03. Synthetic Fibers and Plastics
Exercises
01. Explain why some fibres are called
synthetic.
Ans. The fibers made by a man are known as man made or Synthetic or Artificial
fibers, i.e. Nylon, polyester, tricot etc.
02. Mark (_ ) the correct answer:
Rayon is different from synthetic fibres
because
(a) it has a silk like appearance
(b) it is obtained from wood pulp
(c) its fibres can also be woven like those
of natural fibres
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) man-made
or artificial (b) Answer: petrochemicals (c) polymer
04. Give examples which indicate that nylon
fibres are very strong.
Ans. Nylon
is used in making ropes which are used for heavy-duty purposes; like
mountaineering and in Paragliding parachute. These examples show that nylon
fibres are very strong.
05. Explain why plastic containers are
favoured for storing food.
Ans. Plastic containers are favoured for
storing food because: → The plastics do not react with the food stored in them.
→ The plastics are light weight and are strong. → They are easy to handle and
safe. → They are cheap and ductile.
06. Explain the difference between the
thermoplastic and thermosetting plastics.
Ans.
Thermosetting plastic
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Thermoplastic
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Thermosetting plastic cannot be bent easily. It
may break when forced to bend.
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Thermoplastic can be bent easily.
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Thermosetting plastic cannot be softened by
heating. Thus, it cannot be reshaped once moulded.
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Thermoplastic can be softened easily by heating.
Thus, it can be reshaped.
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07. Explain why the following are made of
thermosetting plastics.
(a) Saucepan handles
(b) Electric plugs/switches/plug boards
Ans. (a) The
handles of saucepans are made of thermosetting plastics because it is a bad
conductor of heat and so, do not get heated up while cooking. So it is easier
to handle the utensil while cooking. Moreover it does not get softened due to
heat.
(b) Electrical plugs, switches and plug-boards are
made up of thermosetting plastics because it is a bad conductor of
electricity. It does not allow the electric current to pass through it, thus
safe in using in electric appliances.
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08. 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.
Ans.
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09. 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 shirts made from cotton. This is because cotton is a good absorber
of water. It can soak the sweat coming out of our body and expose it to the
environment. The sweat would give
cooling effect to the body, due to evaporation, Thus
a cotton shirt would be much more comfortable than a shirt made from
synthetic fibre. Hence, Rana should buy cotton shirts for summer.
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10. Give examples to show that plastics are
noncorrosive in nature.
Ans. Plastics are noncorrosive in
nature because it is a nonreactive substance. It does not react with air,
water, minerals and other chemicals. So in present days most of the
containers, utensils, Sanitary cleaners , Pickles and laboratory equipments are
made with plastics to store food, chemicals etc.
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11. Should the handle and bristles of a
tooth brush be made of the same material? Explain your answer.
Ans. No. The handle and bristles of
a tooth brush should be made of different materials. The handle of a
toothbrush should be hard, strong and
flexible while the bristles should be soft and flexible yet durable; because the bristles should not damage
the tooth or gum but should last longer.
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12.
‘Avoid plastics as far as possible’. Comment on this advice.
Ans. Plastic
has gained popularity because of its versatile nature and unmatched popularity. Plastics
are non-biodegradable materials. They take several years to decompose. Many forms of plastic cannot be recycled. This is
creating a burden on the environment around us. It is
not environment friendly and causes environment pollution. Also burning
process of plastics is quite slow. In the process of burning it releases lots
of poisonous gas into the atmosphere causing air pollution. Some plastics
can’t be recycled and so, it is very difficult to finally dispose off such
materials. Polythene bags, carelessly thrown in an eating garbage can cause
death for the animals like – cows, dogs etc or sometimes even become a cause
for clogging of the drains. Hence, the statement, “Avoid
plastics as far as possible” is a correct statement.
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13. Match the terms of column I correctly
with the phrases given in column II.
Column I
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Column II
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(i) Polyester
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(a) Prepared by using wood pulp
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(ii) Teflon
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(b) Used for making parachutes and stockings
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(iii) Rayon
|
(c) Used to make non-stick cookwares
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(iv) Nylon
|
(d) Fabrics do not wrinkle easily
|
Ans
Column I
|
Column II
|
|
(i) Polyester
|
(d)
|
Fabrics do not wrinkle easily
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(ii) Teflon
|
(c)
|
Used to make non-stick cookware
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(iii) Rayon
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(a)
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Prepared by using wood pulp
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(iv) Nylon
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(b)
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Used for making parachutes and stockings
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14. ‘Manufacturing synthetic fibres is
actually helping conservation of forests’. Comment.
Ans. The natural fibers are obtained
from plants and animals, whereas the synthetic fibers are obtained by
chemical processing of petrochemicals. Unlike natural fibers, manufacturing
of synthetic fibers do not require to cut trees or hunting of any animal. In
this way manufacturing synthetic fibers is actually helping conservation
forests.
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15. Describe an activity to show that
thermoplastic is a poor conductor of electricity.
We will design a circuit
to see that thermoplastics are poor conductors of electricity. We need a
bulb, some wires, a battery, a piece of metal, and a plastic pipe. Set up the
circuit first with the metal and then with the plastic pipe (as shown in the
figure). After you 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.
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Some Important Question asked in Papers
01. Name the Synthetic fiber which resembles wool.
02. Write four advantages of synthetic fibers.
03. What are biodegradable and non biodegradable
substances?
04. Write the four R’s.
05. Define the polymers.
06. Explain why some fibers are called synthetic?
07. Match the terms of column A correctly with the phrases
given in column B.
Column A
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Column B
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(i) Polyester
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(a) Prepared by using wood pulp
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(ii) Teflon
|
(b) Used for making parachutes and
stockings
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(iii) Rayon
|
(c) Used to make non-stick cookwares
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(iv) Nylon
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(d) Fabrics do not wrinkle easily
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