SCIENCE NOTES, CLASS - 7 CHAPTER 1: NUTRITION IN PLANTS...

SCIENCE NOTES, CLASS - 7

CHAPTER 1: NUTRITION IN PLANTS SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (a) 2. (c) 3. (c) B. Very Short Answer Questions. 1. Name any two heterotrophs. Cuscuta and coral root 2. Name any two insectivorous plants. Pitcher plant and Venus flytrap 3. Name the pores through which leaves exchange gases. Stomata 4. Name one plant in which photosynthesis occurs in a plant part other than leaves. Name the plant part. Cactus (fleshy stem) 5. What are the two main modes of nutrition in plants? Autotrophic and heterotrophic C. Short Answer Type-I Questions. 1. What are heterotrophs? 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. Why is mistletoe called partial parasite? 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 synthesize its food. Thus, it is called partial parasite. 3. Why do some plants eat insects? Some plants eat insects for fulfilling their nitrogen requirements for preparing proteins. 4. What is autotrophic mode of nutrition? 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. What is saprotrophic mode of 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. D. Short Answer Type-II Questions. 1. How can we decolorize a leaf? Explain. We can decolourise a leaf by boiling it first in water and then in alcohol. This process is called bleaching. 2. What are plant parasites? Name any two plant parasites. 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. How does the pitcher plant catch its prey? 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. Differentiate between parasitic and insectivorous plants. 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. Algae and fungi live together in lichens. a) What is this association called? Lichens show symbiotic association or symbiosis. b) What value can we learn from this association in nature? We can learn to help others and to work and live together in harmony in the society. D. Long Answer Questions. 1. Write an experiment to show that sunlight is necessary for photosynthesis. 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: Take a healthy potted plant and keep it in a dark room for 2-3 days to destarch the leaves. Cover one of its leaves partly with a strip of black paper and put the plant in sunlight for a few hours. Pluck this covered leaf and remove the black strip. 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. 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. How do Rhizobium bacteria and leguminous plants help each other in survival? 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. Write an experiment to show that carbon dioxide is necessary for photosynthesis. 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: a) 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. b) 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. c) Take a rubber cork which fits tightly to the mouth of the glass bottle and cut it into two halves. d) 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 should remain outside the glass bottle whereas the lower half of the leaf should be inserted in the glass bottle. e) Keep the potted plant in the sunlight for 3 to 4 days. f) Pluck the leaf from the plant and take it out from the glass bottle. g) 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. h) 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. Discuss any two types of heterotrophic nutrition in plants. The two types of heterotrophic nutrition in plants are saprotrophic nutrition and parasitic nutrition.

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 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. E.g. Cuscuta. F. HOTS (Higher Order Thinking Skills) Questions. 1. What will happen if plant leaves are devoid in stomata? 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. All plants are autotrophic in nature. Do you agree? Why/ Why not? No, only the green plants are autotrophic in nature. Non-green plants are heterotrophic in nature. 3. What will happen if all the plants perish from the earth? 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. How can you say photosynthesis maintains balance between oxygen and carbon dioxide in the atmosphere? 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. Application Based Questions.


1. Rohit places a potted plant in a room in complete darkness. After 3 days, he takes out the plant and tests the leaf for the presence of starch. Will he get positive starch test? Give reason for the same. Rohit will not get a positive starch test because keeping the plant in darkness, i.e., without sunlight, destarched the plant and thus, plant is unable to make starch. 2. Meeta discovered a new plant species that is non-green and is found on the green plants. What will you classify it as a parasite or an insectivorous plant? Why? Meeta possibly discovered a parasite and not an insectivorous plant because insectivorous plants are generally green in colour and can synthesize their food. On the other hand, parasites are generally non-green and depend on other green plants for readymade food. ----------------------------------------------------------------------

CHAPTER 2: NUTRITION IN ANIMALS SECTION B A. Multiple Choice Questions (MCQs) Scientific/ Practical skills. 1. (a) 2. (d) 3. (c) B. Very Short Answer Questions. 1. Name four different tastes which can be detected by our tongue. Bitter, sour, salty and sweet. 2. Name the four chambers found in the stomach of ruminants. Reticulum, osmium, rumen and abomasum’s. 3. Name the tearing teeth. Canines. 4. Name the various steps of animal nutrition. Ingestion, digestion, absorption, assimilation and Egestion Short Answer Type-I Questions. 1. What happens to the undigested food in the body? 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 (faces). It is passed out of the body through the anus. 2. What are the effects of tooth decay? 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

3. What are ruminants? 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. What is the difference between milk teeth and permanent teeth? Milk (Temporary) teeth Permanent teeth

The temporary set of teeth that grows when the child is in the age group of 6 months to 8 years are called milk teeth.

The second set of teeth which grow again, after the milk teeth fall out are called permanent teeth.

These teeth are smaller and weaker and are 20 in number.

These remain till old age and are 32 in number.

They are replaced by new natural teeth.

They cannot be replaced by new natural teeth

D. Short Answer Type-II Questions. 1. What do you understand by the term assimilation? The simple, soluble, absorbed food substances are transported to different parts of the body where they are utilized by the body for energy, growth and repair. This process is called assimilation. 2. What is the action of intestinal juice on the following food components? a) Carbohydrates b) Fats c) Proteins? (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. Discuss the different types of teeth along with their structure. Teeth are of following four types on the basis of their structure and functions: a) 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. b) 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. c) 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. d) Molars (grinding teeth): There are three molars present on either side of premolars. They also have broad and flat grinding surfaces and are used to crush and grind food. 4. What are the functions performed by tongue? (i) Tongue helps in mixing saliva with the food.


(ii) It helps in pushing and swallowing the food into the food pipe. (ii) It has several taste buds which help in giving different tastes of food like—sour, salty, bitter, sweet. (iv) It enables us to speak. 5. Draw a well labelled diagram to show the movement of the food in the esophagus. Write the function of esophagus. Esophagus contracts and expands to push the food down into the stomach. Digestion of food does not takes place in the esophagus.

6. Which part of the alimentary canal is involved in? a) Chewing of food b) Killing of bacteria c) Absorption of food d) Formation of faces? (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 faces. E. Long Answer Questions. 1. Describe briefly, how digestion and absorption takes place in Amoeba.

