1 CROP PRODUCTION AND MANAGEMENT - … … · CROP PRODUCTION AND MANAEMENT P-1 ... Soyabean, groundnut, etc. The crop which are grown in the winter ... of boiling milk and water

P-1CROP PRODUCTION AND MANAGEMENT

Ans. 1. A seed drill is a device that allows to plant seeds in the soil.Ans. 2. Sowing is the process of planting seeds.Ans. 3. Harvestingistheprocessofgatheringorcuttingmaturecropsfromthefields.Andthe

process by which grain seeds are separated from harvested crop is called threshing.Ans. 4. Removal of weeds is called weeding. It is necessary because weeds compete the crop

plants and affect its growth.Ans. 5.

Plough HoePlough is a tool used for tilling the soil, adding fertilizers to the crop.

While hoe is a tool which used for removing the weeds, acraping of soil, loosening the soil, etc.

Ans. 6. Some plants may grow naturally along with the crop. These undesirable plants are called weeds.

Farmers use different ways to kill these weeds like use of chemicals called weedicides. Manual removal includes physical removal of weeds by uprooting or cutting them close to the ground, from time to time.

Ans. 7. The various activities of agricultural practices are : (i) Preparation of soil (ii) Sowing (iii) Adding manure and fertilizers (iv) Irrigation (v) Protection from weeds (vi) Harvesting (vii) StorageAns. 8. Tilling or ploughing loosens the soil and improves air circulation in the soil. It also

helps in retention of moisture. Ploughing uproots the undesirable plants growing in thefield.Italsoenhancesthewaterretainingcapacityofthesoilsince,itturnsthesoil upside down.

Ans. 9. Irrigation is an agricultural practice that involves providing water to crops through pipes, ditches, or streams and helps in germination of seeds. It is important for proper growth and development of a plant.

Traditionally we use different methods for lifting up the water from canal, lakes and wells. Some traditional ways are moat, chain pump, dekhli and rahat.

Modern methods are : (i) Sprinkler system : Sprinkler Irrigation is a method of applying irrigation water,

which is similar to rainfall. Water is distributed through a system of pipes usually by pumping.

(ii) Drip system : It minimizes the use of water and fertilizer by allowing the water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves, pipes, tubes, and emitters.

SUMMATIVE ASSESSMENT WORKSHEET-1

1 CROP PRODUCTION AND MANAGEMENT

P-2 SCIENCE – VIII

SUMMATIVE ASSESSMENT WORKSHEET-2Ans. 1. Because it saves labour and time.Ans. 2. Rearing of animals to obtain food from them is called Animal Husbandry.Ans. 3. The plants of same kind are grown and cultivated at one place on a large scale

constitute a crop. Example are wheat and maize.Ans. 4. Proper storage of grains is necessary to protect them from pests and micro-organisms.

If freshly harvested crops are stored without drying, they may get spoil or attacked by organisms, loosing their germination capacity.

Ans. 5. Kharif Season Crop Rabi Season Crop

1. The crops which are sown in the rainy season are called kharif crops.2. Their time period is generally from June to September. Examples : Paddy, Maize, Soyabean, groundnut, etc.

The crop which are grown in the winter season are called rabi season crop.Their time period is generally from October to March.Examples : Wheat, Gram, Pea, Mustard, etc.

Ans. 6. Manure enhances the water holding capacity of the soil. It improves the texture of the soil. It provides a lot of humus to the soil. It increases the number of microbes which are useful for us. On the other hand, fertilizers make the soil rich in Nitrogen, Phosphorus and Potassium. Hence, both provides fertility and help in increasing food production.

Ans. 7. Different practices for proper storage of grains are : (a) Firstly dry the grains so as to reduce moisture from the grains which prevents

the attack by insect, pests, bacteria and fungi. (b) Cleaniness of godowns and stores is essential for safe storage of the agricultural

products. (c) Fumigation, which means exposing the stored grains/seeds to the fumigants. Ans. 8.

Fertilizers

1. Fertilizers can be organic (composed of organic matter), or inorganic (made of simple, inorganic chemicals or minerals) substances.

2. A fertilizer is prepared in factories.

3. A fertilizer does not provide any humus to the soil.

4. Fertilizers are very rich in plant nutrients like nitrogen, phosphorus and potassium.

5. Fertilizers are compound given to plants to promote growth.

Manures

Manure is a natural substance obtained by the decomposition of cattle dung, human waste and plant residues.

As it is naturally obtained so it can be preparedinfields.

Manure provides a lot of humus to the soil.

Manure is less rich in plant nutrient in comparison to Fertilizers.

Manures enhances the water holding capacity of the soil and improves the texture of the soil.

P-3CROP PRODUCTION AND MANAGEMENT


[A] Multiple Choice Type Questions :

1. (b) 2. (a) 3. (d) 4. (c) 5. (c)

[B] Fill in the blanks :

1. tilled, levelled 2. Weeds 3. harvesters and threshers

4. water logging 5. Rhizobium 6. silos and metal bins

7. insects or pests.

[C] Write one word for the following sentences :

(a) Weeds (b) Ploughing (c) Rhizobium

(d) Animal Husbandry (e) Kharif crops (f) Fertilizers.

[D] Match the Column :

(a) Plough (b) Hoe (c) Cultivator

(d) Seed drill

FORMATIVE ASSESSMENT WORKSHEET-4


1. (a) 2. (d) 3. (a) 4. (a) 5. (d)

[B] Name the following :

(a) Leveller

(b)Fallowfield

(c) Sowing

(d) Manure

(e) Winnowing

[C] Match the Columns (Double Matching) :

(A)—(b)—(iii)

(B)—(c)—(ii)

(C)—(a)—(i)

[D] Identifythefollowingfigures(asTraditionalMethodsofIrrigation):

(i) Rahat

(ii) Moat

(iii) Chain Pump

(iv) Dhekli


Ans. 1. Micro-organisms are the living organisms which cannot be seen with naked eyes.Ans. 2. Viruses are considered as the connecting link between living and non-living. (a) The reason for being non-living are : they neither grow nor reproduce, once

they are outside the host. (b) They can be considered living as they multiply very fast and grow when entered

the host.Ans. 3. The word ‘pseudo’ means false and ‘podia’ means feet. Pseudopodia are cytoplasmic

extensions which can be extended or withdrawn. Pseudopodia enables the organism to move and ingest the food particle.

Ans. 4. Theblue-greenalgaehelpinincreasingthefertilityofthesoilbyfixingtheatmosphericnitrogen into useable form.

Ans. 5. Pasteurization is the process of heating liquids for the purpose of destroying virus and harmful organisms such as bacteria, protozoa, moulds and yeasts.

Ans. 6. Nitrogenfixationistheprocessbywhichnitrogenistakenfromitsnatural,relativelyinert molecular form (N2) in the atmosphere and convert it into nitrogen compounds. The bacterium Rhizobiumisinvolvedinthefixationofnitrogeninleguminousplantssuch as beans and peas, with which it has a symbiotic relationship.

Ans. 7. Preservation by sugar : Sugar is used as a preservative as it reduces the moisture and inhibit the growth of bacteria. Mainly jams, jellies, squashes are preserved with the help of sugar.

Preservation by oil and vinegar : Oil and vinegar are used as a preservative for fruits,vegetables,pickles,fish,meat,etc.as itprevents theirspoilagebecausebacteria cannot live in such an environment.

Ans. 8. (a) High temperature kills many micro-organisms. Various practices like practice of boiling milk and water before drinking, cooking raw vegetable before eating kills many micro-organisms.

(b) Low temperature inhibit the growth of microorganisms.Ans. 9. Useful effects of micro-organisms : (a) They help in the formation of curd, cheese, etc. (b) Convert the fruit juices into vinegar and wines. (c) Decompose the complex organic material into simple inorganic molecules. (d) Helps in tanning of the leather. (e) Somehelpsinfixingatmosphericnitrogen. (f) Some of them present in the intestine helps in the process of digestion. Harmful effects of micro-organisms : (a) They cause a large variety of diseases in plants, animals and human beings. (b) They spoil food items as well as clothes, leather, etc.


2 MICRO-ORGANISMS : FRIEND AND FOE


Ans. 1. Fungi helps in the formation of antibiotics. It helps in the decomposition of dead organic matter.

Ans. 2. Bread and Dosa.

Ans. 3. Female Anopheles mosquito carries the parasite of malaria while Female Aedes mosquito acts as a carrier of dengue virus.

P-5MICRO-ORGANISMS : FRIEND AND FOE

Ans. 4. Micro-organisms, which are present is food, sometimes produce toxic substances and make the food toxic. Consumption of such spoiled food can cause food poisoning.

Ans. 5. Some of the micro-organisms cause diseases in human beings, plants and animals. Such disease-causing micro-organisms are called pathogens.

Pathogens enter our body through the air we breathe, the water we drink or the food we eat.

Ans. 6. Antibiotics are medicines which kill or stop the growth of the disease-causing micro-organisms.

Antibioticsshouldbetakenonlyontheadviceofaqualifieddoctor.Antibioticsarenoteffectiveagainstcoldandflu,sowemustcompletethecourseprescribedbythedoctorotherwiseitmayunnecessarilykillthebeneficialbacteriapresentinthebody.

Ans. 7. Immunization helps in eradicating many diseases like malaria, polio, chicken pox, small pox and many more through vaccination. We all should understand the importance of immunization.

Ans. 8. Nitrogen Cycle.

SUMMATIVE ASSESSMENT WORKSHEET-7[A] Multiple Choice Type Questions : 1. (a) 2. (d) 3. (a) 4. (a) 5. (b)

[B] Give the contributions of the following : (a) Louis Pasteur : He discovered fermentation in 1857.

(b) Edward Jenner : He discovered the vaccine for small pox in 1798.

(c) Alexender Flemming : He prepared Penicillin.

(d) Robert Koch : He discovered the bacterium (Bacillus anthracis) which causes anthrax disease.

[C] Match the organisms in column A with their actions in column B : (i)—(e), (ii)—(a), (iii)—(b), (iv)—(c), (v)—(d), (vi)—(f).

