7th Standard General Science Notes PDF

CHETANA R A DE ME G TEACHER’S C MPASS GENERAL SCIENCE Standard 7 Salient Features: Answers are provided to all the questions in the Grade Me Book. Written in simple, student friendly language. Chapters are sub divided into smaller u...

CHETANA R A DE ME G TEACHER’S C MPASS GENERAL SCIENCE Standard 7 Salient Features: Answers are provided to all the questions in the Grade Me Book. Written in simple, student friendly language. Chapters are sub divided into smaller units for better learning practice. Suitable diagrams provided wherever required. Prepared jointly by experienced teachers and technology experts. CHETANA EDUCATION LIMITED 4th Floor, Trade Link, ‘E’ Wing, ‘B’ Block, Kamala City, Senapati Bapat Marg, Lower Parel, Mumbai : 400 013. Tel : +91-22-6121 6000 E-mail : [email protected] Website : www.chetanaeducation.com CWG7170220  Contents 1. The Living World: 11. Cell Structure and Micro- Adaptations and Organisms............................ 79 Classification......................... 3 12. The Muscular System and Digestive System in Human 2. Plants: Structure and Beings................................... 89 Function................................11 13. Changes - Physical and 3. Properties of Natural Chemical............................... 95 Resources............................. 17 14. Elements, Compounds and 4. Nutrition in Living Mixtures............................... 99 Organisms........................... 23 15. Materials We Use.............. 109 5. Food Safety.......................... 31 Test Paper - 3......................114 Test Paper - 1....................... 38 16. Natural Resources.............115 6. Measurement of Physical 17. Effects of Light.................. 124 Quantities............................ 39 18. Sound : Production of 7. Motion, Force and Work.... 43 Sound................................. 132 8. Static Electricity.................. 49 19. Properties of a Magnetic 9. Heat...................................... 56 Field.................................... 137 10. Disaster Management........ 65 20. In the World of Stars........ 140 Test Paper - 2....................... 73 Test Paper - 4..................... 144 Model Test Paper - 1........... 74 Model Test Paper - 2......... 146 The text of this publication, or any part thereof, may not be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, storing in retrieval system, or otherwise, without the prior written permission of the publishers. © Publishers Published by : CHETANA EDUCATION LIMITED 4th Floor, Trade Link, ‘E’ Wing, ‘B’ Block, Kamala City, Senapati Bapat Marg, Lower Parel, Mumbai : 400 013. Tel. : +91-22-6121 6000 l E-mail : [email protected] Website : www.chetanaeducation.com CWG7040220  THE LIVING WORLD: ADAPTATIONS AND 1 CLASSIFICATION (Grade Me pg. no. (5 - 17) Q.1. Fill in the blanks: Ans. (1) Rajasthan (2) waxy (3) Fibrous (4) haustorial (sucking) (5) Charles Darwin (6) World Frog Protection Day (7) Desert plants (8) resistance of air (9) Adaptation (10) Survival of the fittest. Q.2. State whether the following statements are True or False: Ans. (1) True (2) True (3) True (4) True Q.3. Name the following: Ans. (1) Venus flytrap, Pitcher plant (2) Carl Linnaeus (3) Frog, duck (4) genus and species (5) carrots, beets *Q.4. Find my match: Ans. (1 - d); (2 - c); (3 - b); (4 - a). *Q.5. Which is lying? Ans. (1) Cockroach – It has six legs. (2) Hen – Hen’s toes are not webbed. (3) Cactus – It’s fleshy, green part is a stem not a leaf. Q.6. Look at the list of the plants and name the part of the plant which has been adapted. Ans. (1) Stem (2) Roots (3) Stem (4) Roots (5) Roots (6) Roots (7) Roots (8) Roots Q.7. Answer the following in one sentence: Ans. (1) Coniferous trees like pine and deodar. (2) (a) Fungi do not have cholophyll and cannot peform photosynthesis. (b) They obtain food from starchy food stuffs like bhakri and bread. (c) They have root like fibers for absorption of food. (3) Snakes ad earthworms use scaly skin for creeping. (4) Binomial Nomenclature consist of two parts : the first part is ‘genus’ and second ‘species’. (3) 4 Grade Me Teacher’s Guide (Std. 7) Q.8. Give scientific reasons: Ans. (1) (a) Plants need nitrogen, phosphorus and potassium for growth (b) Plants that grow in soil is deficient in nitrogen, like Drosera, Venus flytrap and pitcher plant. They fulfill their need for nitrogen by consuming insects. (c) Hence, they are called insectivorous plants. (2) According to their feeding, there are some adaptation in animals. To eat flesh or to kill other animals, carnivorous animals have canine teeth. (3) (a) Tigers are carnivorous animals. (b) So, their padded paws enable them to silently stalk their prey and capture it easily. (4) Eyes of herbivores are below the forehead on the either side of the head as this gives them wide-angle vision which helps to protect them from predators. (5) Snowy region is covered with snow throughout the year. White or Silver body matches the snow, so it gets camouflaged in snow, and it can save itself from predators and long thick hair gives them protection from cold. (6) (a) A variety of plant – trees, shrubs and herbs are found in forest. (b) These plants compete amongst themselves for sunlight. Hence, trees grow tall and climbers and vines grow to a great height in the forest region. (7) Body of a fish taper towards both its ends so that it can become streamlined. This shape is such that water can flow around it easily and allow the fish to move fast in water. *(8) Camel can live in desert because it has thick skin to prevent loss of water from the body. Their legs are long with flat and cushioned soles. The nostrils are protected by folds of skin. The eyelashes are long and thick, so these adaptations enable Camels to live in desert easily. Q.9. Answer in short: Ans. (1) Gradual changes occur in the body parts and also in the behaviour of organisms which help them to adjust to their surroundings. Such changes are called adaptation. General Science 5 (2) (a) Aquatic plants are the plants that live entirely in the water. (b) Terrestrial plants are the plants that live their entire life on land. (c) Unlike terrestrial plants, aquatic plants have adaptation like waxy coat on the leaves, air spaces in the stem, floating roots etc. *(3) The leaves of lotus plant float on the surface and the presence of waxy substance on the leaves does not allow accumulation of water on leaves. Therefore, the leaves of lotus plant don’t rot in water. *(4) The main function of roots is anchorage and absorption. In aquatic habitat, plants do not need strong roots for anchorage. Therefore, the roots of lotus plant are short and fibrous. (5) The stems in desert plants are green as they perform photosynthesis in the absence of leaves. *(6) In snowy regions, the sloping branches prevents the snow from accumulating on the tree and the thick bark helps the tree to withstand the cold. (7) The following adaptation help frogs to swim easily through water: (a) Webbed toes (b) Slippery, smooth skin (c) triangular head. *(8) Frog, duck and tortoise use their legs like oars. *(9) Frogs have an ability to breathe through skin in water. *(10) Long hind legs of a frog help them to jump. *(11) A duck is covered with waxy feathers which do not allow water to accumulate. Hence, a duck does not get wet in water. (12) Two principles of Darwin’s Theory of Evolution are : (a) Survival of the fittest (b) Natural selection. *(13) Living things are classified in order to make it easy to study and remember all the organisms in this diverse living world at same time. (14) (i) Water trickles off lotus leaves because it is coated with waxy covering on it. (ii) It is one of the adaptations of aquatic plants to survive in water without getting wet and rot or sink to the bottom. Q.10. Answer in brief: Ans. (1) (a) Some of the aquatic plants are properly rooted in the soil at the bottom of the water bodies. 6 Grade Me Teacher’s Guide (Std. 7) (b) Some plants are entirely afloat, their roots are not anchored in the soil. (c) The surfaces of leaves and stems are covered with a waxy layer. (d) Leaves of some aquatic plants are thin and slender like a ribbon. (e) Air spaces in stem and petioles of aquatic plants are useful for floating in water. (2) Desert plants are either leafless or their leaves are like small needles or have been modified into thorns. As a result, they lose very little water by evaporation. The stem stores water and food and is therefore fleshy. The stems are green as they perform photosynthesis in the absence of leaves. Their roots penetrate deep into the soil in search of water. There is a thick layer of a waxy substance on the stems of these plants, too. (3) Diverse types of bushes and grasses are found in the grasslands. Fibrous roots of grasses prevent soil erosion. Grasses in the equatorial region are very tall. Animals like tiger, elephants and deer can remain hidden in these grasses. However, grasses in cold regions are very short. Animals like the rabbit are found in such grasses. Vast meadows are found in hilly areas as well as plains. (4) Plants like dodder (cuscuta) are parasitic. The plant body of dodder consists of yellow wire-like stems. It is leafless and cannot perform photosynthesis. However, it has haustorial (sucking) roots for absorbing nutrients from the host plant. These roots penetrate upto the conducting vessels of the host plant to absorb water and food. (5) Fishes have scales on the skin and fins on the body. Their body tapers towards both its ends, like a spindle. Fish breathe with gills instead of a nose. Their eyes have transparent eyelids. They have air bladders within the body to help them to float. (6) The frog and duck have webbed toes, they can use their legs like oars. Water flows off the waxy feathers of birds like duck and waterhen. Webbed toes, slippery, smooth skin and a triangular head help frogs to swim easily through water. They can live on land as well as in water due to their ability to