Question Bank science · 2018-02-01 · Worksheet-12 ... Project/Activities: 1. Take a handful of...

FULL MARKS PVT LTDEducational Publishers

4238A/1, Ansari Road, Daryaganj

New Delhi-110002

Question Bank

scienceteacher’s Manual

CBSE8

1. Crop Production and Management ......................................................................3 2. Microorganisms: Friend and Foe .........................................................................7 3. Synthetic Fibres and Plastics .............................................................................11 4. Materials: Metals and Non-Metals .....................................................................16 5. Coal and Petroleum ............................................................................................20 6. Combustion and Flame ......................................................................................23 7. Conservation of Plants and Animals ..................................................................27 8. Cell: Structure and Functions .............................................................................30 9. Reproduction in Animals ...................................................................................33 10. Reaching the Age of Adolescence ......................................................................36 11. Force and Pressure .............................................................................................40 12. Friction ...............................................................................................................44 13. Sound .................................................................................................................47 14. Chemical Effects of Electric Current .................................................................50 15. Some Natural Phenomena Adolescence .............................................................53 16. Light ...................................................................................................................57 17. Stars and the Solar System .................................................................................61 18. Pollution of Air and Water .................................................................................64 l Worksheet-1 .......................................................................................................69 l Worksheet-2 .......................................................................................................69 l Worksheet-3 .......................................................................................................70 l Worksheet-4 .......................................................................................................71 l Worksheet-5 .......................................................................................................71 l Worksheet-6 .......................................................................................................72 l Worksheet-7 .......................................................................................................73 l Worksheet-8 .......................................................................................................73 l Worksheet-9 .......................................................................................................74 l Worksheet-10 .....................................................................................................75 l Worksheet-11 .....................................................................................................75 l Worksheet-12 .....................................................................................................76 l Worksheet-13 .....................................................................................................76 l Worksheet-14 .....................................................................................................77 l Worksheet-15 .....................................................................................................78 l Worksheet-16 .....................................................................................................78 l Worksheet-17 .....................................................................................................79 l Worksheet-18 .....................................................................................................80

CONTENTS

(ii)

Teacher’s Manual n 3

Chapter 1 Crop Production andManagement

FORMATIVE ASSESSMENTOral Questions 1. Rainy season 2. Winter season 3. Moat or Pulley system 4. Fish 5. Trowel 6. Sickle 7. Hoe 8. Sprinkler system 9. Cultivator helps in saving time

and labour. 10. A combine harvester saves time

and labour. Fill in the blanks 1. June, September 2. October, March 3. Summer 4. Loosened 5. Friends 6. Iron 7. Wood 8. Funnel 9. Crops 10. Chemical True/False 1. True 2. False 3. True 4. False 5. True 6. True 7. False 8. False 9. True 10. False Rapid Fire Questions 1. Summer 2. Winter 3. Rice and maize 4. Fish 5. Turning over the soil 6. When a single plant is grown on

large scale, it is called crop. 7. Hoe is used for leveling the

ploughed field. 8. Sandy soil

Project/Activities 1. Take a handful of wheat seeds and

keep them in a bowl which is full of water.

l Wait for a few minutes. l Some seeds float on water,

while others sink. l Seeds which float on water are

damaged seeds. l Seeds which sink in water are

good seeds. 2. Take three disposable cups and

label them as A, B and C. l In cup A, fill a mixture of soil

and cow dung. l In cup B, fill a mixture of soil

and chemical fertilizer. l In cup C, fill soil only. l Put some moong seeds in the

soil in these cups and sprinkle some water.

l Wait for about a week and keep the soil moist.

Observations: l Plants in cup B showed the best

growth. l Plants in cup A showed moderate

growth. l Plants in cup C showed the

least growth. This shows that fertilizers are

best to promote plant growth. Manure also helps in plant growth. Plant growth is minimum in the absence of manure and fertilizers.

4 n QuesTion Bank science–8

SUMMATIVE ASSESSMENT

Multiple Choice Questions 1. (d) All of the above 2. (b) Two 3. (c) Groundnut 4. (c) Oxen 5. (d) Animal and plant waste 6. (a) Tractor 7. (a) Root 8. (d) All of the above 9. (d) 90% 10. (c) Drip irrigation Match the Columns (i)-(e) (ii)-(d) (iii)-(b) (iv)-(c)Very Short Answer Type Questions 1. Cultivation of plants and rearing

of animals for food and other beneficial items is called agriculture.

2. When plants of the same kind are grown and cultivated at one place on a large scale, it is called a crop.

3. There are two main types of crops in India, viz. kharif and rabi.

4. Loosening of soil is done by plough and this practice is also called ploughing or tilling.

5. Putting seeds in soil is called sowing. 6. Fertilisers are chemicals which

contain a particular plant nutrient. 7. A field which is left uncultivated

for a couple of seasons is called a fallow field.

8. The supply of water to crops at different intervals is called irrigation.

9. Unwanted plants which grow along with crops are called weeds.

10. Separation of grains and chaff is called winnowing.

Short Answer Type Questions

1. Kharif RabiThese crops are grown during rainy season.

These crops are grown during winter season.

These cropsrequire plenty of water.

These cropsrequire less water.

Examples:paddy, maize, soyabean, etc.

Examples:wheat, mustard, gram, etc.

2. Significance of Ploughing: l This allows the roots to penetrate

deep into the soil. l Loose soil allows the root tips

to breathe easily when they go deep into the soil.

l It allows proper mixing of nutrients from humus into the soil.

l Loosening of soil brings nutrients and minerals to the top and thus plants are able to utilize these minerals.

3. A plough is composed of ploughshare and ploughshaft. The ploughshare is triangular in shape and is made of iron. The ploughshaft is made of wood and is very long. It is harnessed to a pair of bullocks or other cattle with the help of a beam.

4. The traditional seed drill is composed of a funnel with a long and pointed neck. It is attached to the ploughshaft. Seeds are kept in the funnel and they drop slowly through the neck, while the field is being tilled. The pointed neck


of the seed drill pierces the soil and seed goes deep into the soil.

5. Fertilisers are chemicals which contain a particular plant nutrient. Fertilizers are made in factories. Urea, ammonium sulphate, super phosphate, potash and NPK (Nitrogen, Phosphorus and Potassium) are examples of fertilizers.

6. Advantages of Fertilisers: l Fertilizers give quicker results

compared to manure. l Use of fertilizers has helped

farmers in s ignif icant ly improving farm yield.

7. Proper storage of harvested crop is important to prevent damage from moisture and pests. Grains are sun dried before being stored. Grains are stored in silos. Silos can be of varying heights; ranging from one metre to several metres. Fruits and vegetables are stored in cold storage. Suitable pesticides are used while storing grains. Neem leaves are also used as pesticides.

8. In this method, a legume crop is sown between two successive cereal crops. Legume plants harbor Rhizobium bacteria in their root nodules. These bacteria help the plants in nitrogen fixation in soil. Thus, growing a legume crop helps in replenishment of nutrients in soil.

9. Advantages of Manure: l Manure increases nutrients in

soil. l It improves soil texture. l It improves water retaining

capacity of soil.

l It is free of any toxic material and thus is environment friendly.

10. This is used for leveling the soil and for removing weeds. This is made of iron or wood. It is a long beam with a handle. A sharp blade is fixed on one end. This is usually pulled by animals. A hoe is used for leveling the field.

Long Answer Type Questions 1. The supply of water to crops

at different intervals is called irrigation.

Two methods of irrigation which conserve water are as follows:

(a) Sprinkler System: This system is composed of a series of pipelines. Vertical sprinklers are fitted at suitable gaps in these pipes. A jet of water comes out of sprinklers and sprays water on plants.

(b) Drip Irrigation: In drip irrigation system, pipes are laid along the queue of plants. Small holes are made in pipes at frequent gaps. Water drips slowly from these gaps and falls only at the base of the plants.

2. Unwanted plants which grow along with crops are called weeds.

Weeding: Removal of weeds is called weeding. This is usually done manually and by using trowel. Weeds are also removed during ploughing. Chemicals which destroy weeds are called weedicides . For example; 2, 4 - D is a weedicide which is sprayed on weeds. Weedicides are sprayed during vegetative growth


of plants, i.e. before flowering and seeding. Weedicides are health hazards so a farmer needs to take precautions while spraying weedicides.

3. Manure FertilizerManure is an organicsubstance.

Fertilizer is aninorganicsubstance.

Manure is made by decompo-sition of plant a n d a n i m a l waste.

Fertilizer is made in factories.

Manure is slow in working.

Fertilizer gives fast results.

Manureimproves the texture of soil.

Has no effect on soil texture.

It doesnot containpollutants.

It containspollutants.

4. Traditional Methods of Irrigation: In traditional method, human or animal labour is used.

(a) Moat (Pulley System): This is composed of a pulley. A rope passes through the pulley and a bucket is tied to the rope. Pulley makes it easier to pull a bucketful of water from deep wells.

(b) Chain pump: Chain pump is composed of a wheel which is turned with the help of a chain.

(c) Dhekli: Dhekli is composed of a long wooden beam which turns around a lever. A bucket is fitted at the longer end of the beam and shorter end is pressed and raised to fill and lift water.

(d) Rahat: Rahat is also called Persian Wheel. It is a big wheel with buckets fitted on its rim. This is turned with the help of cattle. Buckets are lowered in water and filled buckets are raised to empty water in a drain.

5. Importance of Irrigation: l Plants contain nearly 90%

water. l Water is essential for germination

of seeds. l Water is essential for proper

growth of plants. l Water is essential for proper

development of flowers, fruits and seeds.

l Water protects plants from frost and also from hot air currents.

Higher Order Thinking Skills (HOTS) 1. Adding water to hard soil, helps

in softening the soil. Soft soil can be easily loosened and turned over. Hence, farmers add water to hard soil before ploughing.

2. India is a vast country. There are different types of climatic conditions at different places. Due to this the crop variety is different in different parts of India.

3. Weeds present following challenges: l Weeds compete with crops for

sunlight, water, nutrients and air. l Weeds disturb the normal

growth of crops. l Some weeds are poisonous. 4. Fruits and vegetables can be easily

destroyed by high temperature and moisture. Keeping them in


cold storage prevents spoiling them. This helps in preventing wastage of fruits and vegetables.

5. Freshly harvested grains contain lot of moisture. Moisture provides ambient environment to pests and microbes. Thus, moisture can destroy the grains. Hence, grains are sun dried to remove moisture so that they can be stored for a longer duration.

Value Based Questions 1. Ramdin is showing a concern

for environment. He is utilizing all the farm and domestic waste to prepare manure. By doing

so, he takes care that nothing goes waste. This benefits the environment by helping in nutrient recycling in soil. No use of fertilizers helps in preventing soil pollution, groundwater pollution and environmental pollution.

2. Lata is showing a concern for water which is a precious resource. She is trying to conserve water by using drip irrigation in her orchard.

Puzzle TimeDOWN: 1. KHARIF, 2. PLOUGH, 3. RICE ACROSS: 4. WHEAT, 5. CROP, 6. IRRIGATION

Chapter 2 Microorganisms: Friendand Foe

FORMATIVE ASSESSMENTOral Questions 1. Microbes cannot be seen with

the naked eye. They can be seen through a microscope.

2. Dry fruits and potato chips 3. Jam and jelly 4. Milk 5. Penicillium 6. Mushroom 7. Foot and mouth disease 8. In stagnant water 9. Rainy season 10. Small pox Fill in the blanks

1. Multicellular 2. Four 3. Tuberculosis 4. Human Immunodeficiency Virus 5. Alone 6. Sugar

7. Yeast 8. Antibiotic 9. Doctor 10. 1798True/False 1. True 2. False 3. True 4. False 5. True 6. False 7. True 8. False 9. True 10. TrueRapid Fire Questions 1. Microscope 2. Lactobacillus 3. Edward Jenner 4. Pasteurization 5. Penicillin 6. Mushroom 7. This is a viral disease in cattle 8. Mosquito 9. Plasmodium 10. Human Immunodeficiency Virus

8 n Question Bank science–8

Project/Activities 1. lTake a test tube, distilled water,

sugar and some yeast powder. lFill half of the test tube with

distilled water and dissolve a spoonful sugar in it.

lHeat the solution till it becomes lukewarm.

lAdd a pinch of yeast powder in it and shake well.

lKeep the test tube at a warm place; preferably in sunlight.

lObserve the smell of content after about 3 – 4 hours.

lYou will notice that alcohol like smell comes from the test

tube. This happened because alchohol was produced by fermentation.

2. Nodules can be observed on roots of gram or pea plants. Rhizobium bacteria live in these root nodules.


Multiple Choice Questions

1. (c) Alcohol 2. (a) 78% 3. (b) Malaria 4. (c) Common cold 5. (d) Fungi 6. (a) Bacteria 7. (a) Bacteria 8. (b) Fungi 9. (c) Alexander Fleming 10. (d) AIDS Match the columns (i)-(e) (ii)-(a) (iii)-(b) (iv)-(c) (v)-(d) (vi)-(f)Very Short Answer Type Questions 1. Organisms which cannot be

seen by naked eyes are called microorganisms or microbes.

2. A substance which kills or stops the growth of bacteria is called antibiotic.

3. The process of conversion of sugar into alcohol by yeast is called fermentation.

4. Pulse Polio is a large scale programme to eradicate polio from India.

5. A disease which can spread from one person to another is called communicable disease.

6. Microbes which cause disease are called pathogens.

7. Use of some techniques to prolong the shelf life of a food is called food preservation.

8. The p rocess o f changing atmospheric nitrogen into a suitable form for plants is called nitrogen fixation.

9. The sequence of events by which nitrogen is channelized to the living world and back to atmosphere is called nitrogen cycle.

10. Blue green algae and Rhizobium Short Answer Type Questions 1. Bacteria are found in different

shapes; like rod-shaped, spiral,


spherical and comma-shaped. Examples: Rhizobium, E. coli, Pseudomonas, Streptococcus, etc.

2. Viruses are also microscopic but they are not kept under living beings. A virus is a borderline case between living and non-living. A virus behaves as non-living when it is outside a host cell but once it is inside a host, it behaves like a living being. Examples: HIV, Tobacco Mosaic Virus (TMV), etc.

3. Microorganisms live almost everywhere. They are found on land, water and in air. They are found inside and on human body. They are found in the crater of volcano and in sulphur springs.

4. Alexander Fleming discovered the antibiotic Penicillin in 1929. This was prepared from a fungus Penicillium. Penicillin made it possible to treat many difficult diseases.

5. A vaccine contains a weak or killed strain of a disease-causing microbe. When a vaccine is inoculated in the body, the body prepares antibodies against it. Thus, the body learns and remembers how to fight with that microbe in future.

6. Microbes play significant role in cleaning the environment. Many microbes are decomposers. They decompose dead remains of plants and animals. In this process, they release simple inorganic substances back into the environment. Thus, microbes help in getting rid of all the dead

materials and also play important role in biogeochemical cycle.

7. Some bacteria produce a toxic substance in food. Consuming a food item with toxic substance can result in food poisoning. Food poisoning is a serious case and needs immediate hospitalization. High fever, vomiting and pain in abdomen are some of the symptoms of food poisoning.

8. When a food item is kept in plenty of salt, it results in dehydration of the food item. Lack of moisture helps to prevent the growth of microbes. Lot of salt is added to pickles. Fish and meat are also preserved by adding salt.

9. Pasteurization is a method of food preservation. In this process, milk is heated to 70°C for about 15 to 30 minutes and is then quickly chilled and stored. This helps in killing the microbes which may be present in milk.

10. Some chemicals prevent the growth of microorganisms in food, e.g. sodium benzoate and sodium metabisulphite. These chemicals are used in pickles and jams to preserve them. Salt, acids and oil are also added to food to preserve them.

Long Answer Type Questions 1. Usefulness of microorganisms: (a) Microorganisms help in

making of curd. (b) Microorganisms help in

fermentation of sugar. (c) Microorganisms help in

making of bread and cakes.


(d) Some fungi and bacteria are used for making medicines.

(e) Cheese is processed with the help of some bacteria and fungi.

(f) Many supplementary food items are made from microorganisms.

(g) Many microbes help in cleaning the environment by decomposing dead remains of plants and animals.

(h) Many microbes in our gut help in digestion of food.

(i) Blue green algae and Rhizobium fix atmospheric nitrogen.

(j) Some microbes are used for making vaccines.

2. Types of Microorganisms: (a) Bacteria: Bacteria are found

in different shapes; like rod-shaped, spiral, spherical and comma-shaped. Examples: Rhizobium, E. coli, Pseudomonas, Streptococcus, etc.

(b) Algae: Some a lgae a re microscopic . Examples : Chlamydomonas, Spirogyra, etc.

(c) Fungi: Almost all fungi are microscopic, except mushrooms. Examples: Yeast, Rhizopus (bread mould), Aspergillus, Penicillium, etc.

(d) Protozoa: Amoeba and Plasmodium are examples of Protozoa.

3. When a disease-carrying microbe enters our body, the body makes antibodies to fight this microbe. In this process, the body remembers how to fight with that microbe during future onslaughts. This property of the body has been

utilized to prepare vaccines against many diseases.

Vaccines are now available for many diseases; like small pox, tuberculosis, polio, tetanus, diphtheria, whooping cough, hepatitis, etc.

4. How to prevent Malaria and Dengue:

l Malaria and dengue spread through mosquitoes. So, breeding of mosquito should be prevented.

l Water should not be allowed to stagnate in surroundings. Mosquitoes lay eggs in stagnant water.

l Summer coolers should be cleaned frequently.

l Overhead tanks should be covered.

l Drains should be covered properly.

l Ditches should be filled. l Use mosquito repellant creams

and mosquito nets. 5. Following are the main steps of

nitrogen fixation: lBlue green algae and some

bacteria (like Rhizobium) convert gaseous nitrogen into compounds of nitrogen. These compounds get deposited in soil.

l Some of the nitrogen changes into compounds of nitrogen dur ing l ightning. These compounds reach the soil through rainwater.

l Plants take up nitrogenous compounds and utilize them to make protein and other important molecules.


l During excretion by plants and animals, nitrogenous compounds once again reach the soil. Some of them are taken up by plants. Remaining portion is decomposed by bacteria and fungi and gaseous nitrogen is released in the atmosphere.

Higher Order Thinking Skills (HOTS) 1. Nitrogen is the most abundant gas

in our atmosphere. But gaseous nitrogen cannot be utilized by plants. This needs to be changed into a form so that plants can take up nitrogen. Hence, nitrogen fixation in soil is necessary.

2. Summer provides ambient temperature for microbes to proliferate. Boiling the milk many times in a day helps in killing the microbes which may be present in milk. This helps in preventing spoilage of milk.

3. Most of the roadside vendors do not keep their food items covered. Thus, food is exposed to many microbes which come through flies. Eating contaminated food can cause diarrhoea and dysentery. It can even cause jaundice. So, we should avoid food being sold by roadside vendors.