[D] Fill in the blanks : (a) microscope (b) nitrogen (c) yeast

(d) Air and water bodies of plants and animals (e) antigens

Ammonia

nitriteion

nitriteion

Bacterialdecomposition

(oxidation)

death

NH3

Plantprotein

NO2

NO3

deadorganicmatter

animalprotein

death

wastematter

consumptionof food

fertilizeruptake

Bacterialdecomposition(nitrosomonas)

Bacterialoxidation

(nitrobacter)




1. (b) 2. (c) 3. (a) 4. (b) 5. (b)


(a) Virus

(b) Chicken-pox

(c) Bacteria

(d) Yeast

(e) Bacteria

(f) Bacteria

(g) Bacteria

(h) Bacillus anthracis

(i) Salt

(j) Legumes (Pea)

(k) Yeast

(l) Small-pox

(m) Blight of Potato

[C] Give two uses of micro-organisms in the following areas :

(a) Food industry : Making of curd, making of vinegar.

(b) Medicinal use : Making of antibiotics, making vaccines.

(c) Environmentaluse:Increasingsoilfertility,fixesnitrogeninthesoil.

P-7SYNTHETIC FIBERS AND PLASTICS

Ans. 1. Many small units combine to form a single large unit called as polymer. They are building blocks of many synthetic fibers.

Ans. 2. Rayon is prepared by chemical treatment of wood pulp.

Ans. 3. The fabric made from this fiber does not get wrinkled easily. It remains crisp and is easy to wash. Therefore, it is quite suitable for making dress material.

Ans. 4. PET is a familiar form of polyester.

Uses : It is used for making bottles, utensils, films, wires and many other useful products. PET bottles and PET jars are used for storing rice, sugar and other eatable things.

Ans. 5. Polyester is a synthetic fiber. This fabric melts and sticks to the body of the person wearing it when they catch fire. We should, therefore, not wear synthetic clothes while working in the kitchen or in a laboratory.

Ans. 6. Synthetic fibers are :

(a) usually stronger than natural fibers.

(b) lighter than natural fibers.

(c) cheaper than natural fibers.

Ans. 7. Properties of plastics :

(a) Non-reactive.

(b) Light, strong and durable.

(c) Poor conductors of heat and electricity.

Ans. 8. (a) Plastic bags are non-biodegradable i.e., it does not decompose by micro- organisms easily. So it keeps accumulating inside the earth and in the water, thereby causing soil and water pollution. Moreover on heating, plastic releases harmful gases, so it cannot be destroyed by heating.

(b) The government is trying to ban these. On the other hand, paper bag is biodegradable and hence, eco-friendly.

Ans. 9. (a) Most of the plastics are non-biodegradable. As a result, garbage is increasing a at very fast rate and it is a threat to environment.

(b) The plastic/polythene bags thrown in the garbage are consumed by cows along with the garbage thrown in dumps. The plastic gradually accumulates inside the cow’s intestine and blocks them and the cows die.

(c) Plastics are also carcinogenic.

(d) Plastic is made from the conventional source of energy, petroleum, which is fast depleting resource.

(e) On burning, plastic produces poisonous gases.


3 SYNTHETIC FIBERS AND PLASTICS



Ans. 1. Plastic which once molded cannot be softened and molded into other shape on heating are called thermosetting plastics.

Ans. 2. Bakelite is used in making electrical switches because it is a poor conductor of electricity.

Ans. 3. Electrical wires have covering of plastic because plastic is a bad conductor of electricity.

Ans. 4. Melamine resist fire and can tolerate heat better than other plastics. Therefore it is used for making kitchenware and fabrics which resist fire.

Ans. 5. Acrylic is warm, soft, light-weight fiber having wool like appearance. It is easy to wash and dries up quickly. It retains the shape. It can be dyed easily to different colours. Therefore, acrylic is considered as a cheap substitute of wool.

Ans. 6. Properties of Rayon : It is cheaper than silk and can be woven like silk fibers.

Uses : It is mixed with cotton to make bedsheets or mixed with wool to make carpets.

Ans. 7. (a) Reduce, Reuses and Recycle.

(b) (i) By becoming eco-friendly.

(ii) By planting trees, by not throwing garbage, etc.

Ans. 8.

Ans. 9. Government promote paper bags because :

(i) It does not causes environmental pollution.

(ii) They are biodegradable, hence eco-friendly.

(iii) It does not harm the cattle/animals.

(a) Linear Pattern of Plastic

(b) Cross Link Pattern of Plastic

P-9SYNTHETIC FIBERS AND PLASTICS

SUMMATIVE ASSESSMENT WORKSHEET-11[A] Multiple Choice Type Questions :

1. (d) 2. (b) 3. (d) 4. (c) 5. (c)


1. poor/bad 2. synthetic, 3. cotton, jute, 4. Plastic, 5. light, 6. Rayon, 7. petrochemicals, 8. nylon, 9. cotton, 10. synthetic, 11. polymerization, 12. cellulose.

[C] Match the following :

1. (d) 2. (e) 3. (a) 4. (g) 5. (c) 6. (f) 7. (b).

[D] Write true or false :

(i) True (ii) False (iii) False (iv) True (v) False (vi) False (vii) True (viii) True (ix) False (x) False.



1. (d) 2. (b) 3. (b) 4. (b) 5. (b)

[B] Do as directed :

1. Write one use of the following fibers :

(a) Rayon is used to make carpets.

(b) Nylon is used to make parachutes and ropes.

(c) Polyester is used to make fabrics.

(d) Acrylic is used to make sweaters and shawls.

2. Categorize the following things according to the type of fiber from which they are made as natural/man-made.

(a) Natural (b) Natural (c) Natural

(d) Man-made (e) Man-made (f) Natural.

3. Reduce, Reuse, Recycle.

[C] Write use of following properties of plastic.

(i) They are used as packaging materials and containers for storage of food and chemicals.

(ii) Used to make parts for aircrafts, cars and spacecrafts.

(iii) To make electrical switches, insulating casings.


Ans. 1. The oxides of non-metals are generally basic in nature.

Ans. 2. Sulphur dioxide is formed.

Ans. 3. Aluminium reacts with citric acid present in the lemon. Hence, lemon pickles can’t be stored in aluminium vessels.

Ans. 4. (a) Good conductors of heat and electricity.

(b) Lustrous, i.e., they have shiny appearance.

Ans. 5. When iron nails are dipped in water in a test-tube for a week, a brown layer gets deposited on the iron nails, which is known as rust.

Ans. 6. When copper vessel is exposed to moist air for a long time, it acquires a dull green coating. The green material is a mixture of copper hydroxide and copper carbonate.

The following chemical reaction takes place :

2Cu + H2O + CO2 + O2 → Cu(OH)2 + CuCO3

Ans. 7. 1. Applying protective coating.

2. Alloyed with certain metals.

3. Covering with another metal.

Ans. 8. Zn + H 2SO4 → ZnSo4 + H2

2Cu + H2O + CO2 + O2 → Cu(OH)2 + CuCO3

2Fe + O2 + H2O → Fe2O3 + H2

SO2 + H2O → H2SO3

Cu + HCl → No reaction


4 MATERIALS : METALS AND NON-METALS


Ans. 1. The reactions in which more reactive metals displace less reactive metals from their compounds in aqueous solutions are called displacement reactions.

Ans. 2. Metalloids are those elements which possess some properties of metals and some properties of non-metals.

Ans. 3. Copper is less reactive than zinc. Hence, copper cannot displace zinc from zinc sulphate solution.

Ans. 4. When metals burn in air, the formation of their oxide takes place. Hence, when magnesium reacts with air, magnesium oxide is formed.

Ans. 5. Iron oxide is formed and hydrogen gas is produced. The chemical reaction that takes place is :

2Fe + O2 + H2O → Fe2O3 + H2.

P-11MATERIALS : METALS AND NON-METALS

Ans. 6. Gold is preferred in making jewellery because it is :

(a) Lustrous (b) highly malleable (c) ductile.

Ans. 7. Equipments containing mercury should be handled carefully because it affects our skin and eye, it forms explosive mixtures when come in contact with other chemicals.

Ans. 8. (a) SO2 + H2O → H2SO3.

(b) Coalpieceisabadconductorofelectricityanditdoesnotallowcurrenttoflow in the circuit.

(c) Green coating indicates the corrosion of copper vessel, which is a mixture of copper hydroxide and copper carbonate.



1. (b) 2. (a) 3. (c) 4. (d) 5. (a)


1. Sodium, Potassium, 2. Mercury, 3. red, blue, basic, 4. basic, acidic, 5. hydrogen, pop, 6. more, less, 7. metalloid, 8. chlorine, 9. less, 10. hydrogen.

[C] Match the substance given in column A with their uses given in column B :

(i)—(d), (ii)—(e), (iii)—(c), (iv)—(f), (v)—(b), (vi)—(a)

[D] Write true or false :

1. False 2. True 3. False 4. False 5. False 6. True 7. True 8. True.




1. (b) 2. (b) 3. (c) 4. (a) 5. (a)

[B] Give reasons for the following :

1. Because metals are sonorous.

2. Due to corrosion.

3. It reacts readily with air and water.

4. It reacts readily with air.

[C] Madhya Pradesh, Maharashtra, Andhra Pradesh, Karnataka.

[D] (a) Mercury (b) Bromine (c) Silver (d) Oxygen.

[E] Explain which properties of metals are represented by the following diagrams :

1. Metals are malleable.

2. Metals are good conductors of electricity.

P-13COAL AND PETROLEUM

Ans. 1. Carbonblackispreparedbyburningoilsandthepetroleumgasininsufficientsupplyof air.

Ans. 2. Natural gas contains 95% methane and 5% other hydrocarbons.

Ans. 3. Petroleum was formed from organsims living in the sea. The remians of these organisms got settled at the bottom of the sea and subsequently got covered with sand and clay. Over millions of years, absence of air, high temperature and high pressure, transformed these dead organisms into petroleum.

Ans. 4. The advantages of CNG and LPG are :

(a) They can be burnt directly.

(b) They can be transported easily through pipelines.

(c) They are clean fuels and do not give smoke when burnt.

(d) They give a lot of heat energy when burnt.

Ans. 5. Inexhaustible sources : Sunlight, Air.

Exhaustible sources : Coal, Petroleum.

Ans. 6. Coke is used in the manufacture of steel and in the extraction of many metals.

Coal tar is used for metalling the roads.

Coal gas is used as a fuel in many industries situated near the coal processing plants.

Ans. 7. (a) Use of renewable sources of energy

(b) Population control

(c) Planting trees

We should encourage people to play their role as a responsible citizen in the conservation of energy resources.

Ans. 8. Constituents of petroleum are petroleum gas, petrol, kerosene, diesel, lubricating oil, paraffinwaxandbitumen.


5 COAL AND PETROLEUM

S. No. Constituents of Petroleum 1. Petroleum Gas in Liquid form (LPG)

2. Petrol

3. Kerosene

4. Diesel

5. Lubricating oil

6. Paraffinwax

7. Bitumen

UsesFuel for home and industry.

