water table. 2. Many times, we knowingly or unknowingly contribute in wastage of water by various activities at individual level— (i) Running water is used for cleaning courtyard and vehicles. (ii) Taking bath under shower (iii) Shaving and brushing teeth with running tap (iv) Throwing away the water left in the water bottles (v) Not repairing leaking taps and pipelines (vi) Avoiding the collection of rainwater (vii) Washing the floor with running water rather than mopping. F. HOTS (Higher Order Thinking Skills) Questions. 1. Making of tube wells in the residential areas reduces the water table due to which people do not get sufficient water. This happens because a lot of water is pulled out by the tube wells. 2. India is a vast country and rainfall is not same everywhere. Some regions have excessive rains while some regions have very little rainfall. So, there is uneven distribution of water in our country. Teacher’s Resource Pack SCIENCE-7 73 3. Cutting down a large number of trees at a place is called deforestation. The soil cannot hold moisture. The water just runs off on the ground surface. This leads to low rainfall and less seepage of rainwater under the soil. Hence, deforestation can lead to depletion of groundwater.

Chapter 17: Forests : Our Lifeline Multiple Choice Questions Page No. 233 1. (b) 2. (c) 3. (c) 4. (c) 5. (a) SECTION A CLASS RESPONSE A. Oral Questions. 1. Forests are large areas of land covered thickly with different kinds of trees, shrubs, herbs, grasses, creepers and climbers. 2. One-third of the earth’s total land surface is covered with forests. 3. Rosewood, Teak, sheesham 4. The layer of vegetation in a forest just below the canopy is called understorey. B. Science Quiz. 1. Canopy layer, understorey layer and forest floor 2. Hawk/snake/tiger 3. (a) Plants – Mosses and lichens (b) Animals – Insects, millipedes, tigers, lions, bears, deer, etc. 4. Insects, birds, snakes, lizards, jaguars, pythons and leopards WORKSHEET A. Tick (3) the correct options. 1. (c) 2. (b) 3. (c) 4. (d) 5. (a) B. Circle the odd ones. Give reasons for your choice. 1. Frog → It is a carnivore whereas others are herbivores. 2. Rabbit → It is a herbivore, whereas others are carnivores. 3. Wax → It is obtained from bees, whereas others are obtained from plants. 4. Bacteria → These are decomposers, whereas others are parts of a food chain. C. Fill in the blanks. 1. cleaning 2. food web 3. green 4. afforestation SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (d) 2. (c) 3. (d) 74 Teacher’s Resource Pack SCIENCE-7 B. Very Short Answer Questions. 1. The uppermost branches and leaves of tall trees which act like a roof or umbrella over the smaller trees in a forest is called canopy. 2. Food web 3. Canopy 4. The cutting down of trees on a large scale is known as deforestation. C. Short Answer Type-I Questions. 1. A series of organisms linked together by the process of eating and being eaten for food is called food chain. For example, grass → grasshopper → frog → snake 2. Several food chains of a region interconnect to form a food web. A food web is a complex feeding system. 3. Forests have tall, evergreen trees with large and green leaves. The branches overlap each other forming a continuous cover of dense leaves. This layer is so dense that very little sunlight penetrates through it to reach the lower layers of the forest. So, there is darkness inside the forest. 4. Decomposers are those organisms which feed upon the dead plant and animal tissues and convert them into a dark-coloured substance called humus. D. Short Answer Type-II Questions. 1. Plants are beneficial to animals in the following ways: (i) Plants produce oxygen during photosynthesis which is taken up by animals for respiration. (ii) Animals directly or indirectly depend on plants for food. (iii) Tall trees give shelter to various animals. Most birds make their nests on branches of the trees. Animals like monkeys and apes live on trees. 2. Causes of deforestation— (i) Forest fires: Once the forest fire starts, it does not stop easily and many trees are burnt causing deforestation. (ii) Increase in population: With increasing population, more land is required for housing, educational institutes, offices, etc. Forest area is cleared to obtain this land. (iii) Construction of dams: A large forest area has to be cleared to construct a dam. (iv) Wood for industries: Due to increase of population and better standard of living the demand of wood products, is increased leading to the depletion of forests. 