RBSE Class 8 Science Important Questions Chapter 3 Synthetic Fibres and Plastics

Rajasthan Board RBSE Class 8 Science Important Questions Chapter 3 Synthetic Fibres and Plastics Questions and Answers.

RBSE Class 8 Science Chapter 3 Important Questions Synthetic Fibres and Plastics

Objective Questions

Question 1.    
Polymer of ester is
(a) Rayon    
(b) Nylon
(c) Polyester    
(d) Acrylic
Answer:
(c) Polyester 

Question 2.    
Example of fire resistant plastic is
(a) Melamine    
(b) Polythene
(c) PVC    
(d) Nichrome
Answer:
(a) Melamine    

Question 3.    
Most interfering substance in water drainage system is
(a) Agriculture waste
(b) Plastic waste
(c) Animal waste
(d) Radioactive waste
Answer:
(b) Plastic waste

Question 4.    
Which of the following is non - biodegradable substance?
(a) Paper    
(b) Cotton cloth
(c) Plastic bags    
(d) wood
Answer:
(c) Plastic bags

Question 5.    
Specific plastic on which oil and water do not stick, is
(a) Rayon    
(b) PVC
(c) Melamine    
(d) Teflon
Answer:
(d) Teflon

Fill in the blanks 
1. Nylon is ......................... made fibre.
Answer:
man

2. Bakelite is ......................... of heat and electricity.
Answer:
bad conductor

3 ......................... takes several years to decompose.
Answer:
Plastic

4. As a responsible citizen ......................... theory should remember.
Answer:
5R

True/False

Mark the True (T) or False (F) for the following statements

1. Cotton is a polymer, called cellulose.
Answer:
True

2. Rayon is a natural fibre.
Answer:
False

3. Melamine is a multi useful substance.
Answer:
True

4. Teflon is a specific plastic on which oil and water do not stick.
Answer:
True

5. Plastic is not harmful for environment.
Answer:
False

6. We should avoid the use of plastic as far as possible.
Answer:
True

Match the words given in 'Column-A' with 'Column-B'

Question 1.

Column-A	Column-B
(i) Cotton	(a) Wood pulp
(ii) Rayon	(b) Polyester
(iii) Terylene	(c) Cellulose
(iv) PVC	(d) Polythene

Answer:

Column-A	Column-B
(i) Cotton	(c) Cellulose
(ii) Rayon	(a) Wood pulp
(iii) Terylene	(b) Polyester
(iv) PVC	(d) Polythene

Question 2.

Column-A	Column-B
(i) Clothes	(a) PVC
(ii) Toys	(b) Melamine
(iii) Utencils	(c) Terylene
(iv) Electric switch	(d) Bakelite

Answer:

Column-A	Column-B
(i) Clothes	(c) Terylene
(ii) Toys	(a) PVC
(iii) Utencils	(b)Melamine
(iv) Electric switch	(d) Bakelite

Question 3.

Column-A	Column-B
(i) Nylon	(a) Poly + ester
(ii) Terylene	(b) Poly + ethene
(iii) Polycot	(c) Polyster + cotton
(iv) Melamine	(d)Coal + water + air

Answer:

Column-A	Column-B
(i) Nylon	(d)Coal + water + air
(ii) Terylene	(a) Poly + ester
(iii) Polycot	(c) Polyster + cotton
(iv) Melamine	(b) Poly + ethene

Question 4.

Column-A	Column-B
(i) Thermosetting	(a) plastic
(ii) Biodegradable	(b) Nylon
(iii) Thermoplastics	(c) Melamine
(iv)Strong and elastic	(d) Polythene

Answer:

Column-A	Column-B
(i) Thermosetting	(c) Melamine
(ii) Biodegradable	(a) plastic
(iii) Thermoplastics	(d) Polythene
(iv)Strong and elastic	(b) Nylon

Very Short Answer Type Questions

Question 1. 
What is cotton?
Answer:
Cotton is a polymer called cellulose, which is formed by large number of glucose units.

Question 2. 
What is Rayon?
Answer:
Rayon is obtained from wood pulp which is a natural source. This is a man made fibre.

Question 3. 
Which substances were used in the preparation of Nylon?
Answer:
Nylon was prepared from coal, water and air. It was the first fully synthetic fibre. 

Question 4. 
Which artificial fibre is used for the formation of parachutes and ropes?
Answer:
Nylon is used for the formation of parachutes and ropes because this is very strong fibre.