breathe through the skin in water and using the nose and lungs on land. General Science 7 (7) The eyes of herbivores are below the forehead, on either side of the head. This gives them wide-angle vision which helps to protect them from predators. Their legs are long and tapering with strong hooves, which enables them to run fast taking long leaps. Their long and freely moving ears can receive sounds from long distances and different directions. Deer and blackbucks have colours that merge with their surroundings. Their teeth are strong for chewing tough plant material. (8) (a) Desert animals have a thick skin to prevent loss of water from the body. (b) The legs are long with flat and cushioned soles. (c) The nostrils are protected by folds of skin. (d) The eyelashes are thick and long. (9) The spindle-shaped body of birds also minimises the resistance of air while flying. With hollow bones, a body covering of feathers and modification of forelegs into wings, their body is light in weight and adapted for flying. The body of insects also is light in weight and tapers at both ends. They can fly with two pairs of wings and also walk with six stick- like legs. Bats can fly with the help of the patagium, a thin fold of skin between their forelegs and hind legs. (10) Adaptation is not a sudden process. It is gradual and continuous. Differences in the structure and appearance of present-day animals and animals of thousands of years ago are the adaptations that occured according to prevailing conditions. It is our duty to conserve this diversity. (11) Darwin said that only those organisms are likely to survive which can best adapt themselves to a changing environment. This is called the theory of survival of the fittest. (12) If an organism is born with a new beneficial characteristic and is able to survive, this change is preserved in the next generation. This is called the theory of ‘Natural selection’. (13) The criteria used for classification of plants and animals are their cell structure, body organization, mode of nutrition and reproduction. 8 Grade Me Teacher’s Guide (Std. 7) (14) A hierarchy is formed in the classification that starts with Kingdom Animalia or Kingdom Plantae, further groups and sub-groups are formed depending upon basic similarities and differences. This is called the ‘hierarchy of classification’. (15) Binomial nomenclature is used to identify each organism. Accordingly, a scientific name has been assigned to each organism. It consists of two parts - the first part is ‘genus’ and second, ‘species’. All identified organisms have been assigned a binomial name as per the guidelines of the International Code of Nomenclature. All the organisms of a species are so similar that irrespective of differences in colour, height, habitats and habits, they can reproduce among themselves and form new individuals like themselves. For example, all domestic cats in the world belong to the same species. The same is true in the case of animals like hen, cow, dog, etc. and plants like mango, wheat, maize, etc. *(16) (a) Adaptations of organisms depends on the changes in the surroundings. (b) To adjust with those changes in the surroundings adaptation takes place gradually and continuously in organisms. (c) Changes that take place in the various organs and life processes of organisms, enable them to live, feed, reproduce to perpetuate themselves and to protect themselves from their enemies in specific surroundings, depending upon the habitat and its geographical conditions, are called adaptations. (17) (a) The leaves of cactus and acacia are modified into thorns, thus they lose very little water by evaporation. (b) Stems perform photosynthesis in the absence of leaves and stores water and food. (c) Presence of thick waxy layer on stem also prevents loss of water. (d) Their roots penetrate deep into the soil in search of water. (e) Therefore, plants like cactus and acacia live in deserts with scarce water. General Science 9 Q.11. (A) Observe the pictures given below and state their adaptations. Ans. (1) The spindle-shaped body of birds also minimises the resistances of air while flying. With hollow bones, a body covering of feathers and modification of forelegs into wings, their body is light in weight and adapted for flying. (2) A white or silvery body colour, long thick hair on the skin are typical characteristics of animals of snowy region. (3) Snakes use their muscles for creeping. Snakes also show adaptations like scaly skin. (4) House lizard use its muscles for creeping. Similarly, they show adaptations in skin, soles of feet, body colour etc. The house lizard has clawed toes and thin soles. (5) Frogs have webbed toes, they can use their legs as oars. Webbed toes, slippery smooth skin and a triangular head help frogs to swim easily through water. The typical colours of a frog’s back helps if to hide among grasses. Q.11. (B) Complete the labelling of a given diagram. Ans. Fish Fins Gills Scales Q.12. Listed below are the adaptations in various plants and animals, state the use of these adaptations for each of them. Ans. (1) To prevent accumulation of water and rotting of aquatic plants. (2) Ribbon like slender leaves helps aquatic plants to withstand fast current of water. (3) Air spaces in stem and petioles of aquatic plants are useful for floating in water. 10 Grade Me Teacher’s Guide (Std. 7) (4) Needle like leaves in desert plants helps them to lose very little water by evaporation. (5) Thick bark on trees growing in snowy region helps the tree to withstand the cold. (6) Root like fibres in Fungi are for absorption of food. (7) A fish has air bladders within the body to help them to float. (8) Legs of herbivores are long and tapering with strong hooves enable them to run fast taking long leap. (9) Long and freely moving ears in herbivores can receive sounds from long distance and different direction. *Q.13. (A) Observe and complete the chart. Type of Characteristics Characteristics Ans. Plant Habitat root of leaves of stem Large and Hollow and Lotus Aquatic Fibrous round with flexible waxy layer Modified into Cactus Terrestrial Fibrous Fleshy thorn Oval round Banyan Terrestrial Tap Woody shape *Q.13. (B) Observe and complete the chart.. Ans. Hierarchy Mango Human Kingdom Planfae Animalia Phylum Anthophyla Chordata Class Dicotyledonae Mammalia Order Sapindales Primates Family Anacardiaceae Hominidae Genus Mangifera Homo Species Indica sapiens General Science 11 *Q.14. Complete the following chart from your own observation. Ans. Adaptation Animal Use of adaptation (1) Sharp teeth Lion, tiger To tear the flesh To make hole in (2) Long and pointed beak Woodpecker tree To pick up seeds (3) Short beak Sparrow and worms. (4) Long and sticky tongue Frog To catch insects To search for food (5) Long neck Swan both on land and underwater Q.15. Following are some examples of organisms from Kingdom Plantae and Animalia classified by the binomial method of nomenclature: Living Things Scientific Name Dog Canis lupus familiaris Hibiscus Hibiscus rosa-sinensis Find out the scientific names of other animals and plants in your surroundings and discuss in class. Ans. Students will collect information and write. vvv PLANTS: STRUCTURE AND FUNCTION 2 (Grade Me pg. no. (18 - 22) Q.1. Fill in the blanks: Ans. (1) bud (2) leaf apex (3) receptacle (4) dicotyledonous seeds Q.2. Name the following: Ans. (1) Lamina (2) Petiole (3) Calyx (4) Pedicel 12 Grade Me Teacher’s Guide (Std. 7) Q.3. Define the following: Ans. (1) The part that grows inside the seed towards the soil is called the radicle. (2) The part that grows above the soil is called Plumule. (3) After maturity, anthers burst and the pollen grains which are released fall on the stigma. This process is called pollination. Q.4. Answer in one or two sentences: Ans. (1) Thread-like or fibre-like roots arising from the stem are called fibrous roots. (2) Roots emerging from the trunk and branches of a banyan tree grow towards the soil. These roots are called prop roots. (3) Calyx, Corolla, Androecium and Gynoecium. (4) Seeds which do not divide into two equal parts are called monocotyledonous seeds. Q.5. Answer in short: Ans. (1) The part of the plant that grows below the soil for support are called roots. The main function of roots are absorption of water, minerals, anchoring and supporting the plant. *(2) If plants like tamarind, banyan and mango had fibrous roots they would have fallen down easily. *(3) If the root tip is injured, the root will not grow further. *(4) Fenugreek and spinach have tap roots with a few secondary roots, whereas onion has fibrous root. Fenugreek roots also have some nodules which contain nitrogen fixing bacteria. (5) The leaf is divided into two equal parts by a single mid-vein which lies along the midline of the leaf blade. Secondary veins arise from the mid-vein. Such a type of venation is called reticulate venation. In a leaf all the veins are parallel, running from the leaf base to the leaf apex. Such a venation is called parallel venation. *(6) (a) Insects are pollinating agents. (b) When insects visit a flower, the pollen grains stick to their legs. (c) These pollen grains fall on the stigma and bring about pollination. General Science 13 Q.6. Draw neat labelled diagram of the following: Ans. (1) Tap Root (2) Leaf Leaf Secondary apex Leaf root margin Vein Primary Mid vein root Root hair Leaf blade Petiole Root tip Stipule Root cap Leaf base Q.7. Observe the figure and answer the following: Ans. (1) Plumule Radicle (2) The part that grows from inside the seed towards the soil is called the radicle and the part that grows above the soil is called the plumule. The root that forms from the radicle, grows into the ground. The root is thick near the ground and gradually tapers to a pointed end. This part of the plant growing below the soil for support is called ‘root’. 