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## Q.1.  Fill in the blank and rewrite the completed statements :                         10

1. One compression and one rarefaction together forms one………………….. of the wave.

Ans One compression and one rarefaction together forms one Cycle of the wave.

2. Generation and Propagation of sounds requires a …………… .

Ans Medium

3. Different sound notes have different …………… .

Ans Different sound notes have different frequencies.

4. The total number of compressions and rarefactions produced per second in a sound wave is 500Hz. The frequency of the sound wave is …………… .

Ans The total number of compressions and rarefactions produced per second in a sound wave is 500 Hz. The frequency of the sound wave is 500 Hz.

5. The frequency of sound is measured in …………… .

Ans The frequency of sound is measured in Hertz.

6. Medium is………………………… for generation of sound.

Ans Medium is necessary for generation of sound.

7. In humans, sound is produced in …………… .

Ans In humans, sound is produced in Larynx.

8. The region in a sound wave, with higher pressure and density is called…………………. and that with low pressure and density is called …………… .

Ans The region in a sound wave, with higher pressure and density is called compression and that with low pressure and density is called rarefaction.

9. In loudspeaker, …………… energy is converted into……………………. energy.

Ans In loudspeaker, electrical energy is converted into sound energy.

10. In tuning fork vibration, the region having high air pressure and density is called …………… .

Ans In tuning fork vibration, the region having high air pressure and density is called Compression.

## Q.2. Find the odd one out                          2

#### 1. Bell jar, vacuum pump, electric bell, prong.

Ans:  Prong – its an part of tuning fork rest all are the term used in Propagation of sound and Medium.

2. Vocal cord, larynx, pharynx, magnet

Ans Magnet – its an part of sound produced by loud speaker rest all are the parts of human body which helps in production of sound.

## Q.3. Fill in the blank and rewrite the completed statements 16

#### 1. glass is used in production of spectacles, lenses, etc.

Ans: Optical glass is used in production of spectacles, lenses, etc.

#### 2.  glass is used in pharmaceutical industry to store the medicines.

Ans Borosilicate glass is used in pharmaceutical industry to store the medicines.

#### 3. The plastic that can be molded as per our wish is called as …………...

Ans The plastic that can be molded as per our wish is called as thermoplastic.

#### 5 ………….. is mixed to get bluish green glass.

Ans Ferrous oxide is mixed to get bluish green glass.

#### 6. ………… is a form of complex material called polystyrene.

Ans Thermocol is a form of complex material called polystyrene.

#### 7. ……………. glass dissolves in water.

Ans Alkali silicate glass dissolves in water.

#### 8.The density of glass depends on its …………….

Ans The density of glass depends on its ingredients.

#### 9. A manmade material showing the property of plasticity and made up of organic polymers is …………….

Ans A manmade material showing the property of plasticity and made up of organic polymers is plastic

#### 10.Motor cars are coated with …………….

Ans Motor cars are coated with teflon.

#### 11. Thermocol melts at ………… °C.

Ans Thermocol melts at 100°C.

#### 12. ………….. is a type of plastic used for manufacturing lenses and artificial teeth.

Ans Polyacrylic is a type of plastic used for manufacturing lenses and artificial teeth.

#### 13.  …………….. glass is used to produce laboratory glass-wares.

Ans Silica glass is used to produce laboratory glass-wares.

#### 14. Plastic shows …………..  property, hence it can be molded to any shape.

Ans Plastic shows plasticity property, hence it can be molded to any shape.

#### 15. Being a bad conductor of electricity, glass is used as ………….  in electrical appliances.

Ans Being a bad conductor of electricity, glass is used as insulators in electrical appliances.

#### 16. Naturally occurring polymer is …………….

Ans Naturally occurring polymer is Cellulose.

## Q. 4.  Find the odd one out : 4

#### 1. Plastic plates, Plastic bowls, Electrical switches, Plastic comb.

Ans Electrical switch is the odd one out as it is made from thermosetting plastic while rests are thermoplastic.

