Page 1 : Nutrition in Plants Class 7 Science Extra Questions Very Short Answer Type, Question 1., Potato and ginger are both underground parts that store food. Where is the food prepared in these plants? [NCERT Exemplar], Anwer:, In both the plants, shoot system and leaves are above ground. They prepare food through photosynthesis and transport it to the underground part for storage., Question 2., Plants prepare their food using a different mode of nutrition than us. What is it?, Answer:, The mode of nutrition in plant is autotrophic, i.e. they synthesise their own food., Question 3., Photosynthesis requires chlorophyll and a few other raw materials. Add the missing raw materials to the list given below:, Water, minerals, (a) …… (b) ……., Answer:, (a) Sunlight, (b) Carbon dioxide, Question 4., The tiny openings present on the leaf surface. What are they called?, Answer:, Stomata are the tiny pores present on the surface of leaves through which gaseous exchange takes place in plants., Question 5., What is the function of guard cells of stomata?, Answer:, Guard cells help in controlling the opening and closing of stomata for gaseous exchange., Question 6., Which parts of the plant are called food factories of the plant?, Answer:, Leaves are referred to as food factories of plants. This is because, leaves synthesise food by the process of photosynthesis., Question 7., A carbohydrate is produced by plants as food source. It is constituted from which molecules?, Answer:, Carbohydrates are composed of carbon, hydrogen and oxygen., Question 8., Why do some plants feed on insects?, Answer:, Insectivorous plants grow in soil which lack nitrogen, therefore they eat insects to fulfill their need of nitrogen., Question 9., Define parasites., Answer:, Parasites they are those organisms which grow on other plants or animals for their food, e.g. Cuscuta., Question 10., Name the bacteria that can fix atmospheric nitrogen., Answer:, Rhizobium is the bacterium which can fix atmospheric nitrogen., Question 11., Except plants, why can’t other living organisms prepare their food using CO2, water and minerals? [HOTS], Answer:, Our body does not contain chlorophyll for absorbing solar energy which is necessary for preparing food using air, water, etc., Question 12., A leguminous plant can restore the soil’s concentration of mineral nutrients. Can you give examples of some such plants?, Answer:, Plants such as gram, pulses and beans are leguminous., Question 13., Algae are green in colour. Why?, Answer:, Algae contain chlorophyll which imparts green colour to them., Question 14., what do you understand by nutrition?, Answer:, The process of utilising nutrients like carbohydrates, proteins, fats, etc., to generate energy is called nutrition., Question 15., Fungus can be harmful and useful. Give an example showing both of these traits of fungus., Answer:, Fungus produces antibiotics like penicillin used to treat diseases and fungus can also harm us by causing fungal infections on skin and hair., Question 16., A unique feature in leaves allows them to prepare the food while other parts of plants cannot. Write the possible reason for this. [HOTS], Answer:, Leaves contain chlorophyll which is essential for food preparation and is absent in other parts of plant., Question 17., Algae and fungi form a unique association sharing benefits from each other. What is the name of association between them?, Answer:, Lichens., Question 18., In a plant, photosynthesis occurs in a part other than leaf. Name that plant and the part where photosynthesis occurs., Answer:, Cactus, the part where photosynthesis occurs are stem and branches which are green., Question 19., Why is Cuscuta, categorised as a parasite?, Answer:, Cuscuta derives its nutrition using an association where it deprives its host of all valuable nutrients and absorbs them itself. Hence, it is called a parasitic plant., Question 20., Plant cannot use the nitrogen present in the soil directly. Why?, Answer:, Plants can use nitrogen only in soluble form while in soil nitrogen is present in inorganic form., Question 21., Why are insectivorous plants called partial heterotrophs?, Answer:, Insectivorous plants are autotrophs, i.e. they prepare their own food. They are partial heterotrophs as they eat insects for obtaining nitrogen., Question 22., What is the stored food form in sunflower seeds?, Answer:, In sunflower seeds, glucose is stored in the form of oils (fats)., Question 23., What do you understand by saprotrophic mode of nutrition?, Answer:, The mode of nutrition in which organisms take their nutrients from dead and decaying matter is called saprotrophic mode of nutrition., Question 24., A mutually beneficial relationship that occurs between two plants. It is known by what name? Give an example., Answer:, Symbiosis is the mutually benefitting association between two plants, e.g. lichens., Question 25., For testing the presence of starch in leaves, a boiled leaf is used. Why?, Answer:, Boiling the leaf remove chlorophyll/green colour from the leaves., Question 26., Mosquitoes, bed bugs, lice and leeches suck our blood. Can they be called as parasites? [HOTS], Answer:, Yes, these animals/insects are parasites as they harm the hosts while they suck blood., Question 27., Insectivorous plants have one or the other specialised organs to catch their prey. What is that organ?, Answer:, Leaves of insectivorous plants catches the prey., Question 28., Farmers spread manure of fertilisers in the field or in gardens, etc. Why are these added to the soil?, Answer:, Plants absorb mineral nutrients from soil. Thus, declining their concentration in soil fertilisers and manures enhance or add these essential nutrients back in soil., Question 29., A cell is formed of many sub-components. Identify different constituents of the cell. Are animal and plant cells similar?, Answer:, A cell contains nucleus, cytoplasm, vacuole, cell organelles like chloroplast, mitochondria, etc. No, animal cells are different from plant cells., Question 30., A goat eats away all the leaves of a small plant (balsam). However, in a few days, new leaves could be seen sprouting in the plant again. How did the plant survive without leaves? [NCERT Exemplar; HOTS], Answer:, The plant of balsam survived on the food stored in the stem and roots., Nutrition in Plants Class 7 Science Extra Questions Short Answer Type, Question 1., Different modes of nutrition has been observed in plants. What are they? Give example of each., Answer:, Plants show two major modes of nutrition, i.e., (i) Autotrophs are those which can synthesise their own food., (ii) Heterotrophs are those which are dependent on other plants and animals for their food. They are of following types:, (a) Parasites, e.g. Cuscuta, (b) Saprotrophs, e.g. fungi., Question 2., Sunlight, chlorophyll, carbon dioxide, water and minerals are raw materials essential for photosynthesis. Do you know where they are available? Fill in the blanks with the appropriate raw materials., (a) Available in the plant: ………, (b) Available in the soil: ………, (c) Available in the air: ………, (d) Available during day : ……… [NCERT Exemplar], Answer:, (a) Available in the plant: chlorophyll, (b) Available in the soil : water, minerals, (c) Available in the air : carbon dioxide, (d) Available during day : sunlight, Question 3., Plants are considered an essential part of earth as they keep a check on lot of process occurring all over. What would happen if all the green plants are wiped from earth? [HOTS], Answer:, Green plants are the source of energy for all the living organisms so that they can perform their normal functions. If all green plants and trees disappear, all the organism depending on them for food and shelter will also die., The lack of gaseous exchange will lead to increase in amount of CO2, causing death in humans and other animals also. The cycle of life will gradually disappear., Question 4., Autotrophs and heterotrophs are two different organisms with distinct modes of nutrition state. How are they different from each other?, Answer:, The difference between autotrophs and heterotrophs are as follows:, Question 5., Wheat dough if left in the open, after a few days, starts to emit a foul smell and becomes unfit for use. Give reason. [NCERT Exemplar; HOTS], Answer:, Carbohydrates in wheat dough encourage the growth of yeast and other saprophytic fungi which breakdown carbohydrates into simpler compounds like CO2 and alcohol and emit a foul smell., Question 6., What are the various raw materials for photosynthesis?, Answer:, Plants utilise carbon dioxide from air and water and minerals are derived from soil (through roots) as raw material for photosynthesis. Besides these chlorophyll present in green leaf is necessary for the process and sunlight is the source of energy which is converted into chemical energy during the process of photosynthesis., Question 7., Observe the given figure and label the following terms given in the box. Stomatal opening, guard cell, , Answer:, Labelled figure is given below:, Question 8., Nitrogen is an essential nutrient for plants growth. But farmers who cultivate pulses as crops like green gram, bengal gram, black gram, etc., do not apply nitrogenous fertilisers during t cultivation. Why? [NCERT Exemplar; HOTS], Answer:, Roots of pulses (leguminous plants) have a symbiotic association with a bacterium called Rhizobium. This bacteria convert gaseous nitrogen of air into water soluble nitrogen compounds and give them to the leguminous plants for their growth. Hence, farmers need not use nitrogenous fertilisers., Question 9., Pooja is worried about her new shoes which she wore on special occassions