Class 8 Science Question Answers - Synthetic Fibres and Plastics (Old Syllabus)

Q1. Differentiate between natural and artificial fibres.

Natural Fibres	Synthetic Fibres
Fibres obtained from plants or animals. Expensive. Aluminium They do not dry up quickly and are less durable Example: Cotton, Silk, Wool	Fibres made by human beings. Cheaper than natural fibres. They dry up quickly and are durable. Example: Rayon, Nylon, etc.

Q2. Define polymer and give example of a polymer occurring in nature.

Synthetic fibres and plastics are made up of very large units called polymers, and polymers are made up of many smaller units. For example cotton is a polymer made up of cellulose and cellulose is made from a large number of glucose units.

Q3. What are the advantages of artificial silk over natural silk?

Advantages of artificial silk over natural silk are:

• Artificial silk or rayon is cheaper than silk,
• It can be dyed in a variety of colours
• It can be used to make bed sheets on mixing with cotton, and on mixing with wool can be used to make carpets.

Q4. Explain the first ‘’fully synthetic fibre’’.

The first fully synthetic fibre was nylon. It was prepared from coal, water and air. It is very strong, elastic and light, very easy to wash and is used for making variety of things like socks, ropes, bags, curtains, parachutes etc.

Q5. Why nylon fibre became popular for making clothes?

The first fully synthetic fibre was nylon. It was prepared from coal, water and air. It is very strong, elastic and light, it is very easy to wash and used for making variety of things like socks, ropes, bags, curtains, parachutes etc.

Q6. Why nylon is used for making parachutes and ropes for rock climbing?

Nylon thread is very strong infact it is stronger than steel wire, because of this property of nylon it is used for making parachutes and ropes for rock climbing.

Q7. State the unique characteristic of polyester fabric and is applications

Polyester fabrics do not get wrinkled easily and it remains crisp and can be washed easily than any other fabrics. Thus it is used to make dress, shirts etc. PET is one of the familiar form of polyester that is used to make bottles, utensils, wires and many other things

Q8. Name two polyester fabrics and their uses.

Terylene and PET are two widely used polyester fabrics. Terylene is used to make very fine yarn by which various dress materials are made. PET is one of the familiar form of polyester that is used to make bottles, utensils, wires and many other things

Q9. Name and explain a fibre which appears to resemble wool.

Acrylic fabric resembles wool, it is cheaper than wool and available is variety of colours. It is also more durable than wools

Q10. State the behaviour of natural fibre and synthetic fibre on burning.

On burning a natural fibre while on burning a synthetic fibre the fabric melts rapidly and in the case of synthetic clothes it sticks to the body of the person wearing it and cause severe burn to that person, it is totally disastrous.

Q11. Why we should avoid polyester clothes while working in the kitchen?

Synthetic clothes like polyesters on burning, sticks to the body of person wearing it and cause severe burn to that person, it is totally disastrous.

Q12. State the characteristics of synthetic fibre because of which it is used as dress materials.

Characteristics of Synthetic fibres are:

• Less expensive than natural fibres
• Strong and long-lasting
• Easily available
• Easy to maintain
• Dry up quickly

Q13. Do all plastics have the same type of arrangement of units?

No, all plastics do not have the same type of arrangement of units. In some plastics, there are linear arrangement of units while in others there are cross-linked arrangement of units.

Q14. State some of the characteristics of plastics because of which it is used for making various articles.

Characteristics of Plastics are:

• Light-weighted
• Cheaper than metals
• Strong and long-lasting
• Easy to handle
• Non-reactive: they do not react with water or air, and do not get corroded easily
• Plastics can be moulded into different shapes and sizes
• They are easily mouldable and can be shaped in any form to make different articles.
• They are poor conductors of heat and electricity.
• Thus they are used on large scale in industries and for making household articles.

Q15. What are plastics and its different types?