#### 2. Cloth, Vegetables, Paper, Plastic

Ans Plastic is the odd one out as it is non-degradable while rests are degradable.

#### 3. PVC, Polyester, Melamine, Bakelite

Ans PVC is the odd one out as it is a thermoplastic while others are thermosetting plastic.

#### 4. Plastic, Thermocol, Glass, Paper.

Ans Paper is the odd one out as it is degradable while others are non-degradable.

## Q. 5. Find co-related terms : 7

#### 2. Textile industry: :: Parts of airplane engine: Melamine

Ans Textile industry: Polyester:: Parts of airplane engine: Melamine

#### 3. Borosilicate glass: Store medicines:: Optical glass: ……………

Ans Borosilicate glass: Store medicines:: Optical glass: Lenses

#### 4. Artificial teeth: Polyacrylic:: Vehicles coating: ……………

Ans Artificial teeth: Polyacrylic:: Vehicles coating: Teflon

#### 5. Silica glass: Laboratory glass ware:: Lead glass: ……………

Ans Silica glass: Laboratory glass ware:: Lead glass: Light bulbs, tubes

#### 6. Polystyrene: thermoplastic:: Melamine : ……………

Ans Polystyrene: thermoplastic:: Melamine : Thermosetting

#### 7. Electrical switches: Bakelite:: Raincoat : ……………

Ans Electrical switches: Bakelite:: Raincoat : PVC (Polyvinyl chloride)

## Q. 6. Extra data : 4

##### 1.
 Material Duration for degradation Type of material Plastic …………… …………… …………… One year …………… Fruit peels and vegetables …………… ……………

Ans:

 Material Duration for degradation Type of material Plastic Thousands of years Non-degradable Cotton cloth One year Degradable Fruit peels and vegetables 1-2 weeks Degradable

##### Ans:
 Degradable Material Non-Degradable Material Material which gets decomposed through natural process is called as degradable material. For Material which does not get decomposed by natural process is called as non-degradable material. For
 example: Cotton example: Plastics

3. Thermoplastic and Thermosetting plastic

##### Ans:
 Thermoplastic Thermosetting plastic The plastic that can be molded as per our wish is called as thermoplastic. For example: Plastic combs The plastic that cannot be molded into another shape once a specific shape is given is called as thermosetting plastic. For example: Electrical switch

4. Man-made materials and Natural materials

##### Ans:
 Man-made materials Natural materials Materials made by man through processing in laboratories, industries are called as man-made materials. For example: Plastic, Thermocol. Materials obtained directly from nature are called as natural materials. For example: Cotton.

## Q. 5. .Match the pair 6 :

##### 1
 Column – A Column – B i. Thermoplastic a. Bakelite ii. Thermosetting b. Polyvinyl chloride c. Glass

Ans:

 i. Thermoplastic a. Polyvinyl chloride ii. Thermosetting b. Bakelite
##### 2
 Column – A Column – B i. Alkali silicate glass a. Silica glass ii. Processed glass b. Water glass c. Fiber glass

Ans:

 i. Alkali silicate glass Water glass ii. Processed glass Fiber glass
##### 3
 Column – A Column – B i. Lead glass a. Electric switch ii. Bakelite b. Mattresses c. Electric bulb

Ans:

 i. Lead glass Electric bulb ii. Bakelite Electric switch
##### 4
 Column – A Column – B i. Polyester a. Non-stick cookware ii. Teflon b. Textile c. Bottles

Ans:i. Polyester-Textile

ii. Teflon Non-stick cookware

##### 5
 A B i. Thermocol a. Lens ii. Optic glass b. Plates c. Mattresses

Ans:

 i. Thermocol Plates ii. Optic glass Lens
##### 6
 Column – A Column – B i. Lead glass a. Mattresses ii. Polypropylene b. Plates c. Electric bulb

Ans:

 i. Lead glass Electric bulb ii. Polypropylene Mattresses

## Q.6. State True or False:  15

1. Production of glass releases green-house gases like sulphur dioxide.

##### Ans : True

2. Cotton cloth is a non-degradable material.

Ans False, Cotton cloth is a degradable material.

