Synthetic Fibres and Plastics Class 8 Science Extra Questions and Answers

Synthetic Fibres and Plastics Class 8 Science Chapter 3 Extra Questions and Answers are provided here. We prepared these extra questions based on the latest NCERT Class 8 Science Book. CBSE Class 8 Science Chapter 3 Synthetic Fibres and Plastics Extra Questions will help you to properly understand a particular concept of the chapter.

Class 8 Science Chapter 3 Synthetic Fibres and Plastics Extra Questions

Very Short Answer Type Question

Question 1: Name the plastic whose sheets are used for packing liquids.

Answer: Polythene

Question 2: Name one naturally occurring polymer.

Answer: Cellulose

Question 3: Name the fibre used for making parachutes and ropes for rock climbing.

Answer: Nylon

Question 4: Which synthetic fiber is known as artificial silk?

Answer: Rayon fiber is known as artificial silk.

Question 5: Which is the first fully synthetic fibre?

Answer: Nylon is the first fully synthetic fibre.

Question 6: Write one disadvantage of synthetic fibre.

Answer: Synthetic fibres melt on heating.

Question 7: What are esters?

Answer: Esters are the chemicals which give fruits their smell.

Question 8: What are the 4 R in waste management?
Or
What are the 4 R’s principles of plastic?

Answer: 4 R principles mean Reduce, Reuse, Recycle and Recover.

Question 9: What are the advantages of nylon?

Answer: Nylon fibre is strong, elastic and light. It is lustrous and easy to wash.

Question 10: Write uses of bakelite.

Answer: It is used for making electrical switches, handles of various utensils, etc.

Question 11: Write uses of melamine.

Answer: It is used for making floor tiles, kitchenware and fabrics which resist fire.

Question 12: How is rayon different from synthetic fibres?

Answer: Rayon is different from synthetic fibres because it is obtained from a natural source, wood pulp.

Question 13: Give examples which indicate that nylon fibres are very strong.

Answer: Nylon fibres are very strong as it is used to make parachutes and ropes for rock climbing.

Question 14: What is polythene?

Answer: Polythene (Poly + ethene) is a type of plastic that is used for making commonly used polythene bags.

Question 15: Is plastic bag non-biodegradable? Why?

Answer: Plastic bag is non-biodegradable because it takes several years to degenerate.

Question 16: Can we store jams and pickles in plastic containers? Give reason.

Answer: We can store jams and pickles in plastic containers because plastics do not react with water and air and do not get corroded easily.

Question 17: Do all plastics have same type of arrangement of units?

Answer: All plastics do not have the same type of arrangement of units. In some it is linear, whereas in others it is cross-linked.

Question 18: Why nylon is called fully synthetic fibre?

Answer: Nylon is called fully synthetic fibre because it is prepared from coal, water and air.

Question 19: What is polyester?

Answer: Polyester (Poly+ ester) is actually made up of the repeating units of a chemical called an ester.

Question 20: Write one use of acrylic.

Answer: Acrylic is used as a substitute of natural wool for knitting sweaters, shawls, blankets etc.

Short Answer Type Questions

Question 1: Why is nylon used for making parachutes and ropes for rock climbing?

Answer: Nylon is used for making parachutes and ropes for rock climbing because nylon fibre is strong and can hold heavy weight.

Question 2: What is polymer?

Answer: Synthetic fibres and plastics, like natural fibres, are made of very large units called polymers. Polymers are made up of many smaller units.

Question 3: Define petrochemicals.

Answer: All the synthetic fibres are prepared by a number of processes using raw materials of petroleum origin, called petrochemicals.

Question 4: Why should we use a cotton carry bag or jute bag while going for shopping?

Answer: We should use cotton or jute bags while going for shopping in order to minimise the use of plastic bags.

Question 5: Why plastic articles are available in all shape and size?

Answer: Plastic articles are available in all possible shapes and sizes because plastic is easily mouldable i.e. can be shaped in any form.

Question 6: Why is Teflon used for nonstick coating on cookware?
Or
Which material is used for coating non-stick kitchen wares and why?

Answer: Teflon is used for nonstick coating on cookwares because it is a special plastic on which oil and water do not stick.

Question 7: Explain why plastic containers are favoured for storing food.

Answer: Plastic containers are favoured for storing food because of their light weight, lower price, good strength and easy handling.

Question 8: What is PET? Write its uses.

Answer: PET is a very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.

Question 9: Give the composition of Polycot and Polywool.

Answer: Polycot is a mixture of polyester and cotton.

Polywool is a mixture of polyester and wool.

