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CBSE Questions for Class 8 Chemistry Synthetic Fibres And Plastics Quiz 9 - MCQExams.com
CBSE
Class 8 Chemistry
Synthetic Fibres And Plastics
Quiz 9
Which of the following is not a natural fibre ?
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Cotton
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Jute
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Nylon
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wool
Explanation
The correct answer is option (C) Nylon.
Nylon is synthesised with the help of chemicals in factories whereas jute, flax and cotton are natural fibres obtained from plants.
Nylon yarns are usually.
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Highly inflammable
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Non-inflammable
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Both (a) and (b) types are known
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Uncertain inflammability
Which of the following represents the correct match for items in Column A with those in Column B.
Column A. Column B.
I. Nylon (i) Thermoplastic
II. PVC (ii) Thermosetting plastic
III. Bakelite (iii) Fiber
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I - (ii), II - (iii), III - (i)
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I - (iii), II - (i), III - (ii)
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I - (ii), II - (i), III - (i)
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I - (iii), II - (ii), III - (i)
Explanation
Nylon is a thermoplastic that is processed to make nylon fibers. These are used in fabrics, pipes, tents, ropes, carpets, etc.
PVC is a thermoplastic that becomes mouldable above a specific temperature and solidifies upon cooling.
Bakelite is thermosetting plastic. It is used in making switches, electrical appliances, kitchenware.
$$ I - (iii),$$ Fiber
$$II - (i),$$ thermoplastic
$$III - (ii)$$ thermosetting plastic
The material similar to silk in appearance is
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Nylon
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Rayon
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Polyester
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Terylene
Explanation
$$\text{Rayon has a similar appearance to silk.}$$
Rayon is cheaper than silk and can be woven like silk fibers.
It is obtained by chemical treatment of wood pulp.
Which of the following group contains all synthetic substances?
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Nylon, Terylene, Wool
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PVC, Polythene, Bakelite
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Cotton, Polycot, Rayon
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Acrylic, Silk, Wool
Explanation
Nylon was the first commercially prepared synthetic polymer.
Terylene or Polyethylene terephthalate or polyester are synthetic fibres.
Wool is the textile fibre obtained from sheep and other animals
Cotton is a soft, fluffy staple fibre that grows in a boll, or protective capsule, around the seeds of cotton plants.
The fibre is almost pure cellulose. so it is not synthetic.
Polycot is a mixture of polyester and cotton.
Acrylic yarn is a man-made fibre, formed of polymers created from petroleum products i.e. crude oil.
Silk is a natural fibre obtained from silkworms.
Rayon is derived from natural cellulose and cannot be considered synthetic.
PVC, Polythene, Bakelite three are all synthetic polymers prepared from chemical processes by man-made efforts and raw materials.
Hence the correct option is B.
Which is a thermosetting plastic?
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Melamine
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Polythene
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PVC
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Nylon
Explanation
Thermosetting plastics are the plastics that are once moulded can not be softened by heating. $$\text{Melamine, bakelite}$$ are the examples.
Option $$A$$ is correct.
Which of the following is not a common property of plastics?
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Non-reactive
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Light in weight
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Durable
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Good conductor of electricity
Indicate whether the following statements are True or False. Also, write the false statements in their correct form.
Most of the plastics are biodegradable.
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True
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False
Explanation
Most of the plastics are non-degradable.
The term non-biodegradable describes polymers that do not break down to a natural, environmentally safe condition over time by biological processes.
Hence, the given statement is false.
Indicate whether the following statements are True or False. Also, write the false statements in their correct form.
The fabric tery wool is obtained by mixing terylene and wool.
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True
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False
Explanation
$$\text True,$$
$$\text{The fabric terry wool is obtained by mixing terylene and wool.}$$
Which is not property of plastics?
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Inert
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Durable
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Light weight
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Conduction
Explanation
Plastics are non-reactive due to which they are resistant to the attack of surroundings.
They are very light weighted.
They have high durability i.e., they have a long life.
They are insulators and hence, don't conduct electricity and heat.
Hence, the correct option is D.
__________ is not a natural fiber.
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rayon
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silk
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wool
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cotton
Explanation
Rayon is a synthetic fiber, which means it is made by humans.
Silk is obtained from silk worm, wool is from sheep and cotton from plants hence these are natural fibers.
Option $$A$$ is correct.
Polyester is a polymer of?
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Ester
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Ethane
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Ethylene
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Methane
Explanation
Polyester (Poly+ester) is actually made up of the repeating units of a chemical called an ester. Esters are the chemicals which give fruits their smell. Fabrics are sold by names like polycot, polywool, terrycot, etc.
Which of the following is a bio-degradable polymer?
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PVC
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Cellulose
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Polythene
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Nylon
Explanation
Of all the given options, the only cellulose is a bio-degradable polymer.
All other options are synthetic polymers and are non-biodegradable,
Hence, Option $$B$$ is the correct answer.
Polyester is a natural fibre.
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True
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False
Explanation
$$\text{False}$$
Polyester is a synthetic fiber.
Which fibre is obtained from flax seeds?
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Cotton
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Jute
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Linen
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Nylon
Explanation
Nylon is a synthetic fibre. So, it is not obtained from flax seeds.
Cotton fibre is obtained from cotton plant and jute fibre is obtained from jute plant.
Linen fibre is obtained from flax seeds. So, option C is correct answer.
Which of these fibres is non - biodegradable?
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Cotton.
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Jute.
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Wool.
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Nylon.
Explanation
Nylon fibre is non - biodegradable as it is synthetic fibre.
