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Class 8 | Science | Textbook Solutions | Maharashtra Board
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Class 8 | Science | Chapter 16 | Reflection Of Light | Exercise Solution | Maharashtra Board
Class 8 | Science | Textbook Solutions | Maharashtra Board
21 Feb 2025

Class 8 | Science | Chapter 16 | Reflection Of Light | Exercise Solution | Maharashtra Board

1. Fill in the blanks: i. The perpendicular to the mirror at the point of incidence is called …………. .Answer:The perpendicular to the mirror at the point of incidence is called the normal. ii. The reflection of light from a wooden surface is ……….. reflection.Answer:The reflection of light from a wooden surface is irregular reflection. iii. The working of a kaleidoscope is based on the properties of …………… .Answer:The working of a kaleidoscope is based on the properties of reflection of light. 2. Draw a figure describing the following: The reflecting surfaces of two mirrors make an angle of 90° with each other. If a ray incident on one mirror has an angle of incidence of 30°, i draw the ray reflected from the second mirror. What will be its angle of reflection? Answer:For the ray C, the angle of reflection = 60°. 3. How will you explain the statement ‘We cannot see the objects in a dark room’? Answer:In a room that is completely dark, no light falls on objects. Hence, no light enters our eyes. Hence, there is no sensation of vision, i.e., we cannot see the objects. 4. Explain the difference between regular and irregular reflection of light. Answer:For regular reflection of light, the angles of incidence as well as the angles of reflection are the same for all parallel rays of light incident on the plane and smooth surface. Hence, the reflected rays are also parallel to one another. For irregular reflection of light, the angles of incidence for parallel rays of light incident on the rough surface are not equal, and hence the angles of reflection are also not equal. Here, the reflected rays are not parallel to one another and spread over a large surface. 5. Draw a figure showing the following:(a) Incident ray, (b) Normal, (c) Angle of incidence, (d) Angle of reflection, (e) Point of incidence, (f) Reflected ray. Answer: 6. Study the following incident. Swara and Yash were looking in a water-filled vessel. They could see their images clearly in the still water. At that instant, Yash threw a stone in the water. Now their images were blurred. Swara could not understand the reason for the blurring of the images.Explain the reason for blurring of the images to Swara by answering the following questions: I. Is there a relation between the reflection of light and the blurring of the images?Answer:Yes. ii. Which types of reflection of light can you notice from this?Answer:Regular reflection of light when light is incident on the still water and irregular reflection of light when light is incident on the water as ripples are produced on its surface when a stone is thrown in the water.Still water behaves as a plane and smooth surface while oscillating water behaves as a rough surface. iii. Are the laws of reflection followed in these types of reflection?Answer:Yes. 7. Solve the following examples. a. If the angle between the plane mirror and the incident ray is 40°, what are the angles of incidence and reflection?Solution:The angle between the plane mirror and the incident ray is 40°. Therefore, the angle of incidence (i) = the angle made by the incident ray with the normal to the plane mirror = 90° – 40° = 50°. The angle of reflection, r – i – 50°. b. If the angle between the mirror and reflected ray is 23°, what is the angle of incidence of the incident ray?Solution:The angle between the mirror and the reflected ray is 23°. Therefore, the angle of reflection (r) = the angle made by the reflected ray with the normal to the plane mirror = 90° – 23° = 67°.∴ The angle of incidence, i = r = 67°.

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Class 8 | Science | Chapter 17 | Man Made Material | Exercise Solution | Maharashtra Board
Class 8 | Science | Textbook Solutions | Maharashtra Board
21 Feb 2025

Class 8 | Science | Chapter 17 | Man Made Material | Exercise Solution | Maharashtra Board