3. Forests are important source of wood, variety of products, maintain balance of gases, maintain water cycle in nature, prevent soil erosion, floods and replenish groundwater, provide food and shelter to wildlife, reduce pollution and are also a mode for recreation. Teacher’s Resource Pack SCIENCE-7 75 4. Different ways to conserve forests are as follows: (i) Excessive cutting down of forest trees should not be allowed by the government. (ii) Paper products should be recycled so that minimum cutting down of trees takes place. (iii) Usage of wood as a fuel should be discouraged. (iv) Any breakout of fire in forests should be fought quickly using modern methods. (v) Forests must be protected from insects, pests and infections by treating them with insecticides and pesticides. (vi) ‘Tree for a tree’ principle should be adopted. For every tree that has fallen, a new tree should be planted. 5. Decomposers like bacteria and fungi breakdown the organic wastes into simpler substances and add nutrients to the soil. This helps in recycling of nutrients in the soil. These nutrients are useful for the plants growing in the forest. 6. There is no waste in the forests because even the dead organic matter is decomposed to form nutrients like humus which is required and used by the plants as manure. E. Long Answer Questions. 1. Harmful effects of deforestation are as follows: (i) Deforestation causes soil erosion, leading to loss of soil fertility. (ii) It causes change in the rainfall pattern and results in drought. (iii) Burning of wood, obtained from deforestation, causes increase in the concentration of carbon dioxide in the atmosphere. Excess of carbon dioxide causes air pollution. Carbon dioxide is a greenhouse gas and causes global warming (increase in the earth’s temperature). (iv) In the absence of trees of the forest, the rainwater flows faster causing flood conditions. (v) By deforestation, climate becomes warmer and drier in the absence of humidity in the deforested area. (vi) In the absence of trees and plants, the animals do not get food and shelter. 2. Forests are useful to us in many ways: (i) Forests are a good source of wood like teak, sheesham, rosewood and sal which are used in making furniture, boats, sports goods, houses, etc. (ii) Several plants that grow in forests are used in the preparation of medicines. The bark of Cinchona tree is a source of a medicine called quinine, which is used for treatment of malaria. 76 Teacher’s Resource Pack SCIENCE-7 (iii) Forests maintain balance of gases in nature, maintain water cycle and prevent soil erosion. (iv) Forests prevent floods, replenish groundwater, provide food and shelter to wildlife. (v) Forests help in reducing pollution. (vi) Forests have been developed as recreational parks. People can enjoy camping, hiking, trekking, etc. (vii) Forests give us paper, rubber, gum, oils like eucalyptus and sandalwood. 3. (a) Tiger, lion, giraffe, jaguar, chimpanzee, etc. (b) Forests serve as an important resource to our every requirement and also teach us that everything can be utilised in some or the other way. We learn the judicious utilisation of resources and importance of giving, sharing and maintaining the environmental balance. F. HOTS (Higher Order Thinking Skills) Questions. 1. Recycling of paper helps in the conservation of forests because paper is made from wood which is obtained from forests. We need to cut trees for it. If paper is recycled, cutting down more trees will not be required. 2. Forests are called ‘green lungs’ because the forests help the atmosphere in the same way as lungs in our body. Forests help in exchange of gases, taking in carbon dioxide and giving out oxygen whereas lungs also take the oxygen from the atmosphere, provide it to body parts, collect carbon dioxide and pass it out. G. Application BasedQuestions. 1. In a food web, if any one member is affected, the food web gets disturbed. If number of carnivores, such as lions, becomes more than the herbivores, the population of herbivores (such as deer) would decrease. If there will be too less herbivores, the number of plants will increase rapidly. In other words, both herbivores and producers will be affected, if number of carnivores becomes more. 2. Yes, the occurrence of landslides is due to uncontrolled cutting of forest trees in the area. This is because the roots of trees bind the soil and save it from being washed away by water or the other weathering agents. Chapter 18: Wastewater Story Multiple Choice Questions Page No. 240, 241 1. (b) 2. (c) 3. (a) 4. (d) 5. (b) Multiple Choice Questions Page No. 243 1. (c) 2. (c) 3. (c) 4. (a) 5. (a)

