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CBSE Questions for Class 8 Chemistry Synthetic Fibres And Plastics Quiz 4 - MCQExams.com
CBSE
Class 8 Chemistry
Synthetic Fibres And Plastics
Quiz 4
Which of the following is a property of plastic?
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Flame resistant
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Non-corrosive
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Mouldable
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All of the above
Explanation
Plastics as such are not flame resistant but thermosetting plastics are flame resistant. Plastics are non-corrosive and mouldable that is why they are used in kitchenware.
What characteristic property of plastic makes it useful in making containers for storing food items?
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They do not react with food stored in them
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They are poor conductors of electricity
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They are light weight and strong
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They are non-degradable.
Explanation
Since plastics do not react with water and air, they are noncorrosive in nature and are thus used for storage.
What kind of material should be preferred for clothes during summer?
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Nylon
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Plastic
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Rayon
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Cotton
Explanation
Cotton is a light-weight natural fibre and does not close the tissues as the synthetic fibre does. The cotton clothes have small opened pores that let the air pass through them and makes you feel cool in hot summer.
While on the other hand, synthetic fibre lock the body heat and sweat, which increases the body temperature and you feel hot inside.
Dress material terylene is essentially a/an:
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nylon product
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acrylic product
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polyester product
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rayon product
Explanation
Terylene is a popular polyester. Polyester is a synthetic fibre that remains crisp and easy to wash. So, it is quite suitable for making dress material.
Plastics which when moulded once, cannot be softened by heating are called :
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thermosetting plastics
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thermoplastics
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thermostat plastics
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mould plastics
Explanation
$$\text { Thermosetting plastics have primary bonds } \\$$
$$\text { between molecular chains and held together } \\$$
$$\text { by strong cross - links. They are hugh } \\$$
$$\text { in molecular weight. that's why when } \\$$
$$\text { moulded once, can't be softened by heating } \\$$
$$\text { are called thermosetting plastics. } \\$$
Which of the following material take the longest to decompose?
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Paper
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Cotton cloth
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Cardboard
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Plastic bag
Explanation
Decomposition of naturally derived materials such as paper, cardboard and cotton is much faster than plastics, metals and glass. So, plastic would take the longest to decompose amongst the other materials given.
A silk saree and a nylon saree, both of same length are put to dry under sun. Which one will dry faster?
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Silk saree
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Nylon saree
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Both will take same time
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Depends on weather condition
Explanation
Nylon has various characteristics like a higher impact resistance, a more rapid moisture absorption, greater elasticity and elastic recovery. Nylon absorbs moisture readily as compared to silk so nylon saree dries up faster than silk saree in the sun.
The fibre that burns completely leaving no residue is:
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Cotton
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Acrylic
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Polyester
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Polythene
Explanation
Cotton is the fibre that bums completely, leaving no residue.
Use of plastic bags should be avoided because:
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plastic is non-biodegradable
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plastic emits toxic gases on burning
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both $$A$$ and $$B$$
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none of these
Explanation
Use of plastic bags should be avoided because p
lastic is non-biodegradable and emits toxic gases on burning.
Arrange the following fibers in the order of increasing strength:
Nylon, Cotton, Wool, Polyester, Silk
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Silk, Wool, Cotton, Nylon, Polyester
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Wool, Silk, Cotton, Nylon, Polyester
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Cotton, Silk, Wool, Nylon, Polyester
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Nylon, Cotton, Silk, Wool, Polyester
Explanation
Tensile strength of polymer increases with an increase in chain length and crosslinking of polymer chains.
According to this, the tensile strength of wool < silk < cotton < nylon < polyester.
Artificial fibers like nylon and polyester are designed specially to have more tensile strength.
An example of thermosetting plastic, which is also a poor conductor of electricity, is:
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polythene
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bakelite
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polyester
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PVC
Explanation
Bakelite is an example of thermosetting plastic which is also a
poor conductor of electricity. Due to its insulating character, it is used for switches and other electrical insulators.
Option B is correct.