14 Grade Me Teacher’s Guide (Std. 7) *Q.8. Give examples of 3 plants that have: Ans. (1) Spiny fruits: Jack fruit, Pineapple, Lychee (litchi), Datura (2) Spiny stem: Cactus, Wild rose, Catclaw acacia, Silk cotton (3) Red flowers: Rose, Dahlia, Hibiscus, Tulips (4) Yellow flowers: Marigold, Daffodil, Sunflower, Daisy (5) Leaves which close at night : Mimosa plant, Tallwood, Prayer plant, Gulmohar (6) Single seeded fruits : Mango, Lychee, Jamun (7) Many seeded fruits : Custard apple, Papaya, Watermelon. *Q.9. (A) Describe the functions of various parts of a plant. Ans. The various parts of a plant are root, stem, leaves, flower and fruit. Function: Root : Absorption of water, minerals, anchoring and supporting. Stem : Stem carries water and minerals from roots to other parts of plant. Leaves : Leaves have chlorophyll which helps in photosynthesis. Flowers : Reproductive part of the plant. Fruit : It contains seed. *Q.9. (B) Describe the functions of various parts of a flower. Ans. Female reproductive part is Gynoecium. Corolla is the colourful part of the flower. Ovary develops into fruit. The transfer of pollen grains from the anther to the stigma of flower is called pollination. *Q.10. What are the similarities and differences between (a) Jowar and moong (b) onion and coriander (c) leaves of banana and mango (d) coconut tree and jowar stalk plant? Ans. (a) Jowar and Moong Jowar Moong (1) It has fibrous root. (1) It has tap root. (2) It is a monocotyledonous (2) It is a dicotyledonous seed. seed. (3) It is a rabi crop. (3) It is a kharif crop. General Science 15 Similarities : Jower and Moong both are angiosperms. (b) Onion and Coriander Onion Coriander (1) It is a biennial plant. (1) It is an annual plant. (2) It has monocotyledonous (2) It has dicotyledonous seeds. seeds. (3) It has fibrous root. (3) It has tap root but later on changes to fibrous root system. Similarities: (1) Both are used in cooking. (2) Both are edible. (3) Both belong to Kingdom Plantae. (c) Leaves of banana and Leaves of mango Leaves of banana Leaves of mango (1) It has parallel venation. (1) It has reticulate venation. (2) It is very large in size. (2) It is small in size. (3) It is monocotyledonous (3) It is dicotyledonous plant. plant. Similarities: (1) Both are used in Hindu religious ceremonies. (2) Both have high medicinal value. (d) Coconut tree and Jowar stalk plant Coconut tree Jowar stalk plant (1) It is tall and have thick (1) It is small and have thin stem. stem. (2) It has strong root system. (2) It has weak root system. (3) Each and every part of tree (3) Only seeds are useful. is useful. 16 Grade Me Teacher’s Guide (Std. 7) Similarities: (1) Both are from same Kingdom Plantae. (2) Both are autotrophic. (3) Both are monocotyledonous plant. *Q.11. Certain properties are mentioned below. Find a leaf corresponding to each property and describe those plants: Leaves with smooth surface, leaves with rough surface, fleshy leaf, spines on leaf. Ans. (1) Leaves with smooth surface: e.g. Banana leaf. It is large in size. It is closely rolled up one over the other. Together they look like a trunk but they form only an apparent trunk. It has parallel venation. (2) Leaves with rough surface: e.g. Hibiscus leaf. It has reticulate venation. Leaf margin is toothed. (3) Fleshy leaf: e.g. Jade plant, Water Hyacinth. It has fleshy, glossy and smooth leaves. They are coloured jade green and having a slightly red tinge towards the edge of leaves when exposed to higher level of light. (4) Spines on leaf: e.g. Opuntia, Cycas Kevda. It is a desert plant. Leaf is thick, fleshy and having spines on it. *Q.12. Find the plant parts. Ans. (1) Bud (2) root cap (3) stem (4) radicle (5) flower (6) root hair (7) petals *Q.13. Label the given diagram. Ans. Vertical section of a hibiscus flower Gynoecium or carpel Androecium (Stamen) Corolla Ovary Corolla Pedicel General Science 17 *Observe any one flower and its various parts and describe it in your own words. Ans. Students will answer *Explain the following images in your own words. (A) (B) Ans. (i) Diagram A is of maize seed. It is a monocotyledonous seed and does not divide into two equal parts. The plant has fibrous root system. (ii) Diagram B is of bean seed. It is a dicotyledonous seed and it divides into two equal parts. The plant has tap root system. vvv PROPERTIES OF NATURAL RESOURCES 3 (Grade Me pg. no. (23 - 29) *Q.1. Fill in the blanks with the appropriate term. Ans. (1) temperature (2) shape, volume, mass (3) density (4) Neutral Q.2. Fill in the blanks: Ans. (1) solvent (2) sedimentary (3) Multani (4) Mass (5) acidic Q.3. State whether the following statements are True or False: Ans. (1) False (2) True (3) True (4) False (5) True *(6) True *(7) False *(8) True *(9) True *Q.4. With whom should I pair up? Ans. (1 - b); (2 - a); (3 - c) *Q.5. What will happen if.... Ans. (1) We feel the dampness or humidity. (2) The fertility of the soil decreases. 18 Grade Me Teacher’s Guide (Std. 7) Q.6. Answer in one sentence: Ans. *(1) Air contains nitrogen, oxygen, carbon dioxide, six inert gases, nitrogen dioxide and sulphur dioxide. *(2) Air is made of oxygen, nitrogen, carbon dioxide, water vapour and dust particles. All these are in different proportion. Therefore, air is a mixture. *(3) 1 kilogram = 1000 gm and 1 litre = 1000 cubic cm. Mass 1000 gm ∴ Density = = = 1 gm / cubic cm Volume 1000 cc (4) The molecules of the gases in the air are in constant motion. When these molecules strike a body, they create pressure on that body. This pressure of air is called atmospheric pressure. (5) A solution is a homogeneous mixture of one or more solutes dissolved in a solvent. (6) Soil is tested to find out if there is a deficiency of an ingredient and to decide what measures should be taken to remove the deficiency. (7) (a) Air is a mixture of gases. (b) Air has mass and volume. (c) It spreads in all directions. (d) It exerts the pressure. (e) It is colourless. Q.7. Give scientific reasons: Ans. *(1) (a) In summer, the temperature of air is high, the capacity of air to hold moisture also increases. Thus, clothes dry quickly. (b) During rains, the proportion of water vapour in the air is high, so the capacity to hold moisture decreases. Hence, the clothes do not dry quickly. *(2) When water freezes means it transforms into the solid state, therefore its volume increases. When volume increases, its density decreases. Therefore, density of ice is less than the water, so ice floats on water. *(3) (a) Sea water is saline. It contains salt, whereas it is not so in well or a lake water. General Science 19 (b) Due to salt dissolved in water, density of sea water is more, so swimmer will not sink. Hence, it is easier to swim in the sea than in a well or a lake. *(4) Air is made of oxygen, nitrogen, carbon dioxide, water vapour and dust particles. All these are in different proportion. Therefore, air is a mixture. *(5) Water dissolves more substances than any other liquid so water is called a universal solvent. *(6) Water is a universal solvent. It dissolves more substances than any other liquid, so there is no alternative to water for cleaning purposes. (7) Due to the ice cubes in the glass, the air surrounding the glass cools down. As the water vapour in this air cools down, it condenses and gets transformed into water. It is this water that collects on the outer surface of the glass. (8) The proportion of water vapour in the air in high during the monsoons in the coastal area. As a result, we feel the dampness or humidity. Q.8. Answer in short: Ans. *(1) No, there is no atmospheric pressure on the moon. *(2) (a) Life will not be possible as there is no air in the surrounding. (b) The process of respiration and combustion will come to end. (c) Phenomena like transmission, sound, humidity as well as atmospheric pressure will not exist on moon. (d) There would be no seasons, neither there would be rainfall. *(3) In space, there is no air. Hence, we will not be able to hear sound in absence of medium. *(4) Clay soil has large water holding capacity. Due to this, the soil aggregrates to form large lumps. This makes it difficult to plough. *(5) The proportion of large particles is high in sandy soil. Water drains rapidly through sandy soil. That is why it is easy to plough sandy soil. *(6) Silt soil has a high water holding capacity. *(7) Silt soil is suitable for cultivation. 20 Grade Me Teacher’s Guide (Std. 7) (8) During the night or at dawn, when the temperature is low, the capacity of air to hold the vapour is less. At such times, the excess vapour is transformed into water droplets. This is called dew. (9) (a) Soil is found in different colours: The soil near the land surface is darker in colour than that of the lower layers. (b) Fertility of the soil differs from place to place. (c) Different types of soil have different capacity for drainage of water. (d) Capacity to hold water becomes clear from its colour. (e) The colour of the soil depends upon its texture and its organic ingredients as well as on chemical ingredients like iron, lime. The texture of the soil is determined by the proportion of particles of various sizes in it. (10) (a) Due to anomalous behaviour of water in cold countries when water gets cool and turn to ice, its volume increases so its density decreases. (b) Due to less density ice floats on water. (c) (i) Ice is a bad conductor of heat and electricity. (ii) It doesn’t allow outside heat to go from the ice to water so water temperature below the ice doesn’t change. (iii) It remains as it is so aquatic animals remain alive even after the rivers or lakes freeze in winter. Q.9. Answer in brief: Ans. *(1) Air is a mixture of very fine particles of some gases, dust, smoke and moisture. When rays of light fall on these minute particles, the particles spread the light in all the directions. This natural phenomenon is called scattering of light. *(2) (a) Water has no definite shape but has definite mass and volume. (b) Water is fluid in nature. (c) It is tasteless, colourless and odourless. (d) It is a transparent liquid. *(3) Seawater contains dissolved salt. The dissolved salt increases density. Rainwater does not contain