Motor fuel, aviation fuel, solvent for dry cleaning.

Fuel for stoves, lamps and for jet aircrafts.

Fuel for heavy motor vehicles, electric generators.

Lubrication.

Ointments, candles, veseline etc.

Paints, road surfacing.



Ans. 1. PCRA is Petroleum Conservation Research Association.

Ans. 2. The slow process of conversion of dead vegetation into coal is called carbonisation.

Ans. 3. Due to its great commerical importance, petroleum is called black gold.

Ans. 4. Due to natural processes, dead plants got burried under the soil. As more soil deposit over them, they were compressed under high pressure and high temperature, dead plants got slowly converted to coal. As it was formed from the remains of vegetation, so coal is called fossil fuel.

Ans. 5. (a) Inexhaustible Sources : These resources are present in unlimited quantity in nature and are not likely to be exhausted by human activities.

e.g., Sunlight, Air

(b) Exhaustible Sources : The amount of these resources in nature is limited. They can be exhausted by human activities.

e.g., Coal, Petroleum.

Ans. 6. Second village, because of the quality of bio-gas fuel.

Bio-gas fuel does not produce smoke and also it is easy to handle.

Ans. 7. Petroleum is brought to the surface by drilling a hole in the Earth’s crust and sinking pipesdeepdownthroughtheimperviouscaprock.Naturalgasfirstcomesoutunderhigh pressure. Then, petroleum is pumped out, collected in tanks and transported for further processing.

Fig. Petroleum and natural gas deposits

P-15COAL AND PETROLEUM



1. (b) 2. (a) 3. (a) 4. (b) 5. (a)

[B] Write one use of constituents of Petroleum :

1. LPG : Used as fuel at home.

2. Kerosene : Used as fuel for stoves, lamps, etc.

3. Lubricating oil : Used for lubrication.

4. Petrol : Used as motor fuel, aviation fuel, etc.

5. Diesel : Used as fuel for heavy motor vehicles.

6. Paraffinwax:Usedtomakeointments,candles,vaseline,etc.

[C] Writefivetipstosavepetrol/dieselwhiledriving.

(a) Drive at a constant and moderate speed.

(b) Switchoffengineattrafficlights.

(c) Ensure correct tyre pressure.

(d) Ensure regular maintenance of the vehicle.

(e) Use public transport as far as possible.

[D] 1. Water, 2. Oil, 3. Gas.

SUMMATIVE ASSESSMENT WORKSHEET-19[A] Multiple Choice Type Questions :

1. (b) 2. (c) 3. (a) 4. (a) 5. (a)

[B] Fillintheblanks:

1. carbon dioxide 2. Coke 3. 200 4. bitumen, coal-tar

5. CNG, Diesel or Petrol.

[C] WriteTrueorFalse:

(a) False (b) False (c) True (d) True (e) False.

[D] Writeonewordforthefollowing:

1. Inexhaustible resources 2. Fossil fuels

3.PetroleumRefining 4.Carbonisation

5. Coke 6. Naphthaleae balls.

[E] Write full forms of :

1. CNG-Compressed Natural Gas.

2.LPG-LiquifiedPetroleumGas.


Ans. 1. Petrol and Diesel.

Ans. 2. Combustion is a chemical process in which a substance reacts with oxygen of air to produce heat and light.

Ans. 3. When a burning charcoal piece is covered with a glass jar, the oxygen supply is cut off. Due to the absence of oxygen inside the jar, the fire gets extinguished.

Ans. 4. Water cools the combustible material so that its temperature is brought below its ignition temperature. This prevents the fire from spreading. Moreover, water vapours formed, surround the combustible material. So, the supply of air is stopped and the fire is extinguished.

Ans. 5. Explosion is a combustion reaction that occurs suddenly when a material is heated, liberating a large amount of heat, light and sound.

Ans. 6. When we heat water in a paper cup then the heat supplied to the paper cup is transferred to water by the conduction and the temperature of water goes on rising till it starts boiling. So, in the presence of water, the temperature of paper is not reached to its ignition temperature and paper cup does not burn.

Ans. 7. The three zones of a flame are dark zone, luminous zone and non-luminous zone.

Fig. Candle Flame

Ans. 8. (a) Calorific value of a fuel is the amount of heat energy evolved on complete combustion of 1 kg of a fuel. Its unit is kilojoule per kg (kJ/kg)

(b) The heat produced by burning 4.5 kg of a fuel = 180,000 kJ.

The heat produced by burning 1 kg of a fuel = 180,000 kJ/4.5kg

So, the calorific value of the fuel = 40,000 kJ/kg.


6 COMBUSTION AND FLAME

hottest

part

moderately

hot

least

hot

wax

candle

innermost zone of

unburnt wax

vapours (black)

middle zone of

partial combustion

(yellow)

outer zone of

complete

combustion (blue)

P-17COMBUSTION AND FLAME



1. (b) 2. (a) 3. (c) 4. (d) 5. (a)


1. ignition temperature 2. Water 3. low 4. LPG

5. Oxgyen 6. Carbon monoxide 7. kJ/kg or J/g

8. Pollution 9. CNG 10. Liquid.

[C] Write one word for the following :

1. Ignition temperatrue 2. Acid rain

3. Calorific value 4. Crude oil

[D] Identify the following as combustible and non-combustible substances :

1. Combustible 2. Combustible 3. Non-combustible

4. Combustible 5. Combustible 6. Combustible

7. Combustible 8. Non-combustible

Ans. 1. A candle burns with a flame while coal does not burn with a flame.

Ans. 2. Air or Oxygen.

Ans. 3. The minimum temperature at which a substance catches fire and starts burning is called its ignition temperature.

Ans. 4. Kerosene will catch fire first because its ignition temperature is lower than that of coal.

Ans. 5. CO2 is heavier than oxygen. So, it covers the fire like a blanket. Since the contact between the fuel and oxygen is cut off, the fire is controlled and CO2 does not harm the electrical equipment.

Ans. 6. The rubbing surface of the matchbox contains powdered glass and a little red phosphorus. The head of the matchstick contains antimony trisulphide and potassium chlorate. When the matchstick is struck against the rubbing surface then some red phosphorus gets converted into white phosphorus which readily reacts with potassium chlorate of the head of the matchstick to produce sufficient heat to ignite antimony trisulphide. Thus, the matchstick starts burning.

Ans. 7. Presence of oxygen in case while the (A) keeps the candle burning, (B) candle extinguishes in case, (C) Due to the absence of oxygen.

Ans. 8. The characteristics of an ideal fuel are :

(a) It should be readily available and cheap.

(b) It should produce a large amount of heat.

(c) It should burn without giving any harmful gases.

(d) It should burn easily in air at a moderate rate.

(e) It should not leave behind any undesirable substances after burning.





1. (c) 2. (a) 3. (b) 4. (b) 5. (c)

[B] Match the column A with column B :

(i)—(a), (ii)—(b), (iii)—(d), (iv)—(c)

[C] Name the following :

1. Hydrogen

2. Carbon dioxide

3. LPG and CNG

4. Fuel

5. Bio gas

6. Combustible substance.

[D] Labelthevariouszonesofcandleflameandanswerthefollowing:

Fig. Various Zone of Candle Flame

(i) Outer zone

(ii) Inner-most zone

(iii) Middle zone

hottest

part

moderately

hot

least

hot

wax

candle

innermost zone of

unburnt wax

vapours (black)

middle zone of

partial combustion

(yellow)

outer zone of

complete

combustion (blue)

P-19CONSERVATION OF PLANTS AND ANIMALS

Ans. 1. Clearing of forests to use that land for other purposes is called deforestation.

Ans. 2. Flora includes all the plants of a particular area. Fauna includes all the animals of a particular area.

Ans. 3. Zoo : It is a place where wild animals are kept in captivity or artificial setting.

Wildlife Sanctuary : It is a place where wild animals are kept in their natural environment.

Ans. 4. Animals whose number is decreasing to a level that they might get extinct are called endangered species e.g., Gangetic dolphins.

Ans. 5. We need to save paper for the following reasons :

(a) To save trees, as wood from trees is used in making paper.

(b) To save energy used in making paper.

(c) To reduce the use of harmful chemicals used in making paper.

Ans. 6. (a) Help in recycling in nature by eating dead animals.

(b) Maintaining ecological balance by not harming other creatures.

(c) Scavenger.

Ans. 7. Forests are essential because they :

(a) Form different types of ecosystems and biomas and create an environment which affects various types of animals and plants.

(b) Keep the environment cool by regulating transpiration and precipitation.

(c) Have aesthetic, cultural and spiritual importance.

Ans. 8. (a) Deforestation decreases the number of trees. As the number of trees decrease, soil becomes loose and the top fertile soil gets easily removed. Thus the fertile land gets converted to a desert. This process is called desertification. Thus deforestation causes desertification.

(b) I can help in maintaining the green wealth of my locality by taking care of the plants and trees growing in or around my locality. I can plant more and more trees. I can also encourage people in my locality to plant more trees by informing them about the importance of growing trees. I can make young children aware of the effects that deforestation has on our environment and on our planet. I can also ask them to water the plants daily, which will take very little of their time. I believe planting new trees is as important as taking care of the existing trees.


7 CONSERVATION OF PLANTS AND ANIMALS



Ans. 1. The objective of Project Tiger was to ensure the survival and maintenance of the tiger population in India.

Ans. 2. Deforestation : It is the clearing of forests.

Reforestation : It is the restoration of the destroyed forests.

Ans. 3. An ecosystem is a system made of all living organisms in an area and their non-living environment.

Ans. 4. Two reasons that endanger the existence of endemic species are :

(a) Destruction of their natural habitat.

(b) Introduction of new species in their habitat.

Ans. 5. The objective of forest Act are : (a) To preserve and conserve natural forests.

(b) To meet the basic needs of the people living in or near forests.

Ans. 6. Deforestation causes decrease in the water holding capacity of the soil. This causes reduction in the movement of water from the soil surface into the ground. Hence the floods are caused.

Ans. 7. Conservation of forests and wildlife sanctuary is necessary because they :

(a) balance the biosphere and biological diversity.

(b) control soil erosion and landslides.

(c) arrest rain torrents and maintain soil solubility.

Ans. 8. Deforestation decreases the number of trees. Trees use carbon dioxide for photosyntheses. Decrease in the number of trees causes less use of carbon dioxide. This leads to increased amount of carbon dioxide in air causing global warming, as carbon dioxide traps heat rays reflected by the earth. Global warming disturbs the water cycle and may reduce rainfall leading to droughts.