Teacher’s Resource Pack SCIENCE-7 77 SECTION A CLASS RESPONSE A. Oral Questions. 1. Sewage is the wastewater which is carried away in sewers. 2. An underground water pipe which carries away dirty wastewater (or sewage) is called a sewer. 3. Sewage treatment is the process of removing pollutants or contaminants from the sewage to make it harmless, so that it may be disposed of safely in the water bodies. 4. A manhole is a covered vertical hole in the ground, pavement or road above the underground sewer pipeline. B. Science Quiz. 1. Diarrhoea, cholera, jaundice/dysentery 2. Human faeces and animal wastes/fruit and vegetable wastes/pesticides/ herbicides 3. Cooking oil and fats, chemicals, tea leaves, cotton and solid food remains, motor oils and medicines. 4. Primary treatment, secondary treatment and tertiary treatment WORKSHEET A. Tick (3) the correct options. 1. (b) 2. (c) 3. (b) 4. (b) B. Circle the odd ones. Give reasons for your choice: 1. Composting pits → These are used to make compost, whereas others are used as sewage disposal system. 2. Polio → It is not a water-borne disease, whereas others are water-borne diseases. 3. Absorption tank → It is not involved in wastewater treatment, whereas others are part of waste water treatment plant. 4. Human faeces → It is an organic waste, whereas others are inorganic wastes. C. Fill in the blanks. 1. water pollution 2. manhole 3. Stagnant 4. crops SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (b) 2. (b) 3. (c) B. Very Short Answer Questions. 1. The process of nutrient enrichment of water bodies that stimulates the growth of aquatic plants like algae that may result in depletion of oxygen is called eutrophication. 78 Teacher’s Resource Pack SCIENCE-7 2. The harmful effects of sewage are– (i) Spreading of diseases (ii) Water pollution (iii) Eutrophication 3. (i) Septic tanks/Biogas plant (ii) Vermicomposting-toilets 4. Human faeces, animal wastes, oil, urea, pesticides, herbicides, nitrates, phosphates, fruits and vegetables wastes, disease-causing bacteria and fungi, etc. C. Short Answer Type-I Questions. 1. The treated clarified water is taken into secondary sedimentation tank and allowed to stand there. After several hours, the aerobic bacteria settle down at the bottom of the tank as ‘activated sludge’. 2. Clarified water is the cleared water obtained after the removal of sludge and floating impurities. 3. The place where the process of sewage treatment is conducted is called sewage treatment plant or wastewater treatment plant. 4. The suspended and dissolved impurities of sewage are called contaminants. Eg., organic and inorganic impurities, microbes, etc. D. Short Answer Type–II Questions. 1. The speed of the incoming wastewater slows down in grit and sand removal tank so as to allow the sand, grit and pebbles to settle down. 2. The suspended solids settle down at the sloping bottom of the primary sedimentation tank in the form of primary sludge. It is removed from the bottom of the primary sedimentation tank with a scraper and shifted into a large closed tank called digester tank. The organic matter in the sludge is decomposed by anaerobic bacteria to produce biogas. The leftover sludge after the removal of biogas is taken out, dried and used as manure whereas the floating impurities such as grease and oils are removed by a skimmer. 3. (a) Organic impurities – Human faeces, pesticides, animals, fruits and vegetable wastes (b) Inorganic impurities – Nitrates, phosphates, metals (c) Nutrients – Nitrogen, phosphorus (d) Microbes – Bacteria, fungi 4. Following practices should be followed at public places to maintain sanitation: (i) We should not scatter rubbish such as food wastes, empty plastic bottles at public places. (ii) We should never urinate on the roadside. (iii) We should cover the open drains.

Teacher’s Resource Pack SCIENCE-7 79 E. Long Answer Questions. 1. Many villages in our country are still not connected to a common sewage treatment plant. In such places, a septic tank is used to treat household sewage. Septic tank is a large concrete tank built under the ground with inlet and outlet pipes attached to it to treat household sewage. The inlet pipe present in septic tank carries the household sewage to the tank. The solid matter from the sewage settles at the bottom of the tank. The anaerobic bacteria present in the tank decompose most of the solid organic matter present in the sewage and the excess water flows out of the tank through the outlet pipe into the soil.