dissolved salts in it. General Science 21 *(4) The fertility of soil depends upon soil structure. So, importance of good soil structure is as follows: (a) Roots get sufficient supply of oxygen. (b) Water drainage is good therefore the roots of plants grow well. *(5) The uses of soil are as follows: (a) Plant conservation: To help plants grow. (b) Water conservation: Soil holds water. As a result, by means of bunds and lakes, we can get water for use throughout the year. (c) Plasticity: (i) Soil can be given any required shape. This property of soil is called plasticity. (ii) Because of its plasticity, we can use it to make articles of a variety of shapes. (iii) These articles can be baked to make them hard. (iv) Water storage earthen pots, earthen lamps, idols, bricks etc. are articles made from soil. *(6) (a) The properties of the various ingredients of soil can be determined by soil testing. (b) During soil testing, the soil is examined for colour, texture and the proportion of organic matter in it. (c) Soil is tested to find out if there is a deficiency of any ingredients and to decide what measures should be taken to remove the deficiency. These information would enable the farmers to maintain the fertility of the soil. *(7) Air is useful as a medium for the transmission of sound. Density of the air changes with temperature. If the density of air increases, we can hear the sound more loud and clear. *(8) (a) Due to anomalous behaviour of water when you cool below 4°C, the volume of the water increases. (b) Therefore, when the glass bottle completely filled with water is kept in a freezer, water expands on cooling and its volume increases, so glass bottle breaks. (c) To avoid this, completely filled bottle is never kept in a freezer. 22 Grade Me Teacher’s Guide (Std. 7) *(9) Condition for closed environment: (a) When the temperature increases, the pressure of air also increase. (b) For example, as the air warms up, the molecules in the air become more active. (c) They use up more individual space even though there is the same number of molecules. This causes an increase in the air pressure. *(10) Yes, below 4°C the density of water becomes less as it expands and starts to float on the water body. (11) On pulling the piston with the inlet hole of the syringe closed, more space becomes available to the air in the syringe, and it becomes ratified. As a result, the pressure of the air in the syringe is lowered. Comparatively the pressure of the outside air is very high. That is why, when the pulled out piston is released, it is immediately pushed in. If this experiment is repeated, holding the syringe in different positions like vertical, horizontal or inclined, the piston is found to go in to the same extent in all the cases. From this, we can infer that atmospheric pressure is the same in all the directions. (12) The density of water is peculiar. When water at normal temperature starts cooling, its density increases like that of most liquids. However, if its temperature falls below 4°C its density starts decreasing. This means that the density of water is maximum at 4°C. If the temperature of water is lowered below 4°C, its density decreases and volume increases. It means that water expands when the temperature falls below 4°C. This is called the anomalous behaviour of water. *Q.10. Explain the picture in your own words. Ans. (1) Diagram (a): Water is filled in the crack. Diagram (b): Water in the crack turns to ice due to decrease in temperature. When it turns to ice the volume increases and it expands. Due to expansion, the size of crack widens more than the dia.(a). General Science 23 Q.11. Observe the given picture and answer the following: Ans. (a) (1) No, the stick doesn’t remain horizontal. (2) Air has mass. (b) (1) Fountain of water (2) On blowing through the straw, the air at its open end is pushed away and hence the pressure of the air at the opening goes down. As the pressure of the air near the upper end of the erect straw becomes less than atmospheric pressure, the water in the cup is pushed from where the pressure is higher to where it is lower, that is, in the upward direction, and the water comes out in the form of a fountain. The more forcefully you blow the higher will be the fountain. This straw fountain works on Bernoulli’s principle. (3) Bernoulli’s principle is that the pressure of air decreases when its velocity increases, while the pressure of air increases when its velocity decreases. Q.12. Take a bucket of water. Drop many different kinds of articles in it. Make separate lists of the articles which sink in the water and those that float on it. Ans. Answer may vary. Q.13. Take two big glasses of water. Add 4-5 spoonfuls of salt to the water in one glass and dissolve it completely. Now place a potato in the water in the second glass. What do you observe? Ans. The density of water in that glass is greater due to the dissolved salt. The potato floats in that water because of the increased density. vvv NUTRITION IN LIVING ORGANISMS 4 (Grade Me pg. no. (30 - 37) Q.1. (A) Fill in the blanks: Ans. (1) Glucose, Oxygen (2) xylem, phloem (3) nitrogen (4) Rhizobium (5) iron, vitamin (6) pseudopodia (7) Saprozoic (8) ectoparasitic 24 Grade Me Teacher’s Guide (Std. 7) Q.1. (B) Multiple choice questions: Ans. (1) (D) Nepenthes (2) (A) X-Carbon dioxide, Y-Oxygen (3) (B) Stomata (4) (B) Saprophytic Nutrition (5) (A) Rhizobium bacteria Q.2. Name the following: Ans. (1) Azotobacter (2) Lichen (3) Dodder (4) Mushroom (5) Digestion (6) Carnivores Q.3. State wether the following statements are True or False: Ans. (1) False (2) True (3) True (4) False Q.4. Define: Ans. (1) The process of taking in and using food which takes place in living organisms is called nutrition. (2) Some organisms can produce their own food and thus nourish themselves. This is called autotrophic nutrition. *Q.5. Match the pairs: Ans. (1 - d); (2 - c); (3 - a); (4 - b). *Q.6. Classify according to food-type: Ans. Carnivores : Tiger, Lion Herbivores : cow, deer, goat, buffalo Scavengers : Vulture Decomposers : Fungus, bacteria Granivores : sparrow Insectivores : frog Ectoparasitic : Tick Omnivores : Human, Cockroach *Q.7. Observe the animals around you and complete the following table: Name of Method of Ans. No. Type/Name of food animal Ingestion (1) Cow Grass/hay Chewing (2) Frog Insects like flies, moths, etc. Swallowing General Science 25 Q.8. Complete the following: Ans. No. Nutrient Function Important component of proteins, chlorophyll (1) Nitrogen and cytoplasm Conversion of light energy into chemical (2) Phosphorus energy (3) Magnesium Production of chlorophyll Q.9. Observe the figure and answer the following: Ans. Sunlight, Carbon dioxide, chlorophyll in the leaves and water, minerals, salts. Q.10. Answer in one sentence: Ans. (1) Some organisms depend on other organisms, plants or animals, for their food. This is called heterotrophic nutrition. (2) The xylem transports minerals and water from the root to all aerial parts of the plant. The phloem transports food from the leaves to other parts of plants. (3) When two or more than two different types of plants lie together to fulfill their needs of nutrition, protection, support with each others help is called symmetric nutrition. *(4) Leaves of the loranthus plant carries out photosynthesis. *(5) They obtain water and minerals from the xylem and phloem of the other host plant. *(6) Loranthus is known as partially parasitic plant because it does photosynthesis with the help of leaves but only for water and minerals it depends on other plants. (7) The scientist Johannes Burman identified Drosera burmanii in Srilanka in 1737. Hence, the plant is named so. (8) Animals that obtain their food from both plants and animals are called omnivores. e.g. humans, monkeys. (9) Scavengers obtain their food from dead bodies of animals. Decomposers are some microbes which obtain their food by decomposing dead bodies of organisms or other material. 26 Grade Me Teacher’s Guide (Std. 7) *(10) Yes. I have seen small animals on the bodies of dogs and buffaloes, these are ticks and are called as ectoparasites. *(11) These little animals live on the body of dogs and buffaloes and obtain their food by sucking their blood. *(12) Worms in the intestine obtain their food by absorbing nutrients from partially digested food which comes into the intestine. Q.11. Give scientific reasons: Ans. *(1) (a) Pitcher plant contain chlorophyll, thus they can prepare their own food. (b) Pitcher plant grows in soil deficient in nitrogen compound. (c) To fulfill its nitrogen requirement, pitcher plant feeds on insects even though it produces food by photosynthesis. *(2) Living organisms need nutrition due to the following: (a) To supply the energy required for doing work. (b) For growth and development of the body. (c) To replace the damaged cells and repair tissues. (d) To fight diseases. *(3) (a) Insectivorous plants generally grow in soil or water deficient in nitrogen compounds. (b) The plant body of the Drosera burmanii has a flower like appearance. It grows close to the ground. Even its leaves are attractively pink or red in colour with hairs at the margin. (c) Droplets of sticky substances found on tips of the hairs attract insects. (d) These plants consume insects to fulfill their need for nitrogen. To attract the insects these plants are attractively coloured. *(4) Holozoic mode of nutrition means the feeding of solid and liquid food by animals. Butterflies live on nectar from flowers. Therefore, to suck the nectar from flowers, they have a long tube-like structure called proboscis. General Science 27 Q.12. Answer in brief: Ans. (1) Living organisms need nutrition due to the following: (a) To supply the energy required for doing work, (b) For growth and development of the body, (c) To replace the damaged cells and repair tissues, (d) To fight diseases. (2) The transport system of plants consists of the xylem and the phloem. The xylem transports minerals and water from the root to all