1. Try to find it: a. Plastic shows …………. property, hence it can be moulded to any shape.Answer:Plastic shows plasticity property, hence it can be moulded to any shape. b. Motor cars are coated with ……… .Answer:Motor cars are coated with Teflon. c. Thermocol melts at ………… °C.Answer:Thermocol melts at more than 100 °C (it is about 240 °C). d. …………….. glass dissolves in water.Answer:Alkali silicate or water glass dissolves in water. 2. Who is my partner? Column ‘A’ Column ‘B’ 1. Lead glass a. Plates 2. Bakelite b. Mattresses 3. Thermocol c. Electric bulb 4. Optic glass d. Electric switch 5. Polypropylene e. Lens Answer: Column ‘A’ Column ‘B’ 1. Lead glass c. Electric bulb 2. Bakelite d. Electric switch 3. Thermocol a. Plates 4. Optic glass e. Lens 5. Polypropylene b. Mattresses 3. Answer the following. a. Thermocol is produced from which material?Answer:Thermocol is made from polystyrene which is also a complex thermoplastic substance. b. Write uses of PVC.Answer:PVC or Polyvinyl chloride is used for making bottles, raincoat, pipes, handbags, shoes, electric cable insulation, furniture, ropes, toys, etc. c. Write the natural or man-made raw material of the following items.Mattress, beaker, bangle, chair, gunny bag, broom, knife, pen.Answer: Items Natural raw material Man-made raw materials Mattress Cotton, Coir (Jute fibres) Polypropylene Beaker ___ Glass (Silicate or borosilicate glass) Bangle Gold, silver, lac, copper Plastic, Glass Chair Wood Plastic (PVC) Gunny bag Jute, cotton Plastic (PVC) Broom Plant fibres Plastic fibres (PVC) Knife Metals such as iron Plastic Pen Metals Plastic d. Which are the main ingredients of glass?Answer:The main ingredients of glass are sand and silica. e. How the plastic is produced?Answer: 4. Distinguish between.  a. Man-made material and natural materialAnswer: Man-made material Natural material 1. The man-made materials are obtained from processes in scientific laboratory. 1. Natural materials are obtained from nature. 2. Man-made materials are subjected to rigorous processing to alter the material for serving the intended purpose. 2. Natural materials are subjected to less treatment and processing. 3. Man-made materials are typically much more durable having a very long lifespan. 3. Natural materials have shorter lifespan, because these materials were once alive and so gradually perish over time. 4. Maintaining man-made materials require less care and attention. 4. Maintaining natural materials requires lots of care and continuous attention. 5. Man-made materials can have a negative environmental impact because they are not sustainable.E.g. Glass, plastic, Thermocol, soil, metals, rubber. 5. Natural materials do not have a negative environmental impact because they can be degraded easily.E.g. Cotton, silk, wood. b. Thermoplastic and Thermosetting plastic:Answer: Thermoplastic Thermosetting plastic 1. The plastic that can be moulded as per our wish is called thermoplastic. 1. The plastic in which a specific shape is given with the help of mould and this shape cannot be changed again on heating is called thermosetting plastic. 2. Thermoplastic substances can be recycled and reused.E.g. PVC – Polyvinyl chloride, PS – Polystyrene, PE – Polyethylene and PP – Polypropylene are types of thermoplastics. 2. Thermosetting plastic cannot be reused again.E.g. Bakelite, Melamine, Polyurethane and polyster are the types of thermosetting plastics. 5. Answer the following in your own words. a. Explain the effect of following materials on environment and human health.1. Plastic2. Glass.3. Thermocol.Answer:1. Plastic: 2. Glass: 3. Thermocol: b. Which measures will you arrange to minimize the environmental problems arising due to non-degradable plastic?Answer: 6. Write short notes.  a. Glass production:Answer:The general preparation of the glass is as follows: b. Optic glass:Answer: c. Uses of plastic:Answer:Plastic, the man-made material is used in various forms in modern age. According to the type of plastic, its uses are different. I. Thermoplastic materials are used for manufacturing following articles: II. Thermosetting plastic is used in the manufacturing of the following items:

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Class 8 | Science | Chapter 18 | Ecosystem | Exercise Solution | Maharashtra Board
Class 8 | Science | Textbook Solutions | Maharashtra Board
21 Feb 2025

Class 8 | Science | Chapter 18 | Ecosystem | Exercise Solution | Maharashtra Board