3. Thermocol being a good shock-absorber, it is used in packing of delicate items.

##### Ans : True

4. Vessels used for cooking in microwave are made up of plastic.

##### Ans : True

5. Glass is a degradable material.

Ans False, Glass is a non-degradable material.

6. Each responsible citizen should follow the 4R principle.

##### Ans : True

7. The degradation period of fruits and vegetables peels is 1-2 weeks.

##### Ans : True

8. Plastic is a bad conductor of heat and electricity.

##### Ans : True

9. Plastic is not easily affected by humidity and rain.

##### Ans : True

10. Milk bags, packing bags are made from polyethylene, a type of thermoplastic.

##### Ans : True

11. Ferrous oxide is used to get red glass.

Ans False, Ferrous oxide is used to get bluish green glass./ Copper oxide is used to get red glass.

12. Glass is a slow conductor of heat.

##### Ans : True

13. Liquid styrene may cause skin-burns.

## Q. 7. Name the following : 20

1. A thermosetting plastic used in textile industry.

Ans Polyester

2. Two natural materials.

Ans Wood, Cotton, Plants

3. A material formed from mixture of silica and silicate.

Ans: Glass

4. Unscramble the jumbled words : LPTSACI

Ans: PLASTIC

5. Unscramble the jumbled words: LOPEMRY

Ans :POLYMER

6. A type of a plastic used for manufacturing lenses and artificial teeth.

Ans Polyacrylic

7. A material used for coating vehicles to protect from scratches.

Ans Teflon

8. Another name for alkali silicate glass.

Ans Water glass

9. Material used for manufacturing toys.

Ans Polyvinyl chloride(PVC)

10. A type of a glass used in pharmaceutical industry to store medicines.

Ans Borosilicate glass

11. A type of pure glass useful in production of microscopic lenses.

Ans Optical glass

12. A type of a glass used to produce laboratory glass ware.

Ans Silica glass

13. A transparent glass used in manufacturing of electric bulbs.

14. Carcinogenic ingredient in Thermocol that causes blood cancer.

Ans Styrene

15. Substance that can be molded into any shape due to the property of plasticity.

Ans Plastic

16. A form of a complex material called polystyrene.

Ans Thermocol

17. Select the articles from the following list which are biodegradable.

Paper, Woollen clothes, Wood, Aluminium can, Plastic bag, Peels of vegetables.

Paper, Woollen clothes, Wood, Peels of vegetables.

1. Unscramble the jumbled words: EFOTNL

Ans TEFLON

Ans Plastic, Glass

1. Unscramble the jumbled words : YESPOLTRE

Ans POLYESTER

## Q. 8. Answer in one sentence : 9

1. Define : Glass

Ans Glass is the non-crystalline, hard but brittle solid material formed from mixture of silica and silicate.

1. Thermocol is produced from which material ?

Ans i. Thermocol is a form of a complex material called polystyrene.

ii. It transforms in to liquid state on heating at more than 100oC temperature and returns to solid state on cooling. Thus it can be transformed into any shape.

1. Why do we use plastic cook wares in microwave ovens ?

Ans We use plastic cook wares in microwave ovens because plastic does not get easily affected by heat but the food gets cooked faster.

1. What properties of plastic make it useful for many things ?

Ans Plastics can be recycled, reused, colored, melted, rolled into sheets or made into wires, So they are very useful.

1. Why are electrical wires covered with plastic?

Ans Plastic is a poor conductor of electricity, therefore the wires are covered with it as it acts like an insulator.