aerial parts of the plant. The phloem transports the food (glucose, etc.) from the leaves to other parts of the plant where it is either consumed or stored. (3) Two different types of micro-organisms can bring about biological nitrogen fixation. (a) Root-nodules of leguminous plants contain the Rhizobium micro-organisms. These micro-organisms absorb atmospheric nitrogen and convert it into its nitrate, a compound. (b) Micro-organisms like Azotobacter are present in soil. They also convert atmospheric nitrogen into nitrates. (4) Atmospheric fixation of nitrogen : Lightning (thunderbolts) occur in the rainy season. This causes atmospheric nitrogen and oxygen to react with each other to form nitric oxide (NO) which is again oxidized to form nitrogen dioxide (NO2). The nitrogen dioxide dissolves in rainwater and is converted into nitric acid (HNO3) which gets added to the soil along with the rain-water. Plants use this nitrogen for their growth. *(5) (a) Plants can produce their own food. With the help of sunlight and chlorophyll, plants make their own food in their leaves, using water and nutrients from the soil and carbon dioxide from the air. (b) This process is called as photosynthesis. In this process plants give out oxygen and take in carbon dioxide. Sunlight 6CO2 + 6H2O Chlorophyll Carbon dioxide Water C6H12O6 + 6O2 Glucose (food) Oxygen 28 Grade Me Teacher’s Guide (Std. 7) *(6) (a) In dark red or purple coloured leaves,. chlorophyll pigments are masked by other colourful pigments which are present in large amounts. (b) The chlorophyll pigment present in less amount is capable of absorbing sunlight and helping to convert carbon dioxide and water into food. *(7) (a) Chemosynthesis is the biological conversion of one or more carbon containing molecules and nutrients into organic matter. (b) It uses the oxidation of inorganic compounds or methane as a source of energy rather than sunlight. (c) Riftia pachyptila produce their food by chemosynthesis. *(8) (a) Waste stored in the leaves are shed alongwith them in a specific period. (b) Sticky substances such an resins, gums, latex are the excretory products of plants. *(9) Air contains gaseous nitrogen. However, plants cannot utilize gaseous nitrogen. It needs to be fixed, i.e. converted into compounds. Fixation of nitrogen occurs by biological and atmospheric methods. *(10) Plants produce their own food with the help of sunlight, chlorophyll, water, nutrients from soil and carbon dioxide from the air. This process is called as photosynthesis. sunlight Carbon + water > food + oxygen chlorophyll dioxide 6CO2 + 6H2O > C6H12O6 + 6O2 Glucose Oxygen *(11) Nutrients are used for the following purposes: (a) Obtaining energy (b) Growth (c) To carry out day to day function of the body (d) To fight against diseases. *(12) Steps of nutrition in animals are as follows: (a) Ingestion: Food is taken into the body. (b) Digestion: Conversion of food into simple soluble forms. (c) Absorption: A transfer of soluble food to the blood. General Science 29 (d) Assimilation: Utilization of absorbed food by cells and tissues for energy production, growth and repair. (e) Egestion: Removal of waste products and undigested food from body. *(13) (a) Amoeba does not have organs like hands and mouth. (b) It is unicellular animal. It can take in food through any part of the surface of its unicellular body. (c) It surrounds the food Food particle particle from all sides to Nucleus take it into the cell. (d) After that, it digests the food with the help of different enzymes. (e) Undigested food is left behind as the Amoeba moves further with the help of pseudopodia. Food particle (f) In unicellular animals Nucleus like Amoeba, Euglena, Paramoecium, etc. all the steps of nutrition occur within their unicellular body. *(14) The plants that grow on the body of other plants to obtain food are called as parasitic plants. There are two types of parasitic plants: (a) Holoparasites: e.g. Rafflesiaceae (b) Hemiparasites: e.g. Loranthaceae *(15) Amoeba, Euglena, Paramoecium *(16) (1) Carnivore (2) Herbivore (3) Carnivore (4) Ominivore (5) Herbivore (6) Carnivore (7) Scavenger 30 Grade Me Teacher’s Guide (Std. 7) *Q.13. Think and answer: Ans. (1) (a) We prepare a variety of foodstuffs and dishes at home but we are not autotrophic organisms. (b) In autotrophic organisms, they have chlorophyll in their body and food is prepared here with help of sunlight, water and CO2 for the organisms. (c) But, the food which we prepare at home doesn’t generate in our body. (2) (a) Autotrophs have chlorophyll in the cell and here the organic food is prepared using sunlight, water and CO2. (b) They do not depend on any other organism for survival. (c) But the heterotrophs depend on autotrophs and other organisms for survival. Hence, autotrophs are more in number than heterotrophs. (3) In desert region due to scarcity of water and excess heat, very few cactus are found as autotrophs compared to sea. As autotrophs are less, number of heterotrophs dependent on autotrophs are smaller. Whereas in sea due to greater numbers of autotrophs, greater number of heterotrophs are found. (4) (i) Ectoparasitic animals suck the blood of the animal on which it remains and endoparasitic animals get readymade food from the body of animal in which it remains. (ii) This way both the parasites make the animal weak by sucking their blood or by eating prepared food from them. (5) Plant food is not produced in any other parts of the plant except the green ones because only green part contains chlorophyll and chlorophyll is very necessary for the production of food. General Science 31 Q.14. Prepare and complete the flowchart according to type of nutrition. Ans. Nutrition Plants Animals Autotrophic Heterotrophic Saprophytic Holozoic Saprozoic Parasitic Insectivorous Parasitic Ectoparasitic Endoparasitic vvv 5 FOOD SAFETY (Grade Me pg. no. (38 - 43) *Q.1. Complete the following statements by using the correct option from those given below: Ans. (1) dehydration (2) pasteurization (3) natural (4) chemical Q.2. Fill in the blanks: Ans. (1) World Food day (2) Food Safety and Standardization Authority of India (3) Louis Pasteur (4) Nitrogen *Q.3. Find the odd man out: Ans. (1) Salt (2) Turmeric powder (3) Almond (4) Settling. Q.4. Give two examples of: Ans. (1) Vinegar, Citric acid (2) Salt, Oil (3) Freezing, Drying 32 Grade Me Teacher’s Guide (Std. 7) Q.5. Give scientific reasons: Ans. *(1) Food remains safe at 5° Celsius because at 5°C, micro-organisms stop growing. *(2) Nowadays, food is served buffet style during large gatherings because due to buffet style quantitative wastage of food can be avoided, as people take only as much as they could eat. (3) We boil milk from time to time to kill micro organisms in it and thus prevent it from getting spoilt. (4) Biological and chemical reactions in food materials are slowed down at low temperature. As a result, food remains in good condition for a longer period. Therefore, refrigerators are used in the kitchen. (5) The foodstuffs we consume, whether of animal or plant source, must be of the best quality. Otherwise, we may fall prey to disease or illness. Food is said to be spoiled if there is a change in its colour, odour, texture, quality, taste and there is loss of its nutrient content. *Q.6. What shall we do? Ans. (1) We should tell them to sell the covered sweets because uncovered sweets are harmful to eat because it contains dust, dirt and germs. And buyers also should not purchase these uncovered sweets. (2) We should tell him to wear gloves before serving panipuri because dirty hands contain dirt and germs which are harmful to us. (3) We should keep them in refrigerator because in refrigerator due to low temperature, fruits and vegetables do not spoil and biological and chemical reactions in fruits and vegetables are slowed down at low temperature. (4) (i) If we do not protect foodstuffs from pests like rats, cockroaches, wall-lizards etc. then the food gets spoiled by them and germs carried by them enters in the food. (ii) If we eat this food then we may get food poisoning and we fall sick. So, we need to protect foodstuffs from pests like rat, cockroaches, wall lizards etc. Keep the cooked food items in a place/shelf which is protected by wire mesh. The house must be protected by pest control. General Science 33 Q.7. Answer in one sentence: Ans. (1) Food is said to be spoilt if there is a change in its colour, odour, texture, quality, taste and there is a loss of its nutrient content. (2) Prevention of food spoilage by microbial growth and infestation by pests is called food protection. (3) Use of various preservatives to prevent, for a long period of time, food spoilage due to internal factors is called food preservation. (4) Pasteurisation involves heating the milk or other similar foodstuffs up to a certain temperature; e.g., milk at 80oC for 15 minutes and cooling it quickly. This destroys the microbes present in the milk and it keeps for a longer duration. Q.8. Answer in short: Ans. *(1) Quantitative wastage of food: (a) Wrong methods of farming like hand sowing of seeds, inadequate threshing, improper storage and wrong methods of distribution are some reasons for quantitative wastage of food. (b) Besides, much food is wasted as a result of the custom of offering and serving too much food to guests at traditional feasts or banquets. (c) Had it not been wasted, all this food could have met the need of many others. Qualitative wastage of food: Using wrong methods of protecting food, excessive use of food preservatives, over-cooking, washing the vegetables after cutting them, mis-handling of fruits like grapes and mangoes, mis-calculation of the time required to transport food from producers to consumers, are some of the causes of quantitative wastage of food. *(2) (a) Serve yourself only as much as you can eat. (b) Avoid over-cooking food. (c) Avoid throwing away left-over food. Re-use it in a proper way. (d) Buy only as much grain, vegetables, fruits, milk, etc. as you need. Avoid the temptation to make excessive purchases. (e) Store grains and other perishable foodstuffs like vegetables, fruits, milk, etc. using proper methods. 