1. Complete the following by using the correct option: a. Air, water, minerals, soil are ………….. factors of an ecosystem. (physical, organic, inorganic)Answer:Air, water, minerals, soil are physical factors of an ecosystem. b. River, ponds, ocean are …………. ecosystems, (land, aquatic, synthetic)Answer:River, ponds, ocean are aquatic ecosystems. c. Man is ………….. in an ecosystem. (producer, consumer, decomposer)Answer:Man is consumer in an ecosystem. 2. Match the following: Producer Ecosystem 1. Cactus a. Forest 2. Aquatic plants b. Creek 3. Mangroves c. Aquatic 4. Pine d. Desert Answer: Producer Ecosystem 1. Cactus d. Desert 2. Aquatic plants c. Aquatic 3. Mangroves b. Creek 4. Pine a. Forest 3. Give my information: a. Ecosystem.Answer:Ecosystem is the structure formed by the interrelationships between the living organisms and non-living components in their surrounding habitats. Living organisms are also called biotic factors while the non-living components are called abiotic factors. The abiotic and biotic factors have a reciprocal relationship with each other. The ecosystem has plants as producers, animals as consumers and microbes as decomposers. The decomposers return the substances back to the nature by process of decomposition in which the organic complex molecules are reduced to their inorganic constituents. Thus the dead remains of plants and animals are once again recycled back to the nature in any healthy ecosystem. b. Biome.Answer:Biomes are a larger collection of small ecosystems which are similar in their structure. In a particular biome there are same climatic, abiotic factors and similar living organisms. Biomes are of two main types, land biomes and aquatic biomes. The land biomes exist only on land. Land biomes are of following subtypes based on the abiotic factors. E.g. Grasslands, evergreen forests, deserts, Tundra ecosystem, ecosystems in Taiga, tropical rainforests, etc. Aquatic biomes include freshwater ecosystem, marine ecosystem and brackish water ecosystem found in the creeks. c. Food web.Answer:The complex feeding relationships form a food web. In nature in any ecosystem, the food chains are not straight and linear. But these are quite complex. A prey is consumed by a predator but this predator can itself be a prey to some other predator. E.g. Frog is a predator for variety of insects but frog is preyed upon by snake and the snake can be eaten by a bird. The same bird can also feed on insects or frog. The interrelationships between different biotic components of any ecosystem thus form the complicated food web. 4. Give scientific reasons:  a. Plants in an ecosystem are called producers.Answer:are cut down causing deforestation. The wild animals lose their habitat. Many of them become extinct. There is great loss of flora and fauna due to construction of large dams. There is undue pressure on the land surface caused due to stored water column. This may cause earthquakes. The human settlements are removed as their houses and farms are immersed under water. In all the above ways large dams destroy the ecosystems. b. Large dams destroy ecosystems.Answer:When a large dam is constructed, the original landscape is changed. The trees are cut down causing deforestation. The wild animals lose their habitat. Many of them become extinct. There is great loss of flora and fauna due to construction of large dams. There is undue pressure on the land surface caused due to stored water column. This may cause earthquakes. The human settlements are removed as their houses and farms are immersed under water. In all the above ways large dams destroy the ecosystems. c. Rhinos were restored in Dudhwa forest.Answer:Long ago in last century, Dudhwa forest was the natural habitat of the one-horned Rhino. However, due to hunting and poaching, the Rhino became almost extinct. In order to restore it back the breeding in captivity was attempted and the young ones were released in the natural habitat. Saving the precious wildlife is important and hence these efforts were done. 5. Answer the following: a. What are the effects of increased population (of human beings) on ecosystems?Answer: b. How is urbanization responsible for destruction of ecosystems?Answer:When people do not get sufficient food and other amenities, they migrate to the cities. The cities provide employment for many people due to industries, factories and other facilities. Every day many people migrate to cities. This causes urbanization. Due to increased population in cities, there is more need for housing. This results in loss of agricultural lands, marshlands, wetlands, forests and grasslands, etc. The natural ecosystems are lost in an attempt to have developmental work. Human interference causes changes in the ecosystems. When land usage is changed many naturally occurring species of plants and animals are exterminated. Animal- human conflicts are very common in newly established urban areas which are near the natural forests. c. What are the reasons for war?Answer:There are difference of opinions and competition over land, water, mineral resources, etc. among neighbouring countries. Moreover, there can be economic and political causes which lead to war among different countries. Many times the l religions and ethnicity are also caused for dispute. Due to international conflicts, the peace is disturbed and it results in war. d. Explain the interactions among the factors of an ecosystem.Answer: e. Differentiate between evergreen forests and grasslands.Answer: Evergreen forests Grasslands 1. About seven percent of the Earth’s surface is occupied by evergreen forests. 1. About 30 percent of the Earth’s surface is covered by grasslands. 2. More than half of the earth’s terrestrial plants and animals are seen in evergreen forests. 2. Grazing animals are seen in grasslands. 3. Tropical evergreen forests are dense, multi-layered. 3. Grasslands consist of tall grass. There are wild grasses and there may be some trees. 4. These forests are found in the areas receiving more than 200 cm annual rainfall i.e. very heavy rainfall. 4. There is an average of 20 – 35 inches of rainfall a year in grasslands. 5. Tropical regions show evergreen forests. 5. Several parts of the world have grasslands. 6. Describe the following pictures: Answer:The picture no. 1 is showing desert ecosystem, while the picture no. 2 is showing a forest ecosystem where a wetland (a lake)

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Class 8 | Science | Chapter 19 | Life Cycle Of Stars | Exercise Solution | Maharashtra Board
Class 8 | Science | Textbook Solutions | Maharashtra Board
21 Feb 2025

Class 8 | Science | Chapter 19 | Life Cycle Of Stars | Exercise Solution | Maharashtra Board