1. Define : Plastic

Ans A manmade material showing the property of plasticity and made up of organic polymers is called plastic.

1. Why is melamine used for making kitchenware ?

Ans Melamine resists fire and can tolerate heat better than other plastics. So it is used for making kitchenware.

1. Which are the main ingredients of the glass?

Ans Glass is produced from the mixture of sand, soda, lime and small quantity of magnesium oxide.

1. Thermoplastic

Ans The plastic that can be molded as per our wish is called as thermoplastic.

## Q. 9. Multiple Choice Questions (Activity) 2

1. Electrical switches are made of …………….
1. Nylon b. Bakelite c. Polythene d. Melamine

Ans Option b.

1. Out the following, which is non-biodegradable?
1. Vegetable peels b. Cotton c. Plastic bags d. Jute

Ans Option c.

Q. 10. Multiple Choice Questions (Experiment) 2

1. Plastic used for making plates is ……………. .
1. Ester b. Polyester c. Melamine d. Polyethylene

Ans Option c.

1. Out of the following, which is not a natural fiber?
1. Cotton b. Silk c. Rayon d. Jute

Ans Option c.

## Q. 11. Write Short Notes : 14

1. Thermocol

Ans i. Thermocol is a form of a complex material called polystyrene.

1. It transforms into liquid state on heating at more than 100°C temperature and returns to solid state on cooling.
2. Due to this, Thermocol can be given any desired shape.
3. Being a good shock-absorber, it is used in packing of delicate items.
4. Plates used in mass feasts are also made up of Thermocol.
1. Silica Glass

Ans i. Silica glass is produced by using the silica.

1. Items made up of silica glass show minimum expansion on heating.
2. It is not affected by acid and alkali.
3. Due to this, silica glass is used to produce laboratory glass-wares.
1. Coloured Glass

Ans i. Soda lime glass is colorless.

1. So as to impart a desired color, oxides of specific metal is mixed during manufacturing process.
2. For example: Ferrous oxide is mixed to get bluish green glass and Copper oxide to get red glass.
1. Glass Production

Ans i. Glass is the non-crystalline, hard but brittle solid material formed from the mixture of silica and silicate.

1. For glass production, mixture of sand, soda, lime and small quantity of magnesium oxide is heated in furnace.
2. Sand i.e. silicon dioxide melts at 1700°C. So as to melt the mixture at low temperature, pieces of discarded glass are added to it. Due to this, mixture melts at 850°C.
3. Once all the ingredients of mixture are liquefied, it is heated upto 1500°C and immediately cooled.
4. Due to the sudden cooling, mixture becomes homogeneous, amorphous and transparent instead of crystalline.
1. State uses of plastic.

Ans Plastic are of two types, thermoplastic and thermosetting plastic. Their uses are as follows.

#### Thermoplastic :

1. Polyvinyl chloride(PVC): Used in the manufacture of bottles, raincoat, toys, etc.
2. Polystyrene: Used as thermo-insulating parts of electric appliances like refrigerators, gears of machine, protective coverings likes covers of CD, etc.
3. Polyethylene: Used in making milk bags, packing bags, flexible garden pipes, etc.
4. Polypropylene: Used in the manufacture of parts of loudspeakers and vehicles, ropes, mattresses, etc.

#### Thermosetting Plastic:

1. Bakelite: Used in making cabinets of radio, TV, telephones, electrical switches, etc.
2. Melamine: Domestically useful items like cup-saucers, plate, trey etc, sound insulating coverings.

c. Polyurethane: Used in making surfing boards, small boats, furniture, seats in vehicles.

d. Polyester: Used in making fiber glass, toners of laser printers, textile industry, etc.

1. Used in the manufacture of bottles, raincoat, toys, etc.- Not to be highlighted
2. Optic Glass

Ans i. Optic glass is produced from the mixture of sand, soda, limestone, barium oxide and boron.

ii. This type of pure glass is useful in production of spectacle lenses, microscopic lenses.