inspection inspection opening opening opening ground level scum tertiary tank

inlet pipe household outlet pipe sewage

Septic tank 2. Sewage treatment consists of three stages– (i) Primary treatment: It consists of following steps — (a) Screening: The sewage entering the sewage treatment plant is first passed through bar screens. The bar screens remove the large objects like rags, sticks, cans and plastic packets from the sewage. The solid wastes collected are later disposed in the landfill or are incinerated. (b) Grit removal: The sewage after passing through the bar screen is made to flow through a grit and sand removal tank. The speed of incoming wastewater is slowed down to allow sand, grit and pebbles to settle down. (c) Primary sedimentation: The sewage is then passed in primary sedimentation tank and allowed to stand for 10-12 hours. (ii) Secondary treatment: It is designed to degrade the biological contents of the sewage in the form of human wastes, food wastes, soaps, detergents, etc. It consists of aeration and secondary sedimentation. (iii) Tertiary treatment: Water is disinfected with chemicals like chlorine and ozone before it is discharged into a sea, river or into the ground. 80 Teacher’s Resource Pack SCIENCE-7 3. (a) Manholes are provided at every 50 metres to 60 metres distance in the sewerage, at the junction of two or more sewers and at points where there is a change in the direction of sewer line. (b) Alertness of mind and a quick reaction. F. HOTS (Higher Order Thinking Skills) questions. 1. Oils and fats should not be thrown down the drains because they can harden and block the pipes. In open drains, the fats block the soil pores reducing its effectiveness in filtering water. 2. The untreated sewage should not be discharged into water bodies because they can cause water pollution. 3. Excessive water pollution causes eutrophication. Eutrophication is the process of depletion of dissolved oxygen from the water bodies due to excessive growth of algae. Due to decrease in amount of dissolved oxygen in water bodies aquatic animals like fishes die. Periodic Assessment-1 (Based on Chapters 1 to 4) A. Tick (3) the correct options. 1. (c) 2. (c) 3. (c) 4. (c) B. Fill in the blanks: 1. villi 2. cocoon C. Very short answer questions. 1. Pitcher plant and venus flytrap/Utricularia/Drosera 2. The usual temperature range of a laboratory thermometer is –10 °C to 110 °C. D. Short answer questions. 1. Ruminants digest their food in two steps, i.e. they chew the food rapidly, mixed it with saliva and swallow it hurriedly. As they have to save themselves from being caught by predators and move to a safer place where they bring the food back into their mouth to chew and digest it later. 2. Rearing of sheep means to look after the sheep by providing them food, shelter and health care. Periodic Assessment-2 (Based on Chapters 10 to 13) A. Tick (3) the correct options. 1. (c) 2. (b) 3. (d) 4. (d) B. Fill in the blanks: 1. downwards and inwards 2. transpiration

Teacher’s Resource Pack SCIENCE-7 81 C. Very short answer questions. 1. A small metal ball (bob) suspended by a long thread from a rigid support, such that the bob is free to swing back and forth is called a simple pendulum. 2. The function of red blood cells is to transport oxygen from the lungs to all the cells of the body and also carry carbon dioxide produced by cells to the lungs. D. Short answer questions. 1. (a) Yeast (b) Spirogyra 2. The taking in of air, rich in oxygen, into the body is called inhalation. The giving out of air, rich in carbon dioxide, outside the body is called exhalation. Half Yearly Examination (Based on Chapters 1 to 9) A. Very short answer questions. 1. Leaves are green in colour due to the presence of chlorophyll. 2. Liver is the largest gland in the body. 3. Two breeds of sheep found in India are – Lohi and Marwari. 4. The heat from the Sun reaches the earth through radiation. 5. Two natural indicators are turmeric and litmus. 6. Melting of wax is a physical change. 7. Many birds and some other animals migrate to warmer regions when winter sets in. They come back after the winter is over. This is called migration. 8. Westerlies and polar winds 9. (a) Clayey soil (b) Sandy soil 10. Nutrition is the process of taking food by an organism and its digestion, absorption and utilisation by the body. 11. Salivary amylase. B. Short answer type-I questions. 1. Pitcher plant eats insects to fulfill its nitrogen requirement. 2. The utilisation of absorbed food (in the blood) to build complex substances such as the proteins, required by the body for growth and repair of body tissues is called assimilation of food. 3. Two precautions to be taken while reading a clinical thermometer are– (i) Read the thermometer while holding it horizontally so as to keep the level of mercury along the line of sight. (ii) Do not hold the thermometer by the bulb while reading it. 4. When we suffer from acidity, we take antacid tablet to neutralise the effect of excessive acid as antacids contain weak bases. 82 Teacher’s Resource Pack SCIENCE-7 5. The Toucan bird has a long beak that helps it to reach the fruits on such branches that are too weak to support its weight. C. Short answer type-II questions. 1. Features of loamy soil– (i) It has the right water-holding capacity necessary for the growth of plants. (ii) It has adequate air spaces between its particles to hold sufficient air needed by the roots of plants. (iii) It contains sufficient amount of humus to provide necessary nutrients for the growing plants. 2. We should take the following precautions after the cyclone hits an area– (i) We should not drink water as it could be contaminated by floods. (ii) We should not spread rumours. (iii) We should not touch wet electric switches and fallen electric power lines. 3. The association in which different types of organisms live and work together for their mutual benefit is called symbiosis. The root nodules of leguminous plants provide shelter to the Rhizobium bacteria. In turn, Rhizobium bacteria provide nitrogen to the leguminous plants. In this way, Rhizobium bacteria and leguminous plants benefit each other. 4. We can prevent tooth decay by following the given ways– (i) We should avoid eating too many sweets, ice creams and chocolates. (ii) We should brush our teeth at least twice a day. (iii) We should floss our teeth every day. 5. Conduction is the process of transfer of heat in a body from the hotter end to the colder end without any actual movement of the molecules of the material. The conduction of heat occurs from one body to another only when they are – (i) in contact with each other (ii) at different temperatures 6. S.No. Indicator Acids Bases (i) Methyl orange Orange coloured Orange coloured indicator methyl orange methyl orange indicator turns red indicator turns yellow (ii) Phenolphthalein No effect on Turn colourless indicator colourless phenolphthalein phenolphthalein indicator pink indicator