34 Grade Me Teacher’s Guide (Std. 7) (f) Check the expiry date of bottled, canned, packed food and use within that time. (g) Eat all the food that you have served yourself. *(3) We can use the alternatives as flowers instead of rice as ‘akshata’. We should cook less of food and only as much is required to the amount of guests. If too much food is cooked, it should be distributed among the needy people. Daily lot of people go hungry and the food should be distributed among them rather than being wasted. (4) Pass a magnet through the rava and Iron filings adhere to the magnet. (5) It is necessary to preserve foodstuffs as the food gets spoiled by growth of micro-organisms as well as internal factors. *(6) Boil the milk at 80°C for 15 minutes and cool it quickly. This destroys the microbes present in the milk and it keeps for a longer duration. This process is called pasteurization of milk. *(7) Different types of adulterants affect our health in different ways. Some adulterants cause abdominal discomfort or poisoning, while some may affect the functioning of some organs if consumed over a long period of time or even cause cancer. *(8) Our parents take following care to keep foodstuffs safe: (a) Drying of grains. (b) Boiling of milk, soups and curries from time to time. (c) Refrigeration of vegetables, fruits, milk and cooked food. (d) Candying of jams. (e) Use natural preservatives like oil, spices, neem leaves. (f) Use chemical preservatives in sauces, ketchups, pickles, jams and squashes. *(9) Food spoilage is the process in which food deteriorates to the point in which it is not edible to humans or its quality of edibility becomes reduced. Following are the factors for spoiling of food: (a) Bacteria causes food to spoil (b) Incorrect storage may spoil the food. General Science 35 (c) Infestation by pests. (d) Chemical reaction takes place in food and it gets spoiled. *(10) I use following methods to preserve the food: (1) Freezing (2) Boiling (3) Salting of pickles (4) drying of grains (5) candying of jams. *Q.9. Explain why this happens and suggest possible remedies: Ans. (1) Qualitative wastage of food happens due to wrong methods of protecting food, excessive use of food preservatives, over-cooking, washing the vegetables after cutting them, mishandling of fruits like grapes and mangoes, miscalculation of the time required to transport food from producers to consumers are some of the reasons of qualitative wastage of food. Possible remedies: (a) Avoid overcooking food, (b) Store grains and other perishable foodstuffs like vegetables, fruits, milk etc. using proper methods. (c) Wash fruits and vegetables before cutting it. (2) Sometimes in a hurry if we cook the rice it is underdone. Possible remedies: Use proper pressure cooker to cook the rice. (3) Sometimes due to sudden rain wheat gets a bit moist. Possible remedies: Do not store the moist wheat, it gets spoiled due to fungus. So, first sun dry it and then store in a clean and dry container to avoid microbial growth. (4) The taste of yoghurt is too sour/slightly bitter means it is spoiled. This happens if it is not kept in the refrigerator. Possible remedies: Always keep the yoghurt in refrigerator to avoid biological and chemical reactions in food materials. (5) Fruit contains an enzyme called polyphenol oxidase or tyrosinase that reacts with oxygen. The oxidation reaction basically forms a sort of rust on the surface of fruits so it turns black. Possible remedies: (a) Coat the fruits with sugar syrup (b) Add lemon juice on fruits. 36 Grade Me Teacher’s Guide (Std. 7) *Q.10. Complete the chart below: Ans. No. Foodstuff Adulterant (1) Turmeric Metanyl yellow (2) Black pepper Dried seeds of papaya (3) Rava Iron filings (4) Honey Jaggery (5) Milk Water (6) Red chilli powder Brick dust (7) Black pepper Seeds of Papaya (8) Ice-cream Paper pulp *Q.11. Complete the chart below: Nutrients Ans. No. Food/Source Function in body obtained (1) Jowar, wheat, Carbohydrates To provide energy millet, bajra, rice For growth and (2) Beans and pulses Proteins repair (3) Oil, ghee, etc. Fats To provide energy Fibre, water, (4) Fruits and To fight against vitamins and vegetables diseases. minerals Q.12. Shreya purchased some red chilli powder and turmeric powder from a local vendor. What test would you suggest, she should carry out to find out if the foodstuffs she has purchased are adulterated or not? Food Ans. Adulterant Test Conclusion material Red Brick dust Take a spoonful If a red layer is seen chilly of chilly powder settled at the bottom powder in a beaker, stir of the beaker, it it and leave it must have been undisturbed for a adulterated with few minutes. brick dust. General Science 37 Turmeric Metanil Take a pinch of The mixture powder yellow turmeric powder becomes red on in a test tube, add addition of conc. a small quantity HCl and the of water to it, red colour does shake the mixture not disappear if and add a few metanil yellow is drops of conc. present. HCl Q.13. Sridhar bought some milk from a milk vendor. When he put a drop of milk on a glass slide, it did not leave a milky white spread on the slide. Is the milk adulterated? How will you conclude? Ans. Food Adulterant Test Conclusion material Milk Water Put a drop of milk If the spread-milk on a glass slide and of mark does not slightly incline it to appear milky white, spread the drop. water must have been added to it. *Demonstrate the various methods of detecting food adulteration. Ans. Food Adulterant Test Conclusion material Put a drop of milk If the spread-milk of on a glass slide and mark does not appear Milk Water slightly incline it to milky white, water must spread the drop. have been added to it. Take a spoonful of If a red layer is seen chilly powder in a settled at the bottom Red chilly Brick dust beaker, stir it and of the beaker, it must powder leave it undisturbed have been adulterated for a few minutes. with brick dust. 38 Grade Me Teacher’s Guide (Std. 7) Take a pinch of The mixture becomes turmeric powder red on addition of in a test tube, add conc. HCl and the Turmeric Metanil a small quantity of red colour does not powder yellow water to it, shake the disappear if metanil mixture and add a yellow is present. few drops of conc. HCl Fine iron Pass a magnet Iron filings adhere to Rava filings through the rava. the magnet vvv TEST PAPER - 1 : UNIT TEST (Grade Me Pg.no. 44) LESSON NO. 1 to 5 Marks : 10 Q.1. Name the following : (2) Ans. (1) Pedicel (2) Carnivores Q.2. Answer the following questions in one sentence each: (8) Ans. (1) Food is said to be spoiled if there is a change in its colour, odour, texture, quantity, taste and there is a loss of its nutrient content. (2) Lightning (thunderbolts) occur in the rainy season. This causes atmospheric nitrogen and oxygen to react with each other to form nitric oxide (NO) which is again oxidized to form nitrogen dioxide (NO2). The nitrogen dioxide dissolves in rainwater and is converted into nitric acid (HNO3) which gets added to the soil along with the rain-water. Plants use this nitrogen for their growth. (3) Silt soil is suitable for cultivation. Particles of silt soil are of medium size. Therefore, silt soil is much more ploughable than clay soil. This soil contains a large proportion of organic materials. Its capacity to supply nutrients is much greater. General Science 39 (4) Androecium Gynoecium (1) This is the male (1) This is the female reproductive part of the reproductive part of the flower. flower. (2) It is made up of stamens A (2) It is made up of carpels. stamen consists of anther, A carpel consists of and filament. stigma, style and ovary. vvv MEASUREMENT OF PHYSICAL QUANTITIES 6 (Grade Me pg. no. (45 - 50) Q.1. Fill in the blanks: Ans. (1) mass (2) System International Q.2. State whether the following statements are True or False: Ans. (1) True (2) False (3) True *Q.3. (A) Who is my companion? Ans. (1 - c); (2 - e); (3 - a); (4 - b); (5 - d). *Q.3. (B) Multiple choice questions: Ans. (1 - A) a micrometer; (2 - D) Light Year; (3 - B) Velocity; (4 - D) metric tonnes; (5 - C) metre square; (6 - B) second *Q.4. Explain giving examples: Ans. (1) A quantity that can be completely expressed by its magnitude alone is called a scalar quantity. e.g. length, breadth, area, mass, temperature, density, time, work. In all these examples, a value with a unit is used to express quantities. Thus, we say that the length of a tunnel is 2 km. (2) The quantity that is expressed completely only when magnitude and direction are both given is called a vector quantity. Displacement, velocity are vector quantities. e.g. a displacement of 20 km towards north, the aeroplane flying at a velocity of 500 km/hr towards Mumbai. 