[A] Multiple Choice Type Questions : 1. (a) 2. (b) 3. (d) 4. (a) 5. (a)[B] Fill in the blanks : 1. wildlife sanctuary 2. endemic 3. climatic 4. red data book 5. afforestation.[C] Write one word for the following sentences : 1. Endangered species 2. Ecosystem 3. National park 4. Sanctuary 5. Biosphere reserve.[D] (a) Growing plants and trees in the open area in the school. (b) Arrangement for water harvesting. (c) Reporting any kind of water leakage in the school. With this we will be motivated to act like a eco-club members and participate

actively in its environment saving activities.

P-21CONSERVATION OF PLANTS AND ANIMALS



1. (b) 2. (c) 3. (c) 4. (d) 5. (a)

[B] Complete the quiz :

1. Endangered 2. Red data book 3. Drought/flood

4. Extinct 5. Endemic 6. Flora and Fauna

[C] Do you know :

1. One ton of paper is made from about seventeen fully-grown trees.

2. Each paper can be recycled three to seven times.

[D] Do as directed :

1. Definethefollowing:

(a) Sanctuary : It is the place where wild animals are protected from hunting and damage to their habitat. For example : Madhumalai Wildlife Sanctuary in Tamil Nadu, Chilika Bird Sanctuary in Orissa, etc.

(b) National parks : These are the areas reserved for wildlife where they can freely use the habitats and natural resources. For example : Ranthambore National Park in Rajasthan, Kanha National Park in Madhya Pradesh, etc.

(c) Biosphere reserves : These are large areas of protected land for conservation of wild life, plant and animals resources, and the traditional life of the tribals living in the area. For example : Panchmarhi Bisophere Reserve and Nilgiri Biosphere Reserve in India.

2. Satpura national park, Bori and Panchmarhi wildlife sanctuaries constitute Panchmarhi Biosphere Reserve.

3. Plants : Sal; Teak; Mango

Animals : Chinkara; Barking dear; Blue-bull


Answer the following :Ans. 1. Plasma Membrane.Ans. 2. Because till that time microscope was not invented.Ans. 3. Cell is the structural and functional unit of an organism because a cell in itself is the

smallest part of an organism which is capable of functioning independently and can carry out all the body functions.

Ans. 4. The function of the cell membrane is to let particles move in and out, to or from the cell. It is also protective in nature.

Ans. 5. The basic components of cell are : cell membrane, cytoplasm and nucleus.Ans. 6. Mitochondira provides energy to the cell for carrying out various activities. Chromosomes transfer the characters from parents to the next generation. Plastidsarethecellorganellecontainingpigments.Theygivecolourtoflowersand

fruits.

Ans. 7.

Ans. 8.


8 CELL-STRUCTURE AND FUNCTIONS

Prokaryotic cells

1. The cells having nuclear material without nuclear membrane are called as prokaryotic cells.

2. No cell organelle is present in prokaryotes.

3. Examples : Bacteria and blue-green algae.

Animal Cell

1. Smaller in size.

2. Plastids are obsent.

3. Cell wall is absent.

4. Vacuoles are smaller or absent.

5. Shapeisnotfixedandisirregluar.

6. Centrosomes are present.

Plant Cell

1. Larger in size.

2. Plastics are present.

3. Cell well is present.

4. Vacuoles are large in size and more in mumber.

5. Theyhavefixedandregular inshape.

6. Centrosomes are absent.

Eukaryotic cells

1. The cells having well organised nucleus with a nuclear mem-brane are called as eukaryotic cells.

2. All cell organelles like mito-chondria, chloroplast, ER, etc. are present in eukaryotes.

3. Examples : All higher organisms.

P-23CALL STRUCTURE AND FUNCTIONS

SUMMATIVE ASSESSMENT WORKSHEET-30Ans. 1. Nerve cells.Ans. 2. Mycoplasma, a bacteria that has the smallest cell of the size of 0.1 micron.Ans. 3. Cell of egg of an ostrich.Ans. 4. The nerve cell receives and transfer messages, so it help to control and coordinate the

working of different parts of the body.Ans. 5. Plant cells need protection against variations in temperature, high wind speed,

atmospheric moisture, etc. They are exposed to these variations because they cannot move and that’s why they have cell wall.

Ans. 6. Nucleus contains thread-like structures called chromosomes. Function : Chromosomes carry genes and help in inheritance or transfer of characters

from the parents to the offspring.Ans. 7. Vacuole : It stores food, water, waste products and other materials. Cell wall : It protects plant against variations in temperature, high wind speed,

atmospheric moisture, etc. Nucleus : This is the most important part that controls the activities of living cells.

Ans. 8.

Ans. 9. Plants prepare their food by their own. Chloroplasts provide green colour (Chlorophyll) to leaves which is essential for photosynthesis. Animals do not prepare their food by their own. That’s why chloroplasts are found only in plant cells.

Nucleus

Cell Body

Dendrite

Axon

Schwann cell(Myelin Sheath)

Nodes ofRanvier

AxonTerminals

Cross-Section of a Plant Cell

Cell Wall

CellMembrane

Vacuole

Nucleus

NuclearMembrane

Chloroplast

Golgi Body

Ribosomes

Smooth ER

Rough ER

Centrosome

Amylospast

Mitochondrion

Nucleolus

CytoplasmCross-Section of an Animal Cell

Cell Membrane Centrosome

Cytoplasm

Rough ER

Smooth ER

Ribosomes

Golgi Body

Lysosome

Nucleus

Nucleolus

NuclearMembrane

Vacuole

Mitochondrion





1. (a) 2. (a) 3. (c) 4. (a) 5. (c)


1. Green 2. Million 3. Pseudopodia 4. Protoplasm

5. Robert Hook 6. Amoeba and Euglena 7. Nerve cell

8. Mycoplasm, 0.1 9. Cell wall, centrosome 10. RBC 11. Tissue

12. Mitochondria, golgi bodies.

[C] Write true or false :

1. True 2. False 3. False 4. True 5. False

[D] Name the different parts of a plant cell :

1. Cell wall

2. Vacuole

3. Cell membrane

4. Cytoplasm

5. Chloroplast

6. Mitochondria


1. (b) 2. (c) 3. (c) 4. (d) 5. (c)


1. Identify the following types of cells :

Red blood cell Muscle cells Nerve cells.

2. Label it :

1. Cell membrane 2. Cell wall 3. Cytoplasm 4. Nucleus.

3. Give one word for the following :

(a) Eukaryotic cells

(b) Mitochondria

(c) Nucleus

(d) Chloroplast

(e) Nuclear membrane.

P-25REPRODUCTION IN ANIMALS


9 REPRODUCTION IN ANIMALS

Ans. 1. Organisms give birth to their individuals similar to them by the process of repro-duction Hence reproduction is necessary for the continuation of species.

Ans. 2. ThestageofembryoinwhichallthebodypartscanbeidentifiediscalledFoetus.

Ans. 3. Gametes are the haploid cells that help in sexual reproduction.

Sperm Ova

These are the male gametes produced by These are the female gametes produced

testes. by ovaries.

Ans. 4.

Internal fertilisation External fertilisation

(a) It is the fusion of sperm and ovum (a) It is the fusion of sperm and ovum

inside the body of the female. outside the body of the female.

(b)Itoccursinhumans,hens,cows,etc. (b)Itoccursinfish,frogs,etc.

Ans. 5. In frogs and fish, external fertilisation takes place with the help of water. Theirgametes are released in the water where other animals can feed on them. Hence, to ensure fertilisation of at least few of the gametes, these animals produce a large number of gametes.

Ans. 6. Male reproductive organs are :

(a) A pair of testes : These organs help in production of male gametes.

(b) Sperm ducts :Theseare tube likestructures thatcarrythemalegametes from testes to the penis.

(c) Penis : It helps in deposition of male gametes (sperms) into the body of the female.

Ans. 7. 1. Oviduct

2. Ovary

3. Uterus.

Ans. 8. Buddingisatypeofasexualrepoduction.Inthisprocess,asmallbulb-likeprojectioncalled a bud develops on the body of the organism. The bud gradually grows and getsdetachedfromtheparentorganismandformsaneworganism.Ittakesplaceinhydra and yeast.



Ans. 1. Transformation of a larva into an adult through drastic changes is called metamorphosis.

Ans. 2. Ahensitsonitseggstoprovidesufficientwarmthtotheeggforthedevelopmentofembryo inside the egg.

Ans. 3. IVF-InVitroFertilisationAns. 4. Eggs of a hen Eggs of a frog (a) It is surrounded by a hard shell. (a) No hard shell surrounds the egg.

(b) No Jelly is present. (b) A Jelly surrounds the eggs.

Ans. 5. Foetus Zygote 1. The stage of the embryo in which 1. It results after the fertilisation of nuclei

allthebodypartscanbeidentified. ofthespermandtheegg.

2. Complete development of foetus give 2. It is the beginning of a new individual.

birth to baby.

Ans. 6. After the formation of zygote, it divides to form a structure called embryo made of a group of cells.

Thedevelopmentofahumanembryotakesplaceinsidetheuterus.

Ans. 7. Oviparous Animals Viviparous Animals

These animals lay eggs which develop These give birth to young ones instead of

into young ones later on. eggs.

e.g. Birds, frogs, etc. e.g. Humans, dogs, etc.

Ans. 8. Binaryfissionisatypeofasexualreproductioninsingle-celledorganisms.Inthis,nucleus of the cell divides to form two nuclei. Thus the body of the cell divides to form two cells each containing one nucleus. The two cells formed are the two individuals.

BinaryfissionisamethodofreproductioninAmoeba.

P-27REPRODUCTION IN ANIMALS




1. (d) 2. (c) 3. (b) 4. (a) 5. (b)

[B] Fill in the blanks : 1. Caterpillar, tadpole 2. testes, ovary 3. sperm, testes

4. zygote 5. fallopian tube, ovary and uterus

6. epididymus, testes, vasdeferens

7.Fish, frog 8. Hydra, Amoeba

[C] Write true or false : (a)False (b)True (c)True (d)False (e)False (f)False (g)False (h)True (i)True

(j)False.

[D] Femalefoeticideistheactofobortingafoetusbecauseitisfemale.Thefrequencyoffemale foeticide is indirectly estimated from the observed high birth sex ratio.

The act of aborting or terminating a foetus while its still in the womb, because it is female,isknownasfemalefoeticide.

