1. Fibers And Plastics-
ü Based on source, fibers are of two types viz- natural fibers and synthetics fibers.
ü Natural fibers are those which are obtained from nature, for example cotton, which is a plant based fiber. Another examples are rubber (poly-isoprene) and jute.
ü Synthetic fibers are those which are synthesized in industries. They are man made by chemical processes, for example nylon, polyester etc.
ü Plastics are thick polymers. They are man made, synthesized in industries, for example polyethylene, polyvinyl chloride (PVC) etc.
Note: Synthetic Fibers, they dry up sooner, they are durable, they are cheaper, readily available and easy to maintain.
2. Rayon-
ü It is a man-made fiber obtained from a natural source called wood pulp.
ü It is also known as artificial silk.
ü It can be dyed in a wide variety of colors.
ü Rayon is mixed with cotton to make bed-sheets or mixed with wool to make carpets.
ü Rayon is cheap and durable.
3. Nylon-
ü It was the first man made fully synthetic fibre.
ü It was prepared from coal, water and air.
ü Nylon fibers are strong, elastic, light, lustrous and easy to wash.
ü It is used to make many items like socks, ropes, tents, toothbrushes, car seat belts, sleeping bags, curtains etc.
ü Nylon is also used for making parachutes and ropes for rock climbing.
4. Polyester-
ü It remains crisp, wrinkle-free and it is easy to wash.
ü It is quite suitable for making dress material.
ü Terylene can be drawn into very fine fibers that can be woven like yarn.
ü PET (polyethene terephthalate) is used for making bottles, utensils, films, wires and many other useful products.
ü Acrylic is also called artificial wool.
5. Plastics-
ü Plastics are man made polymers.
ü A polymer is made up by repeated linkage of many small units called as monomers.
ü These monomers can be linked either linear or as cross-linked.
ü Properties of plastic materials are-
n Plastics can be easily molded into any shape.
n Plastics can be recycled, reused, colored, melted, rolled into sheets or made into wires.
n Plastic material is cheap and durable.
6. Thermoplastic-
ü It is a plastic which gets deformed easily when it is heating.
ü It can be bent easily, for example- Polythene and PVC.
ü These are used for manufacturing toys, combs, car grills and various types of containers.
7. Thermosetting Plastics-
ü There are some plastics which when molded once cannot be softened by heating.
ü They are heat resistant and have thermodynamic stability.
ü Examples include Bakelite and melamine.
ü Bakelite is used for making electrical switches, handles of various utensils etc.
ü Melamine is used for making floor tiles, kitchenware etc.
8. Biodegradable And Non-biodegradable Material-
Table 01- Material and its degradation
ü The material which can be decomposed easily by naturally occurring microorganisms is called as biodegradable material.
ü Whereas the material which can not be decomposed by naturally occurring microorganisms is called as non-biodegradable material.
ü Natural fibers such as cotton and jute are easily biodegradable while synthetic polymers like polythene and polyesters are non-biodegradable.
Note: Petrochemicals are the synthetic fibers are prepared by a number of processes using raw materials of petroleum origin.
Note:
ü 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.
ü Special plastic cookware is used in microwave ovens for cooking food. In microwave ovens, the heat
ü cooks the food but does not affect the plastic vessel.
ü Teflon is a special plastic on which oil and water do not stick. It is used for non-stick coating on cookware.
ü Fire-proof plastics: Although synthetic fiber catches fire easily, it is interesting to know that the uniforms of firemen have coating of melamine plastic to make them flame resistant.
NCERT PRACTICE QUESTIONS
1. Explain why some fibers are called synthetic.
Ans.- Some fibers are called as synthetic fibers because these are man made fibers prepared by using chemical reactions. These are made up of small units that join together to form long chains. Example- nylon, rayon, acrylic, polyester etc.
2. Mark the correct answer.
Rayon is different from synthetic fibers because
(a) it has a silk-like appearance.
(b) it is obtained from wood pulp.