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. Describe the process of digestion in ruminants. 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. 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. Different types of teeth in our jaws have different functions, but they all work together to chew the food. a) Discuss the functions of each type of teeth. b) What inspiration do we get from our teeth that have different functions? (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 are two in number in each jaw. These are sharp and pointed teeth which help in tearing the food. (iii) Premolars (Grinding teeth): There are two premolars next to each canine. These have broad and flat grinding surfaces. They grind food and break 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 bacteria present on uncleansed teeth convert the sugar in food into a substance 'X' which causes tooth decay. Name the substance'X'. Which part of the teeth does it affect? The substance ‘X’ is acid and it affects the tooth enamel. 2. How is ruminant’s stomach different from human stomach? Ruminants have compound stomach which enables them to digest cellulose. It is absent in human beings. 3. If a piece of chapathi is chewed for some time, it tastes sweeter. Why? When chapathi 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. Which structure in Amoeba can be compared to the mouth of humans? Pseudopodia or false feet are present in Amoeba which can be compared to the mouth of humans. 5. Is food vacuole in amoeba similar to the small intestine of human beings? How? 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. We have often seen that an infant child after feeding on milk vomits out something like curd. How does this happen? 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. ----------------------------------------------------------------------

CHAPTER 3: FIBRE TO FABRIC A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (a) 2. (b) 3. (c) B. Very Short Answer Questions. 1. Name the steps involved in the production of wool from sheep? Sheep → Shearing → Scouring → Sorting → Combing → Dyeing → Spinning → Wool 2. Which is the strongest natural fiber? Silk 3. What are the basis to decide the quality of wool obtained from sheep? The quality of wool is judged on the basis of thickness, length, shine, strength and fineness of fibers. 4. Name the process of rearing of silkworms for obtaining silk? Sericulture C. Short Answer Type-I Questions. 1. What is meant by selective breeding? 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. What is meant by scouring? The process of washing the fleece of sheep to remove dust, dirt, sweat, grease is called scouring. 3. Give two characteristics of wool. (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. What is silk? How is it obtained? Silk is a fine, strong, soft and shining natural fiber obtained from silkworms. It is separated from the cocoons of silkworms that are reared on large scale. 5. Why are the cocoons boiled in hot water or treated in ovens? Cocoons are boiled in hot water or treated in ovens to kill the larvae inside the cocoon. 6. Why do we not wait for the silk moth to hatch and then boil the cocoon? 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 fibers. 7. Why do we need to boil the cocoons for extraction of silk? 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 fiber as a single continuous thread. D. Short Answer Type-II Questions. 1. Why does shearing not hurt the sheep? 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. 2. Differentiate between silk and wool. Wool is obtained from fur (hair) of sheep, goat, yak, etc., while silk is obtained from the cocoons of silk moth. 3. What are raw silk and spun silk? The fibers 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. With the help of a flow chart, describe the life cycle of a silkworm

Life cycle of a silkworm a) The female silk moth lays pale yellow eggs on the leaves of mulberry tree. b) 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. c) Now, silkworms enter into pupa stage. Each silkworm begins spinning a cocoon. d) 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. What is sericin? How is it softened? 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 fiber. It is softened by hot water. E. Long Answer Questions.


1. What is meant by the following terms? a) Shearing of sheep b) Sorting of wool c) Combing of wool (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. Write the various steps involved in the production of silk cloth from silk moth. The following steps are followed in the production of silk cloth from silk moth.

3. Describe the process of wool production. Wool is obtained from the sheep by a long process which involves the following steps: a) 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. b) Scouring: The fleece of sheep is washed to remove dust, dirt, sweat, grease, etc. c) Sorting: The long fine quality of fleece is separated from the remaining inferior quality or broken pieces. d) Combing: The burrs are removed from the fleece. In this step, the fibers are straightened. e) Dyeing: After combing, the fibers obtained are dyed in various colours. f) Spinning: The straightened fibers are spun or twisted together to make yarn which is either knitted or woven. 4. Removal of sheep wool i called shearing. Shearing is done only in early summers and not in winters. a) Why is shearing done in summers? b) Which value does this act show? (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. If we burn silk fiber, it gives a smell of burning hair. Why? Silk fiber on burning gives a smell of burning hair because it is an animal fiber and is made up of a protein. 2. Animal activists are against the silk production. Why? 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. --------------------------------------------------------------------

CHAPTER 4: HEAT AND ITS EFFECTS A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (b) 2. (b) 3. (b) B. Very Short Answer Questions. 1. What is the usual temperature range of a laboratory thermometer? – 10°C to 110°C 2. What are the two conditions necessary for the conduction of heat? Heat can be conducted from one body to another only when they are (i) In contact with each other (ii) At different temperatures. 3. How does the heat from the sun reach the earth? Through radiation 4. How do we measure heat? Heat is measured by thermometer. C. Short Answer Type-I Questions. 1. Give two precautions to be taken while reading a clinical thermometer. (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. Define conduction. Give one example to show heat transfer by conduction. 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. Define radiation. Give one example to show heat transfer by radiation. 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. What is the sea breeze? How is set up? 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. Why is mercury used in thermometer? 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. Convert 77 °F into degree Celsius. Temperature in degree Fahrenheit = 77 °F We know

𝐶

5 =

𝐹−32

9

C = 𝟓 × 𝟕𝟕 – 160

𝟗 =

385 – 160

9 =

225

9 = 25 °C

D. Short Answer Type-II Questions. 1. Give two similarities and two differences between a laboratory and a clinical thermometer. Similarities between laboratory and clinical thermometer: a) Both are used to measure temperature and their constructions are almost the same. b) Both of them use mercury. Differences between laboratory and clinical thermometer: a) 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. b) Clinical thermometer is used to measure the temperature of human body, whereas laboratory thermometer is used for measuring temperature while performing experiments. 2. What is meant by bad conductors of heat? Give examples of two materials which are bad conductors of heat. The materials which do not allow heat to pass through them quickly are called bad conductors of heat. Examples: Paper and wood are bad conductors of heat. 3. Draw a labelled diagram to show transfer of heat by convection, when water taken in a flask is heated.

4. How is radiation different from conduction and convection for transfer of heat? (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. Nitika’s neighbours Mrs. Sharma is an old lady and lives alone. She does not keep well. Nitika takes some hot home-made vegetable soup made by her mother, in a them flask for her. a) Why does Nikita’s mother use a thermo flask? b) What value can we learn from Nitika? (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. Describe the construction of a laboratory thermometer. Give two precautions to be taken while reading a laboratory thermometer. 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. Give reasons for the following: a) Cooking utensils are made of metals. Metals are good conductors of heat. b) Pressure cooker is provided with Bakelite handle. 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. c) Air conditioned buildings have double-walled windows. 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 ceiling keeps the room warm during winters. 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. Asbestos sheets are preferred over iron sheets for roofing because asbestos is a non-conductor of heat. 3. Draw a labelled diagram of a thermo flask. Answer the following: a) Why is the air removed from space between the two walls of glass bottle? b) Why is the glass bottle held in a place inside the metal case with the help of cork pieces? 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. Explain why a clinical thermometer cannot be used to measure high temperature. 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 person has a white shirt and a black shirt. Which shirt will make him more comfortable in? a) Winters b) Summers? Give reasons for your answer. (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. Why is water not used instead of mercury in thermometer when it is easily available to us? 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. 4. The firefighting suits are always bright and shiny. Why? The firefighting suits are always bright and shiny so that they reflect the heat around. In this way, the firefighter does not absorb heat. --------------------------------------------------------------------

CHAPTER 5: ACIDS, BASES AND SALTS SECTION B A.Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (b) 2.(b) 3.(d) B. Very Short Answer Questions. 1. Name two acids and bases. Acids – Sulphuric acid and nitric acid/ hydrochloric acid Bases – Sodium hydroxide and potassium hydroxide/ calcium hydroxide/ magnesium hydroxide 2. How does litmus indicator work? a) The neutral litmus solution turns red when added to some acidic solution. b) The neutral litmus solution turns blue when added to some basic solution. c) The neutral litmus solution does not change its colour when added to some neutral solution. 3. Which acid is produced in our stomach? Hydrochloric acid