A study of hundreds of years of family trees suggests a man’s genes play a role in him having sons or daughter’s.

So, the approach of society towards mother in this regard is not correct, because Man’s are responsible for a girl or a boy child. Sex of child is depend on the chromosomes present in sperm (that is male gamete) X or Y that fuse with ovum at the time of fertilisation.


1. (a) 2. (b) 3. (c) 4. (d) 5. (a)


1. Sexual and Asexual 2. Clone

3. Asexual reproduction 4. Zygote

5. Binaryfission 6. FrogandButterfly

7. Test-tube babies 8. Frogandfish

9. Dog and hen 10. Hans Dreisch.

[C]

(a)

(b)

Dividing nucleus


Ans. 1. Adolescence is the period of life when the body undergoes changes, leading to reproductive maturity.

Ans. 2. Puberty ends when the person reaches reproductive maturity.

Ans. 3. Periodicflowofbloodfromtheuterusinfemalesiscalledmenstruation.

Ans. 4. Menarche Menopause

Itisthestartofmenstrualflowinthe Itisthestoppageofmenstrualflowina life of a female. female.

It occurs at puberty. It occurs at 45-50 years of age.

Ans. 5. Adrenal glands are important because of the following reasons :

(a) They control salt balance in the blood.

(b) They help in adjusting the stress when one is angry or worried.

Ans. 6. Following health measures should be taken to maintain good reproductive health :

(a) Person should take proper balanced diet.

(b) Person should do adequate physical exercise.

(c) Person should maintain personal hygiene.

Ans. 7. AIDS is a sexual disease caused by a virus called HIV.

It is transmitted by the following three ways :

(a) By sharing syringes between an infected person and a healthy person.

(b) From an infected mother to an infant throught her milk.

(c) By having intercourse with person suffering from AIDS.

Ans. 8. Different hormones along with their roles are :

Hormone Function

(a) Growth hormone Helps in the growth of the body.

(b) Insulin Maintains the amount of sugar in blood.

(c) Testosterone Causes secondary changes in boys.

(d) Estrogen Causes secondary changes in girls.

(e) Adrenalin Maintains correct salt balance in the blood.


10 REACHING THE AGE OF ADOLESCENCE

P-29REACHING THE AGE OF ADOLESCENCE


Ans. 1. Elongation of bones of legs and arms causes increase in height of the person during puberty.

Ans. 2. It is necessary to eat right kind of food during the growing years to provide proper and adequate nourishment to the body for growth and development.

Ans. 3. Testosterone is the male hormone and Estrogen in the female hormone that are secreted at the onset of puberty.

Ans. 4. Endocrine glands do not have ducts. These secrete their secretions called hormones directly into the blood stream. Hence these are called ductless glands.

Examples are Pituitary gland and thyroid gland.

Ans. 5. During Puberty, secretion of sweat and sebaceous glands increases in the skin. Due to this, young people get acne and pimples during puberty.

Ans. 6. Hormones from the pituitary stimulate testes and ovaries to release testosterone in male and estrogen in females.

Through blood stream, these hormones reach the target sites. Then they stimulate the chemical and functional changes in the body for the onset of the puberty.

Ans. 7. 1. Adolescence brings about the hormonal secretion among teenagers. This leads tosomephysicalandemotionalchangesamongthemwhicharedifficulttobear by them.

2. (a) Proper counselling of teenagers should be arranged from the counsellor.

(b) Healthy communication with parents.

(c) Teenagers should be properly motivated to set realistic goals.

Ans. 8. Secondary sexual characters are the visible characters that help to differentiate between a male and a female.

‘‘Two secondary sexual characters of girls are : Region below the waist becomes wider. Increase in the size of breast due to the development of mammary glands.

Two secondary sexual characters of boys are : Growth of hair under arms and on face. Shoulders get broadened.





1. (a) 2. (b) 3. (b) 4. (d) 5. (a)

[B] Answer the following questions :

1. Adrenalin 2. Hormones 3. 23

4. They do not have ducts 5. Diabetes 6. Thyroxine

7. Pituitary gland 8. Thyroxine

9. Salivary glands, Liver, Pancreas 10. Thyroxine/goitre.

[C] Fil in the blanks :

1. adam’s Apple 2. testosterone 3. menopause 4. growth hormone.


1. (a) 2. (a) 3. (a) 4. (a) 5. (a)


1. Do it yourself

2. Complete the following table :

Thyroxine — Thyroid

Insulin — Pancreas

Growth hormone — Pituitary

Testosterone — Testis

Estrogen — Ovary

3. Solve the Puzzle :

Across : 3. Adams Apple 4. Endocrine 7. Pituitary 8. Hormones 9. Insulin 10. Estrogen.

Down : 1. Testosterone 2. Thyroid 3. Adolescence 5. Organs 6. Larynx 7. Puberty.

P-31FORCE AND PRESSURE

Ans. 1. The spring force is the force exerted by a compressed or stretched spring upon any object which is attached to it.

Ans. 2. Push is the press on an object that can change the shape and direction of the motion of an object.

Ans. 3. 1. It can change the direction of a body in motion.

2. It can increase or decrease the speed of a body in motion.

3. It can stop a moving object.

4. It can set a stationary object move.

Ans. 4. Gravitational force depends on the masses of the two bodies concerned. Earth’s mass is much greater than that of the moon. That’s why the earth’s force of gravitation is much greater than that of the moon.

Ans. 5. (1) Pull (2) Push (3) Push

Ans. 6. Atmospheric Pressure : The force exerted by the atmosphere on unit area is called the atmospheric pressure.

Force : A push or a pull on an object is called a force.

Pressure : The force acting on a unit area of a surface in called pressure.

Ans. 7. (a) Liquid : When I make a small hole in a bottle full of water, water comes out of the bottle.

Gas : When we blow air in a ballon it changes its shape due to the pressure exerted by the gas on the wall of balloon.

(b) When we press a rubber sucker on the wall, the air between the wall and sucker comes out. It creates a low-pressure area inside the sucker. So, it sticks to the wall.


11 FORCE AND PRESSURE

Ans. 1. The force exerted by a charged body on another charged or uncharged body is known as electrostatic force.

Ans. 2. The force acting per unit area of a surface is called pressure.Ans. 3. When a force is applied on a rubber ball, force changes its shape.Ans. 4. Frictional force is a force, which always opposes the motion of a body over a given

surface. By using the lubricants on the surface and by polishing a rough surface, we can reduce the friction.

Ans. 5. Three types of force which can act from a distance are :

(a) Magnetic force

(b) Electrostatic force

(c) Gravitational force.





1. (d) 2. (d) 3. (b) 4. (b) 5. (c)

[B] Complete the following sentences :

1. Zero

2. Sharp knife has smaller area

3. They want to reduce pressure

4. Force

5. Magnetic force

6. Pressure

7. Atmospheric pressure

8. Push or lift a book, lift a bucket of water

9. Force between two magnets, magnet attracting iron nails.

[C] Fill in the blanks :

1. force 2. position 3. muscular 4. mechanical

5. magnetic 6. gravitational 7. pressure 8. increase

9. opposite 10. pressure.

Ans. 6. (1) A ball coming towards the wall return with the same speed after colliding with the wall.

(2) Pushing a box (3) Batsman hits the ball coming towards him.

Ans. 7. Net Force : The net force is the vector sum of all the forces which act upon an object. For situation A : Four forces are acting on an object. All of them cancel out each other as they all are opposing each other having equal magnitude. Thus, the net force of these two forces is zero Newton.

For situation B : The net force is 5 Newton acting in the left side of an object.

For situation C : The net force is 0 Newton.

For situation D : The net force is 15 Newton acting in the upward direction.

P-33FORCE AND PRESSURE



1. (c) 2. (d) 3. (c) 4. (b) 5. (a)

[B] m = 1 kg, g = 9.8m/sec2

weight = mass × acceleration due to gravity = m × g.

weight = (1 × 9.8)N = 9.8N.

weight of 1 kg mass is 9.8 N.

[C] Yes

[D] Both the teams are pulling with equal force.

[E] 1. (i) A liquid exerts pressure on the walls of the container.

(ii) Liquids exert equal pressure at the same depth.

2. Rise of water in dropper is due to pressure of rubber bulb. When we release the bulb, the pressure inside the dropper gets decreased. As the pressure of water outside is more, the water comes inside the dropper.


Ans. 1. When two bodies slide over one another, the irregularities on the two surfaces in contact gets interlocked and the force of friction comes to play.

Ans. 2. Liquids and gases exert force of friction, when object moves through them. The frictional force exerted by the fluids is termed as drag.

Ans. 3. When a ball rolls along such a surface, the force of friction acts between the surface of the ball and the ground. The force of friction opposes the motion of the ball along the ground. As a result of this, the speed of ball goes on decreasing and finally it stops.

Ans. 4. Kabaddi players rub their hands with soil while playing to increase the friction for better grip.

Ans. 5. Advantage : Production of heat by rubbing of palms against each other during winter.

Disadvantage : Machine parts gets heated up and lead to wear and tear.

Ans. 6. (a) Static friction : The friction that exists between the surfaces in contact when there is no relative motion is called static friction.

(b) Dynamic or sliding friction : The friction that exists between the surfaces in contact when a body slides on the surface of another body is known as the sliding friction.

(c) Rolling friction : The friction that exists between the surfaces in contact when a body rolls over the surface of another body is known as the rolling friction.

Ans. 7. (i) It helps in walking.

(ii) It helps in lighting matchstick.

(iii) It stops the bodies in motion.

Ans. 8. When two surface slide over each other, the force which opposes the motion of one body over the other, is termed as the force of friction.

Disadvantage of frictional forces are seen as :

(a) Wear and tear of objects coming in contact. Example : soles of shoes and tyres of vehicles.

(b) Loss of energy as heat. Example : Machine parts gets heated up and lead to wear and tear.

(c) Loss of energy to overcome friction. Example : Wastage of fuel in machinery.


12 FRICTION

P-35FRICTION


Ans. 1. When one body slides over the surface of another body, the force of friction that comes into play is called as sliding friction.

Ans. 2. Frictional force acts in the direction opposite to the direction of motion.

Ans. 3. Water of a wet surface acts as a lubricant. It fills the fine pores of the surfaces, which makes them smooth and thus reduces friction. Due to this decrease in friction the surface becomes more slippery.

Ans. 4. A hovercraft travels much faster than a steamer beacuse of the difference in their body shape. Air friction is very less as compared to the friction exerted by the water. This is because gases are less viscous as compared to the liquids.