4. Lactobacillus is required for making curd from milk. But the Lactobacillus needs to be supplied from somewhere. The small amount of curd which is added in the milk works like inoculum. This works like ‘seed’ for making fresh curd.

Value Based Questions 1. Mrs. Khanna is showing a

concern for well being of her family and her neighbours. She is eliminating the chance of stagnant water so that mosquito breeding could be prevented. This will help in preventing cases of malaria and dengue in her family and neighbourhood.

2. Boil ing the milk helps in prolonging the shelf life of milk; especially during summer months. By doing this, Shobha is showing a concern for the health of her family. She is also showing the value of money. Because spoilt milk will mean wastage of money.

Puzzle TimeDOWN: 1. VIRUS, 2. VACCINE, 3. NITROGENACROSS: 4. BACTERIA, 5. FERMENTATION, 6. ANTIBIOTIC

Chapter 3 Synthetic Fibres andPlastics

FORMATIVE ASSESSMENTOral Questions 1. Cotton and wool

2. Nylon and Rayon 3. Petrochemicals


4. Nylon 5. Thermoplastic 6. Thermosetting plastic 7. Silk 8. Wool 9. Wood pulp 10. Coal, water and air Fill in the blanks 1. Beads 2. Repeating 3. Cellulose 4. Carpets 5. Bedsheet 6. Steel 7. Ester 8. Water 9. Poor conductor 10. Teflon True/False 1. False 2. True 3. False 4. True 5. False 6. False 7. False 8. True 9. False 10. FalseRapid Fire Questions 1. Wool and silk 2. Cotton and jute 3. Rayon 4. London and New York 5. Making electrical switches 6. Making cooking utensils 7. Rayon 8. Acrylic 9. Nylon 10. Polyvinyl Chloride

Project/Activities 1. l Take threads of cotton, wool,

silk, rayon and nylon. Take a stand, clamp, some weights and a pan.

l Ensure that all the threads are of same thickness and length.

l Tie a thread to the stand and suspend a pan with it.

l Put some weight on the pan. Increase the weight in small increments till the thread snaps.

l Note down the weight required to snap a thread.

l Repeat this activity with each sample of thread.

Observation: You will notice that cotton takes least weight to get snapped. Nylon takes the most weight to get snapped. This shows that synthetic fibres are stronger than natural fibres.

2. lTake a piece of woollen cloth and another piece of nylon cloth. Both the pieces should be of same size.

l Take two mugs and put equal amount of water in them.

l Soak woollen cloth in one mug and nylon cloth in the second mug.

l Take out the cloth pieces and observe the amount of water left in the mug.

l It is noticed that the first mug contains less water than the second mug.

l This shows that natural fibre absorbs more water than synthetic fibre.


Multiple Choice Questions 1. (c) Silk 2. (a) 1931 3. (d) Polythene 4. (a) Polyester + wool 5. (b) Polythene

6. (d) Toys 7. (a) PET Match the columns (i)-(d) (ii)-(c) (iii)-(a) (iv)-(b)


Very Short Answer Type Questions 1. Fibre which is made by humans

is called synthetic fibre. 2. A chain of a particular chemical

substance is called a polymer. 3. Polyester is made of repeating

units of a chemical called ester. 4. Poly Ethylene Terephthalate 5. Rayon 6. Acrylic 7. A plastic which can be easily

bent and reshaped is called thermoplastic.

8. A plastic which cannot be bent or reshaped is called thermosetting plastic.

9. A mater ia l which can be decomposed by microbes is called a biodegradable material.

10. A material which cannot be decomposed by microbes is called a non-biodegradable material.

Short Answer Type Questions 1. Can be Recycled: Plastic toys,

carry bags, ball point pens, plastic bowls, plastic chairs

Cannot be Recycled: Telephone instruments, cooker handles, plastic covering on electrical wires, electrical switches.

2. Some salient features of rayon are as follows:

l Rayon has qualities similar to silk but it is cheaper than silk. Due to this, rayon is also called ‘poor man’s silk’.

l Rayon can be dyed in various colours.

l It is often mixed with cotton to make bedsheet and dress materials.

3. Characteristics of Synthetic Fibres:

l They are less expensive. l They are readily available. l They can be easily washed. l They are easy to maintain. 4. Thermoplastic Thermosetting

plasticCan be easily bent andreshaped.

Cannot be bent or reshaped.

Used for making toys, bottles and jars etc.

Used for making electric switches, cookwares etc.

Examples:Polythene, PVC

Examples:Bakelite,Melamine

5. Problems by plastic bags: l Keeps on accumulating in the

environment. l Chokes drains. l A stray animal can die if it

accidentally swallows plastic bag. 6. Rayon Nylon

I t was t he first synthetic fibre.

It was the first truly synthetic fibre.

Rayon is made f rom wood pulp.

Nylon is made from coal, water and air.

Rayon is used for making curtains,bedsheets, etc.

Nylon is used for making a large number of items.

Long Answer Type Questions 1. Following are some reasons why

plastic containers are favoured for storing food:

lPlastic does not react with most of the substances. So,


when a food item is kept in a plastic container, it does not react with plastic. Due to this, the food cannot get spoiled because of plastic.

l Plastic jars are lightweight compared to glass or ceramic jars. Earlier, pickles and jams were kept in glass or ceramic jars. But now-a-days, plastic is preferred for keeping these materials.

l Plastic is unbreakable and hence it has replaced glass and ceramic containers for storing food.

2. Nylon was made in 1931. It was made from coal, water and air. Thus, no ingredient from plant or animal source was used in making nylon. Due to this, nylon is called the first truly synthetic fibre.

l Nylon is strong, light and elastic.

l It is lustrous and easy to wash. l Nylon is used in many articles;

like toothbrush, rope, socks, bags, sneakers, parachute, etc.

l A nylon thread is stronger than a steel wire of same thickness.

3. Types of Plastic: (a) T h e r m o p l a s t i c : S o m e

plastics easily get deformed on heating. They can be easily bent and reshaped by heating. Such plastics are called thermoplastics. Polythene and PVC are examples of thermoplastic. Thermoplastic is used for making combs, toys and containers.

(b) Thermosetting Plastic: Some plastics do not get deformed on heating. Once given a particular shape, these plastics cannot be moulded into a new shape. Such plastics are called thermosetting plastics. Bakelite and melamine are examples of thermosetting plastic. Bakelite is a poor conductor of heat and electricity and hence is used for making electrical switches and switchboards. Melamine is fire-resistant and is hence used for making utensils.

4. Reasons for popularity of plastic: l Plastic is non-reactive:

Plastic does not react with air to form rust; unlike iron. Hence, plastic has replaced iron from many articles. Plastic does not react with many chemicals. Hence, plastic containers are used for keeping many materials and chemicals.

l Plastic is light, strong and durable: Plastic is lightweight, strong and durable. Even a small boy can lift a plastic chair. Crates for keeping milk and cold drinks are now made of plastic because they are more durable and strong than wooden crates.

l Plastic is poor conductor of heat and electricity: Switches and many components of electrical appliances are made of plastic. Handles of utensils are made of plastic.


Higher Order Thinking Skills (HOTS) 1. Plastic has replaced many

traditional items for which raw materials were obtained from trees. For example; wooden furniture has been replaced by plastic furniture to a considerable extent. We can find even plastic doors and cabins in many houses; which were earlier made from wood. This has definitely helped in reducing the demand for wood. Thus, it has helped in minimizing the need for cutting down trees. Thus, it can be said that manufacturing plastic is actually helping conservation of forests.

2. While cooking, foot items do not stick to non-stick cookware. This reduces the need for oil in cooking. Thus, less oil goes in food. Thus, non-stick cookware is helping people in making healthy food.

3. Earlier, tent-house owners used to keep wooden or metallic chairs. These chairs were bulky and increased transportation cost. Moreover, these chairs were not durable. Plastic chairs are lightweight and hence can be easily transported. Plastic chairs are designed in such a way that they can be stacked one over another. This reduces the need for storage space. Plastic chairs are more durable than traditional chairs. Thus, plastic chairs have made life much easier for tent-house owners.

4. Terylene does not allow passage to air. Hence, it cannot be comfortable to wear; especially in summer. When cotton is added with terylene, the blended fabric becomes comfortable to wear. Moreover, it gets the durability of terylene and provides comfort of cotton. Hence, cotton is often added with terylene to make dress materials.

Value Based Questions 1. Rahul is showing a concern for

the environment. By carrying a jute bag while shopping, Rahul is preventing the use of plastic bags. We know that plastic is non-biodegradable. Due to this, plastic bags accumulate in the environment and cause many problems; like choking of drains, choking of stray animals and soil contamination. A jute bag can be used for many years and thus helps in preserving scarce resources.

2. Earlier, crates (for carrying milk packets and cold drink bottles) were made of wood. Now-a-days, plastic crates are being used for carrying various items. A plastic crate is durable and can be used for many years. This has helped in reducing the demand of wood for making crates. Thus, it has helped in saving forests.

Puzzle TimeDOWN: 1. NYLON 2. ACRYLIC 3. BAKELITEACROSS: 4. RAYON 5. PLASTIC 6. MELAMINE


Chapter 4 Materials: Metals andNon-Metals

FORMATIVE ASSESSMENTOral Questions 1. Magnesium 2. Iron oxide 3. Blue 4. Green 5. Colourless 6. Hydrogen 7. Copper 8. Aluminium 9. Coal 10. Oxygen Fill in the blanks 1. Physical 2. Iron 3. Aluminium 4. Ringing 5. Powdery 6. Soft 7. Brown 8. Green 9. Litmus 10. Kerosene True/False 1. False 2. True 3. False 4. True 5. False 6. True 7. False 8. True 9. False 10. TrueRapid Fire Questions 1. Lustre 2. Grey 3. Gold 4. Iron 5. Gold and silver 6. Copper and aluminium 7. Brass and bronze 8. Steel and stainless steel 9. Carbon 10. Hydrogen Project/Activities 1. lTake a hammer, iron nail,

aluminium wire, chalk and coal. l Beat the iron nail with hammer. l Repeat this with other materials

also. l You will notice that iron nail

and aluminium wire become flat when beaten with hammer.

l Chalk and coal turn into powder when beaten with hammer.

l This shows that metals are malleable but non-metals are not.

2. Take iron nail, aluminium wire, rubber, wooden piece, electric cell, connecting wires, LED and rubber band.

l With the help of cell, wires and LED; make a circuit as shown in the figure.

l One by one, attach iron nail, aluminium wire, rubber and wooden piece in the circuit.

l You will notice that LED glows when iron nail or aluminium wire is attached in the circuit.

l LED does not glow when rubber or wooden piece is attached in the circuit.

l This shows that metals are good conductors of electricity but non-metals are bad conductors of electricity.

3. Take a test tube, litmus paper, water and rust.

l Collect a small amount of rust from an old iron grill or gate.

l Take water in a test tube and mix rust in it.

l Dip blue and red litmus papers in the test tube.

l There is no change in red litmus paper but blue litmus paper turns red.


l This shows that rust (iron oxide) is acidic. This proves that metal oxides are acidic.

4. Take a test tube, zinc granules, dilute sulphuric acid, etc.

l Take zinc granules in the test tube and pour dilute sulphuric acid over it.

l You will notice that bubbles are formed in the test tube.

lBring a burning matchstick near the mouth of the test tube.

l Matchstick burns with a pop sound.

l This shows evolution of hydrogen gas.

SUMMATIVE ASSESSMENTMultiple Choice Questions 1. (a) Zinc 2. (d) All of the above 3. (c) Copper 4. (c) Sodium 5. (a) Iron 6. (b) Tungsten 7. (c) Mercury 8. (d) Graphite 9. (a) Sodium 10. (d) Gold Match the columns(i)-(d) (ii)-(e) (iii)-(c)(iv)-(f) (v)-(b) (vi)-(a)Very Short Answer Type Questions 1. A substance which is lustrous,

sonorous, ductile and is a good conductor of heat and electricity is called a metal.

2. A substance which is non-lustrous, non-sonorous, non-ductile and is a bad conductor of heat and electricity is called a non-metal.

3. The ability of a substance to be beaten into thin sheets is called malleability.

4. The ability of a substance to be drawn into thin wires is called ductility.

5. The ability of a substance to produce ringing sound is called sonority.

6. The metallic shine is called lustre. 7. Fe2O3 8. MgO 9. Cu(OH)2 10. CuCO3

Short Answer Type Questions 1. Iron reacts with oxygen and moisture to form iron oxide. Iron oxide is

brown in colour and is commonly known as rust. Iron + Oxygen + Water Æ Iron oxide (Fe) (O2) (H2O) (Fe2O3) 2. When copper is exposed to moist air for a long time, it acquires a greenish

coating. The green coat is a mixture of copper hydroxide and copper carbonate. 2Cu + H2O + CO2 + O2 Æ Cu(OH)2 + CuCO3 (copper) (water) (carbon dioxide) (oxygen) (copper hydroxide) (copper carbonate) Due to this, copper utensils develop greenish patches when kept unused

for a long time. 3. Reaction of base with metals

and non-metals: lMetals react with sodium

hydroxide to produce hydrogen gas.

l Non-metals’ reaction with sodium hydroxide is much complex.

4. When zinc granules are kept in copper sulphate solution, the blue colour of copper sulphate


disappears and the solution becomes colourless. This happens because zinc displaces copper from copper sulphate solution and forms zinc sulphate.

CuSO4 + Zn Æ ZnSO4 + Cu 5. When copper turnings are kept in

zinc sulphate solution, no reaction takes place. This happens because copper is less reactive than zinc and hence copper cannot replace zinc from zinc sulphate solution.

6. Usually, metals react with acids and produce a gas which burns with a pop sound. The pop sound indicates evolution of hydrogen gas. But copper does not react with even concentrated hydrocholoric acid, however it reacts with sulphuric acid.

7. Most of the metals are available as solid at room temperature. But mercury is present as liquid at room temperature.

Long Answer Type Questions 1. (a) When dilute sulphuric acid is

produced on a copper plate, it reacts with copper. Hydrogen gas is produced at the end of this reaction.

(b) When iron nails are placed in copper sulphate solution, iron displaces copper from copper sulphate. The blue colour of copper solution changes to green. This happens because of formation of iron sulphate.

CuSO4 + Fe Æ FeSO4 + Cu

2. Property Metal Non-metalMalleability Metals are malleable, i.e.

they can be beaten into thin sheets.

Non-metals are not malleable.

Ductility Metals are ductile, i.e. they can be drawn into thin wires.

Non-metals are not ductile.

Lustrous Metals have metallic shine; called lustre.

Non-metals are usually dull. (exceptions: diamond and graphite)

3. Property Metal Non-metalConductivity Metals are good conductors

of heat and electricity.Non-metals are bad conductors of heat and electricity.(exception: graphite)

Sonorous Metals are sonorous, i.e. they produce a typical metallic sound when hit with something.

Non-metals are not sonorous.

PhysicalState

Most of the non-metals are available as solid at room temperature; except mercury.

Non-metals are available in all the three states of matter.


4. Some metals react vigorously with water, while some others do not react at all.

Sodium is a highly reactive metal and reacts vigorously with water. During the reaction, so much heat is produced that sodium catches fire. Hence, sodium is stored in kerosene to prevent accidental fire.

lIron reacts slowly with water. l Copper does not react with

water but reacts with steam. l Silver and gold do not react

with water at any temperature. Usually, non-metals do not react

with water. But some non-metals react vigorously with air. Such non-metals are stored in water. For example; phosphorus reacts vigorously with air and produces fire. Hence, phosphorus is stored in water to prevent accidental fire.

5. Uses of Metals: l Metals are used for making

machines and tools. l Iron is used for making ships,

bridges, railway lines, etc. l Copper is used for making

electric wires. l Aluminium is used for making

utensils. l Gold and silver are used for

making ornaments. 6. Uses of Non-metals: l Oxygen is used by all living

beings for respiration. l Carbon dioxide is used by

plants for photosynthesis. l Chlorine is used for water

purification.

l Iodine solution is used as antiseptic and applied on wounds.

l Coal (carbon) is an important fuel.

Higher Order Thinking Skills (HOTS) 1. (a) Pour freshly prepared lime

water in the test tube. The lime water turns milky. This shows that the evolved gas is carbon dioxide.

(b) Carbon (charcoal) + Oxygen Æ Carbon dioxide

Carbon dioxide + Calcium hydroxide (lime water) Æ Calcium carbonate

2. Goldsmith cleans jewellery in a mixture of acids. Gold reacts with this mixture and some of the gold is dissolved in acid mixture during cleaning. Due to this, there was slight loss in the weight of jewellery.

3. Gold and silver are least reactive metals. They do not react with air or moisture. Due to this, they are able to maintain their lustre for many years. This is not true for copper or aluminium. Hence, gold and silver are used for making ornaments but this is not true for copper or aluminium.

4. Phosphorus reacts vigorously with air. The reaction generates lot of heat and phosphorus catches fire. To prevent this reaction and accidental fire, phosphorus is stored in water.


5. Sodium reacts vigorously with water. The reaction generates lot of heat and sodium catches fire. To prevent this reaction and accidental fire, sodium is stored in kerosene.

Value Based Questions 1. Putting oil in various parts of

bicycle entails two benefits. This helps in smooth running of the bicycle. It also prevents rusting of those parts. Moreover, it prolongs the life of his bicycle. By doing so, Rahul is showing how to take good care of your belongings.

2. Lemon juice contains acid. An acid reacts with metal carbonates and bicarbonates to liberate

carbon dioxide. Thus, rubbing a brass item with lemon will help in removing the blackish layer which may have deposited because of metal’s reaction with atmospheric gases. This will help in recovering the shine on brass items. Bunty is showing how to help your mother in household chores.

Puzzle TimeDOWN: 1. LUSTRE 2. DUCTILITY 3. GOLDACROSS: 4. MALLEABILITY 5. SODIUM 6. HYDROGEN

Chapter 5 Coal and PetroleumFORMATIVE ASSESSMENT

Oral Questions 1. Water and air 2. Coal and petroleum 3. Carbon 4. Carbon dioxide 5. Carbon dioxide 6. Plants 7. Mathura 8. Gujarat 9. Natural gas 10. Bitumen Fill in the blanks 1. Fossil 2. 300 3. Industry 4. Black 5. Coal tar 6. Heat 7. Petroleum 8. Pennsylvania 9. Black 10. Kerosene

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

Rapid Fire Questions 1. Coal and petroleum 2. Kinetic energy 3. Diesel 4. Coal 5. Petroleum 6. Assam 7. Taj Mahal 8. Bombay High 9. Compressed Natural Gas 10. Liquefied Petroleum Gas


Project/Activities

1. 14

12

10

8

6

4

2

0

Shor

tage

(%)

1991 1992 1993 1994 1995 1996 1997

Year

2. Natural Man-madeWater, air, soil, milk, sand, etc. Machine, curd, brick, ice-cream, clothes,

toys, car, etc.SUMMATIVE ASSESSMENT

Multiple Choice Questions 1. (b) Coke 2. (c) 10,000 years 3. (d) Uttar Pradesh 4. (a) Krishna Godavari Delta 5. (b) Paraffin wax 6. (c) Hydrogen 7. (d) Assam 8. (a) Petrol 9. (b) Diesel 10. (c) Coal tar Match the columns(i)-(f) (ii)-(e) (iii)-(d)(iv)-(c) (v)-(b) (vi)-(a)Very Short Answer Type Questions 1. Resources which are found in

nature are called natural resources. 2. Resources which are available

in huge quantity and cannot be finished by human activities are called inexhaustible natural resources.