1. Search and you will find: a. Our galaxy is called ………… .Answer:Our galaxy is called the Milky Way and Mandakini. b. For measuring large distances, ………… is used as a unit.Answer:For measuring large distances, the light year is used as a unit. c. The speed of light is …………. km/s.Answer:The speed of light is 300000 km/s. d. There are about ………… stars in our galaxy.Answer:There are about 100 billion stars in our galaxy. e. The end stage of the Sun will be …………. .Answer:The end stage of the Sun will be a white dwarf. f. Stars are born out of ………… clouds.Answer:Stars are born out of interstellar clouds. g. Milky way is a ………. galaxy.Answer:Milky way is a spiral galaxy. h. Stars are gigantic spheres of ………… gas.Answer:Stars are gigantic spheres of hot gas. I. The masses of other stars are measured relative to the mass of the …………. .Answer:The masses of other stars are measured relative to the mass of the Sun. j. Light takes ……………. to reach us from the Sun while it takes …….. to reach us from the moon.Answer:Light takes about 8 minutes to reach us from the Sun while it takes about 1 second to reach us from the moon. k. The larger the mass of a star, the faster is its ……….. .Answer:The larger the mass of a star, the faster is its evolution. l. The number of fuels used in the life of a star depends on its …………. .Answer:The number of fuels used in the life of a star depends on its mass. 2. Who is telling lies? a. Light year is used to measure time.Answer:False. (Light year is used to measure distance.) b. End stage of a star depends on its initial mass.Answer:True. c. A star ends its life as a neutron star when the pressure of its electrons balances its gravity.Answer:False. (A star ends its life as a neutron star when the pressure of its neutrons balances its gravity.) d. Only light can emit from the black hole.Answer:False. (Not even light can be emitted by a black hole.) e. The Sun will pass through the supergiant stage during its evolution.Answer:False. (The Sun will pass through the red giant stage during its evolution.) f. The Sun will end its life as a white dwarf.Answer:True. 3. Answer the following question: a. How do stars form?Answer:There are huge clouds of gas and dust in the empty spaces between the stars in a galaxy. These clouds are called interstellar clouds. The size of an interstellar cloud is about a few light years. When an interstellar cloud starts contracting due to some disturbance, its density and temperature increase. This results in formation of a dense sphere of hot gas and nuclear energy generation starts at the centre of the star. Therefore, the gas sphere becomes self-luminous. Thus a star is formed, i.e., a star is born.A huge interstellar cloud can produce thousands of stars at a time. b. Why do stars evolve?Answer:Although stars appear stable for quite a long period of time, their properties do change, though very slowly. A change in the properties of a star, leading to its passing through different stages, is called evolution of the star. Burning of the fuel at the centre of the star and a gradual decrease in its amount is the main reason of evolution of a star. c. What are the three end stages of stars?Answer: d. Why was the name black hole given?Answer:When a star having initial mass larger than 25 times the mass of the Sun reaches its end stage, its gravitational force and density increase exponentially. All nearby objects get attracted towards the star and nothing can come out of it, not even light. All incident light is absorbed by the star. We can probably see a very minute black hole at its place. Hence, the name is given as black hole. e. Which types of stars end their life as a neutron star?Answer:Stars having initial mass between 8 and 25 times the mass of the Sun end up as neutron stars. When these stars pass through ( the supergiant stage, their size increases to 1000 times. Huge explosion that occurs in the last stage of these stars is very powerful and very high energy is given off. After the huge explosion, called the supernova explosion, their central portion contracts in size to about 10 km. In this stage, such stars are completely made up of neutrons and hence are called neutron stars. 4. A. If you are the Sun, write about your properties in your own words.B. Describe white dwarfs. Answer: If you are the Sun, write about your properties in your own words.Answer:There are billions of stars in the galaxy called the Milky Way and Mandakini. I am one of the small stars called the Sun. I have my own family called the solar system. There are planets, satellites, asteroids, comets and meteors in my family. My mass is 2 × 1030 kg which is about 3.3 lakh times that of the earth. With a radius of 695700 km, my size is about 100 times that of the earth. My surface temperature is about 5800 K while it is 1.5 × 107 K at the centre. 72 % of my mass consists of hydrogen while 26 % consists of helium. Rest 2 % is made up of elements heavier than helium. I am about 4.5 billion years old and the scientists on the earth have concluded that not much change has taken place in my properties during this period. According to the scientists, in the end stage of my life, I will turn into a red giant star. Thereafter, I will first explode and then contract to become as small as the earth. I will appear small as well as white and hence, I will be called a white dwarf. This will be my last stage for ever. Depending on the initial mass, stars can reach one of the three end stages. White dwarf is one such stage of stars having initial mass less than 8 times the mass of

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Class 8 | Science | Chapter 6 | Composition Of Matter | Exercise Solution | Maharashtra Board
Class 8 | Science | Textbook Solutions | Maharashtra Board
21 Feb 2025

Class 8 | Science | Chapter 6 | Composition Of Matter | Exercise Solution | Maharashtra Board