1. Borosilicate Glass

Ans i. Borosilicate glass is produces by melting the mixture of sand, soda, boric acid and aluminum oxide.

1. This glass does not show any effect on medicines.
2. Hence, the bottles made up of borosilicate glass are used in pharmaceutical industry to store medicines.

## Q. 12. Write properties, uses, inferences, important factors, examples : 6

1. Name any two types of Thermoplastic and state its uses.

Ans i. Polyvinyl chloride – Used in manufacture of bottles, raincoat, ropes, etc.

ii. Polyethylene- Used in making milk bags, packing bags, etc.

1. Write the uses of PVC.

Ans i. Polyvinyl chloride (PVC ), is a synthetic resin made from the polymerization of vinyl chloride.

1. PVC is the world’s third most widely produced synthetic plastic polymer.
2. PVC is used in an enormous range of domestic and industrial products.
3. PVC is used to manufacture pipes, raincoat, toys, bottles, handbags, shoes, ropes, electrical cable insulation, furniture, etc.
4. Name any two types of Thermosetting plastic and state its uses.

Ans i. Bakelite- Cabinets of radio, TV.

ii. Melamine- Used for making saucers, plates, tray, etc.

## Q. 13. Give scientific reasons : 8

1 Glass is used as an insulator in electrical appliances.

Ans i. Glass is the non-crystalline, hard but brittle solid material formed from the mixture of silica and silicate.

ii. On heating, glass becomes soft and can be molded into any shape.

iii. Glass is a bad conductor of electricity.

iv. Hence, glass is used as insulator in electrical appliances to resist the follow of current.

2. Plastic tanks are used for storage of chemicals.

Ans i. Plastic is a manmade material showing the property of plasticity and is made up of organic polymer.

ii Plastic does not react with air or water i.e. they are non-reactive. Due to this plastic are resistant to corrosion. They are also often unaffected by various chemicals.

iii. Plastic is light in weight and easy to carry and is a bad conductor of heat and electricity.

Hence, plastic tanks are used for storage of chemicals.

3. Every citizen must follow the 4 R principle.

Ans i. Some materials are naturally degraded while some materials do not.

ii. Manmade materials like plastic, glass are non-degradable and become environment pollutant.

iii. Each responsible citizen should follow the 4R principle i.e. Reduce, Reuse, Recycle and Recover.

iv. We should opt for the items made up of degradable material like jute, cotton, paper, etc. instead of plastic.

Then only we can save the environment from pollution.

4. Domestically useful items are replaced by plastic.

Ans i. Plastic is a manmade material showing the property of plasticity and is made up of organic polymer.

ii. Plastic does not corrode and decompose.

iii. Plastic is not easily affected by humidity, heat, rain, etc.

iv. Also, it can be molded into any shape due to its property of plasticity.

Hence, domestically useful items are replaced by plastic.

## Q. 14. Answer the following : 57

1.Give two examples to show that plastics are non-corrosive in nature.

Ans i. Buckets made of iron get rusted but those made of plastic are not rusted,

ii. Food can be stored in plastic containers, as they are resistant to chemicals in food.

2. To prevent degradation due to sunlight, some materials are stores in which type of bottles?

Ans i. Photo-degradation is the alteration of materials by light.

ii. Exposure to ultraviolet(UV) radiation may cause significant degradation of many materials.

iii. Many natural and synthetic polymers are attacked by ultraviolet radiations and hence products should be stored in glass bottles as an alternative to plastic bottles.

iv. It is observed that glass containers in amber, cobalt blue and vintage green offer UV protection for products like food, medicine, beverages and beauty products that are photosensitive.

v. Some materials are stored.

3. A person has to reheat food in a microwave. He has a choice of selecting plastic or borosilicate glass container. Which one should he/she select? Why ?