40 Grade Me Teacher’s Guide (Std. 7) Q.5. Give scientific reasons: Ans. (1) In everyday affairs, we measure many different physical quantities. As these physical quantities are different from each other, a specific unit is used to measure each quantity. Therefore, different units are used while measuring different quantities. *(2) It is not proper to measure quantities by using body parts as units because length of the body parts changes from person to person. So, accurate measurement can not be found with the body parts as units. *(3) It is necessary to get the weights and measures standardized at regular intervals because of that accurate weight and measurement can be taken. Errors will be avoided. Q.6. Answer in one sentence: Ans. (1) A value and a unit are used to express the magnitude of a physical quantity. (2) MKS system and CGS system. (3) The units usually used to measure physical quantities are called standard units. (4) Length and breadth are the quantities taken into account while calculating the area of your classroom. Q.7. Answer in short: Ans. *(1) (a) The gravitational force that acts on the mass is called the weight. (b) The earth is not exactly spherical, it flattens at the poles. (c) As the distance increases, the gravitational force decreases. (d) Therefore, due to reduced distance at the poles compared to the equator, the weight is maximum at the poles than equator. *(2) (a) The gravitational force that acts on the mass is called the weight. (b) The gravitational force is always inversely proportional to the distance. (c) So as the distance increases between the earth and the object, the gravitational force decreases. General Science 41 (d) The gravitational force by which the earth attracts an object towards its centre is called weight. (e) The weight at the sea-level is higher than at higher altitude, as the object is at a greater distance at higher altitudes compared to sea-level. (3) (a) In atomic clock, to measure time, periodic vibrations of cesium atom is used as a standard. (b) 1 sec = 9,192,631,770 vibrations. (c) The cesium atomic clocks are very accurate. (d) In India, 5 atomic clocks are kept in National Physical Laboratory. (4) In older time, hour glass was used for measuring time. (5) To prevent consumers from being cheated, a weight and measures sub-division functions as a part of the Food, Urban Supply and Consumer Protection Mission of the Government. *Q.8. Answer in brief: Ans. (1) The weight of the same object is different on different planets because weight depends on the gravitational force of the planet and gravitational force on every planet is different so the weight also differs from planet to planet. (2) Following precautions will be taken to make accurate measurements in day to day affairs: (a) The balance should carry the stamp of standardisation by the department of weights and measures. (3) Mass and Weight Mass Weight (1) The amount of matter (1) The gravitational force that present in a substance is acts on this mass is called called mass. its weight. (2) It is a scalar quantity. (2) It is a vector quantity. (3) Mass remains same (3) Weight changes from place everywhere on the earth. to place on the earth. (4) Major causes of errors in measurement are: (1) Not using the appropriate device. (2) Not using the device properly. 42 Grade Me Teacher’s Guide (Std. 7) Example: While buying things at grocery shops and the vegetable market remember to look out for the following: (a) The balance should carry the stamp of standardisation by the department of weights and measures. (b) Balance should be stable. The pointer of the balance should be upright. (c) No changes should be done on the underside of the pan of the balance. (d) Weight should be made up of metals and it has to be standardized. (5) (a) Measurement of substances that are precious or of great importance and used in very small quantities is done meticulously and accurately. (b) Due to advancements in technology, devices that measure very small magnitudes of quantities like distance, mass, time and temperature are available now. (c) e.g. distance and time in connection with very important sports competitions, mass of gold, body temperature etc. (d) Devices to be used for this are thermometer, digital balance (Analytical balance) etc. *Q.9. How are the various articles and materials shown in the picture, measured? Ans. Article/materials Measurements Brinjal kilogram Reel of thread metre Leafy vegetable per piece / bunch Liquid litre Ornament carat Fabric metre General Science 43 Q.10. Complete the following tables: Ans. Name of the unit Quantity M.K.S. C.G.S. Length m cm Mass kg g Time s s Speed m/s cm/s Q.11. Identify the wrong methods of measurement shown in the picture and explain why they are wrong. Ans. (1) Measuring length by hand. (2) The length of a line is to be measured from 0 (zero) of the ruler to get the accurate measure. (3) The volume of water( or any liquid) should be measured using a measuring jar, which has the marking on it to read the volume. (4) Weighing any object using standardized weights will give the accurate measure of the weights. It is not proper to measure quantities by using body parts as units because length of the body parts changes from person to person. So, accurate measurement can not be found with the body parts as units. vvv 7 MOTION, FORCE AND WORK (Grade Me pg. no. (51 - 56) *Q.1. Fill in the blanks with the proper words from the brackets: Ans. (1) constant, (2) stationary but not zero, (3) Speed (4) Velocity Q.2. Fill in the blanks: Ans. (1) Joule, (2) Displacement, (3) Change in velocity, (4) Isaac Newton 44 Grade Me Teacher’s Guide (Std. 7) *Q.3. From the groups B and C, choose the proper words, for each of the words in group A. Ans. Group 'A' Answers Group 'B' Group 'C' (1) Work Joule - erg (a) Newton (i) erg (2) Force Newton - dyne (b) Metre (ii) cm (3) Displacement Metre - cm (c) Joule (iii) dyne *Q.4. Find the unit: Ans. Task Speed Velocity Write the Distance Displacement Speed = Velocity = formula Time Time Units of the Distance: metre Displacement: metre quantities Time period: seconds Time period: seconds Q.5. Answer in one sentence: Ans. *(1) When a body is moving, it is said to be in motion. Motion is a change in position of a body with respect to time. *(2) Applying force causes a change in motion. *(3) The distance transversed by a moving body irrespective of the direction in unit, time is called speed. Distance covered *(4) Speed = Time required (5) The velocity at a particular moment of time is called instantaneous velocity. (6) Acceleration is the change in velocity in the given time. *(7) Change in velocity causes acceleration. (8) A stationary body remains in stationary state or a body in motion will continue moving with the same velocity and in the same direction. *(9) Yes force is a vector quantity. (10) The ability to do work is called energy. (11) Work done = Force × Displacement. General Science 45 *Q.6. Answer in short: Change in velocity Ans. Acceleration = Time taken for change Unit of velocity = m/s. Unit of time = second m/s m \ a= = s s×s m a = s2 (2) The direction of the ball moving in a straight line will change only when a force is applied on it in a different direction. (3) The total distance the bird has traversed is the length of the distance covered by circling, but the eventual displacement of the bird is zero as its initial and final position are one and the same. (4) (a) Force: The interaction that brings about the acceleration is called force. e.g: An ox is pulling a cart, applying brakes to a bicycle, lifting heavy iron object with a crane. (b) Work: When an object is displaced by applying a force on it, work is said to be done. e.g: A bucketful of water is to be drawn from a well and taken to the home by walking from well to home. (c) Displacement: The minimum distance traversed by a moving body in one direction from the original point to reach the final point is called displacement. e.g: A rolling of a ball from point A to point B in the same direction. (d) Velocity: Velocity is the distance traversed by a body in a specific direction in unit time. e.g: A truck is covering a distance of 40 km from A to D in a straight line in 1 hour. A D 46 Grade Me Teacher’s Guide (Std. 7) (e) Acceleration: It is change in velocity per second. It can be deduced. Change in velocity Acceleration = Time taken for change e.g: v = 60 km/hr, v = 30 km/hr, v = 40 km/hr A B C D (i) In the above example a truck covered the distance AB at velocity of 60 km/hr, BC at 30 km/hr and CD at 40 km/hr. (ii) It means that the velocity for the distance CD is greater than the velocity for the distance BC. (iii) From the number of seconds required for this change in velocity to take place, the change in velocity per second can be deduced. This is called acceleration (f) Distance: The length of the route actually traversed by a moving body irrespective of the direction is called distance. e.g: Ranjit travelled 1 km. from his home to school. (5) Distance and Displacement Distance Displacement (1) The length of the route actually (1)The minimum distance traversed by a moving body, traversed by a moving irrespective of the direction is body in one direction from called distance. the original point to reach the final point is called dis- placement. (2) It is a scalar quantity. (2) It is a vector quantity. (6) The work is said to be done only if there is displacement of the body when force is applied on it. (7) Unit of work - Joule, unit of force - Newton and Unit of displacement is metre is SI system. (8) If a force of 1N parallel to the surface of the table is applied to a wooden block on the table, and the block is displaced by 1 metre, then it can be said that 1 Joule of work is done. General Science 47 (9) Ans. Speed Velocity (i) Speed is distance (i) Velocity is the distance travelled per unit of traversed by a body in a time. specific direction in unit time. (ii) It is a scalar quantity. (ii) It is a vector quantity. (iii) Formula: (iii) Formula : Distance Displacement traversed Velocity = Speed = Total time Total time *Q.7. Solve the following problems: Ans. F = 1000 N (Force) S = 10 m (displacement) W = ? (work done) W = FS = 1000 × 10 W = 10,000 Joule (2) Force (F) = 2 N Displacement (S) = 50 m Work done (W) = ? W = FS = 2 × 50 W = 100 Joule *Q.8. Observe the figure and answer the questions: ― ― ― ― Ans. (1) (a) Actual distance = AB + BC + CD + DE = 3 + 4 + 5 + 3 Actual distance = 15 km (b) Displacement = AB + BD + DE = 3 + 3 + 3 Displacement = 9 km 48 Grade Me Teacher’s Guide (Std. 7) Distance travelled (c) Speed = Total time Distance = 15 km = 15 × 1000 = 15000 m Time = 1 hr = 1 × 60 × 60 = 3600 sec. 15000 15 km S = or S = = 15 km / hour = 4.16 m/sec. or 15 km/hr. 3600 1 hour Displacement (d) Velocity = Total time Displacement = 9 km = 9 × 1000 = 9000 m Time = 1 hr = 1 × 60 × 60 = 3600 sec 9000 9 km V = or V = = 9 km / hour 3600 1 hour = 2.5 m/sect. or 9 km/hr. (e) Yes, this velocity can be called as average velocity. (2) As its initial and final positions are one and the same, Initial Velocity = 2 cm/s. Final Velocity = 4 cm/s Time taken for the change in