1. Choose the appropriate option and rewrite the following statements: a.The intermolecular force is ……………. in the particles of solid.(a) minimum(b) moderate(c) maximum(d) indefiniteAnswer:(c) maximum b.Solids retain their volume even when external pressure is applied. This property is called …………… .(a) plasticity(b) incompressibility(c) fluidity(d) elasticityAnswer:(d) elasticity c. Matter is classified into the types mixture, compound and element, by applying the criterion …………… .(a) states of matter(b) phases of matters(c) chemical composition of matter(d) all of theseAnswer:(c) chemical composition of matter d. Matter that contain two or more constituent substances is called ……… .(a) mixture(b) compound(c) element(d) metalloidAnswer:(a) mixture e. Milk is an example of type of matter called …………. .(a) solution(b) homogeneous mixture(c) heterogeneous mixture(d) suspensionAnswer:(c) heterogeneous mixture f. Water, mercury and bromine are similar to each other, because the three are ……….. .(a) liquids(b) compounds(c) nonmetals(d) elementsAnswer:(a) liquids g. Valency of carbon is 4 and that of oxygen is 2. From this, we understand that there are …………. chemical bond/bonds between the carbon atom and one oxygen atom in the compound- carbon dioxide.(a) 1(b) 2(c) 3(d) 4.Answer:(b) 2 2. Identify the odd term out and explain. a. Gold, silver, copper, brass.Answer:Brass. (Others are elements.) b. Hydrogen, hydrogen peroxide, carbon dioxide, water vapour.Answer:Hydrogen. (Others are compounds.) c. Milk, lemon juice, carbon, steel.Answer:Carbon. (Others are mixtures.) d. Water, mercury, bromine, petrol.Answer:Petrol. (Others are inorganic compounds.) e. Sugar, salt, baking soda, blue vitriol.Answer:Sugar. (Others are inorganic compounds.) f. Hydrogen, sodium, potassium, carbon.Answer:Carbon. (Others are monovalent elements) 3. Answer the following question. a. Plants synthesize glucose in sunlight with the help of chlorophyll from carbon dioxide and water and give away oxygen. Identify the four compounds in this process and name their types.Answer:Photosynthesis: Carbon dioxide, water, glucose, and Chlorophyll are compounds.Types: Organic compounds: GlucoseInorganic compounds: Carbon dioxide and waterComplex compounds: Chlorophyll. b. In one sample of brass, the following ingredients were found: copper (70%) and zinc (30%). Identify the solvent, solute and solution from these.Answer:Brass is an alloy, it contains 70% copper and 30% zinc. The largest proportion is solvent, i.e. copper. The smaller proportion is solute, i.e. zinc. The solution is Brass. c. Seawater tastes salty due to the dissolved salt. The salinity (the proportion of salts in water) of some water bodies Lonar lake – 7.9%, Pacific Ocean 3.5%, Mediterranean sea – 3.8%, 5 Dead sea – 33.7%. Explain two characteristics of mixtures from the above information.Answer: 4. Give two examples each. a. Liquid element.Answer:Mercury (Hg), Bromine (Br2) b. Gaseous element.Answer:Hydrogen (H2), Oxygen (O2). c. Solid element.Answer:Iron (Fe), Copper (Cu), Silver (Ag). d. Homogeneous mixture.Answer:Sea water, blue vitriol dissolved in water. e. Colloid.Answer:Milk, blood. f. Organic compound.Answer:Glucose, urea. g. Complex compound.Answer:Chlorophyll, Haemoglobin. h. Inorganic compound.Answer:Soda, rust, limestone. i. Metalloid.Answer:Silicon, arsenic. j. Element with valency 1.Answer:Sodium (Na), potassium (K), chlorine (Cl). l. Element with valency 2.Answer:Magnesium (Mg), Calcium (Ca). 5. Write the names and symbols of the constituent elements and identify their valencies from their molecular formulae given below:KCl, HBr, MgBr2. K2O, NaH, CaCl2, CCl4, HI, H2S, Na2S, FeS, BaCl2.Answer: Molecular formula Constituent element/Name symbol Valency 1. KCl Potassium (K)Chlorine (Cl) 11 2. HBr Hydrogen (H)Bromine (Br) 11 3. MgBr2 Magnesium (Mg)Bromine (Br) 21 4. K2O Potassium (K)Oxygen (O) 12 5. NaH Sodium (Na)Hydrogen (H) 11 6. CaCl2 Calcium (Ca)Chlorine (Cl) 21 7. CCl4 Carbon (C)Chlorine (Cl) 41 8. HI Hydrogen (H)Iodine (I) 11 9. H2S Hydrogen (H)Sulphur (S) 12 10. Na2S Sodium (Na)Sulphur (S) 12 11. FeS Iron (Fe)Sulphur (S) 22 12. BaCl2 Barium (Ba)Chlorine (Cl) 21 6. Chemical composition of some matter is given in the following table. Identify the main type of matter from them. a. Chemical composition of some matter is given in the following table. Identify the main type of matter from them. Answer: Name of matter Chemical composition Main type of matter Sea water H2O + NaCl + MgCl2 +… Mixture Distilled water H2O Compound Hydrogen gas filled in a balloon H2 Element The gas in LPG cylinder C4H10 + C3H8 Mixture Baking soda NaHCO3 Compound Pure gold Au Element The gas in oxygen cylinder O2 Element Bronze Cu + Sn Mixture Diamond C Element Heated white powder of blue vitriol CuSO4 Compound Limestone CaCO3 Compound Dilute hydrochloric acid HCl + H2O Mixture 7. Write scientific reason. a. Hydrogen is combustible, oxygen helps combustion, but water helps to extinguish fire.Answer: b. The constituent substances of a colloid cannot be separated by oridinary filtration.Answer: c. Lemon sherbat has sweet, sour and salty taste and it can be poured in a glass.Answer: d. A solid matter has the properties of definite shape and volume.Answer: 8. Deduce the molecular formulae of the compound obtained from the following pairs of elements by the cross multiplication method. a. C (Valency 4) & Cl (Valency 1)Answer:Step 1: Write the symbols of the constituent elements.Step 2: Write the valency below the respective elements.Step 3: Cross-multiply the valencies.The molecular formula: CCl4 b. N (Valency 3) & H (Valency 1)Answer:Step 1: Write the symbols of the constituent elements.Step 2: Write the valency below the respective elements.Step 3: Cross-multiply the valencies.The molecular formula: NH3 c. C (Valency 4) & O (Valency 2)Answer:Step 1: Write the symbols of the constituent elements.Step 2: Write the valency below the respective elements.Step 3: Cross multiply the valencies.The formula: C2O4The number of constituent atoms in the final molecular formula should be the smallest possible whole number. Divide the formula C2O4 by suitable number.Final molecular formula obtained by dividing by ‘2’.Molecular formula: CO2 d. Ca (Valency 2) & O (Valency 2)Answer:Step 1: Write the symbols of the constituent elements.Step 2: Write the valency below the respective elements.Step 3: Cross multiply the valencies.The formula: Ca2O2Divide the formula by suitable number ‘2’.The molecular formula: CaO.

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Class 8 | Science | Chapter 7 | Metals And NonMetal | Exercise Solution | Maharashtra Board
Class 8 | Science | Textbook Solutions | Maharashtra Board
21 Feb 2025

Class 8 | Science | Chapter 7 | Metals And NonMetal | Exercise Solution | Maharashtra Board

