NCERT Class 8 Science Chapter 3 - Synthetic Fibres and Plastics Extra Questions

Chapter 3 - Synthetic Fibres and Plastics Extra Questions

Fill in the blanks
1. Clothes we wear are made up of thin strands called
fibres.
2.
Polymers are made up of small repeating units, joined together through bonds in linear pattern.
3. The another of artificial silk is
rayon.
4. The full form of 4R’s is
Reduce, Reuse, Recycle, Recover.
5. Synthetic fibres do not absorb much
water.
6. Synthetic fibres melt on
heating.

Answer the following questions
7. Name some natural fibres.
Answer:
Cotton, Silk, Wool etc

8. Name some artificial fibres.
Answer:
Nylon, terylene, PET, acrylic, etc.

9. Which fibre is known as artificial silk?
Answer:
Rayon

10. What is ester?
Answer:
Esters are the chemicals which give fruits their smell.

11. What is the full form of PVC?
Answer:
Polyvinyl Chloride

12. What is full form of 4R’s?
Answer:
4R’s stands for Reduce, Reuse, Recycle and Recover.

13. Name a synthetic fibre which is polyamide.
Answer:
Nylon is a synthetic fibre which is polyamide.

14. What are polymers?
Answer:
Polymers are compounds that are made up of same, small repeating units, joined together through bonds in a linear pattern.

15. What is cellulose?
Answer:
Cellulose is a polymer made up of large number of glucose units.

16. List properties of rayon.
Answer:

• Easily dyed and wooven into cloth
• Drapes well
• Lustrous in appearance
• Good absorbent of sweat

17. Write some advantages of synthetic fibres.
Answer:
Some advantages of synthetic fibres are:
• Synthetic fibres are strong so they can take up heavy things easily.
• Synthetic fibres retain their original shape so it's easy to wash and wear.
• Can easily be stretched out.
• Synthetic fibres are generally soft so they are used in clothing materials.
• Varieties of colours are available as they are manufactured.
• Clothes made by synthetic fibres are generally cheaper than those made by natural fibres.

18. List all the properties of plastics.
Answer:
The properties of plastics are:
• Resist corrosion
• Resist high temperatures
• Insulate heat and electricity
• Elastic
• Thermoplastics can be recycled
• Not reactive to chemicals and water
• Water resistant
• Soft when hot

19. Why is it advised not to wear synthetic clothes while working in a laboratory or working with fire in the kitchen?
Answer:
It advised not to wear synthetic clothes while working in a laboratory or working with fire in the kitchen because they melt on heating. If the cloth catches fire it can be very disastrous. The fabric melts and sticks to the body of the person wearing it.

Multiple Choice Questions
20. The basic component of plant fibres is
a) protein
b) cellulose
c) starch
d) none of these
Answer:
b) cellulose

21. Which of the following is known as artificial silk?
a) Nylon
b) Rayon
c) Polyester
d) Silk
Answer:
b) Rayon

22. Which fibre is used as artificial wool?
a) Acrylic
b) Rayon
c) Nylon
d) Cotton
Answer:
a) Acrylic

22. Polymers are made up of small units called
a) layers
b) molecules
c) cells
d) monomers
Answer:
d) monomers

23. Which of the following polyester is made by blending polyester and cotton?
a) Terrywool
b) Terrycot
c) Terrysilk
d) PET
Answer:
b) Terrycot

24. Which of the following is a thermoplastic?
a) Bakelite
b) Melamine
c) PVC
d) All of these
Answer:
c) PVC

25. Plastics that retain their plasticity on repeated heating are called
a) thermosetting plastics
b) thermoplastics
c) thermal plastics
d) none of these
Answer:
b) thermoplastics

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