Ans i. The person should select Borosilicate glass container for reheating in a microwave because there are chances of leaching when plastic containers are used.

ii. Also, borosilicate glass does not react with chemicals nor it gets affected by thermal changes and is more resistant to heat.

4. Write down the Properties of Glass.

Ans i. On heating, glass becomes soft and can be molded into any shape.

ii. Density of glass depends upon its ingredients.

iii. Glass is slow conductor of heat. On quick heating of cool glass or on quick cooling of hot glass, it cracks/breaks.

iv. Being a bad conductor of electricity, glass is used as insulator in electrical appliances.

v. Being transparent, most of light passes through the glass. However, if there are oxides of either chromium, vanadium or iron in the glass, large amount of light is absorbed in glass.

6. Write the natural or manmade raw material of the following items.

Ans i. Mattresses- Polypropylene ( Thermosetting plastic)

ii. Beaker-Silica Glass

iii. Bangle- Coloured Glass( Soda lime)

iv. Chair- Polyvinyl chloride (PVC) –Manmade or Wood (Natural)

v. Gunny bag-Jute

vi. Broom- Plants(Coconut, Corn husk)

vii. Knife- Metal (Irons, Steel)

viii. Pen- Combination of metal and Plastic (tip-Metal, Barrel of the pen is made from Polystyrene, Other parts like cap, ink-tube, etc are made from plastic)

7. Explain why the following are made up of thermosetting plastics.

Ans i. Fry pan handles- They are made of thermosetting plastics as they are bad conductors of heat and it does not become soft on heating.

ii. Electric plugs/switches/plug boards- These are made of thermosetting plastic as they are bad conductor of electricity.

8. What happens to those people, who constantly come in contact with Thermocol ?

Ans i. People staying in contact with Thermocol for long term may develop the problems of eyes, respiratory system, skin, digestive system, etc.

ii. Liquid styrene may cause skin-burns.

iii. The chances of pregnant women having miscarriage are also very high.

9. Which material is wrapped around the items of glass or similar material during transport to prevent from breaking up ?

Ans i. Materials like glass and other fragile items are packed in bubble sheets.

ii. Bubble sheets are transparent plastic having regularly spaced, protruding air filled hemispheres that provides cushioning for fragile items.

10 Which measures will you arrange to minimize the environmental problems arising due to non-degradable plastic?

Ans Environmental pollution due to plastics can be solved by following methods:

i. Avoid the use of plastics as far as possible.

ii. Always use bags, made of jute, cloth or paper.

iii. Biodegradable and non-biodegradable wastes should be separated and disposed off separately.

iv. Plastics should be recycled and reused.

v. Every citizen should follow the 4R principle i.e. Reduce (Minimal use), Reuse (Use again), Recycle(Use again after processing) and Recover(Reclaiming).

11. Explain the effects of following materials on environment and human health. Glass :

##### Ans Glass

1i During glass production, the mixture needs to be heated up to 1500°C.

2. During this, green-house gases like sulphur dioxide, nitrogen dioxide, carbon dioxide are released through burning of fuel.

3. As glass, is non-degradable, if pieces of the waste glass material flow into water body, it may affect that ecosystem.

4. Similarly, drainage may be blocked due to these pieces.

12. How is plastic produced ?

Ans i. Plastic are derived from natural, organic materials such as cellulose, coal, natural gas, salt and crude oil.

ii. Crude oil is a complex mixture of thousands of compounds and is processed before using it for the purpose of plastic production.

iii. The production of plastic begins with the distillation of crude oil in an oil refinery that separates oil into groups of lighter components called fractions.

iv. One of these fractions, naphtha, is the crucial compound for the production of plastics.

v. Plastics are large polymers composed of repeated units of hydrocarbons, along with oxygen, nitrogen, sulfur, etc.

13. Explain why plastic containers are favored for storing food ?

Ans Food can be stored in plastic containers because.

i. Plastics are non-reactive.

ii. Plastics are light and strong.

iii. Plastics are durable.