3. Resources which are available in limited quantity and can be finished

by human activities are called exhaustible natural resources.

4. A fuel which is made from fossils is called a fossil fuel.

5. Dead remains of organisms which are more than 10,000 years old are called fossils.

6. The process of conversion of vegetation into coal is called carbonization.

7. Petrol is a fuel which is used in cars and two wheelers. It is obtained from petroleum.

8. Petroleum is a dark and thick liquid with unpleasant smell. It is taken out from oil wells.

9. The factory in which petroleum is refined is called a petroleum refinery.

10. Compressed Natural Gas.Short Answer Type Questions 1. It has taken millions of years for

the formation of fossil fuels. But


we are using them at a very high rate. They are going to be finished in the near future. Due to this, fossil fuels are called exhaustible natural resources.

2. Uses of coal: lDuring the days of steam

engines, coal was used as fuel in steam engines.

l Coal is widely used in thermal power plants.

l Coal is used as kitchen fuel in some households, dhabas and restaurants.

3. Coke is almost pure form of carbon and is obtained after processing of coal. It is tough, porous and black. It is used in manufacture of steel and extraction of many metals from their ores.

4. Coal tar is used as raw material for making synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, roofing materials, naphthalene balls, etc.

5. Petroleum is taken out from oil wells and sent to oil refineries. In oil refinery, petroleum is subjected to fractional distillation. This separates various constituents of petroleum.

6. Uses of natural gas: l It is compressed to make

CNG which is used as fuel in automobiles.

l It is used as raw material for making fertilizer.

Long Answer Type Questions 1. Formation of petroleum: lMillions of years ago, organisms

lived in seas and oceans.

l These organisms were buried under layers of sand and clay.

l The dead remains of organisms were subjected to intense heat, pressure and lack of oxygen.

l This condition converted the dead remains of these organisms into petroleum.

2. Formation of Coal: l About 300 million years ago,

there were dense forests in low lying areas on earth.

l These forests got buried under the soil due to natural processes.

l Over a period of time, more layers of soil were deposited on these buried forests.

l Due to high pressure and high temperature, these plants were converted into coal.

3. Drawbacks of fossil fuels: l They are exhaustible resources. l They will be exhausted in near

future. l Fossil fuels create environmental

pollution when they are burnt. l Burning of fossil fuels adds

ca rbon d iox ide t o t he atmosphere.

l Excess level of carbon dioxide in the atmosphere creates global warming.

4. Recommendations by PCRA to conserve petrol and diesel:

l Drive at constant and moderate speed as far as possible,

l Switch off the engine at traffic lights or at a place where you have to wait,

l Ensure correct tyre pressure, and

l Ensure regular maintenance of the vehicle.


Higher Order Thinking Skills (HOTS) 1. Petroleum gives many important

materials which are used as raw materials to make many useful items. Moreover, petroleum also gives many fuels which are used by automobiles, trains, aircrafts and factories. Thus, petroleum products are highly valuable for the whole economy. Due to this, petroleum is often referred to as ‘Black Gold’.

2. Coal contains various impurities; apart from carbon. The impurities do not make coal an efficient fuel. One the other hand, coke is almost pure carbon. Hence, coke is a highly efficient fuel. Due to this, it is made to be used in steel plants.

3. CNG is a cleaner fuel compared to petrol or diesel. Burning the CNG produces negligible amount of pollution. Thus, CNG helps in protecting the environment. Due to this, CNG is preferred as

automobile fuel in place of petrol and diesel.

Value Based Questions 1. Mr. Verma is showing a concern

for the environment. Use of solar cooker will help in reducing the use of LPG or any other fuel in the kitchen. This will help in reducing air pollution. This will also help in conservation of fossil fuels.

2. He is showing his concern for conservation of petrol/diesel. If the red signal is for long duration, one should switch off the engine of the vehicle. This helps in saving petrol/diesel. Thus, it helps in conservation of fossil fuels; which are non-renewable sources of energy. Additionally, switching off the engine also helps in minimizing air pollution.

Puzzle TimeDOWN: 1. KEROSENE 2. PETROL 3. COKEACROSS: 4. CARBONISATION 5. FOSSIL 6. CNG

Chapter 6 Combustion and FlameFORMATIVE ASSESSMENT

Oral Questions 1. Petrol and alcohol 2. Wood and coal 3. Carbon dioxide 4. Explosion 5. Water 6. Oxygen 7. Carbon dioxide 8. Spontaneous combustion 9. LPG 10. Firewood, cow dung cakes

Fill in the blanks 1. Chemical 2. Different 3. Egypt 4. Red 5. Fire Brigade 6. Low 7. Oxygen 8. Carbon dioxide 9. Slow True/False 1. True 2. False 3. True 4. False 5. True 6. False 7. True 8. False 9. True 10. True


Rapid Fire Questions 1. Oxygen 2. Inflammable 3. Carbon dioxide 4. Three 5. Fire Brigade 6. Matchbox 7. Phosphorus Project/Activities1.

2. Take a big bowl, a small bowl, baking soda, vinegar and two candles of different sizes.

l Keep the small bowl in the big bowl.

l Light the two candles and keep them erect in the small bowl.

l Put baking soda in the small bowl around the candles.

l Now slowly pour vinegar over baking soda and wait for some time.

l You will notice that foam begins to form in the small bowl.

l The level of foam first covers the smaller candle and candle extinguishes.

l The second candle extinguishes after a short gap.

3. The following pie-chart shows the percentage of different fuels:


Multiple Choice Questions 1. (b) Wood 2. (c) Iron 3. (b) Petrol 4. (c) Three 5. (a) Blue 6. (b) Orange 7. (d) Utensil 8. (a) LPG 9. (a) Blue 10. (d) Coal Match the columns(i)-(d) (ii)-(c) (iii)-(e)(iv)-(b) (v)-(a)Very Short Answer Type Questions 1. The chemical process in which a

substance reacts with oxygen to

give off heat is called combustion. 2. A substance which can undergo

combustion is called a combustible substance.

3. A substance which cannot undergo combustion is called a non-combustible substance.

4. The minimum temperature at which combustion starts in a substance is called ignition temperature of that substance.

5. A substance which has very low ignition temperature and which


can easily catch fire is called an inflammable substance.

6. A substance which is used for putting off fire is called fire extinguisher.

7. Some substances burn rapidly, e.g. gas and petrol. This is called rapid combustion.

8. Calorific value. 9. The amount of heat energy

produced on combustion of 1 kg of a fuel is called calorific value of that fuel. It is expressed as kilo Joule per kg (kJ/kg).

10. In some cases, a substance begins to burn on its own without any apparent cause. This is called spontaneous combustion.

Short Answer Type Questions 1. Combustion can take place under

following conditions: (a) Availability of a fuel (b) Availability of oxygen (c) Presence of ignition temperature 2. Mass of fuel = 4.5 kg Amount of heat = 180,000 kJ Calorific value = number o f

calories/mass of fuel = 180,000 kJ/4.5 kg = 40,000 kJ/kg 3. Combustible

SubstanceNon-combustible

SubstanceIt can undergo combustion.

It cannot undergo combustion.

Examples:Wood, coal, petrol, etc.

Examples: Sand, clay, asbestos, etc.

4. All inflammatory substances are combustible but all combustible s u b s t a n c e s n e e d n o t b e inflammatory. A substance with low ignition temperature is called inflammatory substance. An inflammatory substance quickly catches fire, while this is not true for all combustible substances.

5. Water is frequently used by the Fire Brigade. Water helps in bringing down the temperature. The blanket of steam cuts off air supply. Thus, water helps in putting off fire.

6. Blanket is very useful in controlling fire at small scale. The object on fire is covered with a blanket. Blanket cuts off air supply and helps in putting off fire.

7. When combustion reaction is sudden; it releases a large amount of heat, light and sound. This is called explosion. Firecrackers explode because of this type of combustion.

Long Answer Type Questions 1. Characteristics of a Good Fuel: l It is readily available. l It is cheap. l It burns easily in air and at a

moderate rate. l It produces a large amount of

heat. l It does not leave behind any

undesirable substance. 2. Zones of Flame— Outer Zone: The outermost

zone is blue in colour. Complete combustion takes place in this zone. It is the hottest part of the flame.


Middle Zone: Middle zone is yellow and orange in colour. Partial combustion takes place in this zone. It is moderately hot.

Inner Zone: Inner zone is dark in colour. No combustion takes place in this zone. This is the coolest part of the flame.

3. Harms of Burning a Fuel: l Burning of carbon fuels

(wood, coal, petroleum) releases unburnt carbon particles in air. These particles cause respiratory diseases; like asthma.

l Burning of most fuels releases carbon monoxide which is a poisonous gas; even at low concentration. Hence, we should not burn coal in closed rooms.

l Burning of most fuels releases carbon dioxide in atmosphere. Increased level of carbon dioxide in the atmosphere causes global warming.

lBurning of coal and diesel releases sulphur dioxide in air. Burning of petrol releases oxides of nitrogen. Oxides of sulphur and nitrogen mix with rainwater and it results in acid rain. Acid rain is harmful for buildings, monuments and also for plants and animals.

Higher Order Thinking Skills (HOTS) 1. CNG is a cleaner fuel than

petrol or diesel. It produces negligible amount of pollutants.

Due to this, CNG has helped in reducing pollution in our cities. In many cities; all public transport vehicles are using CNG.

2. A goldsmith uses the outer zone of flame because this zone has the maximum temperature. High temperature allows the goldsmith to heat gold and silver enough so that they can be given new shapes.

3. Candle is made of wax and wax produces vapour on heating. Due to this, candle burns with flame. Coal, on the other hand, does not produce vapour and hence does not burn with flames.

4. White phosphorus is more reactive than red phosphorus and it used to cause explosion. Thus, white phosphorus was dangerous with potential to cause injuries. Red phosphorus is much safer. Hence, red phosphorus replaced white phosphorus in safety matches.

5. The inner zone of flame is the zone with no combustion. It contains many unburnt carbon particles. The black soat is formed on glass rod because of these carbon particles.

Puzzle Time

DOWN: 1. FLAME, 2. COMBUSTION 3. EXPLOSIONACROSS: 4. INFLAMMATORY 5. OXYGEN 6. IGNITION


Chapter 7 Conservation of Plantsand Animals

FORMATIVE ASSESSMENTOral Questions 1. Asiatic Lion 2. Kangaroo 3. Siberian crane 4. Madhya Pradesh 5. Assam 6. Wood pulp 7. Tribe 8. Tawa Reservoir 9. 55 10. Figures of animals and men

fighting, hunting, dancing and playing musical instruments.

Fill in the blanks 1. Natural 2. Forest 3. Flood 4. Photosynthesis 5. Top 6. Prohibited 7. Giant 8. Primitive 9. Ecosystem 10. Biodiversity True/False 1. False 2. True 3. False 4. True 5. False 6. False

7. True 8. True 9. False 10. TrueRapid Fire Questions 1. Gir Forest 2. Australia 3. Siberia 4. Madhya Pradesh 5. Kaziranga National Park 6. Royal Bengal Tiger Project/Activities 1. I will take following activities to

maintain the green wealth in my locality:

l I will plant one tree every month.

l I will take out awareness campaign for planting trees.

l I will use bicycle for going to school. This will help in reducing pollution.

l I will ask my parents to use public transport more often.

2.


SUMMATIVE ASSESSMENTMultiple Choice Questions 1. (a) flying squirrel 2. (c) Wild mango 3. (b) Assam 4. (d) Rajasthan 5. (a) Manipur 6. (b) 1973 7. (c) 1927 8. (a) One 9. (b) Two 10. (c) Red Data Book Very Short Answer Type Questions 1. Clearing of forest and using that

land for other purposes is called deforestation.

2. Conversion of fertile land into desert is called desertification.

3. The part of the earth where all living organisms are present is called biosphere.

4. Variety of organisms existing on earth, their interrelationship and their relationship with the environment together comprise biodiversity.

5. Areas which have been demarcated to protect our flora and fauna and their habitat are called protected areas.

6. The plants found in a particular area are termed as flora.

7. The animals found in a particular area are termed as fauna.

8. A group of population capable of interbreeding is called species.

9. Animals which no longer exist on earth are called extinct animals, e.g. dinosaurs, dodo, etc.

10. A system of interdependencies among all living beings and non-

living things in an area is called ecosystem.

Short Answer Type Questions 1. Causes of Deforestation: l Procuring land for cultivation l Building houses and factories l Making furniture and using

wood for fuel 2. Areas which have been demarcated

to protect our flora and fauna and their habitat are called protected areas. The government lays down rules, methods and policies to protect and conserve forests and wildlife.

3. Species which is found exclusively in a particular area is called endemic species. Sal and wild mango are endemic flora to Pachmarhi Biosphere Reserve. Bison, Indian giant squirrel and flying squirrel are endemic to this region.

4. Following can lead to extinction of endemic species:

(a) Destruction of natural habitat (b) Introduction of an exotic species (c) Increase in population 5. Members of a species show

following features: (a) They look similar (b) They can interbreed (c) They can produce fertile

offspring among themselves only

6. Following are the reasons for migration of animals:

(a) Unfavourable climate (b) Lack of food


7. We know that plants take up carbon dioxide and release oxygen during photosynthesis. This helps in maintaining the balance of carbon dioxide and oxygen in the atmosphere. Deforestation results in loss of green cover on the earth. Less number of plants means level of carbon dioxide increases in the atmosphere. Carbon dioxide traps solar energy and thus leads to overall increase in global temperature. Thus, deforestation causes global warming.

Long Answer Type Questions 1. Consequences of Deforestation: l Increases temperature and

pollution level on earth. This happens because of increased level of carbon dioxide in the atmosphere.

l Reduces groundwater level. l Reduces rainfall. l Reduces soil fertility. l Can result in droughts. l Can also lead to desertification. 2. Different types of protected areas

are as follows: (a) Sanctuary: An area where

animals are protected from any disturbance to them or their habitat is called a sanctuary. Poaching (killing) or capturing an animal is strictly prohibited in a wildlife sanctuary.

(b) National Park: Areas reserved for wildlife where they can freely use the habitat and natural resources are called national parks. Satpura National Park is the first reserve forest of India.

(c) Biosphere Reserve: Large areas of protected land for conservation of wildlife, plant and animal resources and traditional life of the tribals living in that area are called biosphere reserves. Some examples of threatened species which are protected in wildlife sanctuaries in India are; black buck, white eyed buck, elephant, golden cat, pink headed duck, gharial, marsh crocodile, python, rhinoceros, etc.

3. (a) Wild animals may lose their habitat and food because of deforestation.

(b) Deforestation results in increased levels of pollution. This also leads to global warming.

(c) Deforestation results in depletion of groundwater and thus villagers may face shortage of drinking water. Cases of floods and droughts increase which affect the crop.

(d) Depletion of groundwater because of deforestation can result in scarcity of drinking water. Air pollution will increase because of reduced green cover.

(e) Global warming is a serious problem which happens because of deforestation.

Higher Order Thinking Skills (HOTS) 1. Trees make the soil pervious

to seepage of water because roots penetrate deep into the


soil. This helps in recharging the groundwater. Lack of trees disturbs natural recharging of groundwater. Thus, deforestation results in depletion of groundwater.

2. Trees slow down the flow of rainwater by creating a sort of physical barrier. Absence of trees means rainwater encounters no barrier and runs over too swiftly. This creates flood. Increased cases of flood have been thus caused by deforestation.

3. Tiger is an important animal in the ecosystem. We know that each and every component of an ecosystem is equally important. If any component is removed, it disturbs the balance of the ecosystem. If all tigers will be finished, it will destroy the whole ecosystem. Hence, saving tigers is important for saving the ecosystem.

4. Paper is made from wood pulp. Fresh trees need to be cut for making new paper. This results in large scale deforestation. If each student saves at least one sheet of paper in a day, it can result in saving at least 3,000 sheets of paper in our school in a day. This can translate into millions

of sheets of paper being saved every day in our country. This will definitely help in saving a large number of trees.

Value Based Questions 1. Mr. Banerjee appears to be an

animal lover. He provides food for squirrels and many other animals which may be living in the park. Additionally, he is also trying to put the stale bread slices to a more productive use rather than just throwing them in the dustbin.

2. I will request those people not to burn dry leaves. I will explain to them that how burning of dry leaves creates harmful gases. I will explain to them the harmful effects of air pollution. I will also explain the benefits of burying those leaves in a pit. This will help in converting the fallen leaves into compost which can be utilized to enhance soil fertility.

Puzzle TimeDOWN: 1. DINOSAUR 2. EXTINCT 3. ENDEMICACROSS: 4. ENDANGERED 5. ECOSYSTEM 6. RHINO

Chapter 8 Cell: Structure and FunctionsFORMATIVE ASSESSMENT

Oral Questions 1. Dead cells 2. Cork 3. 0.1 to 0.5 micron

4. 170 mm × 130 mm 5. Round, spherical or elongated 6. Yeast and Amoeba 7. Amoeba


8. White Blood Cell 9. Trillions of cells 10. Bacteria and blue green algaeFill in the blanks 1. Cells 2. 150 3. Microscope 4. Stains 5. Organ 6. Nerve 7. millionth 8. Albumin 9. Yolk 10. Gene True/False 1. True 2. False 3. True 4. False 5. False 6. True 7. False 8. True 9. False 10. TrueRapid Fire Questions 1. Robert Hooke 2. Leeuwenhoek 3. Egg of ostrich 4. Neuron 5. White Blood Cell 6. Red Blood Cell 7. Unicellular 8. Multicellular Project/Activities 1.

Nerve cells receive and send messages and facilitate control and coordination in the body.

2.

lTake an onion and peel off its fleshy layers.

l From a fleshy layer, peel off the transparent layer and keep it in water.

l Take a very small piece of this transparent layer on a glass slide.

l Pour a few drops of methylene blue on the slide and cover with cover slip.

l While placing the cover slip, ensure that no air bubble is trapped inside.

l Put the slide under a microscope and observe.

l Plant cells can be seen with distinct partitions. The partitions are cell walls. Nucleus can be seen like small dots.

3.

lClean your mouth by gargling properly.

l Take a toothpick or ice-cream stick and gently scrape the inner side of your cheek.

l Transfer the scrapings on a glass slide.

l Put a few drops of methylene blue on the slide and cover with cover slip.

l While placing the cover slip, ensure that no air bubble is trapped inside.

l Put the slide under a microscope and observe.

l Cheek cells can be seen. Cell membrane and nucleus can be clearly seen.