that they were spoiled by fungus during rainy season. Is she right to worry, if yes, then tell why does fungi suddenly appears during the rainy season? [HOTS], Answer:, Yes, the fungi reproduces by spores which are generally present in the air and grow on any article that are left in hot and humid weather for a long time. During rainy season they land on wet and warm things and begin to germinate and grow., Question 10., In what unique manner does a pitcher plant derive its nutrition?, Answer:, Nepenthes or pitcher plant modifies its leaf axis into a long tubular pitcher to form a pitfall trap. Inside the pitcher sticky liquid is present. When any insect comes in contact with the leaf, the lid present on it is closed and insect is trapped. The liquid contains digestive enzymes which slowly digest the trapped insects., Question 11., Water and minerals are absorbed by the roots and then transported to leaves. How?, Answer:, Water and minerals are transported to the leaves by the vessels which run like pipes throughout the root, stem, branches and the leaves. These vessels are xylem and phloem, forming a continuous path or passage for the nutrients to make them reach the leaf., Question 12., Some plants have deep red, violet or brown coloured leaves. Can these leaves perform the photosynthesis process? [HOTS], Answer:, Yes, plants having deep red, violet or brown coloured leaves can also carry out photosynthesis because they contain chlorophyll. But their green colour of chlorophyll is masked by the large amount of all other coloured pigments., Question 13., If plant has a requirement for nitrogen, then from where will they obtain it?, Answer:, Soil contains nitrogen in the form that is not usable by plants. Bacteria like Rhizobium converts nitrogen into soluble form that can be easily used by plants. So, if plant has a requirement for nitrogen, then it will obtain that which the help of bacteria., Question 14., In the absence of photosynthesis, life would be impossible on earth. Is it true or false?, Answer:, True, because photosynthesis is important for the existence of life on the earth. Photosynthesis is important process as it is provides food to all living organisms and maintains CO2 – O2 balance of nature., Nutrition in Plants Class 7 Science Extra Questions Long Answer Type, Question 1., Describe the process by which plants prepare their food using different raw materials., Answer:, The process by which green plants can prepare their own food is called photosynthesis. Green plants possess chlorophyll in their leaf and utilises carbon dioxide (from air) water, minerals (from soil, through root) as raw material and sunlight as source of energy and convert light energy into chemical energy. The food thus synthesised is in the form of starch (carbohydrate). The overall reaction for photosynthesis can be given as follows:, Question 2., Describe the method for replinishing the soils with minerals and other essential constituents used by plants growing in those soil by farmers., Answer:, Replenishment of Nutrients in Soil, Crops require a lot of nitrogen to make proteins. After the harvest, the soil becomes deficient in nitrogen. Plants cannot use the nitrogen gas available in atmosphere directly. Action of certain bacteria can convert this nitrogen into form readily used by plants. Rhizobium bacteria live in the root nodules of leguminous plants. These bacteria take nitrogen gas from the atmosphere and convert it into water soluble nitrogen compounds making it available to the leguminous plants for their growth., In return, leguminous plants provide food and shelter to the bacteria as Rhizobium cannot prepare its food. They, thus have a symbiotic relationship. This association is very important for the farmers, as they do not need to add nitrogen fertilisers to the soil in which leguminous plants are grown., Question 3., Harish went to visit his grandfather in village where he saw that his grandfather’s field of wheat are infected with fungus but no one is aware of this. Harish rushed to his grandfather’s side and told him that the field have been infected with fungi. He should use an antifungal agent in his fields to stop this infection., (a) What is fungus?, (b) Can fungus only cause diseases or can it be helpful also?, (c) What values are shown by Harish? [Value Based Question], Answer:, (a) Fungus are saprophytic organisms usually present as spores in atmosphere which can germinate on any substrate in optimal conditions., (b) Fungus are also useful in that they produce many antibiotics which can cure different types of infections like penicillin., (c) Harish is sincere, curious and knowledgeable with a keen sense of applying it where necessary., Question 4., Wild animals like tiger, wolf, lion and leopard do not eat plants. Does this mean that they can survive without plants? Can you provide a suitable explanation? [HOTS], Answer:, Animals like tiger, wolf, lion and leopard are carnivores and do not eat plants. They hunt and eat herbivorous animals like deer, gaur, bison, zebra, giraffe, etc., which are dependent on plants for food., If there are no plants, herbivorous animals will not survive and ultimately animals like tiger, wolf, lion and leopard will have nothing to eat., Question 5., Asha went to visit her grandfather in his village. He was having a serious discussion with his fellow members regarding the productivity level of crops for present year. They all were worried about how to increase the productivity of crop Asha listened to this and then suggested to the group that the reason may be decreased level of minerals in soil., She told her grandfather to plant crops like pulses, gram, beans, etc., for a year then follow with regular crops. This will increase the crop productivity?, (a) What will you name the process suggested by Asha? Why is there decrease in crop productivity?, (b) What are noted benefits of this process? Will the results be as what Asha expressed?, (c) What values are shown by Asha? [Value Based Question], Answer:, (a) This process is known as crop rotation. All the plants/crops grown in soil use the minerals present in soil for their own use. This continuous usage depletes the concentration of mineral in soil., (b) After growing leguminous plants, the mineral content of soil is restored and enriched to new level. Yes, the benefit of leguminous plant is the re-enrichment of soil minerals., (c) Asha is observant, sincere and interested in applying her knowledge to situations., Nutrition in Animals Class 7 Science Extra Questions and Answers, Very Short Extra Questions and Answer, 1. Do all animals have the same mode of nutrition?, Answer: No, 2. Name the mode of nutrition in which solid whole food particles is ingested., Answer: Holozoic, 3. What is the organ that stores bile?, Answer: Gall bladder, 4. Which part of the digestive canal is involved in killing bacteria?, Answer: Stomach, 5. Name the part of digestive canal involved in chewing of food., Answer: Mouth, 6. Where are fats digested in the body?, Answer: Fats are mainly digested in the small intestine., 7. Where is the water from undigested food absorbed in the body?, Answer: Water from undigested food is absorbed in the body in large intestine., 8. What kills bacteria that enter along with the juices to act?, Answer: The acid kills many bacteria that enter along with the juices to act., 9. Where food is completely digested?, Answer: The food is completely digested in the small intestine., 10. Where are faeces formed in the human body?, Answer: Faeces are formed in the human body in large intestine., 11. Which glands secrete saliva?, Answer: Salivary glands secrete saliva., 12. Where food is absorbed in our body?, Answer: Absorption of food takes place in small intestine., 13. Which gland in our body secretes bile?, Answer: Bile is a digestive juice that is secreted by the liver., 14. Where faeces are stored?, Answer: Faeces are stored in rectum., 15. What are the end products of carbohydrate?, Answer: The carbohydrates get broken into simple sugars such as glucose., 16. Name the end products of fats., Answer: Fatty acids and Glycerol, 17. Write the end products of proteins., Answer: Amino acids, 18. What causes diarrhoea in human beings?, Answer: It may be caused by an infection, food poisoning or indigestion., 19. Which is the largest gland in the human body?, Answer: Liver is the largest gland in human body., 20. What is ingestion?, Answer: The process of taking food into the body is called ingestion., 21. What are the different types of teeth?, Answer: We have different types of teeth: incisor, canine, premolar and molar., 22. What does saliva do to food in our mouth?, Answer: The saliva breaks down the starch into sugars., 23. How does food pass from the mouth to the stomach?, Answer: Food is pushed down by movement of the wall of the food pipe., 24. What is rumen?, Answer: Ruminants have a large sac-like structure called rumen., 25. How does an amoeba move?, Answer: Amoeba use pseudopodia (false feet) to move., 26. What is the finger like projections present in the inner wall of the small intestine?, Answer: Villi, 27. Which organ expelled out the undigested and unabsorbed residues from human body?, Answer: Anus, 28. What are permanent teeth?, Answer: The second set that replaces a temporary milk teeth are the permanent teeth., Short Extra Questions and Answers, 1. What does animal nutrition include?, Answer: Animal nutrition includes nutrient requirement, mode of intake of food and its utilisation in the body., 2. What do you mean by animal nutrition?, Answer: Animal nutrition includes nutrient requirement, mode of intake of food and