1. Complete the table: Answer: Property of metal Use in everyday life i. Ductility i. Gold, silver ornaments ii. Malleability ii. Aluminium sheets, galvanised sheets iii. Conduction of heat iii. Stainless steel vessels, copper vessels, boilers iv. Conduction of electricity iv. Copper wires v. Sonority v. Brass articles 2. Identify the odd term. a. Gold, Silver, Iron, Diamond.Answer:Diamond. (Others are metals.) b. Ductility, Brittleness, Sonority, Malleability.Answer:Brittleness. (Other properties are metallic properties.) c. Carbon, Bromine, Sulphur, Phosphorus.Answer:Bromine. (Others are solids.) d. Brass, Bronze, Iron, Steel.Answer:Iron. (Others are alloys.) 3. Give scientific reasons: a. The stainless steel vessels in kitchen have copper coating on the bottom.Answer: b. Copper and brass vessels are cleaned with lemon.Answer: c. Sodium metal is kept in kerosene.Answer: 4. Answer the following: a. What is done to prevent corrosion of metals?Answer:By applying a layer of paint, oil, grease or varnish on the surface of a metal to prevent corrosion. Also plating with noncorroding metal is done. Iron is coated with thin layer of zinc. Due to these processes the contact of metal surface with air is lost and corrosion is prevented. b. What are the metals that make the alloys brass and bronze?Answer:The alloy brass is formed from copper and zinc and the alloy bronze is formed from copper and tin. c. What are the adverse effects of i corrosion?Answer: c. What are the uses of noble metals?Answer:Uses of Noble Metals: 5. Three experiments to study the process of rusting are given below. Observe the three test tubes and answer the following questions. a. Why the nail in the test tube 2 is not rusted?Answer:In the test tube 2, oil cuts the supply of air to nail due to which oxidation of nail is prevented and boiled water is free from gases. Hence, the nail in the test tube 2 is not rusted. b. Why is the nail in the test tube 1 is rusted highly?Answer:The nail in test tube 1 is highly rusted because nail is in contact with water and air. The oxidation process is fast. c. Would the nail in test tube 3 get rusted?Answer:No change is observed in the test tube 3. Nail remains as it is because the calcium chloride absorbs moisture, making the air dry, thus preventing rusting of the nail.

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Class 8 | Science | Chapter 8 | Pollution | Exercise Solution | Maharashtra Board
Class 8 | Science | Textbook Solutions | Maharashtra Board
21 Feb 2025

Class 8 | Science | Chapter 8 | Pollution | Exercise Solution | Maharashtra Board

1. Following are some statements about pollution. Which type of pollution do those express: a. Fog seems to be appearing in Delhi during day hours.Answer:Air pollution-Smog(The sentence should have the word Smog and not fog. Smog is fog with smoke. Only fog cannot be polluting, but the smog is.) b. Many times, vomiting and dysentery occurs after eating ‘panpuri’.Answer:Water pollution-Contaminated food and water due to bacteria or virus c. Problem of sneezing occurs sometimes during visit to garden.Answer:Air pollution due to pollens d. Crop does not grow up in some areas.Answer:Soil pollution e. People living in the busy squares face the problems like short breathing and other respiratory problems.Answer:Air pollution due to traffic 2. Read the passage and identify the sentences expressing types of pollution. Nilesh is a student of Std. VII and lives in urban area. It takes about an hour to go to the school by bus. He faces the heavy traffic of two wheelers, four wheelers, rickshaws, buses while going to school. He is facing the problem of asthma since last few days, Doctors recommended him to stay away from urban area. Since then, his mother sent him to the village of his maternal uncle, Nilesh saw the heaps of garbage at many places in village. Foul smell of human and animal wastes was present at many places. Blackish water with foul smell was flowing in a stream. He developed some abdominal disease within few days.Answer: 3. Match the pairs from ‘A’ and ‘B’ columns and explain the effect of pollution on human health. Column ‘A’ Column ‘B’ 1. Water containing cobalt a. Mental retardation 2. Methane gas b. Paralysis 3. Water containing lead c. Inflammation of lungs 4. Sulphur dioxide d. Skin cancer 5. Nitrogen dioxide e. Irritation of eyes Answer: Column ‘A’ Column ‘B’ 1. Water containing cobalt b. Paralysis 2. Methane gas d. Skin cancer 3. Water containing lead a. Mental retardation 4. Sulphur dioxide e. Irritation of eyes 5. Nitrogen dioxide c. Inflammation of lungs 4. True or false. a. Water does not get polluted by washing the clothes in running water of river.Answer:False. (Even if washing of soiled clothes is done in running water, it will cause pollution as the dirt and the waste materials will be added to water. This certainly will cause water pollution.) b. More the use of electric appliances, more will be the pollution.Answer:True. (Most of the electricity is generated in India by burning coal. The power generation plants thus cause lots of air pollution. More the electricity is used by using more appliances, there will be more pollution. However, only power generation through solar energy cannot cause pollution.) 5. Answer the following: a. What is pollution?Answer:Contamination of natural environment that can harmfully affect the environment is called pollution. b. What are Pollutants?Answer:The products which affect the normal functioning of ecosystem and have an adverse effect on plants, animals and humans are called pollutants. c. What is acid rain?Answer:1. When rainwater contains harmful amounts of nitric and sulphuric acids, it is called acid rain.2. Burning of fossil fuels such as coal, wood, petroleum, etc. releases nitrogen oxide and sulphur oxide into the atmospheric air.3. Since these oxides are soluble in water, they dissolve in rainwater. Nitrogen and sulphur oxides dissolved in large quantities of water vapour form acids like nitric acid, nitrous acid, sulphurous acid and sulphuric acid.4. These acids mix with mist, drops of rainwater and snow. They change their composition and fall back on the ground in the form of acid rain.5. Effects of acid rain are as follows: d. What is greenhouse effect?Answer: e. Which are visible pollutants known to you?Answer:1. The polluting substances that are seen easily with the naked eyes can be called as visible pollutants. E.g. Solid wastes, plastic articles, plastic bags, the suspended things in the water, metal refuse, etc. f. Which are invisible pollutants?Answer:The pollutants which are completely dissolved in water or mixed in the air, cannot be seen and hence they can be called invisible pollutants. Since they are not seen, we remain unaware about the presence of these pollutants. E.g. the insecticides spread f on the crops. Aerosols, many hazardous gases in the air, toxic compounds that are totally soluble in water, etc. 6. Answer the following. a. Give two examples of each of water, soil and air pollution from your residential area.Answer:Air pollution: Water pollution: Soil pollution : b. How does the pollution occur due to vehicles? Give the names of vehicles causing least pollution.Answer: These two types of vehicles are eco-friendly. The cars that run on C.N.G. are also said to be lesser polluting. c. What are natural reasons causes for water pollution?Answer:The natural causes of the water pollution:1. If organic pollutants are added to the water there is an overgrowth of weeds such as Eichhornia. The growth of algae also makes the water unsuitable for consumption. These aquatic plants release oxygen during daytime but by night they require oxygen thus depleting the dissolved oxygen level. The natural characters of water are then changed. 2. The decomposing matter when added to the water make it polluted and stinking. 3. Due to deposition of sludge or eroded soil, the rivers change their path and divert from original flow. The currents are also changed. Deposition of sludge makes the water polluted. 4. Due to soil erosion, surrounding the water bodies, the microbes, bacteria, protozoans and the worms and larvae of nematodes enter the water causing severe biological pollution. Many inorganic pollutants are also added to the water. The fungand bacteria present in the water make it non-potable. Such water spreads water-borne diseases. d. Suggest four preventive measures for air pollution.Answer:The following methods are adopted to control air pollution from the industries: e. Explain relation between greenhouse effect and global warming.Answer:Because of greenhouse effect, there is increase in the global temperature. The heat on the earth remains trapped due to envelope of greenhouse gases. The percentage of carbon dioxide and methane is constantly increasing and hence there is