SUMMATIVE ASSESSMENTMultiple Choice Questions 1. (b) Yeast 2. (a) RBCs 3. (c) Green 4. (d) Cell wall 5. (b) Ostrich 6. (a) Neuron 7. (d) All of these 8. (b) Cell membrane 9. (c) Leeuwenhoek 10. (a) Gene Match the columns(i)-(d) (ii)-(c) (iii)-(b)(iv)-(a)Very Short Answer Type Questions 1. Cytoplasm 2. Cell is the structural unit of a

living being. 3. An organism which is composed

of a single cell is called unicellular organism.

4. An organism which is composed of more than one cell is called multicellular organism.

5. A group of specialized cells is called a tissue.

6. A group of tissues which performs a specific set of functions is called an organ.

7. Finger like projections in amoeba are called pseudopodia.

8. Cytoplasm is a jelly-like substance and is present between the cell and nucleus.

9. Organisms in which nucleus is absent are called prokaryotic organisms.

10. Organisms in which nucleus is present are called eukaryotic organisms.


1. Eukaryotes ProkaryotesNucleus ispresent.

Nucleus isabsent.

Nuclearmaterials arebound bymembrane.

Nuclearmaterials arenot bound by membrane.

Examples:humans, amoeba, yeast, etc.

Examples:bacteria, blue green algae, etc.

2. Plasma membrane makes the boundary of a cell. It is also called cell membrane. It is porous and allows various materials to pass through it.

3. It is present in plant cells and in bacteria. Cell wall covers the plasma membrane in these cells. In plants, cell wall is made of cellulose. Cell wall provides additional protection to plant cells.

4. Functions of nucleus are as follows:

l Nucleus controls the function of a cell.

l Nucleus controls inheritance of characters.

5. Functions of pseudopodia: l Movement and locomotion l Catching food 6. Characters are transferred from

parents to offsprings. Genes are responsible for transfer of characters. This process is called inheritance. We resemble our parents because of inheritance.


Long Answer Type Questions

1. Plant Cell Animal CellCel l wal l i s present.

Cel l wal l i s absent.

Chloroplast is present.

Chloroplast is absent.

Vacuoles are large.

Vacuoles are much smaller or absent.

2. Cells show wide variety in terms of shape.

l An amoeba is of irregular shape. It changes shape by making pseudopodia. White Blood Cells in human beings also show irregular shape; similar to amoeba.

l Cells are generally round, spherical or elongated. Some cells are spindle-shaped, i.e. swollen in the middle and pointed at both ends. Red Blood Cells are concave and round. Nerve cells (neurons) appear like a star with long tail.

Higher Order Thinking Skills (HOTS) 1. Nerve cells have to send and

receive messages. Numerous

branches in them help in efficiently receiving and sending messages. Due to this, nerve cells are branched.

2. WBCs are irregular in shape because o f f o rma t ion o f pseudopodia. This helps WBCs in engulfing harmful germs to fight diseases.

3. The size of cell does not depend on the size of animal. It depends on the specific function a cell is going to serve. Due to this, size of cells is similar in rat and elephant.

4. A plant cannot move to safety in case of a hot weather, or on a rainy day. It has to remain static at a place; irrespective of changes in weather and surroundings. Due to this, plant cells are more exposed to various problems. Hence, they need extra protection; in the form of cell wall.

Puzzle TimeDOWN: 1. MITOCHONDRIA 2. CELLULOSE 3. CYTOPLASMACROSS: 4. PROKARYOTIC 5. NUCLEUS 6. CHLOROPLAST

Chapter 9 Reproduction in AnimalsFORMATIVE ASSESSMENT

Oral Questions 1. Uterus 2. Crocodile, pigeon 3. Humans, tiger 4. Platypus 5. Tadpole 6. Larva 7. Shark 8. One 9. Sheep

10. In Vitro Fertilisation Fill in the blanks 1. Reproduction 2. Sexual 3. Sperms 4. Fallopian tube 5. Test tube 6. Queen


7. Unfertilised 8. Foetus 9. Male 10. Female True/False 1. False 2. True 3. True 4. False 5. True 6. False 7. False 8. True 9. True 10. False

Rapid Fire Questions 1. Uterus 2. Reptiles and Aves 3. Mammal 4. 40 weeks 5. Metamorphosis 6. Pupa 7. One 8. Dolly

Project/Activities 1. 2.

SUMMATIVE ASSESSMENTMultiple Choice Questions 1. (d) 40 weeks 2. (c) Amoeba 3. (b) Two 4. (a) One 5. (b) Fallopian tube 6. (c) Nine weeks 7. (d) Whale 8. (a) Frog 9. (b) Edinburgh 10. (b) Two Match the columns(i)-(f) (ii)-(e) (iii)-(d)(iv)-(c) (v)-(b) (vi)-(a)Very Short Answer Type Questions 1. The process by which an organism

produces its offspring is called reproduction.

2. The mode of reproduction which involves zygote formation is called sexual reproduction.

3. The mode of reproduction which does not involve zygote formation is called asexual reproduction.

4. Fusion of male and female gametes is called fertilization.

5. Implantation of embryo in uterine wall is called conception.

6. When fertilization takes place outside the animal’s body, it is called external fertilization.

7. When fertilization takes place inside the animal’s body, it is called internal fertilization.

8. When fertilization is carried out in laboratory, it is called in-vitro fertilization.

9. Animals which lay eggs are called oviparous animals.

10. Animals which give birth to young ones are called viviparous animals.



1. Sexual Reproduction

Asexual Reproduction

Two parents are involved.

A single parent is involved.

Gametes are formed.

Gametes are not formed.

Fertilizationtakes place.

Fertilizationdoes not take place.

Examples:humans, frog, bird, etc.

Examples:amoeba, hydra, sponge, etc.

2. A sperm is very small in size. It is composed of a head, middle piece and a tail. A sperm is composed of a single cell.

3. Zygote divides repeatedly to resemble a ball of cells. After that, the cells begin to differentiate into different kinds of tissue. At this stage, the structure is called embryo.

4. After about nine weeks of conception the embryo develops legs, head, eyes, ear, etc. At this stage, it resembles a human being. This is now called foetus.

5. When fertilization is carried out in laboratory, it is called in-vitro fertilization. After that, zygote is transferred into the uterus. IVF can help those people who fail to produce a child because of some problems.

6. In case of indirect development, transformation of young ones into adult is called metamorphosis. For example; larvae of butterfly undergo metamorphosis to become butterfly. Similarly,

tadpoles undergo metamorphosis to become frogs.

7. Reproduction by budding can be seen in hydra and sponges. In hydra, a small bud develops on the body. This bud develops and resembles a hydra. After that, it gets detached from the mother’s body and begins life as a new individual.

8. Binary fission can be seen in amoeba. In this method, a cell of amoeba divides into two daughter cells. Each daughter cell is a new individual.

Long Answer Type Questions 1. Male Reproductive Organs:

The male reproductive organs are a pair of testes, two sperm ducts and a penis. Male gametes; called sperms are produced in the testes. A testis produces millions of sperms.

Female Reproductive Organs: The female reproductive organs are a pair of ovaries, a pair of oviducts (fallopian tubes) and a uterus. Ovary produces the female gametes, i.e. eggs.

2. Every month, a single egg comes out of the ovary and reaches the fallopian tube. Fertilization takes place inside the fallopian tube.

l A single sperm fertilizes the egg. l After fertilization, zygote

undergoes repeated divisions. l Then, it develops into embryo

and moves to the uterus and gets implanted in the wall of the uterus. This process is called conception. Conception marks the beginning of pregnancy.


l After nine weeks, the embryo develops head, legs, eyes, ears, etc. It begins to resemble a human being. At this stage, this is called foetus.

l It takes about 40 weeks or nine months for embryo to develop into a baby. After that, child birth takes place.

Higher Order Thinking Skills (HOTS) 1. Sperm needs water so that it can

swim to the eggs. Due to this, external fertilization always takes place in water.

2. Tail helps the sperm in swimming. 3. If all individuals in a species will

fail to reproduce, it will be an end of existence for that species. It

won’t be able to continue and will become extinct.

4. A frog lays eggs in water and leaves them unprotected. Most of the eggs are at risk of getting washed away or being eaten. A large number of eggs ensure survival of at least some of them. A bird lays only a few eggs because most of the birds take care of eggs during incubation. There is a better chance of survival hence no need for producing more eggs.

Puzzle TimeDOWN: 1. SPERM 2. OVARY 3. FOETUSACROSS: 4. FERTILISATION 5. TESTIS 6. VIVIPAROUS

Chapter 10 Reaching the Age ofAdolescence

FORMATIVE ASSESSMENTOral Questions 1. Hormones 2. 11 years 3. Reproductive maturity 4. 2 to 7 days 5. Menopause 6. Human Immunodeficiency Virus 7. Acquired Immunodeficiency

Syndrome 8. Thyroid gland 9. Pancreas 10. Iron Fill in the blanks 1. Adult 2. Natural 3. Reproduction 4. Height

5. Larynx 6. Neck 7. Ducts 8. Endocrine 9. Secondary sexual 10. Growth

True/False 1. False 2. True 3. False 4. True 5. False 6. True 7. False 8. True 9. True 10. False

Rapid Fire Questions 1. Hormone 2. Testosterone 3. Estrogen 4. Testis 5. Ovary 6. HIV 7. Thyroid 8. Insulin


Project/Activities 1. (a) People in my village are

highly worried about low sex ratio. They are mature enough to understand the equal importance of girls and boys.

(b) Analysis of amniotic fluidis called amniocentesis. This is done in order to detect any abnormality in the foetus. This test is also done to determine the sex of the foetus. However, this

is being misused in India for getting rid of a female child. In many cases, the girl child is killed while she is still in the womb. This is a shameful practice which has deep social roots. In many families, a male child is given preference over a girl child. To prevent this malpractice, amniocentesis for sex determination is banned in India.


Multiple Choice Questions 1. (a) 18 years 2. (b) Testosterone 3. (c) 28 to 30 days 4. (d) Four 5. (b) Insulin 6. (a) Thyroid 7. (b) Pituitary 8. (c) Adrenaline 9. (d) Calcium 10. (b) Proper diet is needed for the

rapid growth taking place in their body.

Match the columns(i)-(d) (ii)-(c) (iii)-(b)(iv)-(a)

Very Short Answer Type Questions 1. The period of life when many

changes take place in the body; leading to reproductive maturity; is called adolescence.

2. The process of changes during adolescence period is called puberty.

3. Characters which help in distinguishing a male from a female are called secondary sexual characters.

4. Facial hairs, deep voice and hair on chest.

5. Enlargement of breasts and high pitched voice.

6. Hair under armpits, hair in pubic region.

7. The cycle of events which begin from release of an egg and end in shedding off egg is called menstrual cycle.

8. The firstmenstrual bleeding iscalled menarche.

9. Insect hormones control the metamorphosis of larva into adult.

10. T h y r o x i n e c o n t r o l s t h e metamorphosis of tadpole into frog.

Short Answer Type Questions 1. The years during adolescence

period are counted as ‘teen’, e.g. thirteen,fourteenandfifteenandso on. Due to this, the adolescence period is also called teenage.

2. T h e p r o c e s s o f c h a n g e s during adolescence period is


called puberty. Beginning of puberty marks the beginning of adolescence. Adolescence or puberty ends with completion of reproductive maturity.

3. Testosterone and estrogen are sex hormones. They are named so because they are responsible for secondary sexual characters. Testosterone brings secondary sexual characters in boys. Estrogen brings secondary sexual characters in girls.

4. In females, one egg is released by either of the ovaries during each month. The uterus then develops

a thickening to support a foetus to prepare for a possible pregnancy. In case, fertilization does not take place; egg and thickening in uterus are discarded in small fragments. This results in bleeding through the vagina for some days. This is called menstruation.

5. During this period, sweat and sebaceous glands show increased activity. If proper hygiene is not maintained, it can lead to many skin diseases in adolescents. Girls should take special care of hygiene during menstrual period.

6. Maximum possible height for the boy can be calculated as follows: Present Height

% of full height at this age×100 =

132 cm

75×100 = 176 cm

Maximum possible height for the girl can be calculated as follows:

7. Present Height

% of full height at this age×100 =

126 cm

77×100 = 163.6 cm

8. In some boys, the muscles of the voice box go out of control. The voice becomes hoarse due to this. The hoarse voice remains for a few days or a few weeks. The voice becomes normal on its own.

9. In boys, testes and penis develop completely. The testes begin to produce sperms.

10. In girls, ovaries enlarge and eggs begin to mature. Ovaries start releasing mature egg.

Long Answer Type Questions 1. (a) Increase in Height: Sudden

increase in height is the most conspicuous change at puberty. During this period, long bones grow rapidly and

hence height of a person increases rapidly. Initially, girls grow faster than boys. Both girls and boys attain their maximum height by 18 years of age.

(b) Change in Body Shape: A boy’s body becomes more muscular. His shoulders become wide and waist becomes narrow. A girl’s body becomes wider below waist and narrower at shoulder.

(c) Change in Voice: A boy’s voice becomes deep. In most of the cases, the child like voice is first replaced by a hoarse voice. This happens because the voice is said to


crack. Gradually, the voice becomes deep. This happens because voice box in a boy becomes larger. Girl’s voice is usually high pitched.

2. Secret ion from sweat and sebaceous glands increases during this period. Due to this, some people may suffer from acne and pimples. Due to excessive sweating, some people may develop a bad body odour.

For avoiding pimples and acne, one should avoid taking oily food. Moreover, one should clean his/her face many times in a day.

For preventing excessive sweat, one should take shower at least twice a day. Using an antiperspirant also helps.

3. Changes during adolescence are controlled by hormones. Hormones are subs tances secreted by endocrine glands.

In boys, testis secretes the hormone testosterone. Testosterone is responsible for many changes in boys; like growth of facial hair. In girls, ovaries secrete the hormone estrogen. Estrogen is responsible for development of breasts.

Action of these hormones is under the control a hormone secreted by pituitary gland. Another hormone from pituitary gland stimulates the maturation of eggs and production of sperms. A hormone reaches the target site through bloodstream because endocrine glands are ductless glands.

4. A normal cell in human beings has 46 chromosomes, i.e. 23

pairs of chromosomes. Out of them, chromosomes in 22 pairs are identical.

T h e r e a r e t w o t y p e s o f chromosomes in 23rd pair and they a re ca l led X and Y chromosomes. The 23rd pair in a male has XY combination, while that in a female has XX combination.

So, a sperm may have X or Y chromosome as 23rd chromosome. On the other hand, an ovum has X chromosome as 23rd chromosome. It is important to remember that sperm and ovum has 23 chromosomes each.

l When a sperm wi th X chromosome fertilizes the egg, the zygote thus formed will lead to birth of a girl child.

l When a sperm wi th Y chromosome fertilizes the egg, the zygote thus formed will lead to birth of a male child.

Higher Order Thinking Skills (HOTS) 1. It is true that a person physically

becomes capable of reproduction with the onset of puberty. But the person cannot be mentally and emotionally mature to take the responsibility of a family at such a young age. In humans, reproduction not only involves procreation but also taking the responsibility of emotional and financial support to the family. Due to this, the government has specified a minimum age for marriage.


2. Adolescent period is the age when one can easily get influenced and carried away by negative stimulations. Many persons fall in the trap of drug addiction during this age. Drugs not only destroy the person but the whole family and society. Do not buckle under peer pressure and say a big ‘NO’ to all sorts of negative stimulations.

3. Menstruation involves discharge of blood from vagina. Poor hygiene can breed germs and may lead to serious infection. Some infections can result in long term debility. Hence, a girl should take special care of hygiene during menstrual period.

Value Based Questions 1. Ankit is a teenager. During this

age, activity of sweat glands and sebaceous glands is very high. This presents the possibility of some common skin ailments; like pimples and acne. This

can also result in body odour. By maintaining good level of hygiene; Ankit is preventing some common skin ailments. He is also preventing body odour. Thus, Ankit is setting a very good example for others to follow.

2. Plenty of green leafy vegetables and fresh fruits in diet provide many vitamins and minerals. Moreover, it also provides iron which is very important for adolescent girls. We know that iron is essential for making RBCs and thus is good for blood. Priya is showing how to take care of special needs of your body during adolescence.

Puzzle TimeDOWN: 1. TADPOLE 2. ENDOCRINE 3. PUBERTYACROSS: 4. ADOLESCENCE 5. MENARCHE 6. TESTOSTERONE

Chapter 11 Force and PressureFORMATIVE ASSESSMENT

Oral Questions 1. Muscular force 2. One 3. Pascal 4. Newton 5. A charged body 6. Friction 7. Gravitational force 8. All directions Fill in the blanks 1. Force 2. Pull 3. Pulls 4. Push 5. Repels 6. Directly 7. Inversely 8. Motion

9. Muscular 10. Friction True/False 1. True 2. False 3. True 4. False 5. True 6. False 7. True 8. True 9. False 10. FalseRapid Fire Questions 1. Muscular force 2. Gravitational force 3. Magnetic force 4. Newton


5. Electrostatic force 6. Muscular force and frictional

force are called contact forces. 7. Force applied per unit area is

called pressure. Project/Activities 1. lTake two bar magnets and

some pencils. l Place a bar magnet on some

pencils so that the pencils can roll under the magnet.

l Now take the second bar magnet and bring its north pole near the north pole of the first magnet.

l You will notice that it pushes the bar magnet away.

l Now, bring the south pole of the second bar magnet near the north pole of the first magnet.

l You will notice that it pulls the bar magnet.

l In both the cases, magnet was able to show its effect without touching another magnet. This shows that magnetic force is a non-contact force.

2. lTake two drinking straws of same size.

l Suspend one drinking straw with a thread.

l Rub another drinking straw to your hair.

l Then bring this straw near suspended straw.

l You will notice that the suspended drinking straw is pulled towards this straw.

l This happens because of electrostatic force. This activity shows that electrostatic force is a non-contact force.

3. lTake a glass tube which is open at both ends.

l Tie a balloon at one end of this glass tube.

l Keep the glass tube in vertical position; with balloon at the bottom.

l Fill half of the tube with water and observe the size of bulge in the balloon.

l Now, fill the tube up to top and observe the size of bulge in the balloon.

l It is observed that bulge in balloon becomes bigger when more water is filled in the tube.

l This shows that pressure depends on the height of the fluid column.

SUMMATIVE ASSESSMENTMultiple Choice Questions 1. (a) Muscular force 2. (b) Speed will decrease 3. (c) Friction 4. (b) Speed increases 5. (d) All of the above 6. (a) 1000 kg

7. (b) Electrostatic force 8. (c) Air pressure Match the columns(i)-(d) (ii)-(c) (iii)-(b) (iv)-(a)Very Short Answer Type Questions 1. A push or pull on an object is

called force.