velocity from B to D = 4 cm/s – 2 cm/s = 2 cm/s Change in velocity 2 cm/s Acceleration = = = 1 cm/s2 Time taken for change 2 sec Q.9. Observe the figure and answer the following questions. Ans. (1) Coin moves due to displacement when force acts on it. (2) Coin moves smoothly. *(3) Applying talcum powder to the carrom board decreases the friction and coin moves smoothly. Q.10. Observe the diagram and answer the questions given below: Ans. (1) Mechanical force has been applied here. General Science 49 (2) This force can be increased by attaching a heavier weight. (3) If more force is applied, the displacement of the block will be more. (4) When the block starts moving, we can say that work is done by the applied force. l In a tug of war, one team gives way to the other. What work is being done and by whom? Ans. The force applied by the stronger team does the work by displacing other team. l When a book is lifted from a table, against which force is work done? Ans. When a book is lifted from a table, work is done against gravitational force. l Will work be done by a man who pushes a wall? Give reasons. Ans. No work will be done by the man who pushes the wall as there is no displacement. vvv 8 STATIC ELECTRICITY (Grade Me pg. no. (57 - 65) Q.1. Fill in the blanks: Ans. (1) electron (2) repel (3) gold leaf electroscope *Q.2. Choose the correct option and fill in the blanks: Ans. (1) always repulsion (2) Electron (3) copper (4) Steel (5) always attraction (6) charged object Q.3. State whether the following statements are True or False: Ans. (1) False (2) True (3) True (4) False (5) False (6) True (7) False (8) False (9) False Q.4. Name the following: Ans. (1) Plastic comb, human hair (2) Glass rod (3) Ebonite rod (4) The lightning conductor 50 Grade Me Teacher’s Guide (Std. 7) Q.5. Match the following: Ans. (1) Positive charge (2) Negative charge (3) Lightning (4) Charged body. Q.6. Answer in one sentence: Ans. (1) Static electricity also called frictional electricity because static electricity is generated by friction. (2) Lightning conductor is made of copper because copper is good conductor of electricity. (3) We can make extremely thin leaves of gold, so even a small charge also can be detected. (4) Moist air is a conductor of electricity. So, the charge produced on a body due to friction is conducted away by the surrounding moist air. Hence, the experiments on static electricity are not successful. Hence, static electricity experiments be carried out in dry weather. Q.7. Give scientific reasons: Ans. (1) (a) Every atom contains smaller particles with either positive or negative charge. (b) As the number of positively and negatively charged particles in an atom is equal, they neutralize each other. (c) As a result, the atom has no charge. *(2) The electric charge is generated by friction. So, when a plastic comb or ruler rubbed on dry hair it generates electric charge which attracts pieces of papers. *(3) The electric charge is generated by friction. If we pass near a polyester curtain again and again, it generates electric charge and so it gets attracted towards us. *(4) If we rub a blanket with our hands, opposite electric charges are produced on the blanket and on the hand. The blanket carries negative charge and as metals are good conductors of electricity charge is carried from the blanket to metal and spark is seen. (5) There is attraction between unlike electric charges. Similarly, electrically charged body and electrically neutral body also display attraction. So, attraction can not be used as the test for identifying General Science 51 an electrically charged object. Hence, repulsion is used as a test for identifying an electrically charged object. Q.8. Answer in short: Ans.(1) When certain objects are rubbed against each other, the negatively charged particles of one object go to the other object. The object to which they go, becomes negatively charged due to an excess of negatively charged particles. Whereas the first object becomes positively charged. (2) The charge developed by induction disappears quickly because it is very weak. (3) The leaves of a gold leaf electroscope fly apart when a charged body touches its disc because like charges develop on both the leaves and hence they repel each other. (4) As we wear a cardigan, it has layers of clothing which rub against each other and a static charge will be developed on it. The cardigan then discharges its negative charge and as the air around it being a good conductive attracts to it and a crackling sound is produced. *(5) Two charged objects would always influence each others depending upon its charge. If they are like charges they will repel each other and if they are opposite charges, they will attract each other. *(6) No. Only certain pairs of substances give rise to electric charge on rubbing. *(7) (a) Friction causes a charge to develop because on rubbing, some negative particles are transferred from one substance to the other and the later develops a negative charge. (b) The substance from which particles are removed lose negative charge and hence, it develops a positive charge. *(8) A charged balloon sticks to a wall because there is always attraction between a charged object and an uncharged object. *(9) We can use other metals than gold in gold leaf electroscope. (a) Only thing is that metal should be malleable and good conductor of electricity. (b) But the best is gold only because we can make extremely thin leaves of gold so even very small charge also can be detected. 52 Grade Me Teacher’s Guide (Std. 7) (10) When lightning strikes, an opposite electric charge is generated on the roof of a building or on the top of a tree by induction. Due to the attraction between the opposite charges on the cloud and the building, the charge on the cloud flows towards the building. This is called a lightning strike. Q.9. Write short notes on: Ans. (1) This is a simple device to detect the electric charge on an object. It consists of a copper rod which has a metal disc at the upper end and two thin gold leaves at the other. The rod is placed in a bottle so that the disc is above the bottle. When an uncharged object is taken near the disc, the leaves remain closed. When a charged object is taken near the disc, both the leaves are charged by the same electric charge, and repel each other, i.e. move away from each other, or open up. When we touch the disc with our hand, the leaves collapse, because the charge in the leaves goes into the earth through our body, and the leaves get discharged. (2) (i) The lightning conductor is a device used for protection from a lightning strike. (ii) It is fitted on the highest part of the building to the ground. (iii) Whenever an electrically charged cloud passes over the building, the electric charges flowing towards the building are conducted into the ground through the copper strip, and damage to the building is prevented. (iv) When such a lightning conductor earthing is fixed on a tall building, the surrounding area is also protected from lightning. (v) Thick copper strip is used in a lightning conductor because copper is a good conductor of electricity. *(vi)(i) The pointed end makes it possible to increase the electric field near the point. The electric field set up at pointed end is high. (ii) If the discharge of cloud occurs it would be easily passed through the lightning conductor to the ground and damage to the building is averted. *(vii)Coal and salt is filled in the pit and also there is a provision for pouring water into it. This helps to spread electric charge quickly into ground and prevent damage. General Science 53 Q.10. Answer in brief: Ans. (1) (a) This is a simple device to detect the electric charge on object. (b) It consists of a copper rod which has a metal disc at the upper end and two thin gold leaves at the other. Positively charged rod Metal disc Copper rod Gold leaves Bottle (c) The rod is placed in a bottle so that the disc is above the bottle. (d) When an uncharged object is taken near the disc, the leaves remain closed. (e) When a charged object is taken near the disc, both the leaves are charged by the same electric charge, and repel each other. (f) When we touch the disc with our hand, the leaves collapse because the charge in the leaves goes into the earth through our body, and the leaves get discharged. *(2) Large amount of charges get built up in the clouds in rainy and stormy weather. (a) Sometimes these charges are transferred to the earth in the form of a bolt of lightning. (b) Wire of umbrella is made up of metal and cloth is made up of synthetic material. (c) If lightning strikes, then umbrella catches it and there are chances of fire and it would be dangerous. (d) So, it is not safe to go out with an umbrella when there is heavy rain. 54 Grade Me Teacher’s Guide (Std. 7) *(3) Following are the characteristics of a static electric charge: (a) The electric charge generated by friction is called frictional electricity. This charge is produced only at the place of friction, hence it is called static electricity. (b) It remains on the object for a short duration. (c) The charges of static electricity are absorbed in moist air. (d) An electrically charged object attracts another object which has no electric charge. (e) Like charges repel each other. (f) Unlike charges attract each other. (g) Repulsion is the sure test of the existence of a static charge. *(4) Due to lightning, great damage can occur. (a) It may cause fire. (b) Person on whom lightning strikes may die also. (c) It causes more temperature than sun. Awareness to prevent it: (a) Guide the people to install lightning conductor on tall buildings. (b) Do not stand on open ground, below a tree, or on a high location during the thunder storms. (c) Do not use plugged electrical appliances. (d) Do not stand near an electric pole, telephone pole or a tower. (e) Stay in pucca house. (f) Stand on only wood, a plastic sheet or sack of jute. *(5) To protect from the lightning, we have to put lightning condu