Question 5. 
Mohan has a shirt which does not wrinkle. Which fibre is used in the preparation of this shirt?
Answer:
This shirt is prepared by polyester which does not wrinkle.

Question 6. 
Give two examples of non biodegradable substances.
Answer:

• Plastic 
• Aluminium container.

Question 7. 
Give two examples of thermoplastic. 
Answer:

• Polythene 
• PVC 

Question 8. 
The clothes of firemen are fire resistant. Which substance is used to make these cloths. 
Answer:
The clothes of firemen have a layer of melamine which makes them fire resistant.

Short Answer Type Questions

Question 1. 
What is thermosetting plastic. Write its two examples.
Answer:
Thermosetting plastic:
The plastic when moulded once, can not be softened by heating is called thermosetting plastic. 
Example:

• Bakelite 
• Melamine.

Question 2. 
Classify the following substances in biodegradable and non - biodegradable nature, on the basis of their degenerating property :
(i) Peels of vegetable and fruits
(ii) Pieces of glass
(iii) Tin can
(iv) Paper
(v) Plastic
(vi) Wood. 
Answer:

Biodegradable	Non-biodegradable
(i) Peels of vegetable and fruits	(ii) Pieces of glass
(iv) Paper	(iii) Tin can
(vi) Wood	(v) Plastic

Question 3. 
What is the meaning of polymer? Explain.
Or
What is polymer? Give two examples of plant polymers.
Answer:
Polymer means several units, so polymer is a substance which is formed by the repeatation of several small units. Cotton present in nature is also a polymer called cellulose, which is formed by several units of glucose. Cotton (cellulose) and starch are two plant polymers.

Question 4. 
How rayon is prepared? Write the use of rayon.
Or
Name four Synthetic fibres and explain one of these in brief.
Answer:
Four synthetic fibres are as follows: 

• Rayon 
• Nylon 
• Polyster and 
• Acrylic.

Rayon: The fibre of rayon is like silk and it is obtained by chemical treatment of wood pulp. This is a man made fibre.
Uses: Rayon is cheaper than silk but it can be woven like silk fibres. It can also be dyed in a wide variety of colours. Rayon is mixed with cotton to make bed sheets or mixed with wool to make carpets.

Question 5. 
Write the main characteristics of Nylon?
Answer:

• Nylon fibre is strong, elastic and light. 
• Soaks less water so it is easy to wash and dry the Nylon. 
• Clothes of Nylon are wrinkle resistant and durable for a long time. 

Question 6. 
Write the important uses of Nylon. 
Answer:
Nylon is used to make articles which require very strong fibres:

• Nylon fibres are used to make fish net, parachute cloths, ropes, socks and other cloths.
• Nylon fibres are used to make tooth brushes, car seat, belts, sleeping bags and curtains.
• Nylon thread is stronger than a steel wire so it is used to make ropes for rock climbing. 

Question 7. 
Write the main characteristics of polyester fibres.
Answer:
Main characteristics of polyester fibres are

• Polyester fibres are very strong so the clothes made from polyester are durable for a long time.
• Polyester fibres soaks less water so the clothes of polyester dry early after washing.
• Polyester fibres have permanent crease.
• There is no effect of insects and simple chemicals on polyester fibres.
• Polyester fibres are very light and thin.

Question 8. 
Write the important uses of polyester. 
Answer:
uses of polyester are:
1. PET, a very familiar form of polyester is used for making bottles, utensils, films, wires and many other useful products are used in our daily life.

2. Polycot is a mixture of polyester and cotton by which clothes are formed.
3. Polywool is a mixture of polyester and wool, used for making woollen clothes.

Question 9. 
What is Acrylic ? Write the use of it. 
Answer:
Acrylic is also a synthetic fibre which looks like wool. Cloths formed by acrylic is cheaper and durable.
Uses of Acrylic:
Acrylic is used for making clothes used in winter like shawls, blankets, sweaters, etc. Acrylic fibres are available in wide range of colours and cloths formed by these are more durable and within the reach. 

Question 10. 
Write the main differences in natural fibres and synthetic fibres.
Answer:

Natural fibres (Cotton, Wool and Silk)	Synthetic fibres (Nylon and Polyester)
1. Natural fibres are less strong so the clothes formed by these fibres are less durable and tom out early.	1. Synthetic fibres are very strong so the clothes of these fibres are durable for a long time.
2. Natural fibres soak more water so clothes of these take more time for drying after washing.	2. Synthetic fibres soak less water so clothes formed by these take less time for drying after washing.
3. Clothes of natural fibres are spoiled due to effect of insects and simple chemicals.	3. There is no effect of insects and simple chemicals on clothes of synthetic fibres

Question 11. 
What is plastic ? Write the properties of plastic?
Answer:
Plastic is a polymer. But the arrangement of simple units in all types of plastic is not same. Some have linear arrangements whereas others have cross linked arrangements. 
Properties: 

• Plastic is easily mouldable i.e. can be shaped in any form. 
• Plastic can be recycled so it can be reused.
• It can be coloured and melted.
• Plastic is bad conductor of electricity.