Teacher’s Resource Pack SCIENCE-7 83 (iii) Pink China rose Pink China rose Pink China rose indicator indicator turns deep indicator turns pink (magenta) green 7. A vertical section through the soil showing the different layers of the soil is called soil profile.

8. Three applications of radiation are– (i) The containers of solar cooker are painted black to absorb more heat from the Sun. (ii) The bottom of the cooking utensils is painted black so that they absorb more heat from the bottom. (iii) The houses in hot countries are usually painted white or light coloured. This is done so that the houses absorb less heat from the Sun. 9. We should take following precautions during a thunderstorm– (i) Avoid contact with water and metallic objects. (ii) Do not take shelter under an umbrella with a metallic end. (iii) Do not take shelter in a high rise building as they are likely to be struck by lightning. 10. The layer of air surrounding the earth is called atmosphere. The two important properties of air are as follows– (i) Air exerts pressure. (ii) Air expands on heating and contracts on cooling. D. Long answer questions 1. Sea breeze: Land absorbs heat faster than the sea. During the daytime, the land heats up more quickly than the sea water. Thus, the air above the land surface heats up, expands and rises up. The cooler air above the sea surface blows towards the land to take its place. This sets up

84 Teacher’s Resource Pack SCIENCE-7 convection currents. The cool air from the sea blowing towards the land is called sea breeze.

Land breeze: Land loses heat faster than the sea. At night, the land cools more quickly than the sea water. Thus, the air above the sea being warmer, rises up and cooler air from above the land surface blows towards the sea to take its place. This sets up the convection current. The cool air from the land moves towards the sea. This is called land breeze.