2. A force which can produce its effect only by making a contact with object is called contact force.

3. A force which can produce its effect without making a contact with object is called non-contact force.

4. The force applied by muscles of humans or animals is called muscular force.

5. When one surface is moving over another surface, a force opposes their relative motion. This force is called force of friction or friction.

6. The force applied by a magnet is called magnetic force.

7. The force applied by a charged body on another charged or non-charged body is called electrostatic force.

8. Every object in the universe exerts a force on another object. This force is called gravitational force.

9. The force acting on a unit area on an object is called pressure.

10. The pressure exerted by atmospheric air is called atmospheric pressure.

Short Answer Type Questions 1. The state of motion of an object is

described by speed and direction in which it is moving. An object at rest is at zero speed. However, both rest and motion are called states of motion.

2. When one surface is moving over another surface, a force opposes their relative motion. This force is called force of friction or friction. Friction always acts in opposite direction to motion and always

opposes motion. Force of friction arises due to contact between two surfaces.

3. Contact force Non-contact force

T h i s n e e d s to touch the object in order to exer t i t s effect.

It does not need to touch the object in order to exert its effect.

Example:muscular force, friction

Example:magnetic force, electrostatic force

4. The area of pointed end of a nail is very small. Small area increases the pressure by applied force. Due to this, it is easier to push a nail in a wooden plank through its pointed end.

5. A wide tyre has larger area. This reduces the pressure affected by tractor. Due to this, it is easier to drive a tractor on a muddy surface or on a freshly ploughed surface. Due to this, tyres of tractor are very wide and huge.

6. Feet of camel are wider than human feet. Due to this, a camel’s feet exert less pressure on sand. As a result, the camel can easily walk on sand without sinking its feet.

7. The sharp end of knife has much smaller area compared to its blunt end. This helps in increasing pressure with applied force. Hence, it becomes easier to cut a cucumber with sharp end of knife compared to its blunt end.

8. Pressure is very high in the deep ocean. The human body cannot tolerate such a high pressure.


Special diving suits prevent the harmful effects of pressure on human body. Hence, divers need to wear special suit when diving in the deep ocean.

Long Answer Type Questions 1. Following are some characteristics

of force: l At least two objects must

interact for force to come into play. Interaction of one object with another object results in a force between the two objects.

l When two forces are applied on an object in the same direction, the forces have add-on effect.

l When two forces are applied in opposite directions, the net result is equal to the difference between two forces.

l Force is expressed in terms of its magnitude and the direction in which it is working. In case of any change; in direction or magnitude of the force the effect of the force changes.

l In general, more than one force is acting on an object. The effect of forces is due to the net effect acting on the object.

2. A force can have following effects on a moving object.

l If the applied force is in direction of motion, the speed of object increases.

l If the applied force is in opposite direction of motion, the speed of object decreases. In this case, the object may also come to rest.

l If the applied force is at some acute or obtuse angle to the direction of motion, the direction of motion changes.

3. Effect of Force on Shape: l Dough changes into chapatti

because of force. l Lump of clay changes into

clay pot because of force. l A balloon is inflated because

of force. l A piece of chalk is broken into

pieces because of force. 4. Liquids and gases exert pressure

as follows: l Pressure on the bottom of

container depends on the height of column of gas or liquid. Due to this, pressure at the bottom of sea is much larger than at shallower depths.

l A fluid exerts pressure on walls of the container.

l A fluid exerts equal pressure at same depth.

Higher Order Thinking Skills (HOTS) 1. (a) shape (b) muscular, (c) contact,

(d) gravity, friction 2. (a) Fingers are agents of force

and force is acting on lemon. In this case, force is changing the shape of lemon.

(b) Fingers are agents of force and force is acting on toothpaste tube. In this case, the force is changing the shape of toothpaste tube.

(c) Earth is the agent of force and force is acting on load and spring. In this case, force


is pulling the load and spring downwards.

(d) The body of athlete is the agent of force and force is acting on his body. In this case, change in state of motion is the effect of force.

Value Based Question 1. Rohit has made the right choice.

We know that pressure is inversely proportional to the area on which the force is acting.

Wider shoulder straps help in reducing the pressure. This results in lesser burden on shoulders. So, Rahul’s choice is really good.

Puzzle TimeDOWN: 1. MAGNETIC 2. FORCE 3. FRICTIONACROSS: 4. MOTION 5. ELECTROSTATIC 6. REST

Chapter 12 FrictionFORMATIVE ASSESSMENT

Oral Questions 1. Lubricating oil and grease 2. Pliers 3. Birdsandfish 4. Ball bearing 5. Spring balance 6. Force of friction 7. Rubber Fill in the blanks 1. Right 2. Applied 3. More 4. Irregularities 5. Less 6. More 7. Easier 8. Lubricant 9. More 10. Streamlined True/False 1. True 2. False 3. True 4. False 5. True 6. False 7. False 8. True 9. TrueRapid Fire Questions 1. Lubricating oil 2. Streamlined 3. Opposite 4. Rolling friction

5. Static friction 6. Sliding friction Project/Activities 1.

2. Take a writing board, an electric cell, a book, sheet of plastic, cotton cloth, woollen cloth, jute rag, etc.

l With the help of book and writing board, make an incline.

l Keep the plastic sheet on incline and allow the electric cell to roll down the incline.

l Measure the distance covered by the electric cell.

l Repeat above steps for cotton cloth, woollen cloth and jute rag.

l Measure the distance covered by electric cell in each case.


l You will notice that electric cell travels the farthest on plastic sheet. It travels the least on jute rag.

l This activity shows that it is friction depends on nature of surface. A rough surface offers more friction than a smooth surface.

3. lTake a thick book and some pencils.

l Try to slide the book on a table. l Put pencils underneath the

book and then try to slide the book.

l You will notice that it is easier to slide the book when pencils are kept under it.

l This activity shows that rolling friction is less than sliding friction.


Multiple Choice Questions 1. (b) For reducing friction 2. (c) Footballer 3. (d) Tractor 4. (a) Graphite 5. (b) Bicycle handle bar 6. (d) Ice 7. (c) Ice skate Very Short Answer Type Questions 1. When an object moves on a

surface, a force is created between them. This force is called force of friction or friction.

2. The minimum force required to make an object moving is called static friction.

3. The minimum force required to keep a moving object moving at a constant speed is called sliding friction.

4. When an object rolls over a surface, the friction between them is called rolling friction.

5. Static friction > Sliding friction > Rolling friction

6. Friction due to a fluid is called fluid friction or drag.

7. A shape which is wide at middle and tapered at ends is called a streamlined shape.

Short Answer Type Questions 1. Rough surface of towel helps in

increasing friction. This helps in providing a better grip on the lid. Hence, it is easier to open the lid of a bottle by gripping it with a towel.

2. Banana peel is wet and smooth. So, it provides less friction. Due to this a person slips on a banana peel.

3. On a wet road, water makes a thin film on the road. This thin film reduces friction between tyres and road surface. Due to this, it is difficult to drive on a wet road.

4. By using a sand paper, a smooth surface can be made rough. A rough surface will provide more irregularities and hence will increase friction.

5. Glass surface is very smooth. This does not provide friction when the tip of a pen is moved over it. Due to this, it is difficult to write on a glass surface.


6. Friction is required for doing even a simple task; like writing on a page. But friction results in wear and tear and wastage of energy. Thus, friction is beneficial as well as harmful. Due to this, friction is called a necessary evil.

7. A streamlined shape experiences less drag. Due to this, boats and aeroplanes are made of streamlined shape so that they can move smoothly.

Long Answer Type Questions 1. Following are the three types of

friction: Static Friction: A minimum

amount of force is required to overcome the force of friction. This is called static friction. So, the minimum force required to make an object moving is called static friction.

Sliding Friction: The minimum force required to keep a moving object moving at a constant speed is called sliding friction. Sliding friction is always less than static friction. Due to this, it is easier to push a moving box compared to pushing a static box.

Rolling Friction: When an object rolls over a surface, the friction between them is called rolling friction. Rolling friction is less than sliding friction.

2. Benefits of friction: lWithout friction, it is not

possible to even walk on the road. A person slips on a wet surface because of reduced friction.

l It is not possible to keep a ladder against a wall in the absence of friction.

l It is very difficult to drive on a wet road because of less friction. Road surface is made rough to increase friction so that drivers can easily control vehicles.

3. Harms of friction: l It results in wear and tear of

shoes and tyres. It also results in wear and tear of machine parts; resulting in monetary loss.

l A significant amount of energy is wasted in overcoming friction.

l Friction generates heat which causes wastage of energy.

4. Methods to increase friction: l Rubber grips are put on bicycle

handles, electrical tools and on many other tools. Increased friction helps in giving better grip on these objects.

l Sand paper is used to make a surface rough so that friction can be increased.

l Treads of tyres and shoes are made bigger to provide better road grip.

5. Methods to reduce friction: l Lubricating oil and grease are

applied in machines to reduce friction between moving parts.

l In some machines, air cushion is used for reducing friction because use of oil is not advisable in such machines.

l Graphite powder is also used in some machines to reduce friction.


l Ball bearings are fitted in machine parts to reduce friction.

Higher Order Thinking Skills (HOTS) 1. (a) Wet marble floor, dry marble

floor, newspaper and towel 2. In case of static friction, the

minimum required force needs to break the interlocking between two surfaces. But in case of sliding friction, the minimum required force does not need to break the interlocking because the interlocking is already broken by static friction. Due to this, sliding friction is less than static friction.

3. When an object is sliding over a surface, the area of contact between them is larger. But when an object is rolling over a surface, the area of contact between them is negligible. Due to this, rolling friction is less than sliding friction.

Value Based Questions 1. The towel has rough surface.

It helps in increasing friction and thus allows a better grip on bottle cap. Due to this, Sanju is able to open the cap. Sanju is showing how to help your elders in household chores.

2. Aryan should pour some oil on different parts of machine. This will help in reducing friction and in reducing noise to some extent. Aryan’s mother is showing a love for old items. She is showing that we should not discard old items but should try to use them.

Puzzle TimeDOWN: 1. SLIDING 2. STATIC 3. FRICTIONACROSS: 4. TRACTION 5. LUBRICANT 6. ROLLING

Chapter 13 SoundFORMATIVE ASSESSMENT

Oral Questions 1. Stretched membrane 2. Stretched strings 3. Air column 4. External ear 5. Eardrum 6. Less than 20 Hz 7. More than 20,000 Hz 8. Bat 9. Semicircular canals 10. Three

Fill in the blanks 1. Sound 2. Musical 3. Vibrating 4. Upper 5. Narrow 6. Short 7. Vacuum 8. Pitch 9. Musical True/False 1. True 2. False 3. False 4. True 5. False 6. False 7. True


Rapid Fire Questions 1. Stretched membrane 2. String 3. Air column and reed 4. To trap sound waves 5. Cochlea 6. 20 Hz to 20,000 Hz 7. DolphinProject/Activities 1. lTake stainless steel plate and

fill it with water. l Strike the plate with a spoon

to produce sound. l When the plate produces

sound, vibrations can be seen in water. Water vibrates because of vibrations in the plate.

l This shows that a vibrating body produces sound.

2. lTake two rubber bands. lKeeping the rubber bands

together, stretch them by holding with both hands.

lBring the stretched band near your mouth and blow air on them.

lYou will hear the sound produced by rubber bands.

lThis shows a working model of vocal cords.

3.

4. lTake a small plastic jar and a balloon.

l Tie the balloon on the mouth of jar to make a stretched membrane.

l Keep a few grains of rice on the stretched membrane.

l Bring the jar near your mouth and shout loudly.

l You will notice that rice grains jump when sound is produced.

l This happens because stretched membrane vibrates because of sound waves.

l This shows the working of eardrum.

SUMMATIVE ASSESSMENTMultiple Choice Questions 1. (a) Air 2. (c) 330 m/s 3. (a) 10 dB 4. (d) 20 mm 5. (c) 15 mm 6. (b) 20 times 7. (a) Jet engine Match the columns(i)-(e) (ii)-(d) (iii)-(c)(iv)-(b) (v)-(a)

Very Short Answer Type Questions 1. Sound is a kind of wave which

gives us sense of hearing.

2. The to and fro or back and forth motion of an object is called vibration.

3. Voice box 4. Number of oscillations per second

is called frequency of oscillation. 5. Maximum displacement of a

wave from mean position is called amplitude.

6. A sound which is pleasant to ears is called music.

7. Any unpleasant sound is called noise.


Short Answer Type Questions 1. Sound is produced by a vibrating

body. When an object vibrates, it produces sound. When the object stops vibrating, it stops producing sound.

2. Loudness of sound depends on amplitude of vibration. Loudness of sound is proportional to square of amplitude of vibration. Loudness is expressed in terms of decibel.

3. Pitch of sound depends on frequency of vibration. A high pitched sound has high frequency. A low pitched sound has low frequency.

4. Presence of excess noise in environment is called noise pollution. Busy traffic, factories, loud music, construction works, firecrackers, etc. are sources of noise pollution.

5. Continuous exposure to noise pollution can result in lack of sleep, hypertension, anxiety and many other disorders. In some cases, it can also lead to partial loss of hearing.

Long Answer Type Questions 1. Human ear is a complex structure.

It can be divided into three main parts, viz. external ear, middle ear and internal ear.

(a) External Ear: The external ear appears like a funnel. It catches sound waves and directs them towards middle ear.

(b) Middle Ear: There is a stretched membrane and three small bones in middle ear. When sound comes to the middle ear, it sets vibrations in the eardrum. Eardrum transfers these vibrations to the three bones.

(c) Internal Ear: The internal ear is composed of cochlea and semicircular canals. Vibrations from middle ear reach the cochlea. Cochlea sends signals to the brain and then we hear a sound. Semicircular canals maintain the balance of the body.

2. Disability to hear sounds is called hearing impairment. Hearing impairment can be total or partial. Total hearing impairment is rare and is usually by birth. Many people suffer from partial hearing impairment due to some disease or due to ageing.

People with total hearing impairment can be taught sign language so that they can communicate with others.

People with partial hearing impairment can use hearing aids to hear clearly.

Higher Order Thinking Skills (HOTS) 1. Number of oscillations = 40 and time = 4 second

Frequency = number of oscillations

time =

40

4s = 10 Hz

Time Period = 1

frequency =

1

10 = 0.1 s


2. Number of vibrations = 500 and time = 1 s Hence, frequency = 500 Hz

Time period = 1

frequency =

1

500 = 0.002 s

Chapter 14 Chemical Effects ofElectric Current

FORMATIVE ASSESSMENTOral Questions 1. Bulb, electric iron, water heater 2. Mixer grinder, ceiling fan, electric

bell 3. Chromium 4. Light Emitting Diode 5. Yes, because lemon juice has acid

in it. 6.Magneticcompassshowsdeflection. 7. Copper 8. Zinc sulphate 9. Copper sulphate

10. Hans Christian Oersted Fill in the blanks 1. Wet 2. Electric cell 3. LED 4. Glows 5. Does not glow 6. Heating 7. Magnetic compass 8. Beneficial9. Electrodes 10. Positive True/False 1. True 2. False 3. True 4. False 5. True 6. False 7. True 8. False

3. I will suggest my parents to buy the house which is three lanes away from the roadside. The house on the roadside will be exposed to noisefromtraffic,whileanotherhouse would be in less noisy area. So, the second house is less prone to noise pollution.

Value Based Questions 1. His father is showing a concern

for the quality of life of his neighbours. He is also concerned about the noise pollution which Rahul would create while listening pop music at very high volume. We should always think of others while playing music. What may be music to our ears

can prove to be noise for many others.

2. Sanju is showing a concern for his classmate. He is also showing a concern for physically disabled person. He is showing how you can help a physically disabled person. We should take lesson from Sanju and do our bit to help anybody who is suffering from physical disability.

Puzzle TimeDOWN: 1. FREQUENCY 2. AMPLITUDE 3. INFRASOUNDACROSS: 4. VIBRATION 5. DECIBEL 6. HERTZ


Rapid Fire Questions 1. Heating effect 2. Magnetic effect 3. Chromium 4. Because orange juice provides

ions for conduction of electricity. 5. Because sugar solution does not

provide ions for conduction of electricity.

6. Because salt solution provides ions for conduction of electricity.

Project/Activities 1. I will like to electroplate following

objects: (a) Bicycle rims and handles (b) Motorcycle rims and handles (c) Car accessories People usually want to decorate

their bikes and cars. Chrome plated accessories are very popular because of the shine associated with chrome. Hence, setting a chrome plating unit can be highly profitable.

2. Steps to make a tester with magnetic compass:

l Take a magnetic compass and keep it in empty tray of matchbox.

l Use rubber bands to keep the compass fixed in matchbox.

l Tie this arrangement with a conducting wire.

l Connect the conducting wire with a cell.

l Now, two free ends of wire can be used to check conductivity of a given material.

3. lTake two copper plates, a beaker, battery, connecting wires, copper sulphate solution, etc.

l Fill the beaker with copper sulphate solution.

l Connect copper plates with negative and positive terminals of the battery.

l Dip the copper plates in copper sulphate solution.

l The set up for electroplating is ready.

SUMMATIVE ASSESSMENTMultiple Choice Questions 1. (b) Zinc 2. (a) Chromium 3. (d) Honey 4. (c) Salt solution 5. (a) Electroplating 6. (d) Magnetic compass 7. (b) Carbon 8. (b) William Nicholson Match the columns(i)-(d) (ii)-(c) (iii)-(b)(iv)-(a)

Very Short Answer Type Questions 1. Materials which allow electric

current to pass through them

are called good conductors of electricity.

2. Materials which do not allow electric current to pass easily through them are called bad conductors of electricity.

3. The process of depositing a layer of a desired metal on any other material by means of electricity is called electroplating.

4. Electrolysis. 5. Applying a layer of zinc on any

material through electroplating is called galvanization.


6. Applying a layer of gold on any material through electroplating is called gold plating.

7. Electrode which is connected to positive terminal.

8. Electrode which is connected to negative terminal.

Short Answer Type Questions 1. Pure water does not conduct

electricity. We need to dissolve a salt in pure water to make it conducting.

2. It stands for Light Emitting Diode. It is enclosed in a glass housing; with two wires (called lead) coming out. One lead is slightly longer than another. An LED can glow even in the presence of weak current.

3. When electric current passes through a conductor, the temperature of conductor increases. This is called heating effect of electric current. Electric bulb, water heater, electric iron, etc. work because of heating effect of electric current.

4. When electric current passes th rough a conduc tor, the conductor behaves like a magnet. This is called magnetic effect of electric current. Due to this, a magnetic compass shows deflection when it is placed near a current carrying conductor. Electric motor and electromagnet work because of magnetic effect of electric current.

5. When electrodes are immersed in water and current is passed; bubbles of oxygen and hydrogen are produced. Oxygen bubbles

formed at the electrode connected to positive terminal. Hydrogen bubbles formed at the electrode connected to negative terminal.

6. Normal water contains some salts. Presence of salt makes the normal water a good conductor of electricity. So, touching an electric switch with wet hands poses the risk of electric shock. Hence, we are advised against touching electric switch with wet hands.