State True or False.
Plastics are resistant to corrosion.
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True
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False
Explanation
Plastics do not react with water and air. They are not corroded easily. That is why they are used to store various kinds of material, including many chemicals.
Hence, we can say plastics are resistant to corrosion, and the given statement is true.
A person should not wear polyester clothes while cooking in the kitchen because:
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polyester clothes absorb sweat easily
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they catch fire easily
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they are uncomfortable to wear
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they don't look nice
Explanation
Polyester takes longer to catch fire than cotton or linen, but when it does ignite, it melts. When the gluey substance reforms, it can stick to your epidermis. Melting fabric can be extremely dangerous, because it can cause scalding burns above and beyond direct fire damage
Hence, the correct option is $$\text{B}$$
Substances which cannot be decomposed by micro organisms are called :
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Biodegradable substances
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Non biodegradable substances
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Convertable subtances
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Non -convertable
Fill in the blanks by suitable words to make correct statements:
_______ is an artificial fibre resembling silk.
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Rayon
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Nylon
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Terylene
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PET
Explanation
Rayon is an artificial fiber resembling silk.
Rayon is a synthetic fiber, made from natural sources of regenerated cellulose, such as wood and related agricultural products.
A person has to make electric switches and plugs. Which material is recommended ?
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Teflon
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Bakelite
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Rayon
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PVC
Explanation
Bakelite has high heat resistant property which makes it a poor conductor of heat and electricity.it is used for making electrical switches because it high heat resistance property protects us from electric shocks.
also it is used to make handles of cooking utensils because of this property it does not conduct heat and so the handles are prevented from becoming too hot and this makes it easy to handle the handles of cooking utensils.
Hence, the correct option is $$\text{B}$$
When ________ is burnt, it releases toxic gases into the air causing air pollution.
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LPG
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Plastic
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CNG
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None of them
Explanation
The burning of plastic releases toxic gases like dioxins, furans, mercury, and polychlorinated biphenyls into the atmosphere. The burning of plastic also produces black carbon (soot) which contributes to air pollution.
CNG and LPG on complete combustion produce carbon dioxide, water vapor, and heat which are also a cause of climate change and global warming but these are not toxic in nature.
Hence, option $$B$$ is correct.
Why PET is increasingly used
for making bottles, jars and utensils?
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It is light weight and very strong
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It is shatter proof
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Impact resistant
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All of the above
Explanation
PET is light weight, naturally colourless with high transparency, strong and impact resistant. It is shatter proof. All these properties of PET makes a highly more suitable material than glass for making bottles, jars, utensils etc.
Plastics are ________ water and therefore are used
in making buckets.
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lighter than
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soluble in
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insoluble in
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None of these
Explanation
General properties of plastics are strength,
weather resistance, durability
etc. because plastics are high molecular
weight organic
compounds. And these organic compounds are
hydrophobic in nature due to presence of
hydrocarbons and thus make plastics water i
nsoluble & therefore are used in making
buckets.
Hence correct option is $$C$$.
Frying pan handles are made up of:
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thermoplastic
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thermosetting Plastic
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rayon
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PVC
Explanation
Thermoplastics are not suitable for making handles of frying pans because they are flexible and soften on heating. On the other hand thermosetting plastics are used because they do not become soft on heating and are very hard and rigid.
Hence, the correct option is B
State true or false.
Nylon is a thermosetting plastic.
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True
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False
Explanation
Thermoplastics are the polymers which loses their shape on heating and regain their shape on cooling.
Examples: Nylon, PVC, polystyrene, etc.
On the opposite of that Thermosetting doesn't regain its shape after heating.
Nylon is a thermoplastic polymer. Hence the given statement is false.
Statement: The articles made of thermoplastics can be recycled whereas the articles made of thermosetting plastics cannot be recycled.
State whether the given statement is true or false.
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True
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False
Explanation
The intermolecular forces in thermoplastics are weaker while the intermolecular forces in thermosetting plastics are stronger. The thermosetting plastics cannot be moulded on heating. Thus the
articles made of thermoplastics can be recycled whereas the articles made of thermosetting plastics cannot be recycled.