2. A change in which one or more new substances with entirely different chemical composition and properties from the original substances are formed is called a chemical change. The characteristics of chemical changes (chemical reaction) are – (i) Change in the physical state of the substances undergoing chemical changes may occur. (ii) Evolution of a gas may occur during a chemical reaction. (iii) Change in colour and smell of a substance may take place during some chemical changes. (iv) Formation of a precipitate may occur during a chemical reaction. (v) Change in energy takes place during all chemical changes. Teacher’s Resource Pack SCIENCE-7 85 3. Following adaptations help penguins to survive in Antarctic region– (i) They are white in colour that merges well with the white surrounding of ice and snow. (ii) They have black-coloured feathers on their back that absorb heat from the Sun and help them keep warm during the day. (iii) They have thick skin and a layer of fat below their skin which keeps them warm in extreme cold climate. (iv) They huddle together in groups to keep them warm. (v) They have streamlined bodies, flipper-like wings and webbed feet that help them swim. 4. (a) The process by which green plants make their own food (glucose) from carbon dioxide and water by using solar energy in the presence of chlorophyll is called photosynthesis. sunlight 6CO2 + 6H2O → C6H12O6 + 6O2 carbon water chlorophyll Glucose Oxygen (b) Importance of photosynthesis– (i) It enables green plants to make their own food. In the absence of photosynthesis there would be no plants. (ii) The survival of all animals in the world directly or indirectly depends upon the food made by the plants. (iii) Oxygen is produced during photosynthesis that is essential for survival of all living organisms. Carbon dioxide is utilised during photosynthesis. Thus, photosynthesis maintains balance between oxygen and carbon dioxide in the atmosphere. 5. (a) Ingestion:Amo eba eats tiny microscopic plants and animals as food, which float on water in which it lives. When an Amoeba encounters a suitable organism, it pushes out two pseudopodia around the organism. Gradually, the tips of the pseudopodia fuse with each other. As a result, the food is engulfed with a little surrounding water to form a food vacuole inside it. (b) Digestion: The enzymes from the surrounding cytoplasm enter the food vacuole and break down the food into simple, soluble substances. (c) Absorption: The digested food present in the food vacuole is absorbed directly into the cytoplasm. (d) Assimilation: The digested food absorbed by the cytoplasm is stored or utilised for its growth, development, multiplication and release of energy. (e) Egestion:The undigested food gets collected inside the vacuole. The cell membrane suddenly ruptures at any place and the undigested food is thrown outside the body by the vacuole. 86 Teacher’s Resource Pack SCIENCE-7 E. Practical Skill based questions. 1. We can obtain a decolourised leaf in following way— Take a leaf and boil it in water. Take out the leaf and boil it in alcohol. This will remove the chlorophyll from the leaf. 2. (i) Acidic solutions turn blue litmus paper red. (ii) Basic solutions turn red litmus paper blue. (iii) Neutral solutions have no effect on litmus papers. Yearly Examination (Based on Chapters 2, 5, 10-18) A. Very short answer questions. 1. The exchange of gases takes place in alveolus during respiration in humans. 2. Organs in the human excretory system are – kidneys, ureters, urethra and urinary bladder. 3. The fusion of male gamete with the female gamete to produce zygote is called fertilisation. 4. The standard unit of speed is metre per second (m/s). 5. Excessive flow of current occurs in household circuits due to (i) short circuit (ii) overloading Teacher’s Resource Pack SCIENCE-7 87 6. (a) Image will be formed beyond C. (b) Image will be formed between P and F, behind the mirror. 7. A series of organisms linked together by the process of eating and being eaten for food is called a food chain. 8. The four chambers in the stomach of ruminants are rumen, reticulum, omasum and abomasum. 9. The acidic solution which has a small quantity of water and a large quantity of acid is called concentrated acid. 10. When few drops of sodium hydroxide are added to the phenolphthalein indicator (colourless), it turns pink. 11. The process of breakdown of complex, insoluble, food substances into soluble food substances with the help of digestive juices prepared by the body is called digestion. B. Short answer type-I questions. 1. When the pollen grains from the anther of a flower of one plant are transferred to the stigma of a flower of another plant of the same kind, it is called cross-pollination. 2. Time taken from extreme to mean position is 0.25s. So, time taken for 1 oscillation will be 1 minute 40 seconds. Time period is the time taken to complete one oscillation, so time period is 1 minute 60 seconds. 3. The causes of deforestation are – (i) increase in population (ii) wood for industries (iii) construction of dams (iv) forest fires 4. Tooth decay causes the following – (i) Holes or cavities in the teeth (ii) Foul smell (iii) Toothache (iv) Loss of teeth (v) Stomach disorders 5. S.No. Organic acid Mineral acid (i) The acid that are found in The acids prepared from the plants and animals are called minerals of the earth are organic acids. called mineral acids. (ii) These are natural acids. These are human-made acids. Also called laboratory acids.