its utilisation in the body., 3. What are the different modes of feeding in animals?, Answer: Scraping, chewing, brewing, capturing and swallowing, sucking etc. are the different mode of feeding in animals., 4. What is digestion?, Answer: The breakdown of complex components of food into simpler substances is called digestion., 5. Name the glands that secrete digestive juices., Answer: Glands associated such as salivary glands, the liver and the pancreas secrete digestive juices., 6. What is diarrhoea?, Answer: Sometime we may have experienced the need to pass watery stool frequently. This condition is known as diarrhoea., 7. What is ORS?, Answer: Boiled and cooled water with a pinch of salt and sugar dissolved in it is called Oral Rehydration Solution (ORS)., 8. Where is the bile produced? Which component of the food does it help to digest?, Answer: Bile is produced in liver. The bile plays an important role in the digestion of fats., 9. What are ruminant animals?, Answer: The grazing animals like cows, buffaloes and deer are known as ruminants., 10. Where is the pancreas located in human body?, Answer: The pancreas is a large cream colored gland located just below the stomach., 11. How does an amoeba capture its food?, Answer: Amoeba captures its food with the help of finger-like projections, called pseudopodia or false feet., 12. What do pancreatic juices digest?, Answer: The pancreatic juice acts on carbohydrates, fats and proteins and changes them into simpler forms., 13. What is absorption in terms of digestion?, Answer: The digested food passes into the blood vessels in the wall of the intestine. This process is called absorption., 14. What do you mean by rumination?, Answer: A process in which partially digested food returns to the mouth in small lumps and the animal chews it is called rumination., 15. What is cud?, Answer: Cud is partly digested food returned from stomach (called rumen) of ruminants to the mouth for further chewing., 16. What are milk teeth?, Answer: The first set of teeth grows during infancy and they fall off at the age between six to eight years. These are termed milk teeth., 17. What are the major culprits of tooth decay?, Answer: Chocolates, sweets, soft drinks and other sugar products are the major culprits of tooth decay., 18. Why do we get instant energy from glucose?, Answer: In the cells, glucose breaks down easily with the help of oxygen into carbon dioxide and water, and energy is released., 19. What are the main parts of the alimentary canal?, Answer: The canal can be divided into various compartments: (1) the buccal cavity, (2) foodpipe or oesophagus, (3) stomach, (4) small intestine, (5) large intestine ending in the rectum and (6) the anus., 20. How is food prevented from entering the windpipe?, Answer: During the act of swallowing a flap-like valve closes the passage of the windpipe and guides the food into the foodpipe. If, by chance, food particles enter the windpipe, we feel choked, get hiccups or cough., 21. What is small intestine?, Answer: The small intestine is highly coiled and is about 7.5 metres long. It receives secretions from the liver and the pancreas. Besides, its wall also secretes juices., Long Extra Questions and Answers, 1. Why we cannot digest cellulose like the cattle do?, Answer: Ruminants have a large sac-like structure called rumen between the oesophagus and the small intestine. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans., 2. Can we survive only on raw, leafy vegetables/grass? Discuss., Answer: No, human cannot survive only on raw, leafy vegetables, or grass because they are rich in cellulose, which is a type of carbohydrate that humans are not able to digest due to the absence of cellulose-digesting enzymes., 3. Explain the process of digestion in grass eating animals., Answer: Grass eating animals quickly swallow the grass and store it in a part of the stomach called rumen. Here the food gets partially digested and is called cud. But later the cud returns to the mouth in small lumps and the animal chews it., 4. Write a short note on digestion in starfish., Answer: Starfish feeds on animals covered by hard shells of calcium carbonate. After opening the shell, the starfish pops out its stomach through its mouth to eat the soft animal inside the shell. The stomach then goes back into the body and the food is slowly digested., 5. Write a short note on large intestine., Answer: The large intestine is wider and shorter than small intestine. It is about 1.5 metre in length. Its function is to absorb water and some salts from the undigested food material. The remaining waste passes into the rectum and remains there as semi-solid faeces., 6. How can we prevent tooth decay?, Answer: We can prevent tooth decay in the following manner:, By cleaning the teeth with a brush or datun and dental floss at least twice a day and rinse the mouth after every meal., By not putting dirty fingers or any unwashed object in the mouth., 7. What are villi? What is their location and function?, Answer: The inner walls of the small intestine have thousands of finger-like outgrowths. These are called villi (singular villus). These are found in small intestine., Functions, The villi increase the surface area for absorption of the digested food., The surface of the villi absorbs the digested food materials., 8. What are the functions of the tongue in human body?, Answer: Functions of the tongue in human body, It helps in talking., It mixes saliva with the food during chewing and helps in swallowing food., It has taste buds that detect different tastes of food., 9. Draw a labeled diagram of amoeba., Answer:, 10. Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also., Answer: Cellulose is a type of carbohydrate that can be digested by ruminants but not by humans. Ruminants have a large sac-like structure called rumen between the oesophagus and the small intestine. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans., 11. What is tooth decay?, Answer: Bacteria are present in our mouth but they are not harmful to us. However, if we do not clean our teeth and mouth after eating, many harmful bacteria also begin to live and grow in it. These bacteria break down the sugars present from the leftover food and release acids. The acids gradually damage the teeth. This is called tooth decay., 12. Explain the process of nutrition in Amoeba., Answer: Amoeba feeds on some microscopic organisms. When it senses food, it pushes out pseudopodia around the food particle and engulfs it. The food becomes trapped in a food vacuole. Digestive juices are secreted into the food vacuole. They act on the food and break it down into simpler substances. Gradually the digested food is absorbed., 13. What substances are secreted in the stomach?, Answer: The inner lining of the stomach secretes mucous, hydrochloric acid and digestive juices. The mucous protects the lining of the stomach. The acid kills many bacteria that enter along with the food and makes the medium in the stomach acidic and helps the digestive juices to act. The digestive juices break down the proteins into simpler substances., 14. Write one similarity and one difference between the nutrition in amoeba and human beings., Answer: Similarity, In amoeba, digestive juices are secreted into the food vacuole. They act on the food and break it down into simpler substances. Gradually the digested food is absorbed. In human, digestive juices are secreted in buccal cavity, liver and small intestine., Difference, Amoeba captures its food with help of pseudopodia. In human being, food is taken into the body through the mouth., 15. How does the stomach work?, Answer: The stomach is a thick-walled bag. Its shape is like a flattened U and it is the widest part of the alimentary canal. It receives food from the food pipe at one end and opens into the small intestine at the other. The inner lining of the stomach secretes mucous, hydrochloric acid and digestive juices. The mucous protects the lining of the stomach. The acid kills many bacteria that enter along with the food and makes the medium in the stomach acidic and helps the digestive juices to act. The digestive juices break down the proteins into simpler substances., 16. Complete the following table., Answer:, 17. Complete the following table., Answer:, 18. Draw a labeled diagram of digestive system of cow., Answer:, 19. Draw a labeled diagram showing arrangement of teeth and different type of teeth., Answer:, 20. Draw a labeled diagram of human digestive system., Answer:, Fibre to Fabric Class 7 Science Extra Questions and Answers, Very Short Extra Questions and Answer, 1. Of which nutrient silk fibre is made?, Answer:  Protein, 2. What are silkworms?, Answer:  Silkworm are caterpillars of silk moth., 3. Which parts of the black sheep have wool?, Answer: The hairy skin of the sheep has wool., 4. What is meant by the white fleece of the lamb?, Answer: The white fleece of the lamb means white color hairy skin., 5. What is Sericulture?, Answer: The rearing of silkworms for obtaining silk is called sericulture., 6. What is the scientific name of mulberry?, Answer: Scientific name of mulberry is Morus alba., 7. Name some animals which give us wool., Answer: sheep, goat and yak, 8. Which leads the world in silk production?, Answer: China leads the world in silk production., 9. Is silk a good conductor of heat?, Answer: Silk is a protein fibre and is a non-conductor of heat., 10. What do you mean by yarn?, Answer: Yarn is a long continuous thread that is made up of fibre., 11. Name some Indian breed of sheep., Answer: Lohi, Rampur bushair, Nali, Bakharwal, Marwari and Patanwadi, 12. What are the different types of