Question 12. 
Write the types of plastics with two examples of each.
Answer:
Plastics are of two types: 

1. Thermo - plastics 
2. Thermosetting plastics.

Examples of thermoplastics are polythene and PVC whereas bakelite and melamine are thermosetting plastics.

Question 13. 
Is plastic bad conductor of heat and electricity? Explain.
Answer:
Plastic is bad conductor of heat and electricity. This is the reason:
why electrical wires have plastic covering and handles of frying pans are made of plastic. The electrical wires having plastic covering show no current when touching them and the handles of frying pans become less hot after a long time.    .

Question 14. 
What is meant by biodegradable and non - biodegradable.
Answer:
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. 

Question 15. 
How plastic waste creates environUiental pollution? Explain.
Answer:
Since plastic takes several years to decompose so it causes environmental problem. The burning process of plastic material is quite slow and this process releases lots of poisonous gases which cause environmental pollution.

Question 16. 
What are the main points of fibre - wise?    
Answer:
Main points of fibrewise are as follows

• Do not throw the plastic bags on road or in ponds after use.
• Make use of bags made of cotton or jute when you go for shopping.
• Use of plastic materials should be minimum and use utensils of steel in place of plastics. 

Question 17. 
What is 5R theory?
Answer:
5R theory is given to develop the environment friendly habits in the man. This is as follows :

1. R (Reduce) : Decrease the use of plastic
2. R (Reuse) : Use again
3. R (Recycle) : Recycle the plastic waste
4. R (Recover): Again obtain the plastic from waste
5. R (Refuse) : Do not use.

Essay Type Questions

Question 1. 
Describe the characteristic properties of plastic.
Answer:
Characteristic properties of plastic are as follows:
1. Plastic is non - reactive:
Plastics do not react with water and air. They are not corrode easily. That is why they are used to store various kinds of material including many chemicals.

2. Plastic is light, strong and durable:
Plastic is very light, strong, durable and can be moulded into different shapes and sizes. Plastics are generally cheaper than metals so they are widely used in industry and for household articles.

3. Plastics are bad conductor of heat and electricity:
Plastics are bad conductor of heat and electricity. That is why electrical wires have plastic coverings and handles of frying pans are made of plastic.

Question 2. 
Write the important uses of plastic in different fields.
Answer:
The uses of plastic in different fields are as follows:
1. In the field of health - care industry:
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.

2. In the cooking of food: 
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. Teflon is a special plastic on which oil and water do not stick. It is used for nonstick coating on cookwares.

3. Fire - proof plastics: 
Although synthetic fibre catches fire easily, it is interesting to know that the uniforms of firemen have coating of melamine plastic to make them flame resistant.

Question 3. 
Write the biodegradable and non - biodegradable substances in the form of table.
Answer:

Types of waste	Approximate time taken to degenerate	Nature of material
Peels of vegetable and fruits, left over foodstuff, etc.	1-2 weeks	Biodegradable
Paper	10-30 days	Biodegradable
Cotton cloth	2-5 months	Biodegradable
Wood	10-15 years	Biodegradable
Woolen clothes	About one year	Biodegradable
Tin, aluminium and other metal cans	100-500 years	Non-biodegradable
Plastic bags	Several years	Non-biodegradable

Question 4. 
Why the disposal of  plastic waste is not easy? How plastic is harmful for environment?
Answer:
Difficulty in disposal of plastic waste and harm to the environment:
Now a days polythene and plastics are widely used. Synthetic plastic and polythene are non - biodegradable so become danger for ecosystem up to several years. These are decomposed in thousands of years so environment is polluted. The burning process of synthetic material is also quite slow so it takes long time and releases lots of poisonous gases in the atmosphere.

Use of polythene is a big problem in urban environment. The polybags carelessly thrown in rivers, ponds and open spaces after use are responsible for clogging the drains and cause the growth of many types of bacteria. The dirty water and waste are spread out on roads, streets and open spaces and blocks the transport system. So the urban life becomes like hell. Hence use of plastic is very harmful for the environment.