Question 10: “Tin, aluminium and other metal can are considered non-biodegradable.” Give reason.

Answer: Tin, aluminium and other metal can are considered non-biodegradable because they approximately take 100 to 500 years to degenerate.

Question 11: Give two uses of rayon.

Answer:

It is mixed with cotton to make bed sheets.
It is mixed with wool to make carpets.

Question 12: Suggest some ways in which we can contribute towards reducing the use of plastic materials?

Answer: Ways to reduce use of plastic materials are

Avoid the use of plastics as far as possible.
Make use of bags made of cotton or jute when you go for shopping.

Question 13: Give examples to show that plastics are noncorrosive in nature.
Or
Why are the chemicals in the laboratory stored in plastic containers?
Or
Why are plastic containers used to store chemicals in labs?

Answer: Plastics do not react with water and air. They are not corroded easily. That is why they are used to store various kinds of material, including many chemicals.

Question 14: What type of cookware is used in microwave oven and why?

Answer: Special plastic cookware is used in microwave ovens for cooking food. In microwave ovens, the heat cooks the food but does not affect the plastic vessel.

Question 15: How is plastic useful in healthcare industry?

Answer: Plastics find extensive use in the health-care industry. Some examples of their use are the packaging of tablets, threads used for stitching wounds, syringes, doctors’ gloves and a number of medical instruments.

Question 16: Why is melamine used for making floor tiles, kitchenware and fabrics which resist fire?

Answer: Melamine is a versatile material. It resists fire and can tolerate heat better than other plastics. It is used for making floor tiles, kitchenware and fabrics which resist fire.

Question 17: Why electrical wires have plastic covering, and handles of screw drivers are made of plastic?

Ans. Plastics are poor conductors of heat and electricity. That is why electrical wires have plastic covering, and handles of screw drivers are made of plastic.

Question 18: Why should recycled plastic not be used for the storage of food?
Or
Why is recycled plastic not suitable for storage of food items?
Or
Can recycled plastics be used in food containers? Why or why not?

Answer: Most of the thermoplastics can be recycled. However, during recycling certain colouring agents are added. This limits its usage especially for storage of food.

Question 19: Why plastic finds such a variety of uses?

Answer: The fact is that plastic is easily mouldable i.e. can be shaped in any form. Plastic can be recycled, reused, coloured, melted, rolled into sheets or made into wires. That is why it finds such a variety of uses.

Question 20: Should the handle and bristles of a tooth brush be made of the same material? Explain your answer.

Answer: The handle and bristle of a toothbrush should not be made of same material as the handle of the toothbrush should be hard and strong while the bristle should be soft and flexible.

Question 21: List the characteristics of synthetic fibres which make them popular dress materials.
Or
What are characteristics of synthetic Fibres?
Or
Mention the general characteristics of synthetic plastics.

Answer: Synthetic fibres possess unique characteristics which make them popular dress materials. They dry up quickly, are durable, less expensive, readily available and easy to maintain.

Question 22: Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.

Answer: Rana should buy cotton shirts for summer because cotton absorbs sweats away from the body and helps eliminate moisture buildup between clothes and skin in order to keep the body dry.

Question 23: How is rayon made? Write two advantages of using rayon.
Or
What are the advantages of artificial silk over natural silk?

Answer: Rayon is obtained by chemical treatment of wood pulp.

Advantages of Rayon are:

It is cheaper than silk and can be woven like silk fibres.
It can also be dyed in a wide variety of colours.

Question 24: Explain why the following are made of thermosetting plastics.

(a) Saucepan handles

(b) Electric plugs/switches/plug boards

Answer: (a) Saucepan handles are made of thermosetting plastics because it is a poor conductor of heat.

(b) Electric plugs/switches/plug boards are made of thermosetting plastics because it is a poor conductor of heat and electricity.

Long Answer Type Questions

Question 1: Explain why some fibres are called synthetic.

Answer: Some fibres are called synthetic because they are made by human beings by chemical processing. Such fibre is made up of small units that join together to form long chains. Each small unit is actually a chemical substance.

Question 2: Give three advantages of polythene over natural materials.

Answer: Three advantages of polythene over natural materials are:

It is light, strong and durable.
It can be rolled into sheets.
It does not react with water and air.

Question 4: ‘Manufacturing synthetic fibres is actually helping conservation of forests’. Comment

Answer: Natural fibres are obtained from plants and animals, which means cutting off lots of trees. This leads to deforestation. But synthetic fibres are obtained by chemical processing of petrochemicals and hence help in conservation of forests.

Question 5: What properties of plastics make them so useful?