C. Short Answer Type-I Questions. 1. Why do curd, lemon juice and tamarind taste sour? Curd, lemon juice and tamarind taste sour because they contain acids. 2. What happens in the stomach when we eat very spicy food? When we eat very spicy food, the stomach produces large amount of hydrochloric acid which leads to acidity in stomach. 3. Why is an antacid tablet taken when you suffer from acidity? Antacid tablet contains magnesium hydroxide (weak base) which neutralizes the effect of excess acid produced in the stomach and gives relief. D. Short Answer Type-II Questions. 1. Write one use each of a) Sulphuric acid, b) Hydrochloric acid c) Nitric acid. (a) Sulphuric acid – used in manufacturing of fertilizers/ plastics/ textiles/paper (b) Hydrochloric acid – used in manufacture of chemicals/ dyeing/ tanning of leather (c) Nitric acid – used in manufacture of fertilizers 2. Why should factory wastes be neutralized before discharging them into water bodies? Explain? 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. Annie is playing in her garden with her friend, Ishrat. Suddenly, a bee bites Ishrat. Annie immediately brings baking soda and rubs it on the stung area. a) Why does Annie apply baking soda? b) What value can you learn from Annie? (a) Annie applied baking soda (a mild base) to neutralize 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) How does the soil become too acidic in nature? b) What should be added in the soil when it is? i) Too acidic ii) Too basic? (a) Excessive use of fertilizers 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.

2. Differentiate between acids and bases.

Parameters Acids Bases

Taste Sour Bitter

Touch Not soapy Soapy or slippery

Effect on litmus paper indicator

Turn blue litmus paper

red

Turn red litmus paper blue

Effect on yellow turmeric paper

indicator No effect

Turn yellow turmeric paper indicator red

Effect on colourless

phenolphthalein indicator

No effect

Colourless phenolphthalein indicator turns

pink

Effect on pink china rose indicator

Pink china rose indicator turns

dark pink (magenta)

Pink china rose indicator turns

green

Solubility in water

Most of the acids are soluble in

water.

Most of the bases are insoluble in

water.

3. a) What are organic acids? b) Name any two organic acids? c) How are mineral acids different from organic acids? (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. 1. How are acids helpful in maintaining our good health? 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. ----------------------------------------------------------------------

CHAPTER 6: PHYSICAL AND CHEMICAL CHANGES SECTION B A.Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (a) 2.(d) 3.(c) B. Very Short Answer Questions: 1. Give two examples of physical changes a) Melting of wax b) Formation of cloud


2. What happens when magnesium oxide is dissolved in water? When magnesium oxide is dissolved in water, it forms magnesium hydroxide [Mg (OH) 2]. 3. What type of change is burning of coal? Chemical change C. Short Answer Type-I Questions. 1. What is meant by rusting of iron? 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. State any two conditions necessary for the rusting of iron. The two conditions necessary for the rusting of iron are – a) Presence of air (oxygen) b) Presence of water or water vapour (moisture) 3. Why is melting of ice to form water considered a physical change? 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. What are the characteristics of physical change? (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. What are the characteristics of chemical change? (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 e.g. burning of fuel produces large amount of heat. (iv) During a chemical change, both the physical and chemical properties of a substance are changed. 3. Why is explosion of crackers considered a chemical change? 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. Does the change in chemical properties take place during a chemical change? Yes, the chemical properties of a substance get changed during a chemical change. This is because, in a chemical change, entirely new substances with new chemical composition is formed. 5. Ram and Raheem are best friends. Raheem goes to Ram’s house to celebrate Diwali. Both are burning crackers. Suddenly, a spark falls on Raheem’s arm. Ram immediately washes Raheem’s hand and applies a cream for burns. a) Which type of change is burning of crackers? b) Do you think, burning crackers is good for our environment? c) Which value is shown by Ram here? (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. Write the differences between physical and chemical changes?

Parameters Physical change Chemical change

New substance

No new substance is

formed.

One or more new substances are

formed.

Nature of change

It is a temporary change.

It is a permanent change.

Reversibility

It is easily reversible by

simple physical methods.

It is generally irreversible.

Physical and chemical

properties

Only the physical

properties of the substance are changed.

Both the physical and chemical

properties of the substance are

changed.

Amount of energy (in the form of heat

or light)

Generally, there is no overall

change in energy.

Change in energy takes place as a very

large amount of energy is absorbed

or given out.

2. Describe, how crystals of copper sulphate are prepared? a) To prepare crystals of copper sulphate by the process of crystallization b) 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. c) Allow the solution of copper sulphate to cool slowly. Leave the apparatus undisturbed for 24 hours. d) 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. e) The pure large crystals of copper sulphate are obtained. F. HOTS (Higher Order Thinking Skills) Questions. 1. How is the burning of candle a physical as well as a chemical change? 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. Why? 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 condition for rusting to occur. 3. Change A-Animal waste is acted upon by anaerobic bacteria to produce biogas. Change B-Biogas is burnt as fuel. Which of these changes is a chemical change? The change A and change B, both are chemical changes. 4. Which ice cube will melt the faster? Why? a) The ice cube left on the kitchen counter. b) The ice cube left in a hot spot. c) The ice cube with salt on it. d) The ice cube crushed gently with a heavy utensil or hammer. The ice cube crushed gently with heavy utensil or hammer will melt faster because it is broken in small pieces. G. Application Based Question. 1. Jai was very fond of collecting coins of different metals. One day, he observed that the colour of silver and copper coins had changed. Explain reason for his observations. Colour of silver coin changed because silver gets oxidized 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

B. Very Short Answer Questions. 1. Name an instrument used to measure the maximum and minimum temperature during a day? Maximum-minimum thermometer 2. Name the places in India where Siberian cranes comes every year for a few months. Bharatpur in Rajasthan and Sultanpur in Haryana 3. What are big cats? The wild animals such as lions, tigers and leopards are called big cats. 4. Name an animal having sticky pads on its feet? A red-eyed frog C. Short Answer Type-I Questions. 1. What kind of climate do we observe in? a) The Himalayan region b) The Thar Desert and c) Meghalaya? (a) Very cold climate (b) Very hot and dry climate (c) Hot and humid climate 2. What is migration? Birds migrate to warmer regions when winter sets in. They come back when winter is over. This is called migration. 3. What is meant by adaptation? The favorable characteristics (features and habits) which enable the living organisms to survive and breed in their surroundings (habitat) is called adaptation. 4. How do elephants keep themselves cool in hot and humid climate of the tropical rainforest? 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. Why does a toucan have a long colourful beak? 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. State an adaptation in red –eyed frog which helps it climb on trees on which it lives. Red-eyed frog has sticky pads on its feet which help it to climb easily on the tree trunk on which it lives. 7. Which of the following normally live in Polar Regions and in tropical rain forests? a) Penguin b) Seal c) Siberian crane d) Arctic tern e) Lion-tailed macaque? 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. Explain how the following adaptations help the penguins live and survive in Polar Regions: a) Blubber under the thick skin, b) Streamlined body, c) White-coloured body with black-coloured feathers. (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. What are the various types of information usually carried by the daily weather report in a newspaper? 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. What is meant by relative humidity? How is it measured? 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. What the regions far away from the equator cooler? 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. 5. Explain why in summer, we feel so miserable in the afternoon and comparatively comfortable in the early morning? 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. Discuss the differences between weather and climate.