7. Many harmful chemicals are created during electroplating. Disposal of these chemicals is a big problem. Careless disposal of these chemicals can cause soil pollution and water pollution.

Long Answer Type Questions 1. Passage of electric current through

a conducting solution results in chemical reaction in the solution. This is called chemical effect of electric current. Chemical effect of electric current is also known as electrolysis. Some of the signs of electrolysis are as follows:

l Bubbles of gas may be formed at electrodes.

l Deposits of metal may be seen on electrodes.

l Change of colour of solution may occur.

2. Following steps are involved in electroplating:

l The material on which a layer needs to be formed is made the negative electrode.

l The plate of desired metal is made the positive electrode.


2. Sea water has higher concentration of salts compared to drinking water. Due to this, sea water is a better conductor than drinking water. Due to this, magnetic compass needle would show more deflection in case of sea water.

Value Based Questions 1. Electroplating is a process in

which a layer of a metal is applied over any other material. Electroplating a watch and wristband can make it shine like gold or silver. This is a cheaper way than buying a new wristband and watch. So, Rina is showing how to save money. She is also showing a way of preventing unnecessary wastage of money.

2. LED bulbs consume less electricity than incandescent bulbs. So, this will help Pankaj in reducing the electricity bill for his house. Pankaj’s father is showing how to save electricity. He is also showing the importance of the statement, “Power saved is power generated.”

Puzzle TimeDOWN: 1. ELEMENT 2. CHROME 3. ELECTROMAGNETACROSS: 4. ELECTROPLATING 5. DISTILLED 6. LED

l A solution of salt of desired metal is used as conducting solution.

l Electric current is passed through the solution.

l The desired metal dissociates from the plate and gets deposited on the material at negative electrode.

3. Some uses of electroplating are as follows:

l For applying a layer of gold or silver on imitation jewellery.

l For applying a layer of chrome on parts of bicycle, motorbike and sanitary fittings. This is called chrome plating.

l Tin cans a re made by electroplating tin on iron.

l Electric poles and beams on bridges are electroplated with zinc. This helps in protection from corrosion.

Higher Order Thinking Skills (HOTS) 1. Rainwater is indeed as pure

as distilled water. However, some substances may mix with rainwater while it is coming from sky to the earth. Dissolution of a salt, acid or base can make rainwater, a good conductor of electricity. This could be the reason for Paheli’s observations during her experiment.

Chapter 15 Some Natural PhenomenaAdolescence

FORMATIVE ASSESSMENTOral Questions 1. Nepal 2. Thunder

3. Positive charge 4. Negative charge 5. Positive charge


6. Earth is composed of three layers, viz. core, mantle and crust.

7. Gold or silver 8. Charging by rubbing 9. Charging by conduction 10. Zero to ten Fill in the blanks 1. Electric spark 2. Lightning 3. Electric shock 4. Upwards 5. Downwards 6. Unsafe 7. Safe 8. Cordless 9. Crust 10. Earthquake True/False 1. True 2. False 3. True 4. False 5. True 6. False 7. True 8. False 9. True 10. TrueRapid Fire Questions 1. Gujarat 2. Thunderstorm 3. Seismograph 4. Crust 5. Mantle 6. Core 7. They repel each other Project/Activities 1. lTake a drinking straw, two

balloons and a woollen cloth.

l Inflate the balloons and suspend them near each other.

l Rub the drinking straw with woollen cloth.

l Touch the balloons with the charged straw.

l You will notice that balloons move away from each other. This happens because of similar charges on both balloons.

l This shows that like charges repel each other.

2. lTake a drinking straw, two balloons and a woollen cloth.

l Inflate the balloons and suspend them near each other.

l Rub the drinking straw with woollen cloth.

l Touch one balloon with drinking straw and another balloon with woollen cloth.

l You will notice that balloons move towards each other. This happens because of unlike charges on balloons.

l This activity shows that unlike charges attract each other.

SUMMATIVE ASSESSMENTMultiple Choice Questions 1. (a) Positive 2. (b) Negative 3. (c) Electron 4. (d) Gujarat 5. (a) Indian Ocean 6. (b) Eurasian plate 7. (b) The Himalayan region Match the columns(i)-(f) (ii)-(e) (iii)-(d)(iv)-(c) (v)-(b) (vi)-(a)

Very Short Answer Type Questions 1. The sudden electric discharge

from one cloud to another or from a cloud to the earth is called lightning.

2. Electroscope is a simple device to study transfer of charges.

3. Acquiring a charge is called charging.

4. Losing a charge is cal led discharging.

5. Transfer of charge from a charged body to earth is called earthing.


6. Lightning conductor is a safety device which prevents damage to a building due to lightning.

7. The sudden shaking or trembling of earth which lasts for a short time is called earthquake.

8. Earth’s crust is divided into many pieces. Each piece is called a tectonic plate.

9. Boundaries of tectonic plates are more prone to getting hit by earthquakes. These are called seismic zones.

10. The scale on which power of an earthquake is measured is called Richter Scale.

Short Answer Type Questions 1. Some objects get electrically

charged when they are rubbed against one another. This is called charging by rubbing. For example; plastic refill rubbed with polythene, plastic comb rubbed with hair, glass rod rubbed with silk cloth, etc.

2. Lightning conductor is a metallic rod which is inserted in the wall during construction. It is a little bit taller than the building. The top end of this rod is above the building and the bottom end is deep into the ground. The metallic rod provides easy passage to electric charge and thus the charge from lightning does not damage the building.

3. The tectonic plates are always in mot ion . When a p la te brushes against another or goes over another, it creates huge disturbance in plates. This is felt as earthquake.

4. Richter scale is the scale to measure the destructive energy of an earthquake. Earthquake of any intensity more than 2 on Richter scale is detected by seismograph. An earthquake of 3 on this scale is felt by people but rarely causes damage.

5. A machine which records seismic activity in the form of a graph is called seismograph. It is composed of a vibrating rod or pendulum. A pen is attached to the vibrating rod so that it can plot graph on a paper.

6. When a comb is rubbed against hair, the comb acquires some charge. Any charged body can attract another charged or uncharged body. Hence, the comb attracts the bits of paper.

7. Japan i s h igh ly prone to earthquakes. So, Japan shows the best preparedness against earthquakes. Most of the houses in Japan are entirely made of wood to minimize damage from earthquake. Wood is lighter than concrete and hence is less damaging than concrete.

8. A pillow can work like a cushion when something falls on it. It can minimize damage from any falling object. Hence, people are advised to cover their head with a pillow during an earthquake.

Long Answer Type Questions 1. Working of Electroscope: l When the metallic top of

electroscope is touched with a charged glass rod,


electric charge is transferred from glass rod to metal foils through the metallic rod. Both the metallic foils get similar charge and as a result they move away from each other. This happens because similar charges repel each other.

l After the previous step, when metallic top is touched with bare hands, metal foils resume their original position. This happens because of transfer of charge from aluminium foil to hands.

2. Formation of lightning takes place in following steps:

l During the development of thunderstorm, air currents move upward and water droplets move downward.

l Vigorous movements of air current and water droplets result in separation of charges.

l Positive charges accumulate near the upper edges of cloud and negative charges accumulate near the lower edges of cloud. The process of this accumulation is not clearly understood by scientists.

l Positive charge accumulates near the ground also.

l Air is a poor conductor of electricity. But when accumulation of charges becomes too much, air is unable to hold them. As a result, electric charge is passed to the ground. During the process, negative and positive charges meet each other and produce streaks

of bright light and sound. This process is called electric discharge.

3. Safety tips during lightning: l No open place is safe during

lightning. l Hearing a thunder is like a

warning to run to a safer place. l After hearing the last thunder,

one should wait for some time before coming into the open.

l A house or a building is a safe place.

l When on road, a vehicle is a safe place; with doors and windows properly shut.

4. Following provisions make a quake safe building:

l Qualified architects and engineers should be consulted for making the building.

l In earthquake prone areas, lightweight materials; like wood and mud should be used in buildings. Roof should be as light as possible.

l Cupboards and shelves should be fixed to the walls.

l Wall clocks, photo frames, water heaters, etc. should be hanged at suitable places so that they should not fall on a person.

l Fire fighting equipments should be properly installed; especially in tall buildings.

Higher Order Thinking Skills (HOTS) 1. When we take off a sweater, it

rubs against our body. In this process, the sweater gets charged. Our body also gets charged during this process. Interaction


between opposite charges creates sparks which is heard in the form of crackling sound.

2. When we touch a charged body with our hand, the charge is transferred to earth via our body. Due to this, the charged body loses its charge.

3. If both the balloons carry similar charge, they are repelled by each other. A charged body always attracts an uncharged body. Hence, uncharged balloon is attracted by the charged balloon.

4. A tall tree can easily receive charge during lightning. The tree can get badly burnt during the process. Hence, a tall tree is not safe during lightning.

5. An umbrella has a long rod which can attract charge during lightning. It can be highly damaging for the person who is carrying the umbrella. Hence,

carrying an umbrella is not safe during lightning.

Value Based Questions 1. Adarsh is showing the value

of ‘Safety First’. He is trying to minimize the chances of his house being hit by lightning.

2. We know that the foothills of the Himalayas are prone to earthquakes. A wooden house is much lighter than a concrete house. So, in case of an earthquake a wooden house would be much safer. Sherpa is showing a concern for human life and a respect for the all powerful nature.

Puzzle TimeDOWN: 1. EARTHING 2. RICHTER 3. EPICENTREACROSS: 4. ELECTROSCOPE 5. FOCUS 6. CHARGING

Chapter 16 LightFORMATIVE ASSESSMENT

Oral Questions 1. Seven 2. Louis Braille 3. Non-optical aids 4. 40° 5. Blind spot 6. Regular reflection 7. Irregular reflection 8. Eyelids protect our eyes from dust

and bright light. 9. Fashion designer 10. Cone cells Fill in the blanks 1. Light 2. Virtual

3. Real 4. Equal to 5. Equal to 6. Infinite 7. Regular 8. Irregular 9. Vision 10. Touch True/False 1. False 2. True 3. True 4. False 5. True 6. False 7. True 8. False 9. True 10. FalseRapid Fire Questions 1. Violet, Indigo, Blue, Green,

Yellow, Orange and Red 2. Braille 3. Virtual and erect 4. 30° 5. Three


6. Multiple reflections 7. Animator Project/Activities 1. lTake plane mirror, a chart

paper, a torch, pencil and ruler. l Cover the front of the torch

with a thick and black cardboard and make a small hole in the centre. This will give a very thin beam of light.

l Spread the chart paper on table and keep the mirror vertically on it.

l Direct the beam of light on mirror so that it goes along the chart paper.

l Draw a line along the incident ray and reflected ray.

l Draw a line along the surface of mirror.

l Draw a normal at the point of incidence.

l Move the mirror aside and measure angles of reflection and incidence.

l It is observed that angle of reflection is equal to angle of incidence.

2. Most of the steps for this activity would be same as the previous activity.

l Pull the chart paper in a way that some of its portion is out of the edge of the table.

l Tear the extended portion of chart paper in a way that one half can be folded vertically down the edge of the table. The folded portion is in vertical plane, while other portions are in horizontal plane.

l Throw the beam of light towards mirror. The beam of light should be along the vertical plane of chart paper.

l Observe the reflected beam of light. It does not go along the vertical fold of chart paper.

l This shows that reflected ray, incident ray and normal at the point of incidence; all lie in the same plane.

3. Keep the two mirrors on a table and start with an angle of 45°.

In this experiment, following observations can be made:

l Two images are formed between angles 120° and 90°.

l Three images are formed when mirrors are at right angle.

l Five images are formed when mirrors are at 60°.

l Seven images are formed when mirrors are at 45°.

l Below 45° angle, it is very difficult to see the images because of small aperture.

SUMMATIVE ASSESSMENTMultiple Choice Questions 1. (a) 20 cm 2. (b) 15 cm 3. (c) Kaleidoscope 4. (d) 6 5. (d) All of the above 6. (a) Infinity 7. (b) 25 cm 8. (c) 30° 9. (d) Mirror 10. (a) Blue

Very Short Answer Type Questions 1. Light is a form of energy which

gives us the sense of vision. 2. When a ray of light falls on a

shiny surface, there is a change in its direction. This is called reflection of light.


3. The ray of light falling on a reflecting surface is called incident ray.

4. The ray of light coming back from a reflecting surface is called reflected ray.

5. The perpendicular on reflecting surface at the point of incidence is called normal.

6. The angle between incident ray and normal is called angle of incidence.

7. The angle between reflected ray and normal is called angle of reflection.

8. In a plane mirror, image is erect, virtual and of the same size as object. The image is laterally inverted.

9. An image stays on retina for 1/16th of a second. This is called persistence of vision.

10. Sunlight is composed of seven colours, viz. violet, indigo, blue, green, yellow, orange and red.

Short Answer Type Questions 1. When light falls on an object,

some of it is reflected and goes to our eyes. Due to this, we are able to see an object.

2. Laws of reflection: l First Law of Reflection: Angle

of reflection is equal to angle of incidence.

l Second Law of Reflection: The incident ray, reflected ray and normal at the point of incidence; all lie in the same plane.

3. When the incident rays fall on a smooth surface, all the reflected rays are parallel to each other. This is called regular reflection. A clear image is formed in case of regular reflection.

4. When incident rays fall on a rough surface, reflected rays are not parallel to each other. This is called irregular or diffused reflection. A diffused image is formed in case of irregular reflection. Most of the reflections in nature are diffused reflections.

5. When two reflecting surfaces are opposite to each other, they reflect back light rays from each other. This creates multiple reflections and multiple images of an object are formed. Multiple images can be seen in a barber’s shop because large mirrors are usually placed on opposite walls.

6. There is no nerve cell at the junction of retina and optic nerve. This spot is called blind spot because no image is formed at this spot.

7. Light rays enter the eye through pupil and pass through lens. Lens focuses light rays on retina. Real, inverted and smaller image is formed on retina. Optic nerve carries the message to the brain. The brain interprets the message and we get the sense of vision.

8. Some people are unable to clearly see nearby objects, while some others are unable to clearly see far off objects. It happens because of defects in eyes. These defects can be rectified with the help of spectacles of suitable lenses. In some old people, the eyesight becomes foggy. The eye lens becomes cloudy. This condition is called cataract. Cataract can now be cured with surgery and by implanting artificial lens in the eye.


9. This system was developed by Louis Braille in 1821. He himself was visually challenged. This system is composed of 63 characters which are patterns of dots. Each character represents a let ter, a combination of characters, a word or a sign.

Long Answer Type Questions 1. Image Formation in Plane

Mirror:

O

P Q

I

A C

B

D

E

l PQ is the plane mirror. Object is kept at O. Two incident rays OA and OC meet PQ at points A and C.

l Draw perpendiculars to PQ at points A and C.

l After that, draw AB and CD as reflected rays; so that angle of reflection is equal to angle of incidence.

l Extend AB and CD behind the mirror so that they intersect at I. This is the point where image is formed.

2. The human eye has following main parts:

Cornea: Human eye is spherical in shape. It has tough white coat which protects the interior of the eye. The front portion of this coat is transparent and is called cornea.

Iris: This is a dark muscular structure behind the cornea. Unique colour of a person’s eye is because of colour of iris.

Pupil: The small opening in the iris is called pupil. Iris controls the size of the pupil and thus controls the amount of light entering the eye. Light enters the eye through pupil.

Lens: Lens is thicker at the middle and is made of transparent material. Lens focuses the light on the back of the eye; called retina.

Retina: The back of the eye is called retina. It works like a screen; on which image is formed. There are numerous light-sensitive nerve cells on retina. These nerve cells are connected to optic nerve.

3. Care of Eyes: l Always read in proper light. A

light which is too dim or too bright is harmful for eyes.

l Always read by keeping a book at proper distance.

l Never look directly at sun or at any other bright object.

l Never rub your eyes. If something gets into the eyes, wash with cold water.

l If you find any difficulty in your vision, consult an eye specialist.

Higher Order Thinking Skills (HOTS) 1. Objects in the dark room cannot

be seen because no light is falling on them. If objects outside the room are in light, they can be seen because light reflected from them reaches the eyes.

2. Regular reflection will take place only in case of mirror because


mirror has smooth surface. No other surface in the options can be perfectly smooth like mirror and hence diffused reflection will take place in these cases.

3. These are called tactile strips. They are made rough so that a visually challenged person can easily understand that the end of the platform is approaching. Such strips are called tactile strips.

Value Based Question 1. Rakesh understands the importance

of eyes. He knows how precious

our eyes are. Reading in sufficient light prevents strain on eyes. Using a table and chair; for studying helps in maintaining proper distance between the eyes and the book. This also helps in keeping our eyes healthy.

Puzzle TimeDOWN: 1. INCIDENT 2. NORMAL 3. CORNEAACROSS: 4. KALEIDOSCOPE 5. RETINA 6. TRANSPARENT

Chapter 17 Stars and the Solar SystemFORMATIVE ASSESSMENT

Oral Questions 1. Sun 2. Alpha Centauri 3. 24 hours 4. 365.25 days 5. 27 days 6. 27 days 7. 15 days 8. Northern Hemisphere 9. Northern 10. Jupiter Fill in the blanks 1. Stars 2. Gases 3. Star 4. Planet 5. Moon 6. Venus 7. Neil Armstrong 8. Cassiopeia

9. Asteroid 10. Pluto True/False 1. False 2. True 3. False 4. True 5. True 6. False 7. True 8. False 9. True 10. TrueRapid Fire Questions 1. Sun 2. Mercury 3. Moon 4. Elliptical 5. Highly elliptical 6. Pluto 7. Jupiter

Project/Activities 1.


2.

The solar system (not to scale)

Neptune

MercuryVenus

Mars

Saturn

Earth

JupiterUranus

SUMMATIVE ASSESSMENTMultiple Choice Questions 1. (c) A constellation 2. (a) Sirius 3. (c) Mercury 4. (d) Neptune 5. (a) Jupiter 6. (b) Mercury 7. (c) Venus 8. (a) One 9. (d) Australia 10. (a) SiriusMatch the columns(i)-(e), (g) (ii)-(a) (iii)-(c), (f)(iv)-(d)

Very Short Answer Type Questions 1. The stars, planets, the moon and

many other objects in the sky are called celestial objects.

2. The distance travelled by light in one year is called a light year.

3. Some groups of stars form a recognizable shape. Such group of stars is called constellation.

4. The movement of a celestial body in its orbit is called revolution.

5. The movement of a celestial body around its axis is called rotation.

6. A celestial body which moves around a planet is called satellite.

7. Comets are celestial bodies that move around the sun in highly

elliptical paths. 8. 76 years. 9. A celestial object which burns to

disintegrate into small particles is called meteor.

10. Man-made satellites are called artificial satellites.

Short Answer Type Questions 1. Pole star appears in the north in the

northern hemisphere. Pole star is in line with the axis of earth. Due to this, its apparent position does not change in the night sky. All other stars appear to be moving around the Pole star in the night sky.

