DAV Class 8 Science Solution Chapter 13 Synthetic Fibres and Plastics
DAV School Books Class 8 Science Solution Chapter 13 Synthetic Fibres and Plastics all Question Answer. DAV Class 8 13th Chapter Synthetic Fibres and Plastics full Chapter explanation by expert teacher.
DAV School Books Class 8 Science Solution Chapter 13 Synthetic Fibres and Plastics
A.) Fill in the blanks.
1.) ___________ and ___________ are examples of natural fibres.
2.) The simplest molecule of a polymer is known as a ___________.
3.) Rayon is also known as a ___________ fibre.
4.) Nylon is a ___________ fibre.
5.) ___________ plastics cannot be remoulded again on heating.
Answer: (1) Cotton, wool (2) monomer (3) regenerated (4) synthetic (5) Thermosetting
B.) Write True or False for the following statements.
1.) Natural fibres are highly resistant to the effects of chemicals like acids and alkalis.
2.) Synthetic fibres absorb very little water.
3.) Thermoplastics can be easily remoulded on heating.
4.) The plastic, used for insulating electrical wires, is teflon.
5.) All types of plastics are biodegradable.
Answer: (1) False, synthetic fibres are resistant to effects of chemicals like acids and alkalis not natural fibres (2) True (3) True (4) True (5) False, plastics are non-bidegradable.
C.) Tick the correct option.
1.) The correct choice, for the box, in the following sequence, is thermoplastic: PVC; thermosetting plastic: ?
Answer: bakelite.
2.) Which of the following is also known as the wonder polymer’?
Answer: nylon.
3.) A highly durable synthetic fibre, used for making parachutes and ropes for rock climbing and fishing nets, is-
Answer: nylon.
4.) Which of the following is NOT one of the characteristics of synthetic fibres?
Answer: biodegradable.
5.) Melamine is a thermosetting plastic, for it one can say that-
Answer: it has a cross-linked arrangement of molecules.
6.) Which of the following is a correct statement about synthetic plastics?
Answer: synthetic plastics have quite high tensile strengths.
D.) Answer the following questions in brief.
1.) Define the term synthetic fibres.
Answer: Synthetic fibres are man-made, chemically produced fibres that are not found in nature. The synthetic fibres polyester, rayon, acetate, and nylon are a few examples. They are used to create furnishings, blankets, carpets, and clothing, among other things.
2.) Write two uses of rayon.
Answer: two uses of rayon are:
- Due to its silky texture, drape, and durability, rayon is frequently used to produce apparel items including shirts, trousers, costumes, and blouses.
- Because rayon can simulate the feel and appearance of natural fibres like cotton and silk, it is also employed to produce upholstery textiles, curtains, as well as other home décor products.
3.) Name two to three articles that can be made from nylon.
Answer: Carpets, clothes, and toothbrushes.
4.) Why are clothes made from synthetic fibres uncomfortable in summer?
Answer: Typically, synthetic fibres are not breathable, which prevents air from reaching the skin. In hot and humid areas, this may indicate that the user is feeling uncomfortable amounts of heat. Additionally, synthetic fabrics have a propensity to hold onto moisture rather than wick it from the skin, which can increase body temperature.
5.) Give two examples each of thermoplastics and thermosetting plastics.
Answer:
Thermoplastics: Polythene and PVC.
Thermosetting plastics: Melamine and Bakelite.
E.) Answer the following questions.
1.) How is a ‘regenerated fibre’ different from a true synthetic fibre? Give one example of each of these two types of fibres.
Answer: A fibre that is made from previously processed raw materials is known as regenerated fibre. Acetate and rayon are two examples of regenerated fibres. A truly synthetic fibre is one that is created through a chemical process from unprocessed basic resources, including coal and oil. The synthetic fibres nylon and polyester are examples of.
2.) Why do clothes made of nylon last longer?
Answer: Nylon is an artificial material that resists shrinking, fading, and tearing, thus clothes made of it last longer. Additionally, it is lightweight, strong, and simple to clean, which makes it ideal for prolonged use.
3.) Write two points of differences between thermosetting plastics and thermoplastics.
Answer: The difference between them are as follows:
- While thermoplastics can soften and be remoulded when heated, thermosetting plastics congeal by becoming hard when heated.
- Due to their inability to soften and change shape when heated, thermosetting polymers are more brittle and rigid than thermoplastics.
4.) State any three advantages of synthetic fibres.
Answer: The advantages are as follows:
- In comparison to natural fibres, synthetic fibres are much more durable and have a longer lifespan.
- Natural fibres are typically more expensive than synthetic fibres, making synthetic fibres a more affordable option.
- Synthetic fibres have a wide range of applications since they can be created in a variety of textures, sizes, and shapes.
5.) Give your views on the following: ‘Excessive use of plastics is a threat to environment.’
Answer: Plastics are undoubtedly harmful to the environment when used excessively. Since plastics do not really break down for hundreds of years, they remain in the environment, cluttering landfills and contaminating the oceans. This poses a serious risk to wildlife since it allows them to become tangled in plastic waste, consume it, or possibly starve to death from a blocked digestive tract. Additionally, the manufacture of plastics sends harmful chemicals into the environment, which fuels global warming. As a result, it’s critical that we use less plastic and invest in sustainable alternatives.
6.) Why is bakelite a good choice for making electrical switches and handles of cooking utensils?
Answer: Due to its extreme durability and resistance to heat, bakelite is the perfect material for producing electrical switches and the handles of cooking utensils. It has strong electrical insulating qualities, is non-conductive, and does not corrode. Additionally, it is inexpensive to create and lightweight, flexible, and easy to shape.
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