Class 8 science CHAPTER 3 SOLUTION

 CHAPTER 3

 SYNTHETIC FIBRES AND PLASTICS

CHAPTER 3 SYNTHETIC FIBRES AND PLASTICS of CLASS 8 SCIENCE NCERT is here with complete solution of all the textbook questions of CHAPTER 3.All the NCERT solutions are framed in a systematic manner, according to the latest CBSE Class 8 science syllabus (2020-21).

After studying this  you will be able to understand the topics covered in the chapter thoroughly. It is noticed that many questions are directly asked in previous year class 8 examinations. In order to score good marks in the examination, students should study this material in-depth.

Here's the answer of textbook questions of CHAPTER 3 SYNTHETIC FIBRES AND PLASTICS.

Exercise Questions.

Q1. Explain why some fibres are called synthetic.

Ans. There are some fibres that are made by man using chemicals.These are called synthetic fibres. These are made up of small units that are joined together to form a long chains called POLYMER.

For example: Rayon,Nylon,etc

Q2. Mark (✓) the correct answer.

(1) Rayon is different from synthetic fibres because.

(a)It has a silk like apperance

(b) It is obtained from wood pulp

(c) Its fibre can also be woven like those of natural fibres.

Ans. It is obtained from wood pulp.

Q3. Fill ups:

(a) Synthetic fibres are also called________ 

 or_________ fibres.

(b) Synthetic fibres are synthesised from raw material called________

(c)like Synthetic fibres, plastic is also a_______

Ans 

(a)man made, artificial

(b) Petrochemical

(c) polymer

Q4.Give example which indicate that nylon fibres are very strong.

Ans. Nylon fibres are very strong as they are used for making seat belts,sleeping bags ,ropes used for climbing rocks and for making parachutes their  uses show that nylon fibres have high tensile strength.

Q5. Explain why plastic containers are favoured for storing food.

Ans. Plastic containers are favoured for storing food of their light weight ,low price and good strength.

Q6. Explain the difference between thermoplastic and thermosetting plastic.

Ans. THERMOPLASTIC :- Plastic which get deformed easily on heating and can bend easing on heating is known as Thermoplastic.

For example : PVC, and polythene.

THERMOSETTING PLASTIC:- There are some plastic which when moulded once,can not be softened while heating these are called thermosetting plastic.

For example: Bakelite and melamine.

Q7. Explain why the following are made of thermosetting plastic.

(a)Saucepan handles.  (b) Electric plugs/switches/plugboards.

Ans.

(a) Saucepan handles :-  Saucepan handles are made up of thermosetting plastic like Bakelite because this plastic do not get softened on heating and is a poor conductor also.

(b) Electric plugs/switches/plug boards:-  Thermosetting Plastic such as Bakelite is poor conductor of electricity Therefore they are used for making electric plugs/switches/plugboards.

Q8.Categorise the material of the following products into 'can be recycled'and 'can not be recycled'.

Telephone instruments, plastic toys,cooker handles, carry bags,ball point pens, plastic bowls, plastic covering on electrical wires,plastic chairs, electrical switches.

Ans. THINGS CAN BE RECYCLED:- 

Plastic toys, Plastic Chairs, Ball point pens , Plastic bowls, Plastic covering on electrical wires, Carry bags.

THINGS CAN NOT BE RECYCLED:-

Telephone instruments,cooker handles, electrical switches.

Q9.Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from Synthetic material? Advice Rana,giving your reason.

Ans. Rana should buy cotton shirts because cotton is a good absorber of water.It can soak the sweat coming out of our body and expose it to the environment. Thus,it helps evaporating the sweat by cooling our body 

Q10. Give examples to show that plastics are non corrosive in nature 

Ans.

Plastic are non corrosive (non reactive) Metals like iron get rusted when left exposed to moisture and air but plastics do not react with water and air.They are non corroded easily, That's why used to store various kind of materials including many chemicals.

Q11. Should the handle and bristles of our toothbrush be made if same material? Explain you answer.

Ans.

The handle and the bristle made up of different materials. The handles of toothbrush should b made up of hard and strong material while bristle should made up of soft and flexible material.

Q12. Avoid Plastic as far as possible. Comment on this advice,

Ans.

Plastic is non biodegradable is take several years to decompose it cause environmental pollution,in the process of burning it release lots of poisonous fumes  in the atmosphere cause air pollution. Polythene bag carelessly thrown in the garbage which can cause death for the animals like cows,dog,etc. So , instead of using plastic bags we should use cotton or jute bags for shopping.

Q13. Matching the terms  of column A correctly with the ohrasw given in Column B.

A                                B

(i) Polyster           (a) Prepared by using wood pulp

(ii) Teflon.            (b) Used for making parachutes   and stockings.

(iii)Rayon.             (c)Used to make non stick cook

                                     wares.

(iv) Nylon.              (d) Fabrics do not wrinkle

                                       easily.

Ans .

(i) Polyster  (d) Fabrics do not wrinkle

                                       easily.

(ii)Teflon.   (c)Used to make non stick cook

                                     wares.

(iii) Rayon  (a)Prepared by using wood pulp.

(iv) Nylon.   (b) Used for making parachutes  and stockings.

Q14. 'Manufacturing synthetic fibres is actually helping conservation of forests.' Comment.

Ans .

The natural fibres are obtained from plants and animals whereas,the synthetic fibres are obtained by chemical processing of petrochemical unlike natural fibres manufacturing of synthetic fibres do not required to cut the trees or hunting of animals.In this way manufacturing of synthetic fibres is actually helping conservation of forests.

Q15. Describe an activity to show the Thermoplastic is a poor conductor of electricity.

Ans 

In order to show that Thermoplastic is a poor conductor of electricity ,we will design a circuit. For that we need a bulb, Some wires,battery, apiece of metal and plastic pipe .After setting the experiment switch  on the current,you will observe that the bulb glow in the former case. In the latter case, the bulb does not glow. Hence a plastic pipe(which is Thermoplastic) is known to be poor conductor of electricity.

This is the complete solution of CHAPTER 3 SYNTHETIC FIBRES AND PLASTICS of NCERT SCIENCE of CLASS 8.This will helps students to  understand the topics completly.

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