Ans. 5. Drag depends on the :

(a) Speed of an object with respect to that of fluid.

(b) Shape of the object.

(c) Nature of the fluid.

Ans. 6. The three ways of minimizing friction between two surfaces are :

(a) Polishing of the roughened surface.

(b) Use of grease and lubricants.

(c) Use of ball bearings between moving surfaces of machine parts.

Ans. 7.

Sliding Friction Rolling Friction

(a) It is the force of friction between two (a) It is the force of friction between two

surfaces when one surface is actually surfaces when one surface rolls over

moving over another. another.

(b) It is lesser than static Friction. (b) It is lesser than sliding friction.

Ans. 8. Friction is both friend and foe. It is advantageous as :

(a) It helps in walking.

(b) Cars and buses are able to run on roads.

(c) It is possible to light a matchstick

(d) Nails and screws to hold onto walls.

It is disadvantageous as :

(a) it produces heat.

(b) it causes wear and tear.

(d) it causes forest fires.

(d) energy is wasted during friction.





1. (b) 2. (c) 3. (d) 4. (a) 5. (c)


1. Pascal

2. Newton

3. Electrostatic force

4. Gravitational force

5. Muscular force

6. Friction

7. Force

8. Pressure and area

[C] Fill in the blanks :

1. Opposite 2. Static friction 3. Sliding friction 4. Smaller

5. Minimized 6. Opposes 7. Rough 8. Drag

9. Rolling friction 10. Spring balance


1. (c) 2. (a) 3. (d) 4. (b) 5. (c)

[B] Match the following :

1. (c) 2. (a) 3. (b)

[C] Give reasons :

1. To reduce friction

2. Due to less friction

3. To minimize the force of friction so as to avoid wear and tear

4. It is due to friction caused by rubbing

5. It get reduced due to the friction

[D] Name the type of friction in the following two cases :

Static friction : Rolling friction

Rolling friction needs less effort.

P-37SOUND

Ans. 1. Sound is produced by vibration of the objects.

Ans. 2. The maximum distance through which a vibrating body displaced from its mean position is called as amplitude of vibration.

Ans. 3. Whistle used for dog training produce ultrasonic sounds of frequencies above 20,000 Hz. Audible range of dogs is nearly 40,000 Hz. But for humans, it is 20,000 Hz. So, human cannot hear the sound of the whistle used for dog training.

Ans. 4. It is a characteristic of sound through which the listener is able to distinguish between sounds of same pitch and same loudness produced by different musical instrument.

Ans. 5.

Muscial Sound Noise

1. It is produced by regular vibrations. 1. It is produced by irregular vibrations.

2. It has a pleasing effect on the ears. 2. It does not have a pleasing effect on the

ears.

Ans. 6. The loudness of sound depends upon the amplitude of the sound wave. A mosquito produces sound by the vibration of its wings in open air while the lion roars by the vibration of its vocal cords. The amplitude of the vibration produced by mosquito will be less than that produced by a lion. The pitch and loudness of the two sounds is quite different, which makes the two sounds different and distinguishable.

Ans. 7. 1. When the large number of vibrations are produced in one second, its frequency will be high. So, high pitched or shrill sound will be produced.

2. When the amplitude is small, the loudness of sound will be less. So, soft sound will be produced.

3. When the vibrations are produced at irregular intervals, an unpleasant sound or the noise is produced due to these vibration.

Ans. 8. Noise pollution : The disturbance produced in the environment by undesirable, loud and harsh sound from various sources is called noise pollution.

Harmful effects of noise pollution are :

(1) Loss of hearing.

(2) Headaches, irritation and nervous tension.

(3) Anger, tension and interferences with the sleep pattern of individuals.


13 SOUND



Ans. 1. Thephenomenonofreflectionofsoundisusedinsonartechnology.

Ans. 2. Echo is the reflected sound, when the reflecting surface is approximately at thedistance more than 17m from the source producing this sound.

Ans. 3. Full from of SONAR is Sound Navigation and Ranging.

Ans. 4. Soundabsorbingmaterialsarebadreflectorsofsound.Therefore,thereisnegligiblereflection of soundwaves and audience can hear the sound clearly as no echo isproduced.

Ans. 5. Time period = = = =1 20

54

ffwhere no. of oscill ations per = sec = 0.25 second.

Ans. 6. The human voice is the result of vibrations of the vocal cords. It is produced in larynx, a part of throat. Muscles of the vocal cords lighten the cords. Air from the lungs rushes past the tight stretched cords and causes the vocal cords to vibrate . These vibrations transfer the energy to its surrounding. Surrounding air vibrates and we hear the sound. So in this way, human produces the sound. Main cause of sound production is the vibration of vocal cords.

Ans. 7. (1) It is due to difference in the development of larynx.

(2) To prevent noise pollution.

(3) Speech can be developed only if we can hear properly. One can learn to speak only if he can hear what to speak.

Ans. 8. The shape of the ear’s outer part is like that of a funnel. As sound goes inside the outer part of the ear, it propagates in a canal. At the end of the canal, there is a thin membrane which is stretched tightly. It is called eardrum. The eardrum is like a stretched rubber sheet. The eardrum vibrates due to the sound vibrations. Then these vibrations are sent by the eardrum to the inner ear. The signal from the inner ear goes to the brain. In this way, we hear sound.

Temporal bone

Middle EarTymponum(Eardrum)

Stapes

EustachianTube

Inner Ear(Cochleo)

Nerves to theCentral AuditorySystem and Brain

Stopes(Stirrup)

Organs ofBalance

Incus(Anvil)

Ear Canal

Pinna

Outer Ear

P-39SOUND




1. (a) 2. (b) 3. (b) 4. (c) 5. (d)


1. oscillation 2. larynx or adam’s apple 3. Two vocal cords

4. 20 mm 5. 120 6. pitch 7. Plantation

8. Amplitude, frequency 9. Ear 10. amplitude.

[C] Eardrum.


1. (a) 2. (b) 3. (a) 4. (b) 5. (c)

[B] Answer the following questions :

1. Hearing aids

2. Vehicles, explosions including bursting of cracker, machines, loudspeaker.

3. Television and transistor radio at high volumes, some kitchen appliances, desert coolers, air conditioners.

4. Tabla, Sitar.

5. Loudspeakers, birds.

6. Noise.

7. Frequency.

8. 20 mm.

9.Loudspeakers,traffic,jetplanes,machines.

10. Lack of sleep, hypertension (high blood pressure), anxiety.

[C] Ektara—Stretched string

Tabla—Stretched membrane

Flute—Air columm

Dholak—Stretched membrane

Sitar—Stretched string

Harmonium—Brass Reeds

[D] 1. At homes, the television, the radio, the music system should be played at low volume.

2. The use of loudspeakers for various social or religious activities should be banned.

3. Transport vehicles, aircraft engines, home appliances, etc. should be installed withmodifiedandimprovedsilencers.


Ans. 1. The two sources of electric current are :

1. Voltaic cell. 2. Daniel cell.

Ans. 2. Flow of charges inside a conductor is called as electric current.

Ans. 3. The chemical reaction of an electrolyte into its components when electricity is passed through it is called electrolysis.

Ans. 4. A conductor is made up of material which allows electric current to pass throught it. Examples : Copper and Iron.

Ans. 5. Pure water is a bad conductor of electricity whereas acids and bases are good conductor of electricity. When an acid or an ionic salt dissolved in distilled water then the resulting solution conducts electricity.

Ans. 6. Two applications are :

1.Refiningofmetals.

2. Electroplating articles to look attractive.

Ans. 7. Tap water contains dissolved impurities which makes it a good conductor of electricity. So, when tap water is used as a conducting liquid in a closed electric circuit, the bulb glows.

Ans. 8. The process of depositing a thin layer of a desired metal over another metal object with the help of electric current is called electroplating. For electroplating a steel spoon with silver, a solution of silver i.e. AgNO3 is taken as the electrolyte. The spoon and a pure silver bar are dipped into the electrolyte and connected to the negative and positive terminals of a battery respectively. When a electric current is passed through the silver nitrate solution, it dissociates due to chemical effect of electric current. The positively charged silver ions move to the negative electrode (spoon) and form a deposit of silver on it and thus the spoon is silver plated.


14 CHEMICAL EFFECTS OF ELECTRIC CURRENT

Battery BulbSwitch

NaCl

P-41CHEMICAL EFFECTS OF ELECETRIC CURRENT

SUMMATIVE ASSESSMENT WORKSHEET-54Ans. 1. Because tap water coatains ions. Distillad water can be made conducting by adding salts.Ans. 2. Chemical energy.Ans. 3. The combination of two or more cells is called as battery. Ans. 4. The chemical effect of current is used in : 1. electroplating 2. the extraction of metalsAns. 5. Because the particles are held together by strong forces of electrostatic attraction. In

molten state the ions become free and move to conduct electricity, since on heating the bonds between the ions become weak.

Ans. 6. Electrodes are conducters which conduct electric current through a conducting liquid in an electric circuit.

Cathode : The electrode, which is connected to the negative terminal of the battery or cell is called cathode.

Anode : The electrode, which is connected to the positive terminal of the battery or cell is called anode.

Ans. 7. Thenecessaryconditionstoensureasmoothandfirmdepositare: (1) A direct current should be used. (2) A small current should be applied for a longer time. (3) The surface of the article should be free from dirt likes oil or grease. (4) Appropriate temperature should be maintained during electrolysis.Ans. 8. (i) Anode and cathode. (ii) (a) No, it will not glow. In solid state the free particles are held together by

strong forces of electrostatic attraction. (b) Yes, it will glow. In molten state it conducts electricity because the

temperature required to melt compound weakens the bond and ions become free to move.

(c) Yes, it will glow. In aqueous state it conducts electricity because dielectric effect of water weakens the bond and ions become free to move.

SUMMATIVE ASSESSMENT WORKSHEET-55 [A] Multiple Choice Type Questions : 1. (a) 2. (b) 3. (a) 4. (b) 5. (a)[B] Fill in the blanks : 1. bad conductor 2. chemical effect 3. good conductor 4. Electrodes 5. positive terminal 6. Tapwater, nitric acid 7. dissociation of ions 8. zinc.[C] Give examples : 1. Tap water, Hydrochloric acid. 2. Distilled water, Benzene. 3. Zinc, Copper.[D] Habit of consuming electrical energy affects the economical condition of family as

well as the nation because both, renewable and non-renewable source of energy is used to generate large amount of electricity. So, we should conserve the energy.