silk?, Answer: mulberry silk, tassar silk, eri silk, mooga silk, etc., 13. Define spinning., Answer: The process of making yarn from fibres is called spinning., 14. What is the most common silk moth?, Answer: The most common silk moth is the mulberry silk moth., 15. What do you understand by wool?, Answer: Wool is a fibre obtained from sheep, goat, yak and some other animals., Short Extra Questions and Answers, 1. What do you mean by occupational hazards?, Answer: Risks faced by workers in any industry are called occupational hazards., 2. What is cocoon?, Answer: The caterpillar completely covers itself by silk fibres and turns into pupa. This covering is known as cocoon., 3. Where does angora wool come from?, Answer: Angora wool is obtained from angora goats, found in hilly regions such as Jammu and Kashmir., 4. What are silkworms?, Answer: The female silk moth lays eggs, from which hatch larvae which are called caterpillars or silkworms., 5. What is weaving?, Answer: Weaving is the process of arranging two sets of yarns together to make a fabric., 6. What is Rearing?, Answer: Rearing of animal includes day-to-day care, selective breeding and the raising of animal., 7. What is called reeling the silk?, Answer: The process of taking out threads from the cocoon for use as silk is called reeling the silk., 8. Why caterpillars need to shed their skin when they grow bigger?, Answer: Caterpillars’ bodies grow but their exoskeleton doesn’t grow. Hence, they have to shed their exoskeletons when they grow bigger., 9. What do you mean by shearing?, Answer: The fleece of the sheep along with a thin layer of skin is removed from its body. This process is called shearing., 10. Write the sequence of steps involved in the processing of wool., Answer: Steps involved in the processing of wool are: Shearing, Scouring, Sorting, Picking out burrs, Dyeing of fibres, Making of yarn., 11. How are Pashmina Shawls made?, Answer: Wool is also obtained from goat hair. The under fur of Kashmiri goat is soft. It is woven into fine shawls called Pashmina shawls., 12. Why sheep have a thick coat of hair?, Answer: Hair trap a lot of air. Air is a poor conductor of heat. So, thick coat of hair keeps these animals warm., 13. What is fibre?, Answer: A fibre is a long strong thread, which is obtained from natural sources like plants or manmade sources like synthetic fibres., 14. How and when shearing is done?, Answer: Machines similar to those used by barbers are used to shave off hair. Usually, hair are removed during the hot weather., 15. Why shearing does not hurt the sheep?, Answer: Shearing does not hurt the sheep because the uppermost layer of the skin is dead. Also, the hair of sheep grow again just as our hair does., 16. What is scouring?, Answer: The sheared skin with hair is thoroughly washed in tanks to remove grease, dust and dirt. This is called scouring., 17. Where does angora wool come from?, Answer: Angora wool is obtained from angora goats, found in hilly regions such as Jammu and Kashmir., 18. What is silk route?, Answer: Traders and travellers introduced silk to other countries. The route they travelled is still called the ‘silk route’., 19. What do sheep feed on?, Answer: Sheep are herbivores and prefer grass and leaves. Apart from grazing sheep, rearers also feed them on a mixture of pulses, corn, jowar, oil cakes (material left after taking out oil from seeds) and minerals., 20. Where rearing and breeding of sheep is popular in India?, Answer: Rearing and breeding of sheep is popular in Jammu & Kashmir, Himachal Pradesh, Uttaranchal, Arunachal Pradesh and Sikkim, or the plains of Haryana, Punjab, Rajasthan and Gujarat., 21. What are the two types of fibres that form the fleece of a sheep?, Answer: The hairy skin of the sheep has two types of fibres that form its fleece:, (i) the coarse beard hair, and, (ii) the fine soft under-hair close to the skin., 22. Why caterpillars should not be collected with bare hands?, Answer: Caterpillars should not be collected with bare hands because they have thick stingy hair which may causes irritation to our skin. So, use a paper napkin or a paper to hold a caterpillar., Long Extra Questions and Answers, 1. Why sorter’s job in wool industry is a risky job?, Answer: Wool industry is an important means of livelihood for many people in our country. But sorter’s job is risky as sometimes they get infected by a bacterium, anthrax, which causes a fatal blood disease called sorter’s disease., 2. What is selective breeding?, Answer: Some breeds of sheep possess only fine under-hair. Their parents are specially chosen to give birth to sheep which have only soft under hair. This process of selecting parents for obtaining special characters in their offspring, such as soft under hair in sheep, is termed ‘selective breeding’., 3. Explain the process of obtaining silk from cocoon., Answer: A pile of cocoons is used for obtaining silk fibres. The cocoons are kept under the sun or boiled or exposed to steam. The silk fibres separate out. The process of taking out threads from the cocoon for use as silk is called reeling the silk. Reeling is done in special machines, which unwind the threads or fibres of silk from the cocoon. Silk fibres are then spun into silk threads, which are woven into silk cloth by weavers., 4. What do you know about discovery of silk?, Answer: The exact time of discovery of silk is perhaps unknown. According to an old Chinese legend, the empress Si-lung-Chi was asked by the emperor Huang-ti to find the cause of the damaged leaves of mulberry trees growing in their garden. The empress found white worms eating up mulberry leaves. She also noticed that they were spinning shiny cocoons around them. Accidentally a cocoon dropped into her cup of tea and a tangle of delicate threads separated from the cocoon. Silk industry began in China and was kept a closely guarded secret for hundreds of years., 5. Explain various steps involved in the process of making wool?, Answer: Steps, Shearing – The fleece of the sheep along with a thin layer of skin is removed from its body using shearing machine., Scouring – The sheared skin with hair is thoroughly washed in tanks to remove grease, dust and dirt. It is done by machines., Sorting- The hairy skin is sent to a factory where hair of different textures are separated or sorted., Picking of Burrs – The small fluffy fibres, called burrs, are picked out from the hair., Dyeing – The fibres can be dyed in various colours., Combing and Rolling – The fibres are straightened, combed and rolled into yarn., 6. Write a note on rearing silkworm., Answer: Rearing silkworms:, A female silk moth lays hundreds of eggs at a time. The eggs are stored carefully on strips of cloth or paper and sold to silkworm farmers., The farmers keep eggs under hygienic conditions and under suitable conditions of temperature and humidity., The eggs are warmed to a suitable temperature for the larvae to hatch from eggs. The larvae are kept in clean bamboo trays along with freshly chopped mulberry leaves., After 25 to 30 days, the caterpillars stop eating and move to a tiny chamber of bamboo in the tray to spin cocoons., Small racks or twigs may be provided in the trays to which cocoons get attached. The caterpillar or silkworm spins the cocoon inside which develops the silk moth., Heat Class 7 Extra Questions Science Chapter 4, Heat Class 7 Science Extra Questions Very Short Answer Type, Question 1., In a mercury thermometer, the level of mercury rises when its bulb comes in contact with a hot object. What is the reason for this rise in the level of mercury? [HOTSl, Answer:, As the temperature increases, then expansion in mercury takes place which leads to the rise in the level of mercury in thermometer., Question 2., Shopkeepers selling ice blocks usually cover them with jute sacks. Explain why. [NCERT Exemplar; HOTS], Answer:, As we know that jute sacks is thermal insulators, it helps ice not to be melt immediately. So, shopkeepers used to cover ice blocks with jute sacks., Question 3., The radiators in cars are painted black. Explain why. [HOTS], Answer:, Since, the black bodies are better radiators, so due to this reason, radiators in cars are painted black., Question 4., To keep her soup warm, Paheli wrapped the container in which it was kept with a woollen clothes. Can she apply the same method to keep a glass of cold drink cool? Give reason for your Answer: [NCERT Exemplar; HOTS], Answer:, Yes, she can apply the same method to keep a glass of cold drink cool because wool is a thermal insulator, and it cannot allow to heat pass through it., Question 5., A laboratory thermometer A is kept 7 cm away on the side of the flame while a similar thermometer B is kept 7 cm above the flame of a candle as shown in figure. Which of the thermometers A or Swill show a greater rise in temperature? Give reason for your answer: [NCERT Exemplar], , Answer:, Thermometer B will show a greater rise in temperature because heated air above the candle rises immediatly and increase the temperature of bulb of thermometer B quite greater than A., Question 6., While constructing a house in a coastal area, in which direction should the windows preferably face and why?, Answer:, Window should preferably towards the sea beach so that the sea breeze coming from sea keeps the house cool during the day time., Question 7., A circular metal loop is heated at point O as shown in figure. [NCERT Exemplar], , (a) In which direction, would heat flow in the loop?, (b) In which order, the pins at points P, Q and R fixed with the help of wax fall if points O, P, Q and R are equidistant from each other?, Answer:, (a) Heat will flow in both the