Weather Climate

Weather describes the atmospheric conditions on a

particular day, at a place with respect to the temperature, humidity, rainfall, speed and

direction of wind.

Climate is the average weather pattern of a

place taken over a long period of time.

Weather is measured for a smaller region.

Climate is measured for a larger region.

Weather at a place changes suddenly.

Climatic changes are gradual and not sudden.

2. What are tusks? How does an elephant make use of tusks for its survival? 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. Explain how does a camel live and survive in a desert. Adaptations in camel to survive in desert region are— a) It has a hump where fat is stored. The camel utilizes this fat as food in case of its scarcity. b) A large amount of water gets stored in its stomach. c) It sweats very little and also excretes very little water in urine. This helps to conserve water. d) It has large soles which help to walk on soft ground. e) It has long legs which keep the body away from the heat of sand. f) Long eyelashes protect the eyes from sand. 4. Animals living in polar regions adapt themselves to survive and breed in their habitat. a) List the adaptations in polar bears that help them survive in polar region. b) What value can we learn from these animals that adapt themselves? (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. F. HOTS (Higher Order Thinking Skills) Questions. 1. Where will you find an animal with small ears, tails and legs-in Polar Regions or deserts? Why? 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.”Development pf new cities and expansion of the existing ones may affect the climate”. Is the Statement correct? Why? Why not? Yes, the statement is correct. Expansion of cities and increasing urbanization and industrialization 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 B. Very Short Answer Questions. 1. What are the two stages of cyclone warnings? (i) First stage warning – cyclone alert / cyclone watch (ii) Second stage warning – cyclone warning 2. List two situations that generate wind currents on the earth. (i) Unequal heating between the equator and poles of the earth. (ii) Unequal heating of land and water of oceans 3. What are the three conditions to form a thunder storm? (i) Moisture (ii) An unstable air mass (iii) A lifting force C. Short Answer Type-I Questions. 1. Why does hot air (or warm air) rise upwards? 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. State any three observations which tell us that air exerts pressure. (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. Why it is difficult to ride a bicycle while moving against the wind? 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. What is the main cause of rain in winters in some parts of India? 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. What do you mean by high pressure area and low pressure area? 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. 6. What conclusion do you make when you blow air in the space between the two balloons from your mouth and the balloons com closer to each other? 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. How are convection currents setup in air? 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. Explain how the wings of an Aeroplane are designed to help the aircraft to take off. 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. Describe how a cyclone causes widespread destruction. 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. Why is it safe to take shelter in a bus during a thunderstorm? 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. Annie is a member of disaster management society. She lives in a small beach-side town. She is taking a walk on the beach. Suddenly, she hears a warning of the cyclone going to hit their town in around 48 hours. She immediately organizes her disaster management team.


a) Being a member of the disaster management society, what should be her immediate steps to save her town? b) What value you learn from Annie? (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) What is air pressure? b) Why does a closed tin can containing boiling water get crushed, when kept under a cold water tap? (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) What is a cyclone? B) Describe the formation of a cyclone. (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. (b) i) Factors like wind speed, wind direction, temperature and humidity contribute to the development of cyclones. ii) 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. iii) 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. iv) 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. v) Repetition of this cycle ends with the formation of a very low pressure system with very high speed winds revolving around it.

vi) Thus, a huge revolving storm called cyclone is formed. 3. What are summer monsoons? How are summer monsoons caused over India? How are they useful? 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. Neeta read the following news in the morning assembly, a cyclone that started in the deserts of Rajasthan hits Chandigarh today”. Is this news correct? Why/ Why not? 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. Why a cyclone cannot be observed on the land? 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 rickshaw puller has to apply more efforts to pull the rickshaw. Why? 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. 2. Which one of the following would you prefer to take shelter during a thunderstorm and why? a) A car b) A single big tree (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 B. Very Short Answer Questions. 1. Which is the best soil for growing lentils? Loamy soil 2. Which type of soil has the (a) lowest percolation rate of water, (b) Highest percolation rate of water? (a) Clayey soil (b) Sandy soil 3. Which soil absorbs more water sandy soil or clayey soil? Clayey soil 4. What are three most important things for which we depend on the soil? Minerals, agriculture and reservoir of groundwater C. Short Answer Type-I Questions. 1. How is humus formed in the soil? Humus is formed by the decomposition of dead remains of plants and animals by bacteria and other microorganisms present in the soil. 2. What is the difference between clayey and sandy soil?

Clayey soil Sandy soil

It has a very small particles It has quite large particles.

It has little air It is well aerated

Its particles are tightly packed and It is less porous

Its particles have large spaces and It is porous

It has high water –holding capacity

It has low water - holding capacity

3. What is meant by percolation rate? The volume of water (in mL) which passes down the soil per minute is called percolation rate. 4.100ml of water was taken in a measuring cylinder. This water was added drop wise to 50g of dry soil kept on filter paper in the funnel .When the water just started dripping from the soil in the funnel, the amount of water left in the measuring Cylinder was found to be 80 ml. Calculate the percentage of water absorbed by this soil. Percentage of water absorbed by soil:

= mass of water absorbed by the soil

mass of the soil taken

= 100 – 80

= 𝑋100%

50 =

20𝑋100%

50 = 40%

D. Short Answer Type-II Questions. 1. Why is loamy soil the best for growing crops? Loamy soil is best for growing crops because of the following reasons: a) It has adequate air spaces between its particles to hold air needed by the plant roots. b) It contains sufficient amount of humus to provide necessary nutrients for the growing plants. c) It can be ploughed easily.

2. What is the function of air present in the spaces between the soil particles? 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. What are the properties of soil? The properties of soil are as follows – a) It contains air. b) It allows water to percolate. c) It contains water (moisture). d) It can absorb water. 4. Why is soil an important natural resource? Soil is an important natural resource because– a) It supports growth of plants and trees by holding their roots firmly. b) It is a home for many organisms. c) 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. d) Soil supplies water and mineral nutrients to the plants. Thus, soil is an inseparable part of our life. E. Long Answer Questions. 1. What is meant by soil profile? Draw a sketch of the soil profile and label the various layers. 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.

2. Why does clayey soil have a very good water-holding capacity? Explain? 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. Describe an experiment to show that soil contains water. a) Take some dry garden soil in the glass beaker and cover it with a watch glass. Heat the beaker by using a Bunsen burner as shown in the Figure. b) 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). c) This hot water vapour rises, gets cooled and condenses on the cold inner surface of the watch glass to form tiny water droplets. d) Soil contains water (or moisture) present as a thin invisible film around its particles.

4. Alex is a soil specialist and he sells manure best suited for wheat. He goes to a village where farmers are planning to sow wheat which grows best in clayey and loamy soil. He tests the soil sample and finds that the soil is more suitable for the growth of cotton rather than wheat. He tells the villagers about this despite knowing that they will not buy his manure. a) Why is clayey-loamy soil preferred for growing wheat? b) Which value is shown by Alex? (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. To make roads, people break large rocks into smaller ones. Can this be called weathering of rocks? 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. Explain why we cannot make pots, toys and statues with sand and can make these with clay. 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. ----------------------------------------------------------------------

CHAPTER 10: RESPIRATION IN PLANTS B. Very short answer: 1. Name an animal each which breathes through a) Trachea b) Gills c) Skin d) Lungs a) Insects b) Fish c) Frog d) Humans 2. Define breathing rate. What is the average breathing rate of an adult human, at rest? 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. What is meant by respiration? 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. What happens to the ribs and diaphragm during exhalation? During exhalation, ribs move downwards and inwards while the diaphragm relaxes and moves upward to its original position. 5. What is the respiration which can occur without oxygen called? Anaerobic respiration C. Short Answer Type-I Questions. 1. Why we should breathe only through our nose? 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. What is the differences between breathing and cellular respiration?