[E] Method Connect two copper plates to a cell through wires and a switch. Dip them in

copper sulphate solution in a beaker (See Fig.) Leave the current on for about half an hour.


FORMATIVE ASSESSMENT WORKSHEET-56 [A] Multiple Choice Type Questions : 1. (a) 2. (c) 3. (c) 4. (b) 5. (a)[B] Give reasons for the following : 1. Because it can easily be ionised on passing electricity.2. To present rusting which may contaminate the food stuff.3. It is not possible to electroplate large iron bars used in making bridges. 4. Water is a good conductor of electricity. With wet hands we may get electric shock.[C] (i) LEDs (ii) Battery/Cell (iii) Magnetic needle/compass.

[D]

Observations A fresh, shiny, reddish deposit of copper is seen on the negative copper plate. If the

plate is weighed before and after passing the current, we will notice that the negative plate weighs more after the current is passed.

Fig. Electrolysis

+ –

e flow+

+

–

Negative cathodePositive anode

Copper electrode

CuSo4 solution

Copper electrodeCu

Cu2

Cu

Cu2+SO2–4

Electolysis

Current flow

+

1.5

VOLTS

SIZE D

+

1.5

VOLTS

SIZE D

Fig. Electroplating

P-43SOME NATURAL PHENOMENA

Ans. 1. Tremors due to nuclear explosion and volcanic activities may cause earthquakes.

Ans. 2. Large earthquakes that occur under oceans causing huge waves are called Tsunami.

Ans. 3. Lightning conductor is a device used to protect buildings from the damaging effects of lightning. It runs from the top to the bottom, along the outer wall of the buildings or any other object, which is to be protected. If lightning strikes the buildings or any other objects, then the lightning conductor provides an easy and direct path for the lightning bolt to pass to the ground without effecting them.

Ans. 4. The process of transferring of charge from a charged object to the earth is called earthing. For our safety, most of the electrical appliances and the mains of the house are connected to earth, so that we can be prevented from getting an electric shock.

Ans. 5. During the development of thunderstorm, air currents move in the upward direction and the water droplets move in the downward direction. These movements causes the separation of charges. Usually, the negative charges accumulate at the lower part of the clouds and the positive charges are accumulated at its upper part. The positive charges are also accumulated at the ground. When the accumulation of charges becomes large, a high potential difference is set up between the lower part of clouds and the earth, which is sufficient to break the insulation of air. As a result, negative and positive chrages meet, producing streaks of bright light and sound. This process is called an electric discharge.

Ans. 6. The following precautions should be taken :

(a) Find a clear spot, away from buildings, trees, poles and electric poles, signboards and overhead power lines and lie on the gound.

(b) Do not use elevators if they are available at some place outside your house.

(c) If you are in a car or a bus, do not come out and drive slowly to a clear spot. Stay inside a car till the tremors stop.

Ans. 7. Do’s during a Thunderstorm : (a) Stay far away from all trees.

(b) Lie on the ground.

(c) Squat low on the ground.

(d) Open cars are not safe.

(e) Bathing should be avoided.

Don’ts during a Thunderstorm :

(a) Carrying an umbrella is a good idea during thunderstrom.

(b) Don’t touch electrical wires and metal pipes.

(c) Use mobile phones.


15 SOME NATURAL PHENOMENA



Ans. 1. An ebonite rod becomes negativety charged while wood becomes positively charged.

Ans. 2. Flash appears first than thunder while both are coming from the same place, because the speed of light is much more the speed of sound.

Ans. 3. When two bodies are rubbed against each other, frictional force arises between two bodies and equal and opposite charges are acquired by them. Thus, the method of charging the bodies by the friction is known as electrification by friction.

Ans. 4. A thunderstorm is a storm with lightning and thunder. It is produced by a cumulonimous cloud, usually producing gusty winds, heavy rain and sometimes hell.

Ans. 5. An earthquake is a sudden shaking or trembling of the earth. They can cause immense damage to buildings, bridges, dams and people. It results in the severe loss of life and property.

Ans. 6. (a) Heat evolved during nuclear fission.

(b) (i) Damage to property & life (ii) Genetic Disorder (iii) Infertile soil

(c) Yes; if used in a safe manner.

Ans. 7. Causes of earthquake are as follows :

(a) Disturbances deep inside the earth’s crust.

(b) The movement of plates, whose boundaries are the weak zones called fault zones.

(c) Nuclear explosion and volcanic activities.

Earthquake can cause immense damage to buildings, bridges, dams and people. There can be a great loss to life and property. The earthquakes can cause floods, landslides, tremor and tsunamis.

(i) Tsunami : Tsunami is a sea wave of local or distant origin that results from large-scale seafloor displacements associated with large earthquakes, major submarine slides, or exploding volcanic islands.

(ii) Tremor : Tremors are caused when an underground nuclear explosion is carried out, or a meteor strikes the earth, or a volcano erupts. The tremors produce waves on the surface of the earth. These are called seismic waves. An instrument called seismograph is used to record these waves.

Ans. 8. During the development of thunderstorm, air currents move in the upward direction and the water droplets move in the downward direction. These movements causes the separation of charges. Usually, the negative charges accumulate at the lower part of the clouds and the positive charges are accumulated at its upper part. The positive charges are also accumulated at the ground. When the accumulation of charges becomes large, a high potential difference is set up between the lower part of clouds and the earth, which is sufficient to break the insulation of air. As a result, negative and positive charges meet, producing streaks of bright light and sound. These streaks of bright light is called lightning.

P-45SOME NATURAL PHENOMENA



[A] Multiple Choice Type Questions : 1. (a) 2. (c) 3. (c) 4. (c) 5. (b)[B] Fill in the blanks : 1. conduction 2. positive 3. electrostatic force 4. lightening 5. electroscope 6. electric spark 7. repel 8. attract 9. seismic 10. seismograph[C] Write true or false : 1. False 2. True 3. False 4. False[D] Identify and Label the diagram : 1. Inner Core 3. Mantle 3. Outer Core 4. Crust.


1. (b) 2. (a) 3. (b) 4. (b) 5. (a)


1. Benjamin Franklin

2. Electroscope

3. Earthing

4. Lightening

5. Lightening rod

6. Lightening conductor

7. Earthquake

8. Bhuj district of Gujarat

9. Seismic or fault zones

10. Richter scale

11. Tsunami

[C] Seismo graph & lightening conductor.


Ans. 1. A ray of light is the straight line along which light travels.

Ans. 2. In a plane mirror, the distance of image of an object from the mirror is same as the distance of object from the mirror. The image of an object will be formed at a distance of 10 cm behind the mirror.

Ans. 3. Natural sources of light : Sun, star, moon etc.

Artificialsourcesoflight:Bulb,tubelightetc.

Ans. 4. Angle of incidence = 90° - 40 = 50.

Angleofreflection=Angleofincidence=50°.(By2ndlawofreflection).

Ans. 5. Multiple reflection isaprocess inwhicha reflectedbeamof light canbe reflectedagain.

Ans. 6. Our eyes are the most important and wonderful gift nature has provided to us. Eyes serves us for the whole life so proper care and protection is important. The activities that may cause damage to eyes.

(a) Readingintoobrightortoodimlight.

(b) Readinginamovingbusoracar.

Ans. 7. Thelawsofreflectionare: (a) Theincidentray,thereflectedrayandthenormalrayalllieinthesameplane,

at the point of incidence.

(b) Theangleofincidenceisalwaysequaltotheangleofreflection.

Ans. 8. Characteristics of the image formed by a plane mirror :

(a) Itisvirtual.

(b) Itisalwayserect.

(c) Itisofthesizeofobject.

(d) Theimageislaterallyinverted.

(e) Theimageisformedasfarbehindthemirrorastheobjectisinfrontofit.

The position of the image is at the same distance behind the mirror as the object is in front of it.


16 LIGHT

30°

90°Reflected

ray

Incidentray

Normal

P-47LIGHT


Ans. 1. VisuallychallengedpersonscanreadandwriteusingBraillesystem.

Ans. 2. At the junction of the optic nerve and the retina, there are no sensory cells. So, no vision is possible at this spot and is called blind spot.

Ans. 3. Becauseanypersondrivingthevehicle,whichisaheadoftheambulancevan,canseethe laterally inverted alphabets correctly from his rear view mirror, and make way for it to pass through.

Ans. 4. Whan an object is placed in front of a plane mirror then the right side of the object appears to be on the left side of the image and the left side of the object appears to be on the right side of the image. This change of the side of an object and its mirror image is called lateral inversion. This phenomenon of lateral inversion occurs due to reflectionoflight.

Ans. 5. The splitting of white light into seven colours on passing through a transparent medium, like a glass prism is called dispersion of light

(a) Optic nerve : Its function is to carry optical messages to brain.

(b) Retina : Its function is to receive the optical image of the object and convert it into optical pulses.

(c) Cornea : Its function is to allow the light to enter in the eyeball.

Ans. 7. (a) Don’trubeyes.Washthemproperlyofsoftly.

(b) Weshouldfollowthetipotomaintainthegoodeyecore.

Ans. 8. Regular reflection :Whenallparallelincidentraysremainsparallelafterreflectionthen this type of reflection is calledas regular reflection.Regular reflection takesplace from a smooth surface.

Irregular reflection :Whenalltheparallelraysreflectedfromaplanesurfacearenotparallel,thereflectionisknownasirregularordiffusedreflection.




[A] Multiple Choice Type Questions : 1.(b)2.(b)3.(a)4.(d)5.(a)[B] Fill in the blanks : 1.virtualanderect 2.lateral 3.normal 4.dispersion 5. blind spot 6. contract 7. Convex 8. cornea 9.cones/rods 10.regularreflection 11.optic 12.reflection.[C] Write one function of each : 1. Pupil: It regulates the amount of light entering the eye. 2. Rods : It enables us to see in dim light. 3. Cones : It enables us to see in bright light. 4. Retina : Image formation takes place here. 5. Optic nerve : They carry the sight sensations to the brain.


1.(b)2.(c)3.(b)4.(a)5.(a)

[B] Answer the following :

1.Angleofincidence 2.Angleofreflection

3.Lateralinversion 4.Dispersion

5.Retina 6.Pupil

7.Braillesystem.

[C] Reason :Myopia(Shortsightednessdefect)

Precautions : They should get proper check up for the eyes and should wear spectacles as recommended by the doctor.

[D]

Sclerofic

Iris

Aqueoushumour

P-49STARS AND THE SOLAR SYSTEM

Ans. 1. A natural satellite is a heavenly body, which revolves around a planet. Moon is a natural satellite of the Earth.