directions from O to P and from O to R., (b) First of all pin at P and R will fall simultaneously after that pin at Q will fall., Question 8., The mercury does not fall or rise in a clinical thermometer when taken out of the mouth. Explain why., Answer:, Because of the kink present in the thermometer, the mercury does not fall or rise., Question 9., If a pan is removed from the fire, then why does it cool down?, Answer:, When a pan is removed from the fire, it loses heat to the surroundings by radiation and it cools down., Question 10., Name the mode of transfer of heat in which medium is not required., Answer:, Radiation is the mode of transfer of heat in which medium is not required., Question 11., It is preferred to use two thin blankets rather than one thick blanket. Explain the reason. [HOTS], Answer:, In case of two thin blankets, there is an air gap which does not allow heat pass out from the body and it is not as such as in case of one thick blanket., Question 12., Why is it advised not to hold the thermometer by its bulb while reading it?, Answer:, It is advised not to hold the thermometer bulb while reading it as the level of mercury increases from the actual reading by our body temperature., Question 13., Briefly mention one application of kink in the clinical thermometer., Answer:, The clinical thermometer consists of kink which prevents the mercury level from falling on its own., Question 14., Explain how do we find out how hot an object really is., Answer:, By using thermometer, we can measure the degree of hotness of a body., Question 15., Is the body temperature of every person 37°C?, Answer:, No, the body temperature of every person is not 37°C. It is an average temperature. It could be slightly higher or slightly lower., Question 16., How can we measure the temperature of other object rather than human body?, Answer:, Temperature of other object is measured with laboratory thermometer because clinical thermometer is not suitable for higher temperature., Question 17., How does the heat travel in air?, Answer:, Heat travels in air through convection., Question 18., We are advised to use an umbrella when you go out in the sun. Comment., Answer:, We use an umbrella to protect us from heat coming from the sun in the form of radiation., Question 19., You may have noticed that a few sharp jerks are given to clinical thermometer before using it. Why is it done so? [NCERT Exemplar; HOTS], Answer:, Jerks are given to clinical thermometer before using it to settle down the mercury level below normal temperature so that the measurement taken of a body be accurate., Heat Class 7 Science Extra Questions Short Answer Type, Question 1., The handle of a pressure cooker is covered with the thick plastic. Explain why., Answer:, As we know that plastic is a bad conductor of heat due to which the heat from the cooker does not flow to its handle and we can hold it easily., So, this is a reason because of which the handle of a pressure cooker is covered with the thick plastic., Question 2., Differentiate between two modes of transfer of heat, i.e. convection and conduction., Answer:, Difference between convection and conduction, Question 3., While reading a clinical thermometer, what precautions should we take?, Answer:, Reading a Clinical Thermometer, There are following steps to read the temperature on a thermometer., Step I, Firstly, wash the thermometer with an antiseptic solution and if in case, the antiseptic solution is not available, then wash it with a clean water., Step II, Gently, hold the thermometer tube in your hand and give it a jerk in such a way that the mercury thread in the thermometer tube falls below the reading of 35°C., Step III, Now, put the bulb of the thermometer under the tongue of the patient for about one minute. Then take out the thermometer from patient’s mouth., Step IV, In order to read the temperature, hold the thermometer horizontally in your hand and rotate it slowly. When we see a magnified image of the mercury thread in its tube, then a position will come. Now, read the temperature on thermometer tube in level with the top of the mercury thread., Precautions while Reading the Thermometer, A clinical thermometer should not be used for any object other than the human body. There are some following precautions which are to be observed while reading a clinical thermometer., Wash the clinical thermometer before and after using preferably with an antiseptic solution., Be ensure that the mercury level before using the clinical thermometer should be below 35°C., The clinical thermometer should be read by keeping the level of mercury along the line of sight., While reading the clinical thermometer, it should never be held by the bulb., The clinical thermometer should be carefully handled., Question 4., Observe the picture given in figure. Water is being boiled in a pan of wide base., , (a) Which position P or T will feel warmer?, (b) Fill up the boxes P and T to indicate the mode of flow of heat to the hand., Answer:, (a) As in the given diagram, position P will feel warmer because of heat, air rises., (b) The flow of heat to P is a convection process and flow of heat to T is radiation., Question 5., For setting curd, a small amount of curd is added to warm milk. The microbes present in the curd help in setting if the temperature of the mixture remains approximately between 35°C to 40°C. At places where room temperature remains much below the range, setting of curd becomes difficult. Suggest a way to set curd in such a situation.[NCERT Exemplar; HOTS], Answer:, For the setting of curd where temperature is below room temperature, the container in which curd is to be made must be kept in a thermally insulated cover or it can be wrapped with wool or jute sacks so that temperature is maintained for the setting of curd., Question 6., State the limitation of clinical thermometer., Answer:, The clinical thermometer cannot be used for measuring the temperature of any object more than 42°C (i.e. more than the body temperature). If it kept in the sun or near a flame, then this clinical thermometer can be break., Question 7., Explain in brief, why we wear dark coloured clothes in winter and light coloured clothes in summer., Answer:, We wear dark coloured clothes in winter to keep us warm as they absorb all the heat radiation coming from the sun whereas light coloured clothes reflect most of the heat radiation coming from the sun that falls on them and therefore we feel more comfortable wearing them in the summer., Question 8., Explain the reason for the shiny reflectors of room heaters., Answer:, Since, the shiny surface absorbs very little heat due to which the reflectors reflect all the heat which makes the room heaters more effective. So, due to this reason, room heaters have shiny reflectors., Question 9., Describe the effects of heat., Answer:, The effects of heat are, (i) When an object is heated, then it becomes hotter and may get expand. So, in this heat may change the state of the body like ice can also get change into the water., (ii) Heat sometimes acts as a catalyst to speed up the chemical reaction., (iii) Heat can even kill the bacteria as well., Question 10., The freezer is located at the top of the refrigerator. Explain why., Answer:, The freezer is located at the top of the refrigerator. It is because the air inside and around the compartments of freezer gets cool and move downwards and on the other side, the lesser cool air moves upward to get cooled., So, as a result of this, convection of heat are setup in the air and the tower section of the . refrigerator also gets cooled faster. ., Question 11., Instead of water explain the reason, why do the mercury is used in the thermometer?, Answer:, Due to following reasons, mercury is used in the thermometers instead of water, When the thermometer breaks, the mercury can be easily collected., Mercury can has more expansion than the water., Also, mercury do not stick on the walls of thermometer like water., Question 12., Explain the reason for the general fitting of air conditioner at higher level on the wall of the room., Answer:, As a fact that warm air is much lighter than the cold air, so being heavier the cold air from air conditioner moves downwards while the hot air moves upwards at the lower level and gets cooled and come downwards once again. So, due to this convection of heat are set in the air and room gets warmer faster., Question 13., Briefly explain, why do the kites and eagles fly without flapping their wings., Answer:, As it is a fact that the hot air during the day time surrounds the land gradually and rises up, due to which a convection air of heat develops. So, kites and eagles start moving along this rising current of heat without flapping the wings to fly high up in the sky., Question 14., In the arrangements A and B as shown in figure, pins P and Q are fixed to a metal loop and an iron rod with the help of wax. In which case are both the pins likely to fall at different times? Explain., , Answer:, As in the given figures A and B, in case A P and Q got equal heat, so pin fix at P and Q in case of a fall simultaneously., But in case of B pin at point P falls first than after pin at Q will fall as because heat received at P is greater than Q at the same time., Question 15., At a camp site there are tents of two shades. One made with black fabric and the other with white fabric. Which one will you prefer for resting on a hot summer afternoon? Give reason for your choice. Would you like to prefer the same tent during winter? [HOTS], Answer:, We will prefer white fabric tent in case of summer because it reflects all the radiations from the sun and