14. Explain the effects of following materials on environment and human health. Plastic :

##### Ans Plastic:

i. Plastic is considered as non-degradable and hence it is an environmental pollutant.

ii. Careless disposal of plastic bags chokes drains and blocks the soil.

iii. If disposed plastic bags are eaten by cows, it can kill them.

iv. Plastic bags can also contaminate foodstuffs due to poisonous dyes getting absorbed into food. This may prove carcinogenic.

v. Burning of plastic causes environmental pollution by releasing poisonous gases.

15. Should the handle and the bristles of the tooth brush be made of the same material? Explain.

Ans i. No, the handle used in the tooth brush has to be hard and strong whereas the bristles need to be soft and flexible.

ii. Also the bristles are continuously exposed to the teeth and gums and hence the quality of plastic needs to be of better quality than the handle.

16. Where does the plastic litter end up ?

Ans i. Plastic is non-biodegradable and hence if the plastic waste is segregated properly and correctly most of these can be recycled.

ii. But most of the plastic wastes are present in landfills, dumping ground and even in oceans, thus causing environmental pollution.

17. Properties of Plastic.

Ans i. Plastic does not corrode.

i.Plastic does not decompose.

ii. Plastic is not easily affected by humidity, heat, rain, etc.

iii. Items of any color can be made from it.

iv. Plastic can be molded into any shape due to the property of plasticity.

v. Plastic is a bad conductor of heat and electricity.

vi. Plastic is light in weight, hence is easy to carry.

18. Even though plastics are very useful, they are not environmental friendly’. Justify this statement.

Ans i. Plastics are very useful, but their disposal is a big problem.

ii. Plastics are non-biodegradable and take many years to decompose.

iii. They release a lot of poisonous fumes, when burnt so they cause environmental pollution.

iv. Hence the above statement is justified.

19. Explain the effects of following materials on environment and human health. Thermocol :

##### Ans Thermocol :

i. Thermocol contains carcinogenic ingredients in styrene, the person in contact with Thermocol for long duration may have the possibility of blood cancer like leukemia and lymphoma.

ii. Thermocol is non-biodegradable, hence many people opt to destroy it burning. This releases poisonous gases in atmosphere.

iii. If the food kept in Thermocol is reheated, styrene may dissolve in that food and this may lead to health problems.

iv. People staying in contact with Thermocol for long term may develop the problems of eyes, respiratory system, skin, digestive system, etc.

v. Pregnant women may face the miscarriage.

vi. Liquid styrene may cause skin-burns.20

20. Which type of glass is used in vehicles to avoid injuries in accidents?

Ans i. Modern windshields glasses are used in vehicles to avoid injuries in accidents as it will not shatter into sharp pieces.

ii. hese are created from laminated safety glass, which is treated glass and combines two curves glass sheets and a plastic lamina ted layer between for safety. Two curved glass sheets.

iii. They are then bonded to the window frame.

## Q. 15. Draw a well labeled diagram and explain. : 5

1

1. Name the raw materials used in the preparation of glass.
2. What is added to lower the temperature of the mixture in the preparation of glass?
3. In the final stages of glass preparation, at what temperature is the mixture heated and cooled immediately?
4. The density of the glass depends on what factor?
5. Which type of a glass is fiber glass?

Ans 1.Glass is produced from the mixture of sand, soda, lime and small quantity of magnesium oxide.

2. Sand melts at 1700°C, so as to melt the mixture at a lower temperature, pieces of discarded glass are added to it. Due to this, the mixture melts at 850°C.