Ans. 2. The Sun is a huge hot celestial body having its own light. It emits heat and light like a star. So we classify the Sun as a star.

Ans. 3. Halley’s comet appears after every 76 years.Ans. 4. LightYearisdefindasthedistancetravelledbylightinvacuuminoneyear. One light year = 9.46 × 1012 km.Ans. 5. It is the star located close to the North Pole on the axis of rotation of the earth and so,

it appears stationary relative to the earth. It is also called the North Star or Dhurv Tara. It is not so bright and has no other star around it. In ancient time, sailors use the Pole star for navigation.

Ans. 6. A star : is a shining ball of glowing gases. It is formed when a lump of hot gas condenses into a globe like form. The glow of star comes from the heat that is inside the star where helium gas gives out heat energy.

Group of stars arranged in a pattern is called constellation. These patterns form the figuresofanimalsorhumanbeings.Allconstellationappeartorevolvearoundthepolestar,whichreamainsfixed.

All stars in constellation stay together. Some of the constellation are Orion, Kalpurush, Great bear, Taurus, Virgo, Leo, etc.

Ans. 7.

Fig. Position of Sten in Cassiopeia Constellation


17 STARS AND THE SOLAR SYSTEM


SUMMATIVE ASSESSMENT WORKSHEET-66Ans. 1. The stars, the planets, the moon and many other objects in the sky are called celestial

bodies.

Ans. 2. Aryabhatta.

Ans. 3. Twoartificialsatilletesofourcountryare:(a)INSAT-3E(b)EDUSAT

Ans. 4. Meteros are small stone like objects moving around the sun. Sometimes, a meteor enters the earth’s atmosphere at a very high speed and burns due to friction. It begins to glow and evaporates with in a short time. The path of the meteor appears as a streak of light in the night sky. Hence meteors are known as shooting stars.

Ans. 5. A galaxy is a large cluster of stars. Each galaxy contains billions of stars held together by gravitational force of attraction. There are about 100 galaxies in the universe.

Ans. 6.

Ans. 7. Earth and Jupiter can be considered as two spheres with radii R and R’ respectively. Given that the radius of Jupiter is 11 times the radius of the Earth.

Ans. 8. Star

1. A star has its own light.

2. Stars twinkle at night, i.e., their light incereases, decreases and continuously.

3. Stars are very big in size. They appear small because they are very far off.

4. A star is a huge mass of extremely hot gases and its temperature is very high.

5. Stars do not revolve around another the star.

Planet1. A planet has no light of its own.

It shines because it reflects light received from the sun.

2. Planets do not twinkle at night.

3. Planets are very small in size as com-pared to stars.

4. A planet is made of rocks and metal. Its temperature depends on its dis-tance from the sun.

5. Planets revolve around a star.

Ursa Major

Orion

P-51STARS AND THE SOLAR SYSTEM



[A] Multiple Choice Type Questions : 1.(a)2.(b)3.(d)4.(d)5.(d)[B] Fill in the blanks : 1.mercury 2.mars 3.constellation 4.satellite 5.meteor 6.marsandJupiter 7. full moon day 8. new moon day 9. full moon day 10. light.[C] Answer the following questions : 1.Mercury 2.Jupiter 3.Westtoeast 4.Itispresentontheearth’saxis 5.JupiterandMars 6. Halley’s Comet 7. It glows and evaporates quickly 8.Artificialsatellite 9.ItmeansIndianSatellite 10. Aryabhatta.

[A] Multiple Choice Type Questions : 1.(d)2.(c)3.(b)4.(d)5.(c)[B] Fill in the blanks : 1.one 2.atmosphere,water 3.away 4.elliptical 5.76 6.artificialsatellite 7.Aryabhatta 8.Artificialsatellite 9.Moon 10.Neptune.[C] The earth rotates from west to east around its axis. So, the sun rises in the east and

sets in the west. [D] (a)Areusedforlongdistancecommunication. (b)Areusedforresearchandremotesensing. (c)Facilitateradioandtelevisionprogramme transmission.[E] 1.Neptune 2.Sun 3.Earth 4.Jupiter 5.Uranus 6.Mars 7.Saturns 8.Venus

Thus, R’ = 11 R

Volume of a sphere of radius r is given as 34

3Rπ=

Volume of the Earth 34

3Rπ=

And, volume of the Jupiter ( ) ( )3 3 34 4 4' 11 1331

3 3 3R R Rπ π π = = =

The ratio of the volumes of Jupiter and Earth Volume of Jupiter

Volume of Earth=

3

3

41331

31331

4

3

R

R

π

π

= =

Hence, this ratio suggests that Jupiter can accommodate 1331 number of Earthswithin it.


Ans. 1. The introduction of contaminants into an environment which cause harm to living organisms and non-living components is known as pollution.

Ans. 2. Two examples of air pollutants are smoke and gases like NO 2, SO2, etc.

Ans. 3. The water, which is purified and made suitable for drinking, is called potable water. Boiling and chlorination methods are used for the purification of water.

Ans. 4. Ozone is a gas having molecular formula O3. It forms a layer around the atmosphere called ozone layer. This layer protects earth from the harmful ultraviolet rays of the sun.

Ans. 5. The rain, which is acidic in nature due to the presence of sulphuric acid and nitric acid, is called acid rain. Sulphur dioxide and nitrogen dioxide present in air reacts with the water vapour to form sulphuric acid and nitric acid. When these acids fall on the earth along with rain water, it is called acid rain.

Ans. 6. Ozone is present in the stratosphere, the upper part of the atmosphere. The ozone layer shields the earth from the harmful ultraviolet rays coming from the sun. Chlorofluorocarbons (CFCs) used in refrigerators, air conditioners and aerosol sprays are responsible for the depletion of ozone layer and producing a hole called ozone hole.

Ans. 7. The various sources of water pollution are as follows :

(a) Sewage and domestic wastes : It includes human excreta, soaps and detergents etc. The sewage from homes are collected and disposed off in rivers nearby. This untreated sewage is the prominent cause of water pollution.

(b) Human activities : People bath and wash their clothes on banks of rivers. This makes water polluted.

(c) Industrial and Agricultural discharges : Toxic chemicals (like cyanides, acids, lead, etc.) from industries are discharged directly into rivers or streams. The pesticides, fertilizers, insecticides which are used in agriculture are dissolved in water and washed into water bodies from the fields.

(d) Religious Rituals : Dispersion of Statues of God and Goddess, dead bodies and remains of dead bodies in rivers is causing pollution of water.

(e) Thermal Pollutants : Nuclear and thermal power plants discharge their unutilized heat into nearby flowing water. It raises the temperature of the water body and this water is the life of water animals and plants.


18 POLLUTION OF AIR AND WATER

P-53POLLUTION OF AIR AND WATER


Ans. 1. Sulphur dioxide and Nitrogen dioxide Ans. 2. Green house effectAns. 3. Lead and ArsenicAns. 4. The absorption of solar energy by the gases like carbon dioxide, methane in the

atmosphere, is known as Green house effect. Green house gases warm the atmosphere by efficiently absorbing thermal infrared

radiation emitted by the Earth’ surface by the almosphere itself, and by clouds.Ans. 5. When air is contaminated by unwanted substances which have a harmful effect on

both the living and the non-living, it is referred to as air pollution. Diseases caused by air pollution are Asthama & Skin allergy.

Ans. 6. When water bodies contain nutrient enriched water, then a dense growth of plants like algae develops. Once these algae die, they become food for decomposers. These decomposers consume a lot of oxygen present in water. As a result, other aquatic animals do not get oxygen for respiration and ultimately they die. This process is called eutrophication.

Ans. 7. Causes : (a) By industrial waste. (b) By human activities. Measures : 1. By not throwing waste materials and garbage into water. 2. By

sensitizing people about harmful effects of water pollution. (or any other methods)Ans. 8. Air pollution can be controlled with the help of following measures : (a) Use of CNG and unleaded petrol instead of leaded petrol and diesel in automobiles

can reduce air pollution. (b) Use of alternative fuels like solar energy, wind energy and hydropower instead

of fossil fuels can reduce air pollution. (c) We should plant trees and nurture the ones already present. (d) We should not burn crackers on Diwali or on other celebration. (e) Instead of burning dry leaves, they should be put in a compost pit to make

manure.


[A] Multiple Choice Type Questions : 1. (b) 2. (a) 3. (a) 4. (b) 5. (c)[B] Fill in the blanks : 1. 3/4, 1/4 2. carbon monooxide, poisonous 3. reduces 4. SO2 and NO2 5. CFC’s 6. ultraviolet 7. 3/4 8. reduce, reuse, recycle 9. acids 10. CO2.[C] Write the full forms of : (i) CFC—Chlorofluorocarbon (ii) CNG—Compressed Natural Gas (iii) LPG—Liquefied Petroleum Gas (iv) WWF—World Wildlife Fund (v) RRR—Reduce Reuse Recycle




1. (b) 2. (a) 3. (b) 4. (d) 5. (b)


1. Carbon dioxide and methane

2. Sulphur dioxide and nitrogen dioxide

3. (a) Smoke and dust due to fire in forests or volcanic eruptions.

(b) Smoke and poisonous gases emitted by power plants and produced by burning of fossil fuels.

4. (a) The sewage from houses are collected and disposed off in rivers nearby. This untreated sewage is the prominent cause of water pollution.

(b) Toxic chemicals like cyanides, acids, lead coming out from industries are discharged directly into rivers or streams.

5. Define the following terms :

(a) Potable water : Water fit for drinking purpose is called potable water.

(b) Green house effect : The absorption of solar energy by the gases like carbon dioxide, methane in the atmosphere, is known as Green house effect.

(c) Global Warming : The gradual increase in the average temperature of the earth’s atmosphere due to green house gases like carbon dioxide is called global warming.

(d) Acid Rain : The rain, which is acidic in nature due to the presence of sulphuric acid and nitric acid, is called acid rain.

(e) Chlorofluoro Carbons : These are released from refrigerators, air conditioners, and aerosol spray. They cause damage to the ozone layer resulting in the formation of ozone hole.

6. Steps that can be taken to restore river Ganga to its glory are :

(a) Ganga must be completely free from Industrial effluents.

(b) It must be free from sewage of the cities and towns.

[D] Agreed. One should minimize the use of water, should not keep the taps open when not in use,

should use bucket of water for cleaning purpose, for taking both, as these practices consume less water.

[E] We need to filter water before drinking because it kills the bactera in the water. Two water borne diseases are : 1. Diarrhoea 2. Malaria

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