2. It is also known as Great Bear, Big Dipper and Saptarishi. There are seven main stars in this constellation and it appears like a big ladle with a handle. It appears in the northern sky; near the Pole star.

3. The planets and the celestial bodies which move around the Sun make the solar system. The solar system is composed of eight planets, comets, asteroids and meteors. The eight planets in the solar system are; Mercury, Venus,


Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

4. There is a large gap between the orbits of Mars and Jupiter. This gap has many small objects that revolve around the sun. These objects are called asteroids. This belt is called asteroid belt.

5. Sometimes, a part of an asteroid or star or any other celestial body enters the earth’s atmosphere. When it enters the earth’s atmosphere, it is burnt into small particles due to high heat created by friction. This is called meteor. It appears like a shooting star. Sometimes, the particle can be so large that most of it falls intact on the earth. In that case, it is called a meteorite.

6. Uses of Artificial Satellites: l Remote sensing to collect data

about minerals, cities, forests, etc.

l Collecting data about atmosphere which can be utilized for weather prediction.

l Transmission of signals for telecommunication and television.

7. Star PlanetHuge celestial bodies made of hot gases.

Huge celestial bodies made of rocks and gases.

Are luminous. Are non-luminous.Do not revolvearound any other celestial body.

Revolve around a star.

Example: Sun,AlphaCentauri.

Example: Earth, Venus.

8. Inner Planets Outer PlanetsAre present b e f o r e t h e asteroid belt.

Are present after the asteroid belt.

Mainlycomposed of rocks.

Mainly composed of gases.

Have very few satellites.

Have large number of satellites.

Examples:Mercury,Venus, Earth and Mars.

Examples:Jupiter, Saturn, Uranus andNeptune.

9. This is closest to the sun and is the smallest planet. Mercury is so close to the sun that it is difficult to see it from the earth. It can be seen at horizon just after the sunset or before the sunrise. Mercury has no satellite.

10. Venus is visible as a bright star in the evening sky or morning sky. After the moon, it is the next brightest object in the night sky. Due to these reasons, it is called the morning and evening star.

Long Answer Type Questions 1. The bright part of the moon

appears to be in different shapes on different days of a month. These are called phases of moon. When no moon is visible in the night sky, it is called a new moon day. This is followed by crescent moon, first quarter moon, gibbous moon and full moon in that order. The period when the moon appears to be gaining in shape, it called waxing. The waxing is followed by waning of moon and both the phases last about 15 days each.


Reason of Phases of Moon: The moon takes same time in completing a revolution and a rotation. Due to this, only one surface of the moon is visible from the earth. The surface which is visible from the earth gets varying ratios of light and shadow. Due to this, we are able to see different phases of moon.

2. Earth is the third planet from the sun. It is the only planet where life is known to exist. Earth has unique atmosphere which supports life. It has the right mixture of air, water and other elements to support life. Earth is neither too cold nor too hot. From the space, earth appears blue because of reflection of light from its water bodies and landmass. Due to this, earth is also called the Blue Planet.

Earth’s orbital plane is tilted at 23.5° on its equatorial plane. This means that earth’s axis is tilted at 66.5° on its orbital plane. Seasons change on earth because of this tilt.

Higher Order Thinking Skills (HOTS) 1. The distance between stars can be

in millions or billions of km. It is difficult to express such a large number on paper. Light year is a convenient unit to express such

huge distances; without error. Hence, the distance between stars is expressed in light years. A star eight light years away from the earth means that it takes eight years for light to travel from that star to the earth.

2. Mercury is so close to the sun that most often it is not visible due to glare of the sun. But it can be seen at far horizon from a suitable place. For this, you need to go to a large open place from where you can see very far on the horizon. Then mercury can be seen just before sunrise or just after sunset.

3. In normal course, only one full moon appears in a month. But sometimes, two full moons may appear in month. The additional full moon is called the blue moon. Since a blue moon is very rare so this term is used in the phrase.

4. The gases in the atmosphere of Venus trap heat from the sun. This feature is not present on Mercury. Due to this, Venus is the hottest planet.

Puzzle TimeDOWN: 1. VENUS 2. MERCURY 3. JUPITERACROSS: 4. URANUS 5. CONSTELLATION 6. EARTH

Chapter 18 Pollution of Air and WaterFORMATIVE ASSESSMENT

Oral Questions 1. Nitrogen 2. Carbon dioxide and methane 3. Cold climate 4. Plants; especially fruits and

vegetables

5. Kanpur 6. 1985 7. Untreated sewage 8. Algae 9. 25% 10. Chlorofluorocarbon


Fill in the blanks 1. Seven 2. Air 3. Small 4. Ozone 5. Marble 6. Delhi 7. July 8. Ganga 9. 10 10. Chlorine True/False 1. False 2. True 3. False 4. True 5. False 6. True 7. False 8. True 9. True 10. FalseRapid Fire Questions 1. 21% 2. 78% 3. Carbon dioxide 4. Mathura 5. Kanpur 6. Algae 7. Ozone layerProject/Activities 1. Following measures would help to

ensure supply of clean water to all residents:

l Setting a water treatment plant. l Repair in water supply pipelines. l Preventing untreated sewage

being discharged in the river. l Educatingpeopleaboutbenefits

of clean drinking water. l Educating people about

conservation of water. 2. Respected teachers and dear

friends. I feel privileged at being given this opportunity to present a speech on global warming.

Global warming can be termed as a curse of modern lifestyle. We are using more and more cars. We are using many products which may not be really needed. All of this is necessitating the burning of fossil fuels on an ever increasing scale. We know that burning of fossil fuels creates carbon dioxide which is a potent greenhouse gas. This has resulted in global warming.

Disastrous effects of global warming can be clearly seen in our day-to-day life. Summers are becoming warmer and winters are becoming colder. Every year, we witness horrific stories of flashfloodsandlandslides.Casesof devastating cyclones are on the rise around the world. Many cities are predicted to sink because of rising sea levels.

It is high time that we take corrective steps to prevent the world from becoming an unsafe place. We should give up using our private vehicles and switch to public transport. We should stop using buses and cars to reach school and instead begin using bicycles for this purpose. We should develop the healthy habit of walking whenever possible. We should follow the principles of three Rs of conservation to reduce global warming.

If proper measures are not taken in time, our future generations will receive a badly bruised environment as gift from our generation.

3. (a) 3,000 (b) 10 minute (c) Carbon dioxide, carbon

monoxide, SPM, oxides of nitrogen and sulphur, mercury, lead, etc.

(d) A sensor is inserted into exhaust system of vehicle. Data from the sensor is transferred to a computer. The computer analyses the data and produces a report in the form of a printout.

(e) As per the guidelines, permissible level of different gases depends on the type of


vehicle and year of manu-facture of the vehicle. The following link gives detail:

http://www.delhi.gov.in/wps/wcm/connect/do i t_transport/Transport Home/Pollution+Control/Know

+the+Exhaust+Emission +Standards

(f) The owner of the vehicle is suggested to go for replacement of exhaust system and servicing of engine.

(g) After every three months.SUMMATIVE ASSESSMENT

Multiple Choice Questions 1. (a) 78% 2. (b) Nitrogen 3. (c) Sulphur dioxide 4. (d) Kitchen 5. (a) Asthma 6. (b) Digestive system 7. (c) Kanpur 8. (d) Oxygen 9. (a) Oxygen 10. (d) 5000Match the columns(i)-(e) (ii)-(d) (iii)-(c)(iv)-(b) (v)-(a)Very Short Answer Type Questions 1. When air is contaminated with

unwanted substances which can be harmful for the living and non-living, this is called air pollution.

2. Smoke and dust from forest fire and volcano pollute the air.

3. Ozone layer prevents harmful ultraviolet radiations from the sun from entering our atmosphere.

4. A mixture of smoke and fog is called smog.

5. Presence of acid in rainwater is called acid rain.

6. Overall increase in global temperature is called global warming.

7. Addition of unwanted substances in water makes water harmful for living beings and non-living things. This is called water pollution.

8. Water which is fit for drinking is called potable water.

9. Boiling kills the germs in water. 10. Reduce, Reuse and Recycle.Short Answer Type Questions 1. Petrol and diesel are burnt in

automobiles. Burning of these fuels produces many polluting gases; like carbon dioxide, carbon monoxide, sulphur dioxide, nitrogen dioxide, etc. Automobile engines also produce tiny particles which remain suspended in air.

2. Fine dust particles are created at construction sites and stone quarries. Dust particles are also produced by mining activities and by power plants.

3. Ozone layer is a protective layer in the atmosphere. It prevents harmful ultraviolet radiations from the sun from entering our atmosphere. Ultraviolet radiations can cause skin cancer in humans and animals. It is also harmful for plants. So, damage to the ozone layer can be highly detrimental to the living beings. CFCs damage the ozone layer.

4. Oxides of sulphur and nitrogen mix with rainwater to create acid rain. Acid rain can be harmful for living beings and also for non-living things. Acid rain corrodes the outer layer of buildings and monuments. Taj Mahal has turned pale because of acid rain.


5. Greenhouse is a glass enclosure which is used for growing plants in cold climates. The glass enclosure traps heat and thus provides ambient temperature to plants. Carbon dioxide and methane trap solar radiations and thus increase atmospheric temperature. This is called greenhouse effect and results in global warming.

6. Global warming is resulting in melting of icebergs and glaciers. Increased cases of flash floods are because of global warming. Sea level is rising around the world because of global warming. Drastic changes in weather patterns have been witnessed because of global warming.

7. Excess quantity of chemicals in a water body provides nutrients to algae. This condition is called eutrophication. This results in proliferation of algae in water bodies with stagnant water. Once these algae die, they provide food to decomposers. The process of decomposition utilizes most of the oxygen from water. Thus, negligible amount of oxygen is left for aquatic plants and animals. This results in death of aquatic plants and animals.

Long Answer Type Questions 1. Effects of Air Pollution: l Carbon dioxide is a potent

greenhouse gas. It results in global warming.

l Smog is created because of air pollution. It reduces visibility and causes problems for drivers and pilots.

l Carbon monoxide is a poisonous gas even at low concentration. It reduces oxygen carrying capacity of blood.

l Oxides of sulphur and nitrogen mix with rainwater to create acid rain. Acid rain can be harmful for living beings and also for non-living things.

l Suspended Particulate Matter in air can cause respiratory problems; like asthma and other respiratory diseases.

l Carbon dioxide and methane result in greenhouse effect which causes global warming.

2. Methods to prevent air pollution: l Petrol and diesel should

be replaced with CNG in automobiles. CNG is a cleaner fuel and creates negligible pollution.

l Use of public transport should be promoted in order to reduce the use of private vehicles.

l People should use bicycle as often as possible.

l People should walk for short distance commute instead of using a vehicle.

l Government agencies are monitoring air quality at important locations on a regular basis. This data can be utilized to assess the situation and to take timely action.

l Alternate sources of energy should be explored. Solar energy, wind energy and hydel energy are non-polluting sources of energy. Use of alternate sources of energy can minimize air pollution.

l We should plant more trees in our surroundings. Trees absorb carbon dioxide and release oxygen during photosynthesis. Thus, trees help in reducing the level of carbon dioxide in atmosphere.


l Dry leaves should not be burnt. They should be utilized to make compost.

3. Some of the causes of pollution of Ganga are as follows:

l Untreated sewage and effluents from nearby cities are discharged into this river.

l People use this river for bathing and washing clothes. People also bath their cattle in this river.

l Cremating dead bodies on the banks of the Ganges is an age old practice. Many a times, half burnt corpses are disposed off in the river.

l Rivers are also used for immersing idols, flower and many other leftovers of rituals and worships.

l Many important towns are situated on the banks of this river. The stretch of the river near Kanpur is highly polluted.

l There are about 5000 industrial units in Kanpur. These include fertilizer, tanneries and paint industries. Harmful chemicals from these factories are discharged into Ganga. There are rules and regulations to prevent addition of harmful chemicals in the river but these rules are often flouted.

4. Effects of water pollution: l Contaminated water becomes

unfit for humans and cattle. l Fish population drastically

reduces; resulting in loss of livelihood for fishermen.

l Many water borne diseases; like cholera, diarrhoea, jaundice, etc. are on the rise because of water pollution.

l Presence of faecal matter results in high concentration of E.coli in water. This also leads to water borne diseases.

l Contamination of groundwater results in high levels of toxic materials in fruits, vegetables and grains.

l Untreated effluents from factories can raise the pH and temperature of water. This is also harmful for aquatic plants and animals.

5. Methods of Water Purification: l Municipal bodies purify

water by various physical and chemical methods to supply drinking water to households.

l Filtration is a common method of purification of water. Various types of water filter are available in the market.

l Boiling is another common method of water purification. Boiling kills the germs in water.

l Chlorination also helps in killing the germs in water. Chlorine tablets are available for free at government hospitals so that people can use them to get clean water.

Higher Order Thinking Skills (HOTS) 1. Clear and transparent water may

not be fit for drinking. It may contain germs which can cause water borne diseases. It may also contain harmful substances. Thus, clear and transparent water does not necessarily mean that it is safe for drinking.

2. Pure air Polluted airIt has normal ratio of different gases.

Ratio of some gases may be higher or lower than normal.

Is ideal for the environment.

Is bad for the environment.


Is good forhuman health.

Is bad forhuman health.

Value Based Questions 1. Sonia understands the precious

nature of water. She shows how to conserve water. She is following one of the three Rs of conservation, i.e. reuse.

2. Ram Singh needs to stand at traffic intersection which is full of highly polluting gases and SPM. Using a mask prevents harmful gases and particles from going inside the lungs. This will

help Ram Singh in avoiding respiratory disorders. Ram Singh shows how to take care of your body in the face of bad situations. He also understands the harmful effects of air pollution.

Puzzle TimeDOWN: 1. POLLUTION 2. ACID RAIN 3. JAUNDICEACROSS: 4. CARBON MONOXIDE 5. POTABLE 6. ASTHMA

WORKSHEET - 1A. Fill in the Blanks 1. Ploughing 2. Sickle 3. TrowelB. State True or False 1. False 2. True 3. FalseC. Multiple Choice Questions 1. (b) Wheat 2. (c) PulsesD. Give Answer in one word 1. Seed drill 2. Hoe 3. Rainy 4. Winter 5. ApicultureE. Answer the following questions 1. Growing fruits and vegetables is

called horticulture. Five plants which are grown under horticulture are as follows:

Apple, Guava, Orange, Brinjal, Okra 2. Combine harvester is a farming

machine which does more than one farming operation in one go. A combine harvester harvests and threshes the crop simultaneously. Combine harvester saves time and labour.

F. Answer the following questions in about 100 words. 1. Advantages of using chemical

fertilizer: The use of fertilizers helps farmers to get better yield of crops such as wheat, paddy and maize. Fertilizers are very rich in plant nutrients like nitrogen, phosphorus and potassium and hence act quickly.

Disadvantages of using chemical fertilizer: Chemical fertilizer badly affects soil quality in the long run. Excessive use of chemical fertilizer results in contamination of groundwater. It also results in contamination of food.

Therefore, in order to maintain the fertility of the soil, we should use organic manure instead of fertilizers or leave the field uncultivated in between two crops.

WORKSHEET - 2A. Fill in the blanks 1. Microscope 2. Vaccine 3. Milk

B. State True or False 1. False 2. True 3. True


C. Multiple Choice Questions 1. (a) Lactobacillus 2. (c) FungiD. Give Answer in one word 1. Lactobacillus 2. Yeast 3. Edward Jenner 4. Jaundice 5. MosquitoE. Answer the following questions 1. Conversion of atmospheric

nitrogen in a form so that plants can utilize it, is called nitrogen fixation. Root nodules in pulses play important role in nitrogen fixation. Root nodules provide shelter to Rhizobium bacteria. Rhizobium bacteria carry out nitrogen fixation in soil.

2. A vaccine helps the body to learn to fight a particular disease. A vaccine provides advanced protection against a disease. An antibiotic stops further growth of bacteria. Thus, an antibiotic helps in curing a disease. A vaccine is

given before a disease affects a person, while an antibiotic is given after a disease affects a person.

F. Answer the following questions in about 100 words. 1. Following steps can be taken to

prevent diarrhoea: l Always use clean drinking

water. l Keep drinking water and food

covered. l Wash your hands with soap

after coming from toilet. l Wash your hands before eating

anything. l Do not eat food sold by

roadside vendors. l Wash fruits before eating

them. l Make sure that food is cooked

thoroughly. l Store all perishable food

properly in the refrigerator. l Always use clean utensils.

WORKSHEET - 3A. Fill in the blanks 1. Monomers 2. Man-made 3. Plastic bottles B. State True or False 1. True 2. False 3. TrueC. Multiple Choice Questions 1. (b) Rayon 2. (d) Melamine D. Give Answer in one word 1. Thermoplastic 2. Thermosetting

plastic 3. Acrylic 4. Rayon 5. PETE. Answer the following questions 1. Plastic does not react with most of

the substances. Moreover, plastic

is not affected by moisture. They can be easily vacuum sealed. So, an edible item can be safely kept in plastic containers.

2. Bakelite is a thermoplastic. It can be very strong and durable and can withstand heat. Moreover, being a plastic; it is a bad conductor of electricity. Due to these properties, Bakelite is used for making electric switches.

F. Answer the following questions in about 100 words. 1. Today plastic has become a material

of choice because of its following characteristic properties:

l Plastic does not react with most of the substances.


l It has light weight. l It is available at lower price. l It has good strength. l It is easy to handle. l It is not corroded easily. l It is easily moulded into

different shapes and sizes. l Thermosetting plastic is bad

conductor of heat and electricity

and hence is used for making electricity switches, handles and different kinds of utensils.

l Melamine plastic is a versatile material. It resists fire and plerates heat. People use it for making floor tiles, kitchen ware and fabrics.

l It lasts long.WORKSHEET - 4

A. Fill in the blanks 1. Good 2. Bad 3. Sonorous B. State True or False 1. True 2. False 3. TrueC. Multiple Choice Questions 1. (b) Mercury 2. (a) Sodium D. Give Answer in one word 1. Phosphorus 2. All metals 3. Hydrogen 4. Carbon dioxide 5. Oxygen E. Answer the following questions 1. A homogenous mixture of more

than one metal or a metal and non-metal is called alloy. Alloy is stronger than its component. Alloys have higher melting point. Some alloys have better properties in terms of resistance to corrosion, e.g. stainless steel.

2. Metals can be beaten into thin sheets. This property of metals is called malleability. Due to this property,

we can make sheets of iron, aluminium, copper, etc. Due to this, we can make silver and gold foils.

F. Answer the following questions in about 100 words 1. When a metal reacts with acid,

then hydrogen gas is released and a salt is formed. This can be shown by following equation:

Metal + Acid Æ Metal salt + Hydrogen

Example: When zinc reacts with sulphuric acid then zinc sulphate and hydrogen gas are formed.