keeps us cool inside the tent., But in ease of winter, we should not use white fabric tent, we should use black fabric tent as it absorbs all colours of light from the sun and keeps us warm inside the tent., Question 16., Briefly explain the maximum and minimum thermometers., Answer:, Maximum and minimum thermometers are the special thermometers which automatically record the maximum and minimum temperature of the day. The maximum and minimum temperature of the last day reported in weather reports in TV and newspapers are measured by the maximum and minimum thermometers., Question 17., Explain the reason for serving of tea in China clay cup and plates., Answer:, Tea is generally served in China clay cup and plates because China clay is a bad conductor of heat which do not allow the heat to pass through it and hence keep the tea hot., Question 18., Describe briefly about the direction of the convection current during ventilation., Answer:, Since, with the help of ventilators, warm air being higher get rises up and leaves the room. Even the fresh air enters the room from outside through the doors and windows., Question 19., Explain the reason for wrapping of ice in gunny bags., Answer:, Since, we know that gunny bags consist of number of fine pores which are filled with air. As air is a bad conductor of heat, so due to this reason, it does not allow the external heat to move inside and melts the ice., Question 20., Mention any two examples each of insulators as well as of conductors., Answer:, Copper and aluminium are the examples of conductors which allow the heat to pass through them. While wood and plastic are the examples of insulators which do not allow the heat to pass through them., Question 21., The clinical thermometer is not used to measure high temperature. Why?, Answer:, Clinical thermometer has the range 35°C to 42°C. If we use it to measure high temperature, it may break and mercury present in the clinical thermometer is harmful. So, we cannot use clinical thermometer to measure high temperature., Heat Class 7 Science Extra Questions Long Answer Type, Question 1., Explain the differences between heat and temperature., Answer:, The differences between heat and temperature are given as below, Question 2., Explain the reason for the following statement, “When heat is applied at the bottom of the water vessel, then, it gets heated more quickly than when it is heated at the top.” [HOTS], Answer:, The particles of water become more lighter and rise up in the middle. Due to this, the cold particles of water which are heavier come down along the sides of the vessel. So, the convection currents of heat are setup and water becomes hot. The moment, when the heat is applied at the top, then the water present in the upper portion becomes hot and these hot water molecules get fixed over the surface. Since, water is a bad conductor of heat, due to which water present at the lower end (or bottom) of the vessel remains., Question 3., Prove with the help of an experiment that heat radiation can travel through vacuum., Answer:, First of all, take a flat bottom flask and fix a rubber stopper having two holes in the mouth of the flask. Shift a thermometer through one hole and a glass tube with stopper through the other hole. Now, with the help of a vacuum pump, remove the air from the flask and try to record the temperature from the thermometer. Put a flask in the bright sunlight and we will observe that the thermometer records a rise in temperature. So, on this basis, we can say that this experiment proves that the heat radiation can travel through vacuum., Question 4., On last Monday, Pankaj was dealing immense cough and cold. Besides this, he was suffering from a great headache. So, he decided to take a leave on that day so that he could take some rest at his home. After one hour he thought to check his fever through a clinical thermometer, so before using it, he washed it and started shaking it very fastly in his hand, so that the mercury level of thermometer gets reduced. At the same time, his elder brother Vishwas scold him and suggested him to shake the thermometer slowly., (a) State some precautionary measures while checking the fever through a clinical thermometer., (b) Mention the values showed by the elder brother of Pankaj (i.e. Vishwas). [Value Based Question], Answer:, (a) The following precautionary measures while checking the fever through a clinical thermometer are, (i) While reading the clinical thermometer, it should never be held by the bulb., (ii) The clinical thermometer should be washed properly (before and after use)., (b) The values showed by the elder brother of Pankaj, Vishwas, are concern towards the way of using the clinical thermometer and the importance of money as well., Question 5., Last Sunday, Pooja on her week off entered in her kitchen to cook rice for her family in lunch time. The moment she put fry pan on the gas stove and lighted it through the matchstick, all of sudden her 5 years small daughter entered into the kitchen and tends to touch the hot fry pan. At the same time, Pooja saw her and pushed her away from the hot fry pan. In this way, she saved her child., (a) Explain why do the fry pan are provided with the plastic handles?, (b) Mention the values represented by Pooja here towards her 5 years small daughter. [Value Based Question], Answer:, (a) As we know that plastic is a bad conductor of heat which does not allow the heat to pass through itself. So, heat from the fry pan does not flow to the handle due to which we can hold it easily. So that’s why, the fry pans are provided with the plastic handles., (b) The value showed by Pooja here is a great concern and careness towards her five years old small daughter., Question 6., Describe in detail about the occurrence of oceanic currents., Answer:, Since, it is a fact that the water present in the ocean (near the equator) is heated by the sun to a very higher temperature than the water near the poles of the earth. It is due to the falling of the sun rays perpendicularly in the equatorial region. So, in the equatorial region, the ocean water expands and becomes lighter., While on the other side, the water in the polar region remains cold and heavy. It leads to the flow of convection currents of heat of warm water from the equator towards the poles., Heat of the cold water flow from the poles towards the equator just below the surface of ocean. So, these types of currents are known as oceanic currents., Heat Class 7 Science Extra Questions Miscellaneous, Multiple Choice Questions, Question 1., A marble tile would feel cold as compared to a wooden tile on a winter morning because the marble tile, (a) is a better conductor of heat than the wooden tile, (b) is polished while wooden tile is not polished, (c) reflects more heat than wooden tile, (d) is a poor conductor of heat than the wooden tile, Answer:, (a) is a better conductor of heat than the wooden tile, Question 2., A beggar wrapped himself with a few layers of newspaper on a cold winter night. This helped him to keep himself warm because [NCERT Exemplar], (a) friction between the layers of newspaper produces heat, (b) air trapped between the layers of newspaper is a bad conductor of heat, (c) newspaper is a conductor of heat, (d) newspaper is at a higher temperature than the temperature of the surroundings, Answer:, (b) air trapped between the layers of newspaper is a bad conductor of heat, Question 3., Heat always flows, (a) from a colder object to a hotter object, (b) from a hotter object to a colder object, (c) in both the directions, (d) None of the above, Answer:, (b) from a hotter object to a colder object, Question 4., Paheli and Boojho measured their body temperature. Paheli found her to be 98.6°F and Boojho recorded 37°C. Which of the following statements is true?, (a) Paheli has a higher body temperature than Boojho., (b) Paheli has a lower body temperature than Boojho., (c) Both have normal body temperature., (d) Both are suffering from fever., Answer:, (c) These two temperatures are different scales but their actual values are equal., Question 5., Boojho has three thermometers as shown in figure. He wants to measure the temperature of his body and that of boiling water. Which thermometer(s) should he choose? [NCERT Exemplar], , (a) Thermometers (i) and (iii) for measuring body temperature and (ii) for measuring the temperature of boiling water, (b) Thermometer (i) for measuring temperature of both, (c) Thermometer (ii) for measuring temperature of both, (d) Thermometer (iii) for measuring temperature of both, Answer:, (a) Thermometers (i) and (iii) are clinical thermometer and (ii) is laboratory thermometer., Question 6., Four arrangements to measure temperature of ice in beaker with laboratory thermometer are shown in figure (a, b, c, d). Which one of them shows the correct arrangement for accurate measurement of temperature?, , Answer:, (a) Thermometer (a) has been put in correct way to measure the temperature., Question 7., Figure (a, b, c, d) shows the reading of four different thermometers. Indicate which of the reading shows the normal human body temperature?, , Answer:, (c) As we know that normal body temperature is 37°C. So, correct option is (c). ., Question 8., Figure (a, b, c, d) shows a student reading of a doctor’s thermometer. Which of the figure indicates the correct method of reading temperature? [NCERT Exemplar], , Answer:, (a) In first case, eyes of student are in level of the thermometer, so it is correct way to measure temperature using clinical thermometer., Fill in the Blanks, Question 1., Temperature is the measure of …….. of an object., Answer:, Fill in the