3. What happens to the ribs and the diaphragm during inhalation? During inhalation the ribs are pushed upwards and outwards. The diaphragm contracts and moves downwards.

Parameters Breathing Cellular

respiration

Process

It is a physical process in which exchange of

gases (oxygen and carbon dioxide) takes place. No chemical

reaction takes place.

It is a biochemical

process in which the breakdown of food takes

place.

Energy Energy is not released. Energy is released.

Occurrence It occurs outside the

cells. It occurs inside

the cells.

Enzymes Enzymes are not

involved.

Enzymes are involved at

certain stages of respiration.


4. What is meant by inhalation and exhalation? 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. Why does the breathing become faster during exercise? 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. Describe the mechanism of exchange of gases in the alveolus of the lung? The oxygen of the air diffuses in from the thin walls of alveolus into blood capillaries. The oxygen combines with hemoglobin in the blood to form oxyhaemoglobin which is carried to all the cells of the body. Similarly, carbon dioxide produced by breakdown of food during respiration enters the blood and reaches alveolus in the lungs through diffusion. 2. Write the main differences between aerobic and anaerobic respiration?

Parameters Aerobic

respiration Anaerobic respiration

Presence of oxygen

It takes place in the presence of

oxygen.

It takes place in the absence of oxygen.

Breakdown of food

Complete breakdown of food (glucose)

takes place.

Incomplete breakdown of food

(glucose) takes place.

End products

The end products are carbon dioxide and

water.

The end products are carbon dioxide and

alcohol.

Amount of energy

released

A large amount of energy is released.

A very small amount of energy is released.

Occurrence It takes place in

living organisms.

It takes place in yeast and in some form of

bacteria.

3. Explain the process of respiration in the roots of a plant? 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. Distinguish between photosynthesis and respiration. Photosynthesis is the process of synthesizing food by utilization 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. Draw a well labelled diagram of human respiratory system. In which part of the lungs does exchange of gases takes place?

The exchange of gases takes place in alveolus present in the lungs. 2. Describe the process of breathing and respiration in the following organisms: a) Insects b) Earthworm c) Frog d) Fish 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. With the help of a flow-chart, show how the exchange of gases takes place in the lungs. The air containing oxygen reaches the alveoli through the trachea, bronchi and bronchioles. From alveoli, the oxygen of the air diffuses into the blood capillaries. The oxygen combines with hemoglobin in the blood and forms oxy hemoglobin which is carried to all the cells of the body. During breakdown of food, Co2 is produced which is diffused out from the blood to alveoli of lungs. From lungs, Co2 is removed along with the air we breathe out. 4. Nitika is practicing for the upcoming athletic championship. Suddenly, while running, she sits down and starts crying because of pain in her legs. Monika immediately brings a hot water bath for her. a) Why did Nitika suddenly feel the pain in her legs while running? b) What value should you learn from Monika? (a) Nitika felt pain due to a muscle cramp which happened because of anaerobic respiration in muscle cells in which lactic acid is formed. (b) Kind, concerned, compassionate and helping nature 5. Look at the diagram given alongside and answer the questions: a) What does fig a) and b) Depict? b) Explain what happens when air is inhaled and exhaled. (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. F.HOTS (Higher Order Thinking Skills) Questions. 1. What will happen if our diaphragm shows no movement? We will not be able to breathe if our diaphragm shows no movement.

2. Why does a frog have a dual mode of breathing? 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. Why does an athlete breathe faster and deeper than usual even after finishing the race? 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. How does sneezing protect us from germs? 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. ---------------------------------------------------------------------- CHAPTER 11: TRANSPORTATION IN ANIMALS AND

PLANTS B. Very Short Answer Questions. 1. What is the function of septum in the heart? Septum prevents the mixing of oxygenated blood with the deoxygenated blood in heart. 2. Name the waste product excreted by a) Large intestine b) Lungs c) Skin (a) Undigested food (b) Carbon dioxide (c) Excess water, urea, some salts and other metabolic wastes in the form of sweat. 3. Name the two types of vascular tissues present in plants. Xylem and phloem 4. What is the size of human heart? 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. Explain why the heart beats faster during and after a physical exercise. 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. What is meant by ‘excretion’? The process of removal of waste products produced in the cells of the living organisms is called excretion. 3. What is dialysis? What type of patients are put on dialysis machine? 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.


4. What is blood? What are its two components? Blood is a red-coloured fluid which flows in the blood vessels to every part of the body. The components of blood are – Fluid component – blood plasma Solid component – blood cells (WBCs, RBCs and platelets) 5. Which part of the heart: a) Receives blood from the lungs? b) Pumps blood to the lungs? c) Pumps blood into the body organs (Except lungs)? d) Receives blood from the body parts (Except lungs)? a) Left atrium b) Right ventricle c) Left ventricle d) Right atrium D. Short Answer Type-II Questions. 1. Give reasons for the following: a) Arteries have thick and elastic muscular walls. b) Arteries are not easily seen. c) Veins have thin and less elastic muscular walls. (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. How does transpiration help in the transport of water and minerals in plants? 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. Write the differences between arteries and veins

Parameters Arteries Veins

Direction of blood flow

Carry blood from the heart to

various body parts

Carry blood from different body parts

to the heart

Nature of blood

Carry oxygen-rich blood (except

pulmonary artery)

Carry carbon dioxide- rich blood (except pulmonary vein)

Flow of blood

Blood flows at a high speed and high pressure.

Blood flows at a low speed and low

pressure.

Walls Walls are thick and

elastic. Walls are thin and

less elastic.

Valves Valves are absent. Valves are present.

Position in the body

Arteries are deeply seated.

Veins are not deeply seated.

4. What are the functions performed by sweating in human beings? The functions performed by sweating in human beings are —

a) Sweating helps in removing excess water, some salts and urea as liquid waste from the body. b) Sweating helps in keeping the body cool during summers. E. Long Answer Questions. 1. Describe an activity to show xylem conducts water in plants. 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 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. Describe an activity to show phloem transports food produced by leaves. 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 Trans located 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. Tanmay’s mother is diagnosed with kidney failure. He requests that one of his kidneys be given to his mother. a) What happens when both the kidneys of a person stop working? b) What value can you learn from Tanmay? (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. What will happen if blood does not have enough platelets? If the blood does not have enough platelets, then blood clotting will get affected. 2. Why is the heart divided into two halves by a thick wall? The heart is divided into two equal halves to segregate the oxygenated blood from the deoxygenated blood and avoid their mixing. 3. Xylem transports sap upwards only whereas phloem transports food in both directions. Why do you think there is a difference? Xylem can only conduct water from the soil and transport it to all parts of the plant in upward direction. Phloem Trans locates the food from leaves to all parts of the plant for utilization as well as storage. It supplies food to the aerial parts as well as the roots in both directions. 4. WBC’s are often called soldiers of the body. Why? 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. ----------------------------------------------------------------------

CHAPTER 12: REPRODUCTION IN PLANTS B. Very short answer: 1. Name any two plants which are reproduced by asexual method of reproduction. Onion and Potato 2. Name two types of pollination. i) Self-pollination ii) Cross-pollination 3. Name two types of methods of reproduction in plants. Sexual and Asexual reproduction 4. Name any two plants which are reproduced by sexual method of reproduction. Mustard and Tomato C. Short Answer Type-I Questions. 1. What is pollination? The transfer of pollen grains from the anther to the stigma of a flower is called pollination. 2. Name two plants pollinated by the following agents: a) insects b) Wind c) Water. (a) Rose, Jasmine (b) Grass and Wheat (c) Vallisneria and Hydrilla 3. Name any two seeds or fruits which are dispersed by water. Fruits of coconut, seeds of lotus and water lily are dispersed by water. 4. Name two plants whose seeds are dispersed when their fruits burst with a sudden jerk. Pea, Balsam D. Short Answer Type-II Questions.

