Short Answer Type-Questions:
Write any two uses of plastics.
2. What is 5-R principle?
3. Write the differences between thermosetting plastics and thermoplastics.
4. Why do we wear cotton clothes in summers?
5. Why are saucepan handles, electric plugs and switches made of thermosetting plastics?
E. Long Answer Questions:
1. Write any five advantages of synthetic fibres over natural fibres.
2. Write any five environmental hazards of plastics.
3. Give reasons for following:
(a) Cooking pans have plastic handles.
(b) Burning of plastic causes air pollution.
(C) Nylon is used for making climbing ropes. (d) Refrigerators have a plastic foam core.
(e) Electric wires have a plastic covering. (1) Bakelite is used for making electric switches.
F. HOTS (Higher Order Thinking Skills) Questions:
1. Natural wool is attacked by moths whereas acrylic wool is not. Explain.
2. Production of synthetic fibres helps in the conservation of forests. Comment.
ustions.
Answers
Answer:
short answer
1) Plastics are used in a growing range of applications in the construction industry. They have great versatility and combine excellent strength to weight ratio, durability, cost effectiveness, low maintenance and corrosion resistance which make plastics an economically attractive choice throughout the construction sector.
2) The 5 R's – reduce, reuse, recycle, recover and residual management. Reduce, reuse, recycle, recover and residual management. – Five actions that can make your organization and you a better steward.
3) Thermoplastics can be heated and shaped over and over again - Thermosetting plastics can only be heated and shaped once.
Thermosetting plastics have high melting points and have high tensile strength but thermoplastics have low melting point and are easy to mould.
4)We sweat more in the summer session. Cotton is a strong water absorber helps to absorb the sweat and introduce to the environment of evaporation. Our body takes out heat as the sweat evaporates from our body.
5)(a) the handles of a saucepan are made of thermosetting plastic because it is a bad conductor of heat and does not get heated up while cooking. (b) Electric plugs/ switches/ plug boards are saucepan is made of thermosetting plastic because it is a bad conductor of electricity.
Long answer
1) SYNTHETIC FIBERS...
1) Synthetic fibers are hydrophobic so they dry up quickly. They are:
2) durable
3) less expensive
4) readily available
5) easy to maintain
NATURAL FIBRE...
1) Natural fibres are more 2)Comfortable to wear then synthetic.
3) Synthetic are cheaper to produce.
4) Longer lasting than natural.
5)Not so comfortable to wear.
2) Plastic bags causes land pollution.
Plastic bags lying on the ground are eaten up by animals such as cows and this causes great danger to them.
Plastic bags don't decompose and they decompose after millions of years.
They cause loss to the country's economy.
They do water pollutions and make the marine life suffer.
The foods stores in plastic containers are not safe to eat.
3) (A) cooking pans have handles as metal conduct heat but plastics not they are insulators
(B) burning of plastics cause air pollution as they are made up of harmful chemicals
(C) nylon is used for making climbing ropes as they are made by chemicals and are considered as the strongest fiber
(E) electric wires have plastic coating as plastic is not a conductor of electricity
hots answers
1) That would be because the natural wool fiber is produced by a living thing, a sheep. So the wool is the remains of a living cells, which could be used as a food source by insects, such as moths. Acrylic wool, on the other hand, is produced from synthetic sources, such as plastics or nitriles. Acrylic wool is basically a form of plastic, much the same as plastic bottles or milk jugs. A simple test would be to take a length of wool yarn and an acrylic yarn and set them on fire. The wool yarn will burn easily, leaving a fragile ash behind. The acrylic yarn will have a blackish smoke and smell oily. Another test would be to cut two pieces of yarn and try to twist them together. The wool yarn will twist together easily, forming one piece between the two. The acrylic yarn will not meld together easily, will tend to come apart.
2) Raw materials for natural fibres are mainly derived from plants and this means cutting a lot of trees. This leads to deforestation. But raw materials of synthetic materials are mainly petrochemicals. Hence, manufacturing synthetic fibres helps in the conservation of forests.
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