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Class 8 | Science | Chapter 9 | Disaster Management | Exercise Solution | Maharashtra Board
Class 8 | Science | Textbook Solutions | Maharashtra Board
21 Feb 2025

Class 8 | Science | Chapter 9 | Disaster Management | Exercise Solution | Maharashtra Board

1. Answer the following in your own words. a. Explain the relation between continuous rains and landslide. Give reasons.Answer:Before the actual landslide, many changes occur in the surrounding hilly ground. The hard rocks develop cracks and crevices. These are natural changes but due to man-made activities, the cracks are widened due to erosion. These cracks make the big rocks to break into smaller stones. The cracks widen further due to excessive rainfall. These rocks further get eroded and they fall down along with soil from the slopes. The entire process is speeded up due to rainwater. b. Prepare a chart showing ‘Dos’ and ‘don’ts’ at the time of earthquake.Answer:At the time of the earthquake Do’s Don’ts 1. Go in the open grounds. 1. Don’t wait in the multi-storeyed buildings. Do not use lifts. Use stairs to descend. 2. Keep the electrical appliances and cooking gas closed. 2. Do not stand near buildings, trees or electric wires and poles. 3. Use battery or torch. 3. Do not light candles, lantern or match- sticks. 4. Stand silently at one place. Do not panic or get scared. 4. Do not sit in uncomfortable posture for a long time. 5. Take protection under some hard covering, especially to protect the head and face. Cover the face. 6. If, in vehicle, find a safe place and stop the vehicle, sit in the vehicle than coming out in open. c. What are the specifications of an earthquake-proof building?Answer:The earthquake-proof building is such that even if the earthquake is caused, it should not cause damage to the buildings due to these earth movements. There are some codes of conduct while constructing such buildings. Advanced technology is used for earthquake resistant construction. The foundation of earthquake-proof building is separated from lower land. The walls are of less weight or they are wooden. The house constructed with special light materials are preferred in earthquake-prone regions. d. Explain the effects of landslide.Answer:1. Mostly rivers originate in the hills and mountains. When there is landslide, the rivers naturally get flooded.2. The paths of the riverine water changes due to landslide.3. Waterfalls are displaced from their original positions.4. New and artificial water reservoirs are created.5. The falling debris, soil and rocks make the trees at the base of hillside uprooted. All the plant life is lost.6. The constructions done by the villagers on the slope can be totally damaged due to landslide. There is large scale damage to property and life. In few cases like Malin the entire village was buried due to landslide and accompanied rainfall.7. Transportation is affected as the roads and railway tracks are blocked due to debris. e. Is there any relation between dam and earthquake? Explain.Answer:There is abundant water stored in the dams. This water column puts additional weight on the ground. Initially there may not be any weight, but later due to construction of dam, suddenly the pressure of this weight is so high that this ground experiences the tension. If such area is already earthquake-prone, then there can be chances of earthquake. According to theory of plate tectonics, there are continuous movements in the earth’s surface. If over such fragile plates, the dams are constructed then the chances of earthquake are enhanced. 2. Give Scientific reasons. a. It is safer to find shelter under things like a bed, table at the time of earthquake.Answer:When earthquake takes place, due to the vibrations in the earth’s surface, there is possibility of the roof and walls of the house to fall. This collapse can cause severe head injury which can be fatal. Thus, one must take shelter below the hard-supporting structures such as bed or table. This precaution can save one’s life. b. In monsoon, don’t take shelter near hillside.Answer:The excessive rainfall can cause landslides. The soil and rocks from the hillside can be pushed down along with the flow of rainwater. This debris slides to the lower heights from the hills. This explains us that taking shelter near the base of the hillside can be disastrous as one can be buried in the debris due to sudden landslide. Therefore, in monsoon, one should not take shelter near hillside. c. Don’t use lifts at the time of earthquake.Answer:Lifts or elevators run on electricity. The electricity supply can be hindered due to earthquake. There may be chances of fire due to short circuit. We may get trapped in the elevator at such times. The building may also collapse due to earthquake. It is always better to use stairs at the time of such calamities, so that one can safely come out of the building. Therefore, it is said that lifts should not be used at the time of earthquakes. d. The foundation of earthquake- proof building is separated from lower land.Answer:The surface of the earth trembles at the time of earthquake. These tremors cause seismic waves which are responsible for the movements of the earth’s surface. The ground thus shakes or it goes up-down. These shocks and waves formed in the interior of the earth spread on the surface in all directions. This causes collapse of the building and other structures on the land.To prevent such disasters the foundation of earth-quake proof building is separated from lower land. 3. If a crowd gathers at the place of earthquake, what would be the difficulties in relief work? a. If a crowd gathers at the place of earthquake, what would be the difficulties in relief work?Answer:If people flock in crowd, the rescue work will not be possible. The ambulances and the fire engines will not reach the spot where the help is needed. The personnel from disaster management cells cannot thus act in time. It will be difficult to manage the situation and thus such crowding should never be done. 4. Make a list of the institutes and organizations who provide help for disaster managment. Collect more information about their work. Answer:International government organisations working for disaster management are:a. The United Nations and its organisations:1. The Food and Agricultural Organisation

