Question-1
Explain the reason why some of the fibres are called synthetic.
Answer-
The reasons why some of the fibres are called synthetic is
because man has prepared them by using chemicals. These are made of small units
that join together to form long chains. Some of the examples of synthetic
fibres are nylon, rayon, acrylic, polyester etc.
Question-2
Why is rayon different from synthetic fibres?
Answer-
Rayon is different from synthetic fibres because it is obtained
from wood pulp.
Question-3
Fill in the blanks with the correct words:
1.
a) _____and_______ fibres are also called synthetic fibres.
2.
b) Synthetic fibres are synthesized from raw materials
called________.
3.
c) Like synthetic fibre, plastic is also a _______.
Answers-
a)Artificial and man-made fibres are also called
synthetic fibres.
1.
b) Synthetic fibres are synthesized from raw materials called petrochemicals.
2.
c) Like synthetic fibres, plastic is also called a polymer.
Question-4
List out a few examples that prove that nylon fibres are very
strong.
Answer-
Nylon fibres are very strong as it is used for making ropes used
for climbing rocks and for making parachutes. This shows the strength of the
nylon fibre.
Question-5
Whydo you think only plastic containers are mostly favored for
storing eatables?
Answer-
Here are some of the reasons that are responsible for plastic
container being favoured for storing food
1.
a) good strength
2.
b) light weight
3.
c) Cheap price
4.
d) easy to handle
Question-6
Differentiate between thermosetting plastics and thermoplastics.
Answer-
The difference between the thermosetting plastics and
thermoplastics are
Thermosetting plastic
|
Thermoplastic
|
Thermosetting plastic cannot be
easily bent but if we force to bend, it will break.
|
We can bend thermoplastics
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.
|
Question-7
Why the following are made of thermosetting plastics? Explain.
1.
i) Electric plugs/switches/plug board
2.
ii) Saucepan handles
Answer-
1.
i) Bakelite is a kind of thermosetting plastic and is a bad
conductor of heat and electricity. That is why it is used for making electric
plugs, switches, plug boards, etc.
2.
b) Thermosetting plastics are used to make saucepan handles
because on heating, these plastics do not get softened and also it is a bad
conductor of heat and electricity.
Question-8
Classify the following products as to which can be recycled and
which cannot be.
Plastic chairs, plastic bowls, plastic covering on electrical
wires, plastic toys, carry bags, electrical switches, cooker handle, ball point
pens and telephone instruments.
Answer-
Can be
Recycled
|
Cannot be
recycled
|
Plastic chairs
|
Cooker handles
|
Plastic bowls
|
Electrical switches
|
Plastic toys
|
telephone
|
Plastic covering on electrical
wires
|
|
Carry bags
|
|
Ball point pens
|
Question-9
By giving a reason, suggest Mahesh as to why he should buy a
cotton shirt for summer and not a synthetic shirt.
Answer-
Mahesh should buy a cotton shirt for the summer and not a
synthetic shirt because 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.
Question-10
Give a reason as to why plastics are non-corrosive in nature
with an example.
Answer-
Plastics are non-corrosive in nature even if they come in
contact with strong chemicals which is because of their non-reactive nature
with most of the materials. For example, the cleaning chemicals that we use at
home are stored in plastic bottles, instead of metal containers.
Question-11
Explain why the handle and bristle of a tooth brush should not
be made of the same material.
Answer-
The handle and bristle of a toothbrush not be made of same
material as the handle of the toothbrush should be hard and strong while the
bristle should be soft and flexible.
Question-12
Why should we avoid plastics as far as possible?
Answer-
We should avoid plastics as far as possible because plastics are
non-biodegradable in nature. Once introduced into the environment, it takes
several years to decompose. They pollute the environment. We cannot burn them
as well because if burnt, it releases poisonous gases. Likewise, the plastic
bags thrown in the garbage dumb are swallowed by animals like cows, which choke
their respiratory system and can even prove fatal. Therefore, we should avoid
plastics as far as possible.
Question-13
Match the terms of side A correctly with the phrases given in
side B.
A
|
B
|
i) Teflon
|
a) used for making parachutes
and stockings
|
ii) Nylon
|
b)fabrics do not wrinkle easily
|
iii) Polyester
|
c) prepared by using wood pulp
|
iv) Rayon
|
d) Used to make non-stick
cookware.
|
Answer-
A
|
B
|
i) Teflon
|
d) Used to make non-stick
cookware.
|
ii) Nylon
|
a) Used for making parachutes
and stockings
|
iii) Polyester
|
b) fabrics do not wrinkle easily
|
iv) Rayon
|
c) prepared by using wood pulp
|
Question-14
Why do you think is manufacturing of synthetic fibre helpful in
the conservation of the forest?
Answer-
The manufacturing of synthetic fibres is helpful in the
conservation of forests because if we use natural fibres, the raw materials for
them have to be derived from the plants, which means cutting off lots of trees.
This leads to deforestation. But raw materials of synthetic fibres are mainly
petrochemicals. Hence this proves to be helpful in the conservation of forests.
Question-15
Show and describe an activity to prove that thermoplastic is a
poor conductor of electricity.
Answer-
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 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.