3. Once all the ingredients of the mixture are liquefied, it is heated to 15000C and cooled immediately.

4. The density of the glass depends upon its ingredients.

5. Fiber glass is a type of processed glass.

# Q. 16. Read the given paragraph and answer questions based on it : 5

Plastic bags are crude oil products. They are derived from petroleum and natural gas. One of the main drawbacks of the bag is that they are non-biodegradable. It takes years to breakdown plastic. Recycling of plastic bags is very long process and not a viable option. Plastic is also responsible for global warming. The burning of plastic releases carbon monoxide which adversely affects the ozone layer of the earth. The thinning of this layer has become the major cause of global warming. While we cannot think of totally eliminating its use but we can significantly reduce using them.

1. What is the main drawback of plastic bags?
2. Which gas is released on burning of plastic? iii.What is the effect of global warming?
3. Is there an eco-friendly alternative to use plastic bags?
4. State any one property why plastic bags are widely used?

Ans i. Plastic bags are non-biodegradable.

1. Carbon monoxide gas is released on burning of plastic.
2. The ozone layer of the earth is getting badly affected due to increase in global warming.
3. Eco-friendly cotton or jute bags can be used as an alternative to plastic bags.
4. Plastic bags are widely used because they are light in weight and easy to carry. They do not get wet by water and hence the things kept in them are safe.
 industries are called as man-made materials. For example: Plastic, Thermocol. Materials obtained directly from nature are called as natural materials. For example: Cotton.

## Q. 17. Match the pair 6 :

##### 1
 Column – A Column – B i. Thermoplastic a. Bakelite ii. Thermosetting b. Polyvinyl chloride c. Glass

Ans:

 i. Thermoplastic a. Polyvinyl chloride ii. Thermosetting b. Bakelite
##### 2
 Column – A Column – B i. Alkali silicate glass a. Silica glass ii. Processed glass b. Water glass c. Fiber glass

Ans:

 i. Alkali silicate glass Water glass ii. Processed glass Fiber glass
##### 3
 Column – A Column – B i. Lead glass a. Electric switch ii. Bakelite b. Mattresses c. Electric bulb

Ans:

 i. Lead glass Electric bulb ii. Bakelite Electric switch
##### 4
 Column – A Column – B i. Polyester a. Non-stick cookware ii. Teflon b. Textile c. Bottles

Ans:i. Polyester-Textile

ii. Teflon Non-stick cookware

##### 5
 A B i. Thermocol a. Lens ii. Optic glass b. Plates c. Mattresses

Ans:

 i. Thermocol Plates ii. Optic glass Lens
##### 6
 Column – A Column – B i. Lead glass a. Mattresses ii. Polypropylene b. Plates c. Electric bulb

Ans:

 i. Lead glass Electric bulb ii. Polypropylene Mattresses

## Q.18. State True or False:  15

1. Production of glass releases green-house gases like sulphur dioxide.

##### Ans : True

2. Cotton cloth is a non-degradable material.

Ans False, Cotton cloth is a degradable material.

3. Thermocol being a good shock-absorber, it is used in packing of delicate items.

##### Ans : True

4. Vessels used for cooking in microwave are made up of plastic.

##### Ans : True

5. Glass is a degradable material.

Ans False, Glass is a non-degradable material.

6. Each responsible citizen should follow the 4R principle.

##### Ans : True

7. The degradation period of fruits and vegetables peels is 1-2 weeks.

##### Ans : True

8. Plastic is a bad conductor of heat and electricity.

##### Ans : True

9. Plastic is not easily affected by humidity and rain.

##### Ans : True

10. Milk bags, packing bags are made from polyethylene, a type of thermoplastic.

##### Ans : True

11. Ferrous oxide is used to get red glass.

Ans False, Ferrous oxide is used to get bluish green glass./ Copper oxide is used to get red glass.

12. Glass is a slow conductor of heat.

##### Ans : True

13. Liquid styrene may cause skin-burns.

#### 14. Plastic can be molded into any shape due to its property of elasticity.

Ans False, Plastic can be molded into any shape due to the property of plasticity.

#### 15. Melamine is used for making cabinets of radio, TV, etc.

Ans False, Bakelite is used for making cabinets of radio, TV, etc.

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