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Class 8 | Science | Chapter 10 | Cell and Cell Organelles | Exercise Solution | Maharashtra Board
Class 8 | Science | Textbook Solutions | Maharashtra Board
21 Feb 2025

Class 8 | Science | Chapter 10 | Cell and Cell Organelles | Exercise Solution | Maharashtra Board

1. Who am I? a. I am ATP producing factory.Answer:Mitochondria b. I am single-layered but maintain cellular osmotic pressure.Answer:Vacuole c. I support the cell, but I am not cell wall. I have a body resembling net.Answer:Endoplasmic reticulum d. I am chemical factory of the cell.Answer:Chloroplasts in case of plant cells can be called chemical factory as they synthesise carbohydrates. Ribosomes also synthesise proteins, so those can also be called chemical factory. Golgi complex is secretory in function, hence it can be also called factory. Mitochondria though mainly referred to as powerhouse of the cell, it is also mentioned as chemical factory by some authors. e. Leaves are green because of me.Answer:Chloroplast. 2. What would have happened? If………. a. RBCs had mitochondria.Answer:Mitochondria continuously carry out oxidation and form energy inside the cell. They produce energy-rich compound, ATP. In this process, they utilize carbohydrates, fats and proteins present in the cell. If RBCs has mitochondria, they would have used oxygen for this purpose than carrying it to all the cells of the body. The cells would not have obtained oxygen. b. There had been no difference between mitochondria and plastids.Answer:Mitochondria carry out oxidation of carbohydrates, fats, etc. with the help of enzymes. Plastids are synthesising carbohydrates with the help of solar energy and chlorophyll. Both the cell organelles have their own sets of different enzymes as per their role. If there would have been no difference between mitochondria and plastids, the specific functions would not have been taken place. c. Genes had been absent on the chromosomes.Answer:Genes are functional segments on the chromosomes which are responsible for transmitting the hereditary information. d. Plasma membrane had not been selectively permeable.Answer:Selectively permeable membrane allows some substances to enter the cell, while prevents other unwanted or harmful substances. If plasma membrane would not have been selectively permeable, there would be no control over entry and exit of any substances. The process of osmosis would also be erroneous in such case. e. Plants lacked anthocyanin.Answer:If plants lacked anthocyanin, no part of the plant would display purple or blue colour. Anthocyanin attracts the insects for pollination and seed dispersal. These processes will be affected due to lack of anthocyanin. These pigments are also said to be protective in nature for the plant. This protection will not be given to the plant in absence of anthocyanin. 3. Who is odd man among us? Give reason. a. Nucleolus, mitochondria, plastids, endoplasmic reticulumAnswer:Nucleolus. (All the others are cell organelles but nucleolus is not a cell organelle present in cytoplasm.) b. DNA, Ribosomes, ChlorophyllAnswer:Chlorophyll. (DNA and Ribosomes are present in plant as well as in animal cells. Chlorophyll is present only in plant cells.) 4. Give functions. a. Plasma membrane. Answer: b. Cytoplasm.Answer: c. Lysosome. Answer: d. Vacuole. Answer: e. Nucleus. Answer: 5. Who gives me the colour? (Select the correct option). Question a. Column ‘A’ Column ‘B’ 1. Red tomato a. Chlorophyll 2. Green leaf b. Carotene 3. Carrot c. Anthocyanin 4. Violet d. Lycopene Answer: Column ‘A’ Column ‘B’ 1. Red tomato d. Lycopene 2. Green leaf a. Chlorophyll 3. Carrot b. Carotene 4. Violet c. Anthocyanin

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