1. Explain the differences between self-pollination and cross-pollination.

Self-pollination Cross-pollination

The pollen grains from another of a flower are

transferred to the stigma of the same flower or another

flower of the same plant.

The pollen grains of a flower of one plant are

transferred to the stigma of a flower of another plant of the same kind.

2. Why is dispersal of seeds essential for plants? Seed dispersal is essential for plants because it provides following benefits to the plants:

It prevents overcrowding of plants in an area.

It prevents the competition for water, minerals and sunlight among the same kind of plants.

It helps the plants to grow in new areas or new places.

3. What is meant by germination of seeds? What are the necessary conditions for germination of seeds? 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. What are the special features of seeds and fruits which are dispersed by wind? Seeds and fruits dispersed by wind have the following special features: a) They are small and lightweight. Thus, they are easily blown away by the wind. b) They have wings or hair around them. E. Long Answer Questions. 1. Explain how fertilisation takes place in a flower. 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.


2. Distinguish between sexual and asexual reproduction.

Parameters Sexual

reproduction Asexual

reproduction

Involvement of parent

Both parents, the male and female

are involved.

Only one parent is involved.

Involvement of gametes

Gametes are involved.

No gametes are involved.

Production of seeds

Plants are obtained from

existing parents through seeds.

Plants are obtained without the

production of seeds.

Similarity to the parent

plant

Newborn plants are not identical

to the parent plant.

Newborn plants are identical to the parent plant.

Example grass, wheat, corn,

apple, pea, Hydrilla

Spirogyra, mosses, fern, potato, onion,

ginger

3. How do animals help in the dispersal of seeds and fruits? Certain seeds and fruits are dispersed too 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 faces at some other distant places. 4. A beggar begs for some eatables from Riya. She finds some bread in her kitchen. But, these are covered with some greenish-black patches. So, she gives some fruits to him. a) What are these greenish-black patches found on the bread called? How do they reproduce? b) What value do you learn from Riya? (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. What would happen if all the seeds of a plant were to fall at the same place below the plant and grow there? 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.

2. Why are flowers generally so colourful and fragrant? If flowers are not so colorful and sweet smelling, will fruit formation be seen in these plants? 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. Which flowers are more attractive-insect pollinated or wind pollinated? Why? 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. Why are methods of artificial vegetative reproduction so commonly used nowadays? 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. ----------------------------------------------------------------------

CHAPTER 13: TIME AND MOTION B.Very short answer questions: 1. Write the formula for calculating speed.

Speed= 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑

𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛

2. Write the standard unit of speed. Metre per second or m/s 3. What kind of graph is used to represent the motion of a body? Distance-time graph 4. Name the device used to measure small intervals of time. Stop watch C) Short answer type-I questions: 1. What is a simple pendulum? 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 bob of a simple pendulum takes 0.25 seconds to go from one extreme position to mean position. Calculate the time period of the pendulum. 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. In a distance –time graph: a) What type of motion does a straight line represent? b) What type of motion does a curved line represent? (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. Monica takes 20 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 3m/calculate the distance between her house and the school in kilometers. 1. Here, speed = 3 m/s 20 minutes (We know, time taken = 60 s)

= 20 × 60 = 1200 seconds

We know, Speed = 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑


Or distance travelled = speed x time taken 3m/s x 1200s = 3600 m = 3.6 km (We know, 1 km = 1000 m) 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. A Car moves at a speed of 20km/h for 15 minutes and then at a speed of 60km/h for next 15 minutes. Calculate the total distance covered by the car. (i) Here, in the first case Speed = 20 km/h Time taken = 15 minutes

= 15

60=

1

4 h (we know, 1hour = 60 minutes)



Or distance travelled = speed x time taken

= 1

20 𝑘𝑚/ℎ𝑥 4ℎ \ distance travelled = 5km

(ii) In the second case Speed = 60 km/h Time taken = 15 minutes

= 15

60=

1

4 h (we know, 1hour = 60 minutes)



Or distance travelled = speed x time taken

= 60 𝑘𝑚/ℎ x1

4ℎ = 15 km

Total distance covered = 5 + 15 km = 20 km Thus, the total distance covered by car is 20km. 3. The distance between two stations is 300 km. A train takes 5 hours to cover this distance. Calculate the speed of the train. Time taken = 5 hours

Speed =𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑


Speed of the train = 300 𝑘𝑚

5 ℎ𝑜𝑢𝑟 = 60 km/h

Thus, the speed of the train is 60 km/h.

4. Piya invites all her friends to her birthday party that is to begin at 6pm.Everyone reaches on time except Vandana. She reaches at 8 pm. They could not start the function on time. a) What principle is used for measuring time in clocks and watches? b) Why should we be punctual? (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. What type of motion is shown by the following distance –time graph? (a) Uniform motion (b) Non-uniform motion (c) Rest E.Long Answer Questions. 1. Define the following terms related with the simple pendulum: a) Length of the pendulum: The length of the string from the point of suspension to the centre of the bob is called the length of the pendulum. b) Oscillation of the pendulum: The one complete to-and-fro motion of the bob about its mean position is called an oscillation of the pendulum. c) Amplitude of the pendulum: The maximum displacement of the bob from its mean position on either side is called the amplitude of the pendulum. d) Time period of the pendulum: The time taken by the bob of a pendulum to complete one oscillation is called the time period of the pendulum. 2. Draw a distance time graph: a) For an object moving at a constant speed. b) For a stationary object. (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) HOTS (Higher Order Thinking Skills) Questions. 1. Which unit of speed will you use to express the speed of the following? a) Aeroplane-km/h b) Tortoise-m/s c) Ant-cm/s d) horse-km/h


2. The figure given alongside shows the distance-time graph for the motion of two car A and B. Which one of them is moving faster? Car A moves faster. Car A travels faster in a short period of time. ---------------------------------------------------------------------- CHAPTER 14: ELECTRIC CURRENT AND ITS EFFECTS