Blanks, hotness, Question 2., The thermometer used to measure human body temperature is called …….. thermometer., Answer:, clinical, Question 3., The normal temperature of human body is …….. °C., Answer:, 37, Question 4., A …… near the bulb of a clinical thermometer prevents mercury level from falling of its own., Answer:, kink, Question 5., In ……. generally, the heat is transferred by the process of conduction., Answer:, solids, Question 6., The water and air are …… conductors of heat., Answer:, poor, Question 7., In coastal areas, cold air flows in the day from sea to land. It is called ……., Answer:, sea breeze, Question 8., When we come out in the sun, we feel …….., Answer:, warm, Question 9., All hot bodies radiate …….., Answer:, heat, Question 10., Wool is a ……. conductor of heat., Answer:, poor, True/False, Question 1., Our sense of touch about hotness or coldness is not always reliable., Answer:, True, Question 2., Normal temperature of human body is 98.6°C., Answer:, False, it is because the normal temperature of human body is 37°C., Question 3., In all cases, heat flows from a hotter object to a colder object., Answer:, True, Question 4., Water at higher temperature feels more hot., Answer:, True, Question 5., Marking on clinical thermometer is from 0°C to 100°C., Answer:, False, it is because the markings on the clinical thermometer is from 35°C to 100°C., Question 6., Shining thread in thermometer is the column of mercury., Answer:, True, Question 7., The materials which allow heat to pass through them easily are called conductors., Answer:, True, Question 8., Water and air are good conductors of heat., Answer:, False, it is because water and air are the poor conductors of heat., Match the Columns, Question 1., Match the Column I with Column II., Answer:, (a)-(ii). (b)-(v), (c)-(ii), (d)-(iv), (e)-(i), Question 2., Match the Column I with Column II., Answers:, (a)-(i), (b)-(v), (c)-(iv), (d)-(iii), (e)-(ii), Acids, Bases and Salts Class 7 Extra Questions Science Chapter 5, Acids, Bases and Salts Class 7 Science Extra Questions Very Short Answer Type Questions, Question 1., What is the test for acids and bases using litmus paper?, Answer:, Acids turn blue litmus paper red while bases turn red litmus paper blue., Question 2., What name is given to those substances which do not change the colour of either red or blue litmus paper?, Answer:, The solutions or substances which do not change the colour of either red or blue litmus paper are neutral., Question 3., Write the name of two indicators which occur naturally., Answer:, Turmeric, China rose, Question 4., Name the acid present in lemon juice and tomato., Answer:, Citric acid in lemon juice and oxalic acid in tomato., Question 5., Name a substance which is used to cure the discomfort caused by indigestion due to over eating., Answer:, Milk of magnesia which contains magnesium hydroxide (base) is used to neutralise the effect of excessive acid in stomach., Question 6., Why does a turmeric stain on white shirt is turned to red when it is washed with soap? [HOTS], Answer:, Turmeric stain on white shirt is turned to red when it is washed with soap because the soap solution is basic in nature., Question 8., Is lime water an acidic or basic solution?, Answer:, Lime water (calcium hydroxide) is a basic solution., Question 9., Name the reaction when an acid is mixed with base., Answer:, Neutralisation reaction., Question 10., Which acid is injected into our body by an ant sting that causes pain? [HOTS], Answer:, The acid is formic acid which is injected into the skin of a person when an ant bites., Question 11., Name the salt formed when hydrochloric acid reacts with sodium hydroxide solution (a base)., Answer:, When hydrochloric acid reacts with sodium hydroxide solution, then sodium chloride salt is formed., Question 12., Write two basic substances which we use in our daily life., Answer:, Baking soda, Soap or detergent, Question 13., Name one acid which is responsible for acid rain., Answer:, Carbonic acid., Question 14., Name two gaseous pollutants which are responsible for acid rain., Answer:, Two gaseous pollutants are nitrogen dioxide (NO2) and sulphur dioxide (SO2)., Question 15., (a) Name one indicator which turns red on adding an acid., (b) Name one indicator which turns red on adding a base., Answer:, (a) Litmus (blue litmus paper), (b) Turmeric, Question 16., Form a sentence using the following words: baking soda, ant bite, moist, effect, neutralised, rubbing [NCERT Exemplar; HOTS], Answer:, The effect of an arft bite can be neutralised by rubbing moist baking soda., Acids, Bases and Salts Class 7 Science Extra Questions Short Answer Type Questions, Question 1., Write the characteristics of acids by which we can identify acids., Answer:, Characteristics of acids are, They are sour in taste., They turn blue litmus paper/solution to red., Dilution of acid in water is an exothermic reaction, i.e. heat energy is evolved., Question 2., Look at the figure which shows solutions taken in test tubes A, B, C and D. What colour is expected, when a piece of red litmus paper is dropped in each test tube? Nature of the solutions is given in the table for your help., [NCERT Exemplar], Answer:, Nature of solution is given below:, Question 3., While playing in a park, a child was stung by a wasp. Some elders suggested applying paste of baking soda and others lemon juice as remedy. Which remedy do you think is appropriate and why? [NCERT Exemplar; HOTS], Answer:, Wasp sting inject a liquid in the skin which is acidic in nature. Hence, baking soda is the appropriate remedy as it is basic in nature and neutralises the acid., Question 4., Which of the following are acidic and which are basic?, Lime water, Vinegar, Toothpaste, Stomach juices, Lemon juice, Baking soda solution, Milk of magnesia, Ammonia solution., Answer:, Question 5., A small amount of hydrochloric acid is always produced in the stomach. Is it useful or harmful for us? If excess of acid is produced in the stomach, what should we do?, Answer:, A small amount of hydrochloric acid produced in the stomach is useful as it can kill the harmful bacteria that may enter into the stomach along with the food., However, if excess of acid is produced, there is a burning sensation in the stomach. We should take milk of magnesia as an antacid medicine to neutralise the excess acid., Question 6., Write the effect of China rose petals on acidic and basic solutions., Answer:, China rose petals when added to warm water, form a light pink coloured solution which may be used as an indicator. This indicator turns acidic solution to magenta (deep pink) and basic solution to green., Question 7., To test the presence of an acid in any substance, what methods can be used?, Answer:, Acid can be tested in any substance by the following methods, Take a drop of the dilute solution of the substance on the tips of your tongue. If tastes sour, it is acidic., Dip a blue litmus paper in the solution. If the colour of the litmus paper turns red, the solution is acidic., Question 8., Why are sodium bicarbonate and lemon juice used during indigestion?, Answer:, Sodium bicarbonate neutralises the acidity in the stomach. Hence, it is used during indigestion. Lemon contains acid. It reacts with undigested food and suffers it., Question 9., After carrying out the neutralisation reaction, the test tube immediately found to be somewhat hot. Explain why., Answer:, In neutralisation reaction, heat is always produced or evolved. The evolved heat raises the temperature of the reaction mixture. Therefore, if we touch the test tube immediately after the neutralisation reaction, it is found to be hot., Acid + Base → Salt + Water (heat is evolved), Question 10., Name three acids used in the laboratory., Answer:, Acids which are mostly used in laboratory as below, Hydrochloric acid (HCl), Sulphuric acid (H2SO4), Nitric acid (HNO3), Question 11., Paheli is suffering from indigestion due to acidity. Is it advisable to give her orange juice in this situation and why? |NCERT Exemplar; HOTS], Answer:, No, because orange juice is acidic in nature. Excess of acid in the stomach causes indigestion. We take an antacid such as milk of magnesia which contains magnesium hydroxide., Question 12., Explain two neutralisation reactions related to daily life situations., Answer:, (i) Ant bite When an ant bite injects the acidic liquid (formic acid) into the skin, the effect of the acid can be neutralised by rubbing moist baking soda (sodium hydrogen carbonate) or calamine solution, which contains zinc carbonate., (ii) Indigestion Our stomach contains hydrochloric acid. It helps us to digest food but too much of acid in the stomach causes indigestion. Sometimes, indigestion is painful. To relieve indigestion, we take an antacid such as milk of magnesia which contains magnesium hydroxide., It neutralises the effect of excessive acid., Question 13., How lime water is prepared in the laboratory?, Answer:, To prepare lime water, dissolve some lime (chuna) in water in a bottle. Stir the solution and keep it for sometime. Pour a little more from the top. This is lime water., Question 14., Name three types of salts. Give one example of each type of salt., Answer:, Type of salts, Neutral salts e.g. sodium chloride (NaCl), Acidic salts e.g. Ammonium chloride (NH4Cl), Basic salts e.g. sodium hydrogen carbonate (NaHCO3), Question 15., Paheli observed that most of the fish in the pond of her village were gradually dying. She also observed that the wastes of a factory in their village are flowing into the pond which probably caused the fish to die., (a) Explain why the fish were dying?, (b) If the factory waste is acidic