Synthetic Fibres and
Plastics
Q1: Explain why some fibres are called synthetic?
Answer: Some fibres are called synthetic because they are not made from natural fibres. Instead, they are made by chemical processing of petrochemicals. The synthetic fibres are made up of very large units called polymers. Some of the synthetic fibres are: rayon, nylon and acrylon.
Q2: 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
Answer: (b) it is obtained from wood pulp
Q3: Fill in the blanks with appropriate words:
Answer:
(a) Synthetic fibres are also called man-made or artificial
fibres.
(b) Synthetic fibres are synthesised from raw material calledpetrochemicals.
(c) Like synthetic fibres, plastic is also a polymer.
Q4: Give examples which indicate that nylon fibres are very
strong.
Answer: Nylon is a very strong fibre that is why nylon is used for
making parachutes, rock climbing ropes, fishing nets seat belts etc. A nylon
thread is actually stronger than a steel wire.
Q5: Explain why plastic containers are favoured for storing
food.
Answer: Plastic containers are favoured for storing food for the
following reasons:
1.
Plastic containers are light weight so they are easy to handle.
2.
The price of plastic containers is very less as compared to
other containers.
3.
They have good strength.
4.
Plastic containers are durable.
Q6.Explain the difference between the thermoplastic and
thermosetting plastics.
Answer:
|
Thermoplastics
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Thermosetting plastics
|
|
|
1
|
Plasticcs
which can be deformed and bend easily on heating are known as thermoplastics.
|
Plastics
which when moulded once cannot be bent and deformed on heating are known
thermosetting plastics
|
|
2
|
They
are used for making toys, containers, etc
|
They
are used for making switches, handles of utelsils, floor tiles etc.
|
|
3
|
Example:
PVC, Polythene
|
Bakelite
and Melamine
|
Q7.Explain why the following are made of thermosetting plastics.
(a) Saucepan handles
(b) Electric plugs/switches/plug boards
Answer:
(a) Saucepan handles: Saucepan handles are made from
thermosetting plastics because these are bad conductors of heat and
electricity. They do not bend or deform on heating.
(b) Electric plugs/switches/plug boards: Electric
plugs/switches/plug boards etc. are made up of thermosetting plastics because
thermosetting plastics are bad conductors of heat and electricity. It does not
allow the current to pass through it.
Q8: 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
|
|
|
1
|
Plastic
toys
carry bags ball point pens plastic chairs plastic covering on electrical wires, plastic bowls |
cooker
handles
electrical switches telephone instruments |
Q9: 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 is advised to buy a cotton shirt for summers
because cotton absorbs the sweat and the pores in cotton allows easy
evaporation and keeps our body cool, whereas synthetic shirts don’t absorb
sweat and they are very uncomfortable to wear in summers.
Q10: Give examples to show that plastics are noncorrosive in
nature.
Answer:
1.
We can store various kinds of chemicals and other materials in
plastic containers because they are non-reactive and does not react with water
and air.
2.
Teflon, a kind of plastic is used as a coating to manufacture
non-stick cookwares.
3.
Melamine is used for making floor tiles and kitchenware.
4.
Bakelite is a poor conductor of heat and electricity so it is
used for making electric switches and handles of the utensils.
Q11: Should the handle and bristles of a tooth brush be made of
the same material? Explain your answer.
Answer:
The bristles of a tooth brush should be made of soft material so
that it does not harm the gums and the handle should be made of hard material
so that it can give a firm grip. Therefore, the bristles are made up of nylon
fibres which are strong, elastic, lustrous, light weight and easy to handle and
the handle is made of hard plastic as it is strong, durable, poor conductor of
heat and electricity.
Q12: "Avoid plastics as far as possible". Comment on
this advice.
Answer:
Although plastics have become important in our daily life, we
should avoid them as far as possible.
1.
Plastics are non-biodegradable and take a lot of time to
decompose.
2.
Plastics are not eco-friendly. By burning plastics, poisonous
fumes are released that cause air pollution.
3.
Sometimes cows and other animals may eat plastics present in the
garbage which may choke their respiratory system and even cause death.
4.
The plastic left in the soil results in soil pollution.
5.
Plastic bags drained into the water bodies cause threat to the
aquatic life also.
6.
Polybags choke the drains and sewage pipes thus causing lot of
trouble.
So we should use plastic judiciously and give preference to
other alternatives like jute bags etc.
Q13: Match the terms of column I correctly with the phrases
given in column II.
|
Column I
|
Column II
|
|
|
i
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Polyester
|
(a)
Prepared by using wood pulp
|
|
ii
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Teflon
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(b)
Used for making parachutes and stockings
|
|
iii
|
Rayon
|
(c)
Used to make non-stick cookwares
|
|
iv
|
Nylon
|
(d)
Fabrics do not wrinkle easily
|
Answer: i-d, ii-c, iii-a, iv-b
Q14: Explain, ‘Manufacturing synthetic fibres is actually
helping conservation of forests’.
Answer: 'Manufacturing synthetic fibres is actually helping
conservation of forests’ because synthetic fibres are man-made fibres. These
fibres are made from petrochemicals. For manufacturing synthetic fibres cutting
of trees or killing of animals is not required and hence we conserve our
natural environment.
Q15: Describe an activity to show that thermoplastic is a poor
conductor of electricity.
Answer: Take a small piece of thermoplastic material and connect it as
shown in the figure When we close the switch, no current passes and the bulb
does not glow.
Q16: Terylene is used in making ...
(a) Dressing material
(b) Food packaging
(c) Non-sticky utensils
(d) All of the above.
Answer: (a) Dressing material
Q17: What are polymers?
Answer: Many small chemical units (called macro molecules)
combine to form a large unit. Polymer is made up of such repeating units.
Q18: What is the polymer unit of cotton?
Answer: Cellulose.
Q19: What type of polymer units arrangement are found in
plastics?
Answer: In general two types:
·
Linear arrangement
·
Cross-linker arrangement
Q20: Give examples of (a) natural fibres (b) semi-synthetic
fibres and (c) synthetic fibres
Answer:
(a) Natural fibres: Cotton, silk, jute
(b) Semi-synthetic fibres: Rayon
(c) Synthetic fibres: PVC, Nylon, Terylene, Teflon
Q21: What is full form of PVC and PET
Answer: PVC: Polyvinyl Chloride
PET: Polyethylene tetrapthalate
Q22: Name the R's in 4R principle.
Answer: Reduce, Reuse, Recycle and Recover.
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