Zinc + Sulphuric acid Æ Zinc sulphate + Hydrogen

Example: When sodium reacts with hydrochloric acid then sodium chloride and hydrogen gas are formed.

Sodium + Hydrochloric acid Æ Sodium chloride + Hydrogen

WORKSHEET - 5A. Fill in the blanks 1. Carbon 2. Well 3. Coke B. State True or False 1. False 2. True 3. FalseC. Multiple Choice Questions 1. (c) Coal tar 2. (a) Petroleum jelly

D. Give Answer in one word 1. Power plant 2. Petrol and diesel 3. Carbon dioxide 4. Methane 5. Kerosene E. Answer the following questions 1. Exhaustible resources of energy

are not going to be replenished in


foreseeable future. We are using them at a very fast rate. At this rate, they are going to be finished within hundred years. After that, we will be left with no energy resources if suitable actions are not taken. Moreover, burning of coal and petroleum (which are exhaustible energy resources) creates air pollution.

2. Benefits of using renewable sources of energy:

l They are replenished in foreseeable future. Thus, they ensure a steady supply of energy source.

l Most of them are non-polluting and thus are safe for the environment.

F. Answer the following questions in about 100 words 1. The energy resources which are

replenished in foreseeable future are called renewable sources of energy. Two such resources are as follows:

Hydel Energy: Kinetic energy from moving water is utilized to produce electricity. This is called hydel energy of hydroelectricity. Developing hydel energy can help in reducing our dependency on coal.

Solar Energy: The energy from sun is called solar energy. This can be harnessed by photovoltaic cells to produce electricity. Solar energy is not going to exhaust as long as the solar system exists. This non-polluting and hence is safe for the environment.

WORKSHEET - 6A. Fill in the blanks 1. Outermost 2. Innermost 3. Carbon dioxide B. State True or False 1. True 2. False 3. FalseC. Multiple Choice Questions 1. (a) Water 2. (c) OxygenD. Give Answer in one word 1. Three zones 2. Outermost zone 3. Innermost zone 4. Calorific value 5. Firewood E. Answer the following questions 1. The reaction of a substance with

oxygen in which heat and light are produced is called combustion. The reaction for burning of coal is as follows:

Carbon + Oxygen Æ Carbon dioxide + heat and light

2. Goals during fighting a fire are as follows:

l Removing the combustible substance

l Increas ing the igni t ion temperature

l Cutting off oxygen supply F. Answer the following questions in about 100 words 1. Soda-acid fire extinguisher

contains soda and acid. These substances get mixed when the plunger of fire extinguisher is pulled. When sodium bicarbonate (soda) reacts with acid, the reaction produces carbon dioxide.

Carbon dioxide does not support combustion and thus helps in controlling the fire. It is the best extinguisher. It is heavier than oxygen and hence a spray of carbon dioxide helps in cutting of oxygen supply to the combustible substance. Moreover, in most cases it does not harm the electrical equipment.


WORKSHEET - 7A. Fill in the blanks 1. Red 2. Forests 3. Endemic speciesB. State True or False 1. True 2. False 3. FalseC. Multiple Choice Questions 1. (a) Asiatic lion 2. (c) Uttar PradeshD. Give Answer in one word 1. Bharatpur 2. Kaziranga National Park 3. Flora 4. Fauna 5. Species E. Answer the following questions 1. Species which are under the danger

of being wiped out or becoming extinct are called endangered species. Every species plays important role in the ecosystem. Extinction of any species is going to disturb the ecological balance. Hence, we need to take care of endangered species.

2. The general increase in earth’s temperature is called global warming. The causes of global warming are as follows:

Excess use of fossil fuels; which has increased the level of carbon

dioxide in the atmosphere. Increased population of cattle has resulted in increase of methane in the atmosphere. These two gases are potent greenhouse gases and cause global warming.

F. Answer the following questions in about 100 words 1. The re a re many ha rmfu l

consequences of deforestation. It increases the temperature and pollution level on the earth. It causes loss of habitat for wildlife. Trees prevent the soil erosion. So, deforestation results in soil erosion. The lower layer of the soil is hard and rocky. It has less humus and is less fertile. After sometime, the soil turns into deserts. Besides, it will cause global warming as fewer trees means more carbon dioxide. Carbon dioxide traps the heat rays reflected by the earth and causes rise in temperature on the earth. It also disturbs the water cycle and reduces rainfall. consequently, we may meet with droughts. Deforestation also leads to floods as it decreases the water holding capacity of the soil.

WORKSHEET - 8A. Fill in the blanks 1. Nucleus 2. Absent 3. CellB. State True or False 1. False 2. True 3. TrueC. Multiple Choice Questions 1. (a) Cork 2. (b) WBCsD. Give Answer in one word 1. Mitochondria 2. Chloroplast 3. Leeuwenhoek 4. Cellulose

5. Transport

E. Answer the following questions 1. The organisms in which nucleus is

present are called eukaryotes. The nuclear materials are bound by a nuclear membrane in such organisms. Amoeba, cockroach, humans, etc. are examples of eukaryotes.


2. Functions of plasma membrane: l Provides a container for the

contents of a cell. l Separates a cell from external

environment. l Se rves a s channe l fo r

transportation of materials. F. Answer the following questions in about 100 words 1. Animal cell is usually irregular

in shape. It is bound by a cell membrane.

Plasma membrane: Cell membrane is also called plasma membrane. It provides a boundary to the cell.

Exchange of materials takes place through plasma membrane.

Endoplasmic reticulum: This is a ne twork of f ine tubes . Endoplasmic reticulum transports materials.

Mitochondria: Respiration takes place in mitochondria.

Golgi complex: Packaging of materials takes place in Golgi complex.

Nucleus: This is present in the center of a cell. It controls the functions of a cell. Chromosomes are present in nucleus.

WORKSHEET - 9A. Fill in the blanks 1. Asexual 2. Binary 3. FoetusB. State True or False 1. False 2. True 3. TrueC. Multiple Choice Questions 1. (a) Testosterone 2. (c) TestisD. Give Answer in one word 1. Estrogen 2. Plasmodium 3. Fallopian tube 4. Uterus 5. Tadpole E. Answer the following questions 1. The mode of reproduction in

which two parents are involved and gamete formation takes place is called sexual reproduction. The male parent produces the male gamete, while the female parent produces the female gamete. Fusion of male and female gametes is necessary for sexual reproduction to take place.

2. The life cycle of frog has following stages:

Eggs: The female frog lays thousands of eggs in water and the male frog releases sperms on them.

Fertilization takes place in water. The cluster of frog’s eggs is called spawn.

Tadpole: Fertilised eggs develop into tadpoles. A tadpole looks like a small fish.

Adult: The tadpole undergoes metamorphosis to change into frog.

F. Answer the following questions in about 100 words 1. The asexual reproduction in which

an animal reproduces by dividing into two individuals is called binary fission. Amoeba is a single-celled organism. During binary fission the mother cell of amoeba divides into two daughter cells. First of all, the nucleus divides into two nuclei. After that, the cytoplasm divides into two daughter cells. Each daughter cell gets a nucleus.

1. Parent cell 2. Nucleus divides

4. Two daughter cells3. Cytoplasm divides


A. Fill in the blanks 1. Teenage 2. Secondary sexual 3. GirlsB. State True or False 1. True 2. False 3. TrueC. Multiple Choice Questions 1. (a) Adrenaline 2. (b) Umbilical cordD. Give Answer in one word 1. Puberty 2. Estrogen 3. Endocrine glands 4. One 5. Menstruation E. Answer the following questions 1. Stoppage of menstrual cycle is

called menopause. Menopause marks the end of reproductive phase in women. After the menopause, a woman cannot bear a child.

2. When tadpoles are borne in iodine-deficient water, they fail to change into frogs and die prematurely. Iodine is an important component of the hormone thyroxin. Tadpoles borne in iodine-deficient water are unable to produce thyroxin

and hence they fail to undergo metamorphosis.

F. Answer the following questions in about 100 words 1. Best practices to maintain hygiene

during teenage: l Teenager’s have to do many

physical activities and hence their sweat glands become more active and sometimes make the body smelly. So, they must take a bath at least once everyday. If they do not do so, there are chances of catching bacterial infection.

l Special care should be taken for maintaining cleanliness under armpits and pubic area.

l Face should be washed frequently to avoid pimples and acne.

l Anti-perspirants should be used to avoid body odour.

l Girls should take special care during menstruation.

WORKSHEET - 10

WORKSHEET - 11A. Fill in the blanks 1. Push, pull 2. Decreases 3. Increase B. State True or False 1. True 2. False 3. FalseC. Multiple Choice Questions 1. (a) Dust particles stick to TV screen 2. (c) Using skateboardD. Give Answer in one word 1. Gravitational force 2. Air pressure 3. Electrostatic force

4. Muscular force 5. Mechanical force E. Answer the following questions 1. We know that pressure decreases

when area increases. Using shoes with wide heels helps in reducing pressure on ice. This helps an Eskimo in walking safely on ice.

2. A horse applies muscular force to pull a cart. Muscular force is a contact force. We need to harness the horse to the cart so that contact between the horse and the cart could be established.


F. Answer the following questions in about 100 words 1. Pressure is defined as force

applied per unit area. This can be given by following equation:

P = F/a In this equat ion, force is

in numerator while area is in denominator. This means that pressure increases with increase in force. This also means that pressure decreases with increase

in area. For example, if we try to push a nail into a wall by its head, it would not pierce into the wall whereas if we push it by the pointed end. It would easily pierce into the wall. It happens because the nail of head covers more area and decreases the pressure while its pointed end covers less area and increases pressure. We can use this knowledge to increase or decrease pressure as per our needs.

WORKSHEET - 12A. Fill in the blanks 1. Increasing 2. Reducing 3. LessB. State True or False 1. True 2. False 3. FalseC. Multiple Choice Questions 1. (d) Wet road 2. (c) A ball bearing D. Give Answer in one word 1. Lubricant 2. Static friction 3. Traction 4. Streamlined shape 5. Sliding friction E. Answer the following questions 1. We know that friction is caused by

irregularities in surface. A rough surface has more irregularities compared to a smooth surface. Due to this, a rough surface offers more friction than a smooth surface.

2. During motion, heat is created because of friction. This heat is created by the energy utilized in overcoming friction. Thus,

energy is wasted in the form of heat; because of friction.

F. Answer the following questions in about 100 words 1. Examples of increasing friction: l We use grooved shoes. The

grooves in the shoes provides the shoes better grip on the floor and enable us to walk on the floor safely.

l The tyres of our vehicles are treaded to provide better grip with the ground.

l The brake pads in our bicycle stop the motion of the rim because of motion.

l Kabaddi players rub their hands with soil for a better grip of their opponents.

l We use a towel to open a bottle cap for a better grip.

l We prefer to use rough tiles in our bathroom to increase the friction.

l We use a rubber grip on our bicycle/bike handle for this purpose.

WORKSHEET - 13A. Fill in the blanks 1. Musical instrument

2. Stretched membrane 3. Vocal cords

teacher’s Manual n 77

B. State True or False 1. False 2. True 3. FalseC. Multiple Choice Questions 1. (b) Sitar 2. (b) 20 Hz to 20,000 HzD. Give Answer in one word 1. Vocal cords 2. Decibel 3. Metre per second 4. Air column 5. Audible sound E. Answer the following questions 1. Children and women produce

sounds of high frequency, while men produce sound of low frequency. Due to this, children and women produce high pitched sound, while men produce low pitched sound. As a result, the voice of children and women is shrill compared to the voice of men.

2. Uses of ultrasound: l In diagnosing the abnormalities

of internal organs. l In detecting any cracks in

metal components.

l In detecting enemy ships with the help of SONAR.

F. Answer the following questions in about 100 words 1. Steps to reduce noise pollution: lBanning the use of loudspeakers

after a particular time; like 10 PM.

l Planting trees on the roadside. l Regulating the timings of flights;

if an airport is in the vicinity. l Using silencing devices in

aircraft engines, transport vehicles, industrial machines and home appliances.

l Using sound barriers on flyovers. l Using thick upholstery in

rooms. l Running TV and music systems

at low volumes. l Stopping unnecessary honking

of horns. l Setting noise producing

industries away from residential areas.

WORKSHEET - 14A. Fill in the blanks 1. LED 2. Electroplating 3. Distilled B. State True or False 1. True 2. False 3. FalseC. Multiple Choice Questions 1. (b) Sodium hydroxide solution in water 2. (b) Deflection in magnetic needles by electric current D. Give Answer in one word 1. LED 2. Two 3. Sulphuric acid 4. Zinc 5. Anode E. Answer the following questions 1. Liquids which conduct electricity

provide ions for this purpose. So,

free ions are available in liquids which conduct electricity. For example; when common salt is dissolved in water, it dissociates into ions. Due to this, a salt solution conducts electricity.

2. Galvanization results in application of a layer of zinc on electric pole. The coat of zinc prevents the reaction between iron and atmospheric moisture. We know that rusting of iron happens because of reaction between iron and atmospheric moisture. Hence, galvanization helps in preventing rusting of iron and thus in prolonging the life of an electric pole.


F. Answer the following questions in about 100 words 1. The apparatus for electroplating

is composed of a container, two electrodes and battery. The rod of pure gold is made the anode (positive terminal), while the article on which gold is to be applied is made the cathode (negative terminal). Suitable

electrolyte (like gold nitrate solution) is kept in the container.

When electric current is passed through the apparatus then a layer of gold is deposited on the article.

battery

electrode

copperspoon

Gold nitrate(aq)

WORKSHEET - 15A. Fill in the blanks 1. Thunder 2. Core 3. Small B. State True or False 1. False 2. True 3. FalseC. Multiple Choice Questions 1. (d) 8 Richter 2. (b) Under a small tree D. Give Answer in one word 1. Electroscope 2. Silver 3. Earthing 4. Discharging 5. Earthquake E. Answer the following questions 1. When a glass rod is rubbed with

silk then transfer of electrons takes place between glass rod and silk. If an object gains electrons, it acquires negative charge. On the other hand, if an object loses electrons, it acquires positive charge. As per conventions, the glass rod acquires positive charge and silk acquires negative charge.

2. The point of origin of earthquake is called focus. The point on

ground directly above the focus is called epicenter of earthquake. An earthquake’s effect is strongest at its epicenter. The effect decreases as we move away from the epicenter.

F. Answer the following questions in about 100 words 1. Do’s and Don’ts when outside

during lightning: l If you are on open vehicles

like motorbikes, tractors, construction machinery or open cars, then find a covered spot.

l If you are in closed vehicle then remain in that vehicle.

l If you are in open space, then look for a covered spot.

l Do not hold an umbrella. l Do not stand under a tall tree

or electric pole. l Stand under a short tree. l Do not lie on the ground.

Squat low on the ground and hold your head between your knees.

WORKSHEET - 16A. Fill in the blanks 1. right 2. irregular 3. laterally inverted

B. State True or False 1. False 2. True 3. FalseC. Multiple Choice Questions 1. (a) 3 cm 2. (c) Kaleidoscope

teacher’s Manual n 79

D. Give Answer in one word 1. Regular reflection 2. Diffused image 3. Spherical 4. Optic nerve 5. Cataract E. Answer the following questions 1. The water surface in a lake is

not smooth rather it has some irregularities; even in calm water. Due to this, irregular reflection happens from the water in lake. Due to this, we are unable to see clear image of a tree above.

2. Aids for visually challenged which work on sense of touch are called tactile aids.

A visually challenged person uses his/her sense of touch to get suitable message from a tactile aid. Tactile strips can be seen in metro rail and platforms to alert the visually challenged person.

F. Answer the following questions in about 100 words 1. There are two types of reflection,

viz. regular and irregular reflection. Regular Reflection: When

reflection happens from a smooth surface then all the refracted rays are parallel to each other. This is called regular reflection. Sharp image is formed in case of regular reflection. A plane mirror causes regular reflection.

Irregular Reflection: When reflection happens from a rough surface then the refracted rays are not parallel to each other. This is called irregular reflection. Blurred or smooth image is formed in case of irregular reflection. Most of the surfaces in nature cause irregular reflection.

WORKSHEET - 17A. Fill in the blanks 1. Eight 2. Asteroid 3. EllipticalB. State True or False 1. True 2. False 3. TrueC. Multiple Choice Questions 1. (c) Pluto 2. (d) Hale BoppD. Give Answer in one word 1. Halley’s comet 2. 365.25 days 3. Equal to the distance between earth and sun 4. Saturn 5. Circular E. Answer the following questions 1. Orion is also known as hunter.

The three prominent stars in this constellation mark the belt of the hunter. This constellation is visible in southern sky; especially during late evenings in summer.

2. The atmosphere of Mercury is quite thin as compared to that of Venus. Due to this, most of the heat from Mercury escapes from its atmosphere. But in case of Venus, heat is trapped by its atmosphere. Hence, Venus is the hottest planet in spite of Mercury being the nearest to the sun.


F. Answer the following questions in about 100 words 1. A group of stars which resembles

a recognizable shape is called constellation. Ursa Major is a well known constellation. It is visible in the northern sky during summer time in the early part of a night. It is also called the Big Dipper, the Great Bear or the Saptrashi. There are seven prominent stars

in this constellation. Its shape appears like a saucepan. This constellation appears to move around the Pole Star.

Ursa Major moves around the Pole Star

Pole star

A. Fill in the blanks 1. Bad 2. Carbon monoxide 3. Germs B. State True or False 1. False 2. True 3. TrueC. Multiple Choice Questions 1. (b) Carbon dioxide 2. (b) 1985D. Give Answer in one word 1. Chlorofluorocarbon 2. 21%, 3. 78% 4. Households 5. Ultraviolet radiations E. Answer the following questions 1. C o m p o u n d s o f c h l o r i n e /

fluorine and carbon are called chlorofluorocarbons. These compounds are used in refrigerators and in pressurized cans. CFCs react with ozone to produce oxygen. This reaction damages the ozone layer. Damage to the ozone layer is dangerous for the environment.

2. A mixture of fog and smoke is called smog. Smog happens because of high level of air pollution. Harms of smog are as follows:

l Reduces visibility for drivers on highways.

l Reduces visibility for pilots and creates problems during takeoff and landing.

l Tarnishes the natural view of the skyline.

F. Answer the following questions in about 100 words 1. Methods to prevent water pollution: l Untreated sewage should not

be discharged into rivers or lakes.

l Oil spills in water bodies should be prevented.

l Open defecation should be stopped.

l Bathing and washing in rivers should be prevented.

l Immersion of idols in rivers and lakes should be prevented.

l Cremation of dead bodies near water bodies should be prevented.

l Non-biodegradable things should not be thrown into water bodies.

l Use of chemical fertilizers and pesticides should be reduced.

l The government should be active to punish the people who violates the rule.

WORKSHEET - 18

Question Bank science · 2018-02-01 · Worksheet-12 ... Project/Activities: 1. Take a handful of...

Documents

Transcript of Question Bank science · 2018-02-01 · Worksheet-12 ... Project/Activities: 1. Take a handful of...