Answer: Characteristic properties of plastics as follows

Plastic is non-reactive
Plastic is light, strong and durable
Plastics are poor conductors

Question 6: Why is a plastic bucket preferred over an iron bucket?

Answer: Plastic bucket preferred over an iron bucket because

Plastic is non-reactive
Plastic is light, strong and durable
Plastics are poor conductors

Question 7: What are some uses of nylon?

Answer: Uses of Nylon

Nylon is used to make articles such as socks, ropes, tents, toothbrushes, car seat belts, sleeping bags, curtains etc.
It is also used for making parachutes and ropes for rock climbing.

Question 8: Why is acrylic fibre more popular than wool?

Answer: Acrylic fibre is more popular than wool because

Clothes made from acrylic are relatively cheaper.
They are available in a variety of colours.
Synthetic fibres are more durable.

Question 9: Name two polyester fabrics and write their uses.

Answer: Terylene is a popular polyester. It can be drawn into very fine fibres that can be woven like any other yarn.

PET is a very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.

Question 10: Why should we not wear synthetic clothes while working in in the kitchen or in a laboratory?

Answer: Synthetic fibres melt on heating. If the clothes catch fire, it can be disastrous. The fabric melts and sticks to the body of the person wearing it. We should, therefore, not wear synthetic clothes while working in in the kitchen or in a laboratory.

Question 11: Differentiate between natural and synthetic fibres.

Answer: Difference between natural and synthetic fibres

Natural Fibres	Synthetic Fibres
Natural fibres are obtained from plants and animals.	Synthetic fibres are made by human beings by chemical processing of petrochemicals.
Example: cotton, wool, silk, etc.	Example: rayon, nylon, polyester and acrylic

Question 12: “Even though plastics are very useful, they are not environment friendly.” Justify the statement.

Answer: Since plastic takes several years to decompose, it is not environment friendly. It causes environmental pollution. Besides, the burning process in the synthetic material is quite slow and it does not get completely burnt easily. In the process it releases lots of poisonous fumes into the atmosphere causing air pollution.

Question 13: ‘Avoid plastics as far as possible’. Comment on this advice.

Question 14: Suggest some ways to solve plastic pollution.
Or
How can pollution due to plastics be solved?

Answer: Ways to solve plastic pollution

Avoid the use of plastics as far as possible.
Make use of bags made of cotton or jute when you go for shopping.
The biodegradable and non-biodegradable wastes should be collected separately and disposed off separately.
Recycle the plastic waste.

Question 15: Explain the difference between the thermoplastic and thermosetting plastics.

Answer:

Thermoplastic plastics	Thermosetting plastics
1. There some plastic which gets deformed easily on heating and can be bent easily are known as thermoplastics plastics.	1. There are some plastics which when moulded once, cannot be softened by heating. These are called thermosetting plastics.
2. Example: polythene and PVC	2. Example: bakelite and melamine.

Question 16: Why we should not throw polybags in the water bodies or on the road?

Answer: We should not throw polybags in the water bodies or on the road because:

Cow while eating garbage waste food items swallow the polythene bags and wrappers of food. The plastic material chokes the respiratory system of these animals, or forms a lining in their stomachs and can be the cause of their death.
The polybags carelessly thrown here and there are responsible for clogging the drains, too.

Question 17: Categorise the materials of the following products into ‘can be recycled’ and ‘cannot be recycled’: Telephone instruments, plastic toys, cooker handles, carry bags, ball point pens, plastic bowls, plastic covering on electrical wires, plastic chairs, electrical switches.

Answer:

can be recycled	cannot be recycled
telephone instruments	plastic toys
cooker handles	carry bags
electrical switches	ball point pens
	plastic bowls
	plastic covering on electrical wires
	plastic chairs

Question 18: Describe an activity to show that thermoplastic is a poor conductor of electricity.

Answer: 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, a battery, a piece of metal and a plastic pipe. After switching on the current, the bulb glows in the former case. In the latter case, the bulb does not glow. Hence a plastic pipe (which is a thermoplastic) is shown to be a poor conductor of electricity.

Question 19: Differentiate between biodegradable and non-biodegradable materials.

Answer: Difference between biodegradable and non-biodegradable materials

Biodegradable materials	Non-biodegradable materials
A material which gets decomposed through natural processes, such as action by bacteria, is called biodegradable.	A material which is not easily decomposed by natural processes is termed as non-biodegradable.
Example: Peels of vegetable and fruits, leftover foodstuff, Paper, Cotton cloth, Wood, Woollen clothes etc.	Example: Tin, aluminium, and other metal cans, Plastic bags etc.

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