(c) its fibers can also be woven like those of natural fibers.
Ans.- (b) it is obtained from wood pulp.
3. Fill in the blanks with appropriate words.
(a) Synthetic fibres are also called __________ or __________ fibres.
(b) Synthetic fibres are synthesised from raw material called __________.
(c) Like synthetic fibres, plastic is also a __________
Ans.- (a) artificial or man made (b) petrochemicals. (c) polymer.
4. Give examples which indicate that nylon fibers are very strong.
Ans.- Parachutes and ropes of rock climbing are made of nylon; Nylon is used in making seat belts, fishing nets and tyre cords; Nylon is used in making sports accessories like rackets.
5. Explain why plastic containers are favored for storing food.
Ans.- It is because plastic is non-reactive and will not react with the ingredients of the food items.
6. Explain the difference between thermoplastic and thermosetting plastics.
Thermosetting plastic | Thermoplastic |
Cannot be bent, it will break if we attempt to bend thermosetting plastic | Thermoplastic can be bent easily |
On heating thermosetting plastics, it cannot be softened. This is the reason it cannot be reshaped once it is molded. | On heating the thermoplastics, it becomes softened and can be molded and reshaped easily. |
7. Explain why the following are made of thermosetting plastics.
(a) Saucepan handles (b) Electric plugs/switches/plug boards
Ans.- (a) Thermosetting plastics are used to make saucepan handles because they are bad conductors of heat and also on heating, these plastics do not get softened.
(b) Bakelite is a kind of thermosetting plastic which is a bad conductor of heat and electricity. Because of this property it is used for making electric plugs, switches, plug boards, etc.
8. 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.
Can Be Recycled | Cannot Be Recycled |
Plastic chairs | Cooker handles |
Plastic bowls | Electrical switches |
Plastic toys | telephone |
The plastic covering on electrical wires |
|
Carry bags |
|
Ballpoint pens |
|
9. Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.
Ans.- Rana should buy a cotton shirt for the summer and not a synthetic shirt. Cotton is a good absorber of water. So it can soak the sweat coming out of the body and expose it to the environment. Thus, it helps in evaporating the sweat and helps in cooling our body.
10. Give examples to show that plastics are noncorrosive in nature.
Ans.- Plastics are non-corrosive in nature, they do not react even if they come in contact with strong chemicals. For example, the cleaning chemicals that we use at home are stored in plastic bottles, instead of metal containers.
11. Should the handle and bristles of a tooth brush be made of the same material? Explain your answer
Ans.- The handle and bristle of a toothbrush should not be made of the same material as the handle of the toothbrush should be hard and strong while the bristle should be soft and flexible.
12. ‘Avoid plastics as far as possible’. Comment on this advice.
Ans.- We should avoid plastics as far as possible because plastics are non-biodegradable in nature. Once introduced into the environment they cause pollution. If burnt they release poisonous gases and the the plastic bags thrown in the garbage dumb are swallowed by animals choke their respiratory system and causes fatalities in animals.
13. Match the terms of column A correctly with the phrases given in column B
Ans.-
A | B |
(i) Polyester | (d) Fabrics do not wrinkle easily |
(ii) Teflon | (c) Used to make non-stick cookware |
(iii) Rayon | (a) Prepared by using wood pulp |
(iv) Nylon | (b) Used for making parachutes and stockings |
14. ‘Manufacturing synthetic fibers is actually helping conservation of forests’. Comment.
Ans.- The manufacturing of synthetic fibers is helpful in the conservation of forests because if we use natural fibers, the raw materials for them have to be derived from the plants, which require cutting off lots of trees. This proves to be helpful in the conservation of forests.
15. Describe an activity to show that thermoplastic is a poor conductor of electricity
Ans.- 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 (as shown in the figure below). After setting the experiment switch on the current, you will observe that 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.
Junior Science Topic - Fibers And Plastics. Chapter notes, video lectures, power point presentation and NCERT exercise solution. (Class 8, CBSE syllabus, chapter 03)
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