in nature, how can it be neutralised? [NCERT Exemplar; HOTS], Answer:, (a) If the wastes of a factory flow into waterbodies, it can cause a threat to the lives of sea creatures and to anybody who drink the water. Since, factory wastes may contain acids or bases and it can kill the fish., (b) If the factory waste is acidic in nature, it can be neutralised by adding basic substances., Question 16., What is a salt? Name any salt and give their formulae., Answer:, A substance formed by the neutralisation of an acid with a base is called salt. Salt may be acidic, basic or neutral in nature., For example,, Hydrochloric acid (HCI) +, (Acid), Sodium hydroxide (NaOH) →, (Base), Sodium chloride (NaCI) + Water (Salt), (Salt), Question 17., Look at the given reaction., Hydrochloric acid + Sodium hydroxide (base) → Sodium chloride (salt) + Water, Sodium chloride formed in this reaction remains in solution form. Can we get solid sodium chloride from this solution? Suggest a method (if any). [NCERT Exemplar], Answer:, We can get solid sodium chloride by evaporation method. Evaporation is the process by which water changes from a liquid to a gas or vapour., Rate of evaporation increases with temperature., Question 18., Name three bases used in the laboratory with their formulae., Answer:, Bases which are mostly used in laboratory as below, Sodium hydroxide (NaOH), Calcium hydroxide [Ca(OH)2], Ammonium hydroxide (NH4OH), Acids, Bases and Salts Class 7 Science Extra Questions Long Answer Type Questions, Question 1., A farmer was unhappy because of his low crop yield. He discussed the problem with an agricultural scientist and realised that the soil of his field was either too acidic or too basic. What remedy would you suggest the farmer to neutralise the soil? [HOTS], Answer:, The reason for low crop yield in farmer’s field was that the soil at a place is either too acidic or too basic. The soil may be acidic or basic naturally. The excessive use of fertilisers in the fields also makes the soil too acidic. When the soil is too acidic, it is treated with base such as quicklime (calcium oxide) or slaked lime (calcium hydroxide) which neutralises the excess acid present in the soil and reduces its acidic nature. If the soil is too basic, then decaying organic matter (called manure or compost) is added it. The decaying organic matter releases acid which neutralises the excess bases present in the soil and reduces its basic nature., Question 2., You are provided with three test tubes A, Sand Cas shown in figure with different liquids. What will you observe when you put, (a) a piece of blue litmus paper in each test tube?, (b) a piece of red litmus paper in each test tube?, (c) a few drops of phenolphthalein solution to each test tube?, , Answer:, Question 3., Boojho, Paheli and their friend Golu were provided with a test, each containing China rose solution which was pink in colour. Boojho added 2 drops of solution ‘A’ in his test tube and got dark pink colour. Paheli added 2 drops of solution ‘S’to her test tube and got green colour. Golu added 2 drops of solution ‘C but could not get any change in colour. Suggest the possible cause for the variation in their results. [HOTS], Answer:, China rose (gudhal) is an acid-base indicator., China rose solution in different medium shows following changes:, China rose + acid → Give dark pink colour, hence A is an acidic solution., China rose + base → give green colour, hence 6 is a basic solution., China rose + neutral → No change in colour, hence C is a neutral solution., Question 4., Nitesh was playing with his friends in the garden. Suddenly, Nitesh was stung by a honeybee and was in great pain. Immediately, his friends call his mother. She applied baking soda solution on the affected area and then took him to the doctor., Read the above passage and answer the following questions:, (a) What could be the reason for this burning pain?, (b) Why did his mother applied baking soda solution on the affected area?, (c) What values are shown by Nitesh’s friends? [Value Based Question], Answer:, (a) The reason for this burning pain is honeybee sting which causes pain and irritation. This is due to the acidic liquid (formic acid) injected into the skin by the honeybee., (b) The effect of acid can be neutralised by rubbing the affected area by baking soda solution which is a mild base., (c) Nitesh’s friends are caring , supportive and helpful., Question 5., One day Rahul’s mother after taking meal felt pain and irritation in her stomach. His father was out of station. Rahul was an intelligent boy. He remembered his teacher’s statement and gave his mother some baking soda solution Which gave her a relief from pain and irritation of stomach., Read the above passage and answer the following questions., (a) Which information given by Rahul’s teacher that helped him to select the baking soda as remedy?, (b) Why he selects baking soda as a cure?, (c) What values are shown by Rahul? [Value Based Question], Answer:, (a) Rahul knows that our stomach contains hydrochloric acid. It helps us to digest food. But, too much acid in the stomach causes indigestion. Sometimes, indigestion is painful and some mild base should be taken to relief from this pain. So, this information given by his teacher helped him., (b) He gave her mother baking soda solution which was available in the kitchen easily. He selects baking soda because it is a mild base and neutralises the excess acid in the stomach and it will give relief from pain., (c) Rahul is very intelligent and caring boy., Acids, Bases and Salts Class 7 Science Extra Questions Miscellaneous Questions, Multiple Choice Questions, Question 1., The correct way of making a solution of acid in water is to [NCERT Exemplar], (a) pdd water to acid, (b) add acid to water, (c) mix acid and water simultaneously, (d) add water to acid in a shallow container, Answer:, (b) add acid to water, Question 2., Products of a neutralisation reaction are always, (a) an acid and a base, (b) an acid and a salt, (c) a salt and water, (d) a salt and a base, Answer:, (c) a salt and water, Question 3., Turmeric is a natural indicator. On adding its paste to acid and base separately, which colours would be observed?, (a) Yellow in both acid and base, (b) Yellow in acid and red in base, (c) Pink in acid and yellow in base, (d) Red in acid and blue in base, Answer:, (b) Yellow in acid and red in base, Question 4., Phenolphthalein is a synthetic indicator and its colours in acidic and basic solutions respectively are [NCERT Exemplar], (a) red and blue, (b) blue and red, (c) pink and colourless, (d) colourless and pink, Answer:, (d) colourless and pink, Question 5., When the soil is too basic, plants do not grow well in it. To improve its quality, what must be added to the soil? [NCERT Exemplar], (a) Organic matter, (b) Quicklime, (c) Slaked lime, (d) Calamine solution, Answer:, (a) Organic matter, Question 6., Neutralisation reaction is a [NCERT Exemplar], (a) physical and reversible change, (b) physical change that cannot be reversed, (c) chemical and reversible change, (d) chemical change that cannot be reversed, Answer:, (d) chemical change that cannot be reversed, Question 7., A solution changes the colour of turmeric indicator from yellow to red. The solution is, (a) basic, (b) acidic, (c) neutral, (d) either neutral or acidic, Answer:, (a) basic, Question 8., Which of the following sets of substances contains acids?, (a) Grapes, lime water, (b) Vinegar, soap, (c) Curd, milk of magnesia, (d) Curd, vinegar, Answer:, (d) Curd, vinegar, Question 9., Which of the following is an acid-base indicator? [NCERT Exemplar], (a) Vinegar, (b) Lime water, (c) Turmeric, (d) Baking soda, Answer:, (c) Turmeric, Fill in the Blanks, 1. Lemon juice and vinegar taste ……………… because they contain ……………… . [NCERT Exemplar], 2. Turmeric and litmus are ……………… acid-base indicators., 3. Phenolphthalein gives ……………… colour with lime water., 4. When an acidic solution is mixed with a basic solution, they ……………… each other forming ……………… and water. [NCERT Exemplar], 5. The acidic or basic nature of a substance is tested by using an ……………… ., 6. The substances which show different colours in acidic, basic and neutral solutions are called ………………, 7. Acid + Base → ……………… + Water, 8. When an acid mixed with a base, a ……………… reaction takes place., 9. Acetic acid is present in ……………… while ……………… is present in lemon., 10. Excessive use of chemical fertilisers make the soil ……………… ., 11. Hydrochloric acid + Sodium hydroxide → ……………… + Water, 12. Acids turn blue litmus ……………… ., Answers:, 1. sour, acids, 2. natural, 3. pink, 4. neutralise, salt, 5. indicator, 6. indicators, 7. salt, 8. neutralisation, 9. vinegar, citric acid, 10. acidic, 11. Sodium chloride, 12. redTrue/False, True/False, 1. All substances are either acidic or basic. [NCERT Exemplar], 2. A compound if acidic will turn all indicators red., 3. Lime water turns red litmus blue. [NCERT Exemplar], 4. Common salt dissolved in water turns blue litmus red., 5. Phenolphthalein is a natural indicator., 6. Calamine can be used to treat ant’s sting., 7. Lemon water is basic in nature., Answers:, 1. False, substances can be neutral as well., 2. False, acids do not turn all indicators red., 3. True, 4. False, it does not change the colour of litmus at all., 5. False, it is a man-made indicator., 6. True, 7. False, it is acidic in nature., Match the Columns, Question 1., Match the substances in Column I with those in Column II., Question 2., Match the items in Column 1 with Column II., Answers:, 1., (a)-(iii), (b)-(v), (c)-(iv), (d)-(i), (e)-(ii), 2., (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)