B.Very Short Answer Questions. 1. Name any four insulator. Wood, plastic, wool and rubber 2. Name the materials used for making: a) Filament of an electric bulb b) Heating element of an electric heater (a) Tungsten metal (b) Nichrome alloy 3. Name any four electrical appliances in which the heating effect of current id utilized. Electric room heater, electric iron, electric toaster and electric oven/ electric kettle/water heater (geyser)/immersion rod C. Short Answer Type-I Questions. 1. What is meant by resistance of a wire? The property of a material by virtue of which it opposes the flow of an electric current through it is called its resistance. 2. What is an electromagnet? A magnet produced by passing an electric current through a coil of insulated wire wound around soft iron rod is called electromagnet. 3. What is the relationship between the amount of electric current passed and the heat produced? 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. Give the electrical symbols for: a) resistance, b) electric bell, c) Battery, d) Electric bulb, e) Switch in ‘ON’ position, f) Wire

2. What is short-circuit? What the causes are of short-circuit? 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. Write any three uses of an electromagnet. Electromagnets are used in— a) Motors that drive fans, mixers, washing machines, etc. b) Cranes to lift heavy loads like big machines, steel girders and scrap iron objects for loading and unloading purposes. c) Electric bells, telegraphs, telephone instruments, loudspeakers, etc. d) Used by doctors to remove tiny iron particles from the eyes of a person. 4. Ram and Neeraj are alone at home. Ram is watching TV while Neeraj is playing with his toy. The battery in his toys get discharged. He decides to charge it and connects the plug to the same socket to which the TV is connected. The table fan in their room is also connected to that socket. Suddenly, after a few seconds, Ram sees a heavy spark near the socket. He immediately puts off the main switch and calls his neighbours for help. a) What do you think is the reason for the heavy spark in the socket? b) What do you learn from Ram’s behaviour? a) Overloading of the electric circuit. b) We learn to be alert all the time and doing right things at the right time. E.Long Answer Questions. 1. What is a solenoid? Draw a diagram with a solenoid connected in a circuit. How can you increase the strength of a solenoid?

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) Give two advantages of electromagnets over a permanent magnet. What type of magnet is used in an electric bell? B) Draw a labeled diagram of an electric bell. (a) Advantages of an electromagnet over a permanent magnet are –


The magnetism of an electromagnet can be switched ‘ON’ or ‘OFF’ as desired. This is not possible with a permanent magnet. 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. b) An electromagnet is used in an electric bell as it works on the magnetic effect of current.

3. What is overloading? Why is a fuse wire necessary in a circuit? How does it work? 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. Why can’t we use a copper wire for making an electric fuse? 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 coil suspended freely, points in some direction when no currents is passed through it. Can you tell what will happen when a current is passed through it? 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. ----------------------------------------------------------------------

CHAPTER 15: LIGHT B.Very Short Answer Questions. 1. Give one example of a virtual image. An image of a boy in the plane mirror

2. Write any three uses of concave mirrors. Concave mirrors are used a) As shaving mirrors. b) As reflectors in torches and headlights of vehicles, such as cars, buses, etc. c) By dentists to see an enlarged image of teeth. d) By doctors to examine body parts such as eyes, ears, nose and throat. 3. Define Spectrum. 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. Which surface of a spoon always forms an erect image of your face? Bulging surface of a spoon always forms an erect image of the face. C.Short Answer Type-I Questions. 1. Write the differences between a convex and a concave lens.

Parameters Convex lens Concave lens

Structure

A convex lens is thicker in the middle and thinner at the edges.

A concave lens is thinner in the middle and thicker at the edges.

Action It is a converging lens. It is a diverging lens.

Focus It has a real focus. It has a virtual focus.

Image

The image formed may be real/virtual, enlarged/small/equal to size of the object.

The image formed is always virtual, erect and smaller than the size of the object.

2. Write the differences between convex and concave mirrors.

Convex mirror Concave mirror

A spherical mirror whose reflecting surface is curved outwards.

A spherical mirror whose reflecting surface is curved inwards.

Reflection of light takes place at bulging out surface.

Reflection of light takes place at bent-in-surface.

Principal focus is virtual and lies behind the mirror.

Principal focus is real and lies in front of the mirror.

It always forms a virtual, erect and diminished image.

It always forms a real, inverted and highly diminished image.

3. Define the principal focus of a concave lens. 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. Which kind of lens can form a) an inverted image smaller than the object b) an erect image smaller than the object? (a) Convex lens (b) Concave lens D. Short Answer Type-II Questions. 1. What are the characteristics of the image formed by a plane mirror? The image formed by a plane mirror is a) Of the same size and shape as the object. b) Virtual and erect. c) Laterally inverted with respect to the object. d) At the same distance from the mirror as the object. 2. How does light enable us to see objects around us? 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. Give differences between a real and a virtual image. 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. What did Newton demonstrate with the help of the Newton's disc? Newton with the help of Newton’s disc demonstrated that all seven colours combine together to make white light. 5. Nitika’s grandmother is not able to see distant objects properly. Nitika takes her to the nearby eye specialist. a) Which type of lens would be suggested by doctor for Nitika's grandmother? b) What value can you learn from Nitika? (a) Concave lens (b) Love and concern for the grandparents E.Long Answer Questions. 1. With the help of a ray diagram, explain the following terms: a) Focus of a convex lens b) Optical centre of a convex lens c) Focal length of a convex lens

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) What is meant by dispersion of light? b) With the help of a diagram, show the dispersion of white light of a prism? c) Name the natural phenomenon which is caused by the dispersion of light. (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. How can you distinguish between a plane mirror, a concave mirror and a convex mirror without touching them? We can distinguish between a plane mirror, a concave mirror and a convex mirror by looking at the images formed by them. 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. When the image is erect, magnified and becomes inverted on moving the mirror away from the face, the mirror is a concave mirror. 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. Why do in automobiles, the rear view mirrors have warning written as object seen in the mirror may be closer than they appear? 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. A Person standing 6cm away from a plane mirror3m towards the mirror. Can you tell the distance between the person and the image? 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. If you are given two lenses convex and concave, to read a dictionary, which lens would you use? Convex lens 4. Write down the English alphabet in which the image formed in a plane mirror appears to be the same as the alphabet. Give reason. 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. --------------------------------------------------------------------

CHAPTER 16: WATER: A PRECIOUS NATURAL RESOURCE

B.Very Short Answer Questions. 1. Name a) Solid form of water: Ice/snow b) Gaseous form of water: Steam/water vapour 2. What is meant by 'Water table'? The upper limit of groundwater is called water table. 3. What is the minimum amount of water per person per day recommended by the United Nations for various basic needs? The minimum amount of water recommended by the United Nations for various basic needs is 50 liters per person per day. C. Short Answer Type-I Questions. 1. What happens to the water table during -? a) Heavy rainfall b) Drought? a) During heavy rainfall, water table rises. b) During drought, water table falls. 2. What is meant by 'Rainwater harvesting'? The process of collecting rainwater from roofs and street corners and storing it for later use is called rainwater harvesting. 3. What is meant by drip irrigation? 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. Short Answer Type–II Questions. 1. What are the steps involved in the purification of water of natural source for drinking purposes? 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. How can you minimize the wastage of water at home? Wastage of water at home can be minimized in the following ways: a) Avoid brushing teeth, washing hands or cleaning utensils with running water tap. b) Collect rainwater in drums and use it to water plants. c) Use a bucket and mug instead of using shower for a bath. d) Get leaking pipelines and leaking water taps repaired. e) Mop the floor instead of washing with running water. f) Clean your vehicle with wet cloth instead of washing with running water. g) Do not throw the unused water left in the bottles, use it for watering plants or cleaning vehicles. 3. List out the various ways for proper management of water. Various ways for proper management of water are:

Rainwater harvesting Prevention of wastage of water

Reuse of water Revival of bawris

Drip irrigation Construction of dams

4. Nitika studies in class 7.One day, she studied spout water in her science class. She came home, called her friends, prepared pamphlets on the tips to save water and distributed in her colony. A) Why do you think that saving water is important for us? B) What can we learn from Nitika? (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. 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 minimize its wastage. E.Long Answer Questions. 1. Explain the factors which deplete the water table at a place. Following are the factors which deplete water table at a place— a) 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 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. b) Increase in industries: The number of industries is also increasing continuously so more water is used by industries leading to depletion of water table. c) 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. d) 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. f) 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. g) 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. Describe the mismanagement of water at the individual level (household level). Many times, we knowingly or unknowingly contribute in wastage of water by various activities at individual level— a) Running water is used for cleaning courtyard and vehicles. b) Taking bath under shower c) Shaving and brushing teeth with running tap d) Throwing away the water left in the water bottles e) Not repairing leaking taps and pipelines f) Avoiding the collection of rainwater g) Washing the floor with running water rather than mopping. F. HOTS (Higher Order Thinking Skills) Questions. 1. Why is making of tube wells prohibited in residential areas? 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. Why is distribution of water uneven in our country? 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. 3. Explain, how deforestation can lead to depletion of groundwater? 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 B.Very Short Answer Questions. 1. What is meant by 'Canopy' in a forest? 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. What do the interconnected food chains form? Food web 3. What do we call the cover of branches of tall trees in a forest? Canopy 4. What is meant by deforestation? The cutting down of trees on a large scale is known as deforestation. C.Short Answer Type-I Questions. 1. Define food chain. 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. What is meant by food web? Several food chains of a region interconnect to form a food web. A food web is a complex feeding system. 3. Why there is dark inside the forest? 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. What are decomposers? 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. How are plants beneficial to animals? Plants are beneficial to animals in the following ways: a) Plants produce oxygen during photosynthesis which is taken up by animals for respiration. b) Animals directly or indirectly depend on plants for food. c) 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. What are the causes of deforestation? Causes of deforestation— a) Forest fires: Once the forest fire starts, it does not stop easily and many trees are burnt causing deforestation. b) Increase in population: With increasing population, more land is required for housing, educational institutes, offices, etc. Forest area is cleared to obtain this land. c) Construction of dams: A large forest area has to be cleared to construct a dam. d) 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. How are forests important to us? 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. 4. What are the ways to conserve forests? Different ways to conserve forests are as follows: a) Excessive cutting down of forest trees should not be allowed by the government. b) Paper products should be recycled so that minimum cutting down of trees takes place. c) Usage of wood as a fuel should be discouraged. d) Any breakout of fire in forests should be fought quickly using modern methods. d) Forests must be protected from insects, pests and infections by treating them with insecticides and pesticides. e) ‘Tree for a tree’ principle should be adopted. For every tree that has fallen, a new tree should be planted. 5. Explain how decomposers help in maintaining the supply of nutrients to the growing plants in a forest. 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. Explain why there is no waste in a forest. 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. What are the harmful effects of deforestation? Harmful effects of deforestation are as follows: a) Deforestation causes soil erosion, leading to loss of soil fertility.

b) It causes change in the rainfall pattern and results in drought. c) 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). d) In the absence of trees of the forest, the rainwater flows faster causing flood conditions. e) By deforestation, climate becomes warmer and drier in the absence of humidity in the deforested area. f) In the absence of trees and plants, the animals do not get food and shelter. 2. Give five ways in which forests are useful to us. Forests are useful to us in many ways: a) Forests are a good source of wood like teak, sheesham, rosewood and sandal which are used in making furniture, boats, sports goods, houses, etc. b) 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. c) Forests maintain balance of gases in nature, maintain water cycle and prevent soil erosion. d) Forests prevent floods, replenish groundwater, provide food and shelter to wildlife. e) Forests help in reducing pollution. f) Forests have been developed as recreational parks. People can enjoy camping, hiking, trekking, etc. g) Forests give us paper, rubber, gum, oils like eucalyptus and sandalwood. 3. Forests provide shelter to a wide variety of organisms and also maintain balance of nature. Still, they do not need our care to sustain, as nature fulfill all of their requirements. a) Give examples of some animals that are only found in forests. b) What do you learn from forests? (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. Explain. 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. Why are forests called 'Green lungs'? 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. --------------------------------------------------------------------

CHAPTER 18.WASTEWATER STORY B.Very Short Answer Questions. 1. What is eutrophication? 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. 2. List three harmful effects of sewage. The harmful effects of sewage are– (i) Spreading of diseases (ii) Water pollution (iii) Eutrophication 3. Name any two low cost onsite sewage disposal systems for human wastes. (i) Septic tanks/Biogas plant (ii) Vermicomposting-toilets 4. Name the various contaminants present in sewage. Human faeces, animal wastes, oil, urea, pesticides, herbicides, nitrates, phosphates, fruits and vegetables wastes, disease-causing bacteria and fungi. C. Short Answer Type-I Questions. 1. What is activated sludge? 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. What is meant by clarified water? Clarified water is the cleared water obtained after the removal of sludge and floating impurities. 3. What is meant by wastewater treatment plant? The place where the process of sewage treatment is conducted is called sewage treatment plant or wastewater treatment plant. 4. What are contaminants? The suspended and dissolved impurities of sewage are called contaminants. Eg. Organic and inorganic impurities, microbes, etc. D. Short Answer Type–II Questions. 1. Why does the speed of the incoming wastewater slowdown in grit and sand removal tank? 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. What is primary sludge? Explain how it is treated. 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. Name two a) Organic impurities b) inorganic impurities c) Nutrients d) Microbes present in sewage.

(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. What practices should be followed to maintain sanitation at public places? Following practices should be followed at public places to maintain sanitation: a) We should not scatter rubbish such as food wastes, empty plastic bottles at public places. b) We should never urinate on the roadside. c) We should cover the open drains. E.Long Answer Questions. 1. What is a septic tank? How is it used? How it works? 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.


2. Outline the main steps used in sewage treatment. Sewage treatment consists of three stages– a) Primary treatment: It consists of following steps 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. 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. a) Primary sedimentation: The sewage is then passed in primary sedimentation tank and allowed to stand for 10-12 hours. b) 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. c) Tertiary treatment: Water is disinfected with chemicals like chlorine and ozone before it is discharged into a sea, river or into the ground. 3. Ravi sees a man falling into a manhole. He shouts for help and gest the man out of it safely. a) Where are manholes provided and at what distance? b) What value do you learn from Ravi? (a) Manholes are provided at every 50 meters to 60 meters 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. Why should oil and fats not be thrown in the drains? 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. Why is discharge of untreated sewage into water bodies not desirable? The untreated sewage should not be discharged into water bodies because they can cause water pollution. 3. Why do fishes die due to the excessive water pollution? 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. ----------------------------------------------------------------------

SCIENCE, CLASS – 7, NOTES

SCIENCE NOTES, CLASS - 7 CHAPTER 1: NUTRITION IN PLANTS...

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