88 Teacher’s Resource Pack SCIENCE-7 C. Short answer type-II questions. 1. S.No. Inhalation Exhalation (i) Ribs move upwards and Ribs move downwards and outwards. inwards. (ii) Diaphragm contracts and Diaphragm relaxes and moves moves downwards upwards. 2. Following changes occur in a flower after fertilisation – (i) The ovary of the flower swells and develops to form the fruit. (ii) The ovules present in the ovary grow to become seeds. (iii) The other parts of the flower like stamens, style and stigma, dry and fall off. 3. A magnet produced by passing an electric current through a coil of insulated wire wound around a soft iron rod is called an electromagnet. The strength of an electromagnet can be increased by– (i) increasing the number of turns in the coil. (ii) increasing the current passing through the coil (solenoid) 4. The characteristics of an image formed in a plane mirror are– (i) The image is of the same size and shape as the object. (ii) The image is virtual and erect. (iii) Laterally inverted with respect to the object. 5. Advantages of rainwater harvesting are– (i) It increases the water table. (ii) It reduces flood and topsoil erosion. (iii) It increases the availability of clean water. 6. We can conserve forest in following ways– (i) Excessive cutting down of forest trees should not be allowed by the government. (ii) For every tree that has been fallen, a new tree should be planted. (iii) Paper products like old newspapers, magazines and notebooks should be recycled. (iv) Use of wood as a fuel should be discouraged. 7. Importance of transpiration in plants– (i) It helps in the upward movement of water and minerals from roots to the leaves by generating a suction pull. (ii) Transpiration produces cooling effect which protects the delicate cells of the plant from the heat of the sunlight. (iii) When there is more transpiration, rate of absorption of water increases. Teacher’s Resource Pack SCIENCE-7 89 →intestinal 8. (a) carbohydrates juice Glucose (partially digested)

→intestinal (b) Fats juice Fatty acid + Glycerol intestinal → (c) Proteins juice Amino acid 9. Properties of bases are – (i) They have bitter taste. (ii) They are soapy to touch. (iii) They turn red litmus blue. (iv) They are corrosive in nature. (v) They conduct electricity. (vi) They react with acid to form salt and water. 10. Functions of tongue are – (i) It helps in mixing saliva with food. (ii) It helps in swallowing the food into food pipe. (iii) It helps in getting different tastes of food. (iv) It enables us to speak. D. Long answer questions 1. S.No. Parameter Aerobic respiration Anaerobic respiration (i) Presence of It takes place in the It takes place in the oxygen presence of oxygen. absence of oxygen. (ii) Breakdown Complete breakdown Incomplete breakdown of food of food (glucose) of food (glucose) takes takes place. place. (iii) End products The end products are The end products are carbon dioxide and carbon dioxide and water. alcohol. (iv) Amount A large amount of A very small amount of of energy energy is released. energy is released. released

2. Heart is enclosed in double layered membranous sac called pericardium. The heart has four chambers. The upper two chambers of the heart are called atria and the lower two chambers are called ventricles. The left side of the heart is completely separated from its right side by a partition wall called septum. A tricuspid valve is present between right atrium and right ventricle. A bicuspid valve is present between left atrium and left ventricle. 90 Teacher’s Resource Pack SCIENCE-7 3. (a) Focus: The focus/principal focus of a lens is the point on the principal axis at which parallel rays of light after passing through a lens meet or appear to meet. ‘F’ is the principal focus. (b) Optical Centre: The centre of the lens is called optical centre. ‘O’ is the optical centre. (c) Focal length: The distance between the optical centre (O) and focus of the lens is called focal length (f). 4. Where there is no proper sewerage system, low cost onsite sewage disposal systems are used. Septic tanks, biogas plant and vermicomposting toilets are examples of low cost onsite sewage disposal system. (i) Septic Tank: A large concrete tank is built under the ground. The inlet pipe carries the household sewage to the tank. The solid matter of sewage settles at the bottom of the tank and is decomposed by the anaerobic bacteria in the tank. (ii) Biogas plant: The excreta from the toilets flows through covered drains into a biogas plant. The biogas so produced is used as a fuel. (iii) Vermi-composting toilet: In this toilet, the human excreta is treated by earthworms. It uses less water and its operation is simple and hygienic. 5. An electric bell has a U-shaped electromagnet. A small iron bar, called armature, is held in front of the poles. The lower end of the armature is attached to a flat spring and the spring is itself fixed to a metal bracket. The upper end of the armature has a hammer attached to it. There is a contact screw which just touches the armature at point E. A metal gong is fixed near the hammer. The electromagnet is connected to a battery, a push button switch and the armature in a circuit. Teacher’s Resource Pack SCIENCE-7 91 E. Practical Skill based questions. 1. After girdling of the stem, the portion of the plant below the girdled stem dries because phloem gets removed due to girdling. The lower part of the plant does not get food prepared by the leaves and thus dries up. This proves that food is translocated by phloem. 2. (i) Fig. (i) is a stronger magnet because the number of turns of the coil are more around the iron rod. (ii) Iron is a stronger magnetic substance than the steel.

92 Teacher’s Resource Pack SCIENCE-7