Plastics are synthetic or semi-synthetic organic solids that are mouldable. Units of some plastics have linear arrangements while some plastics are formed by the cross-linked arrangement of their units. Thus, plastic is used in making toys, suitcase, bags, cabinets, brush, chairs, tables, and many other countless items. Polythene is one of the most famous types of plastic, which is used in the manufacturing of carry bags.
Different types of plastics are:

• Thermoplastic
• Thermosetting

Q16. Why handles of screw drivers are made of plastics?

Handles of screw drivers are made of plastics because plastics are poor conductors of heat and electricity.

Q17. State some of the uses of plastics in the health care industry. 

Plastics are used in the healthcare industry for the following purposes:

• Packaging of tablets
• For making threads used for stitching wounds
• For making syringes
• Making gloves used by doctors
• For making many medical instruments

Q18. What type of cookware is used in the microwave oven and why?

Special plastic cookware is used in microwave oven for cooking food, such that inside the oven the heat cooks food but does not affect the plastic container containing food items to be cooked.

Q19. Identify whether the following wastes are biodegradable or non-biodegradable?

Pape
Aluminium
Plastic bags
Cotton clothes

• Biodegradable
• Non- biodegradable
• Non- biodegradable
• Biodegradable

Q20. What do you mean by environment friendly?

Products or articles that do not cause environmental pollution, and get burnt completely with releasing less poisonous fumes into the atmosphere are called environmental friendly products. They cause less harm to the environment and are thus called as eco- friendly products.

Q21. Why we should not throw polybags in the water bodies or on the road?

We should not throw polybags in the water bodies or on the road because animals like a cow while eating garbage waste food items swallow the polythene bags and food wrappers, the plastic materials chokes the respiratory system of these animals and form a lining in their stomachs and may cause the death of these animals.

Q22. State some of the ways to reduce the use of plastic bags in our day to day life.

Ways to reduce the use of plastic bags in our day to day life

• Avoid the use of plastics as far as possible.
• Use bags made from cotton or jute while going shopping.
• Try to recycle plastic wastes by returning them back to your grocery shop for recycling, and by using them as garbage bag liners.
• We can urge plastic manufacturers to develop biodegradable plastic.
• We can urge our legislators to ban plastic in children's toys and food and beverage containers.

Q23. What do you mean by the "4R principle" to develop environment friendly habits? 

The "4R principle" to develop environment friendly habits:

• Reduce
• Reuse
• Recycle
• Recover

Q24. Write short notes on plastics and the environment.

Plastic is polymers like synthetic fibres, it is non-eco-friendly as it takes several years to decompose and it causes environmental pollution. When it burns it releases lot of poisonous fumes, and harmful gases into the atmosphere causing air pollution.

Q25. Explain the differences between thermoplastics and thermosetting plastics.

Thermoplastics	Thermosetting plastics
Plastics that can be bend easily on heating and deformed easily on heating. Example: polythene and PVC Used for manufacturing toys, combs, etc	Plastics which when moulded once can’t be softened by heating. Example: Bakelite, melamine Used for manufacturing electrical switches, floor tiles, kitchenware etc.

Q26. Neha want to buy a shirt for summer, should she buy shirt made from synthetic fibre or cotton fibre and why?

She should purchase cotton clothes for summer because it is very light fabric, easy to wear and air flow process is also good in cotton clothes so it keeps body cool during summer season.

Q27. Give some examples illustrating the fact that plastics are non-corrosive in nature. 

Following examples show that plastics are non-corrosive in nature

• They are used to store chemicals in laboratories as they don’t react with chemicals or other items in the laboratory.
• Plastic does not decompose even when left in the open for a long period.
• Plastic does not react even with air and water and so it dies not get rusted.
• They are used to store all types of food, as plastic does not react to materials stored in it.

Q28. State the source of the following fibres
a. Cotton, b. Rayon, c. Nylon

a. Plants, b. Wood pulp, c. coal water and air.

Q29. What is Terylene?

Terylene is an artificial textile fibre made from polyester, it is used to make light, crease-resistant clothing, bed linen, and sails.