Padma observes that screwdrivers have a plastic handle and electrical wires have a plastic covering. What is the reason for the use of plastic in electric appliances?
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It is strong and durable
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It is hard
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It is non-reactive
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It is a poor conductor
Explanation
Electric screwdrivers and electrical wires have plastic covering because plastic is a poor conductor of electricity or a good insulator and therefore prevents an electric shock.
Rayon is different from synthetic fibres because
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it has a silk-like appearance
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it is obtained from wood pulp.
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its fibres can also be woven like those of natural fibres.
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none of the above
Explanation
Rayon is different from synthetic fibres because: it is obtained from wood pulp.Hence option (B) is correct.
Which of the following is thermoplastic?
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Nylon
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Polyethylene
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Terylene
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All of these
Explanation
A thermoplastic is a polymer that becomes pliable or moldable above a specific temperature and returns to a solid-state upon cooling.
Nylon is a thermoplastic silky material that is used in fibers, films, or shapes.
Polyethylene is a lightweight, durable thermoplastic with a variable crystalline structure.
Polyethylene terephthalate or Terylene is the most common thermoplastic polymer resin of the polyester family and is used in fibers for clothing, containers for liquids, and foods.
All the given compounds are thermoplastic polymers.
Hence, option $$D$$ is correct.
Shellac secreted by lac insects is:
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Natural plastic
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Natural resin
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Natural elastic
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Any of these
Explanation
Shellac is a resin secreted by the female lac bug on trees in the forests of India and Thailand. So a natural resin.
Shellac is a natural bioadhesive polymer and is chemically similar to synthetic polymers, and thus can be considered a natural form of plastic.
It can be turned into a molding compound when mixed with wood flour and molded under heat and pressure methods, so it can also be classified as thermoplastic. So a natural elastic.
Hence, option $$D$$ is correct.
For which of the following purposes is a coating of melamine plastic used?
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Fire proof plastic.
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Good conductor of heat.
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Remouldable.
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Strong and flexible.
Melamine are:
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Thermosetting
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Thermoplastic
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Both A and B
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None of these
Explanation
Melamine are thermosetting plastics as on heating it can be moulded and reshaped.
Hence, option $$A$$ is correct.
What kind of silk is rayon?
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Natural silk
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Synthetic silk
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Mulberry silk
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None of the above
Explanation
Rayon is obtained from wood pulp which is a natural raw material. But wood pulp has to be chemically processed to give rayon.
Properties of rayon are similar to those of silk. So it is considered synthetic silk. Hence option B is correct.
Which of the following properties of synthetic plastic makes it the most convenient to use?
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Good electrical conductor
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Malleable
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Light, strong and remouldable
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Reactive
Explanation
Platic is non-reactive, light, strong, easily mouldable. These properties of plastic make it convenient to use.
Option $$C$$ is correct.
Match the following with the correct answers.
(a) Scouring (i) Yields silk fibers
(b) Mulberry leaves (ii) Cleaning sheared skin
(c) Sheep (iii) Food of silk worm.
(d) Cocoon (iv) Wool yielding animal.
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a --> ii, b--> iii, c--> iv, d--> i
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a--> i, b--> ii, c--> iii, d--> iv
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a--> iv, b--> iii, c--> ii, d--> i
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a--> ii, b--> i, c--> ii, d--> iv
Explanation
(a) Scouring means cleaning the sheared skin of animals.
(b) Silkworms feed on mulberry leaves.
(c) Sheep gives us wool.
(d) Cocoon gives us silk fibers.
Hence, the answer is option A.
Which of the following statements is incorrect?
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Nylon clothings can with stand high temperature and are, therefore, good to wear in summers.
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Thermosetting plastics do not become soft on heating.
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Addition polymers are formed without the elimination of byproduct molecules.
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Natural rubber is obtained as latex from rubber trees.
Explanation
Nylon clothes when subjected to high-temperature results in a chemical change, that cannot be reversed. nylon clothes can easily catch fire.
Therefore, it is not good wear for summers.
Thermosetting plastics once cured cannot be reversed and becomes permanently rigid solid.
Addition polymers are formed by linking of monomers no by-product is eliminated.
The latex extracted from the rubber trees is treated to obtain natural rubber.
Hence, option A is correct.
Which of the following is a correct statement(s)?
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The process of making yarn from fibres is called spinning.
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In this process, fibres from a mass of cotton wool are drawn out and twisted.
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A simple device used for spinning is a hand spindle, also called takli.
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Another hand operated device used for spinning is charkha.
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All of the above
Explanation
The process of making yarn from fibres is called spinning. In this process, fibres from a mass of cotton are drawn and twisted to bring the fibres together to form a yarn or thread. Spinning is done at home using simple devices like the hand spindle, or takli, and charkha. It is also done using machines. So, all the given statements are correct.
These are generally the bad conductor of heat.
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Natural fibre
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Synthetic fibres
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Cranes
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Plastic
Explanation
Materials that do not allow heat and electricity to pass through them are called insulators. Plastic is an insulator.
$$\therefore$$ Option $$D$$ is correct.
Which of the following is not a thermoplastic?
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PVC
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Polythene
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Melamine
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Teflon
Explanation
Melamine is a thermosetting plastic whereas PVC, polythene and Teflon are thermoplastics.
Thermoplastic among these is?
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Bakelite
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Melamine
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Acrylic
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None of these
Explanation
Examples of thermoplastics are polythene and PVC.
Melamine and bakelite on the other hand are thermosetting plastics.
Acrylic is not a plastic. It is a synthetic fibre.
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