Hence, the given statement is $$\text{true}$$
Which material is responsible for the cause of animal death?
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Plastic
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Sand
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Plants
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None of the above
Explanation
Most of the wandering animals eat plastic bags which take thousand of year to decompose and remain in the body of animals and become cause of death.
Thermoplastics are:
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linear polymers.
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soften or melt on heating
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molten polymer can be moulded in desired shape.
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All of these
Explanation
$$\bf{Final \ answer:}$$ Option $$D$$
$$\bf{Explanation:}$$
Thermoplastic is a form of plastic which have the following properties :
Soften on heating.
It is a long linear chain polymer.
It is formed by addition polymerization.
It can be reshaped and reused.
Easily soluble in an organic solvent.
Examples of thermoplastics are PVC, Teflon
As it has all the above properties, therefore, all given options are correct.
Formation of addition polymer $$PVC$$ which is thermoplastic is shown below:
Containers that are lightweight, affordable, durable, and easy to handle are generally made up of :
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plastic
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metal
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wood
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brick
Explanation
Plastic is lightweight, affordable, durable, and easy to handle. So, plastic is a good choice to make containers out of the other three options.
Match the column A and B
Column A
Column B
(i) Thermoplastics
(a) Handles of utensils, floor tiles
(ii) Thermosetting plastics
(b) Melamine
(iii) Biodegradable
(c) Teflon
(iv) Fire proof plastic
(d) Wood
(v) Oil and water do not stick
(e) Combs, containers
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i-d, ii-e, iii-a, iv-b, v-c
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i-e, ii-a, iii-d, iv-b, v-c
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i-a, ii-d, iii-b, iv-c, v-e
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i-c, ii-b, iii-a, iv-e, v-d
Explanation
Thermoplastic
materials are those materials that are made of polymers linked by intermolecular interactions or van der Waals forces, forming linear or branched structures.
Melamine is a versatile material. It resists fire and can tolerate heat better than other plastics. It is used for making fire-resistive uniforms, floor tiles, kitchenware and fabrics which resist fire.
Thermosetting
plastics are generally strong and resistant to heat, but they melt the first time they are heated to a high enough temperature and harden (set) permanently when cooled. They can never be melted or reshaped again.
They are used in situations where resistance to heat is important, e.g. on kitchen work surfaces, good-quality plastic cups, saucepan handles and plug casings.
Wood is a biodegradable material since it is obtain from plants.
Oil and water do not stick to cookware coated with Teflon on its surface.
Rayon is mixed with __________ to make ___________ and mixed with __________ to make ____________.
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cotton, bed sheet, wool, carpets
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teflon, bed sheet, jute, carpets
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nylon, bed sheet, cotton, carpets
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wool, bed sheet, cotton, carpets
Explanation
Rayon or artificial silk is obtained from a natural source, wood pulp. It is cheaper than silk and can be woven like silk fibres. Rayon is mixed with cotton to make bed sheets or mixed with wool to make carpets.
Hence, option $$A$$ is correct.
A common form of polyester is :
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Nylon
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Rayon
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PET
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Acrylic
Explanation
As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include naturally occurring chemicals, such as in the cutin of plant cuticles, as well as synthetics such as polybutyrate.
Ropes made of nylon and polyester are commonly
used in cranes and elevators because :
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Nylon is inflammable
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It is a good conductor of heat and electricity
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It is very strong, fairly elastic and light weight
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It is heat resistant
Explanation
Ropes made of nylon and polyester are commonly used in cranes and elevators because
It is very strong, fairly elastic and light weight.
Why the waste created by plastics is not friendly with environment?
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Plastics are non biodegradable
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Plastics are biodegradable
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On burning it causes pollution due to evolution of poisonous gases
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A & C both
Explanation
Plastics are not environment friendly because it is non-biodegradable and on burning them releases poisonous gases.
Option D is correct.
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