Synthetic Fibres And Plastics - Class 8 Chemistry - Extra Questions

Name two varieties of cloth materials which are commonly used.

Two varieties of cloth materials that are commonly used are cotton and silk. Cotton is used as it is very comfortable. Silk is soft,smooth, shiny therefore it is used in making clothing, comforters, etc.


Write the examples of animal fiber.

Examples of animal fiber are wool and silk.
Wool is obtained from the sheep and silk is obtained from the silkworm.


Name some modern fabrics formed by unstitched piece of fabric.

The modern fabrics formed by unstitched pieces of fabric are Saree, dhoti, lungi and turban.


Can pickles be stored in plastic containers? Give reason for your answer.

Pickles should be stored in glass and not plastic containers as they have high salt and acid content and thus will react with the plastic. Such eatables should be kept in glass containers to avoid any chemical reaction.


Describe an activity to show that thermosetting plastic is a poor conductor of electricity.

If we set up an apparatus as shown, we will see that the bulb does not glow. But the bulb would glow if the thermoplastic object is removed from the circuit. This shows that a thermoplastic object is a poor conductor of electricity.

298589_285143_ans.JPG


Is it advisable to use recycled plastic containers for storing food?

No. It is not advisable to use recycled plastic containers for storing food because when we store food items in the plastic container this reacts with food and make this acidic and if we eat this harmful food this affect us and we get unhealthy


Match the terms of List I correctly with the phrases given in List II.

1. Polyester fabrics do not wrinkle easily because it is very hard and strong.

2. Teflon consists of hydrocarbon and fluorine. It has London dispersion forces due to low electronegativity of fluorine.

3. Rayon is prepared by using wood pulp which is converted into a soluble compound.

4. Nylon is a strong fibre that can hold a strong amount of weight so it is used for making parachutes and stockings.

5. Melamine is thermosetting plastic that does not meltdown on heating so it is used for making clothes of fireman.

6. Cotton and jute are biodegradable because they can be decomposed easily by action of microorganisms.


Classify the following into thermosetting platics and thermoplastic:

(a) Melamine (b) PVC

(a) Melamine is a thermosetting plastic. Once set, it cannot be reheated and remoulded again. 

(b) PVC is a thermoplastic. It can be recycled as it can be softened and remoulded using heat.


Explain why plastic containers are favored for storing food.

The main advantage of using plastic for storing food are: 
Plastic has lightweight, has Good strength, Easy to handle, and is durable. They are easily molded into various shapes and containers. Plastics are also cheaper than metals and hence considered for storing food.


What are natural fibres? Give two examples.

Natural fibers are made from plant, animal, and mineral sources. Natural fibers can be defined as substances produced by plants and animals that can be spun into filament, thread, or rope and in the next step be woven, knitted, matted, or bound. The oldest fibers used by mankind are flax, cotton, and silk, but even jute and coir have been cultivated since antiquity. 
e.g. Cotton, Silk


Explain recycling of thermoplastics.

A thermoplastic is a plastic that melts to a liquid when heated and freezes to a brittle, very glassy state when cooled sufficiently. Thermoplastics can go through melting and freezing cycles repeatedly and, the fact that they can be reshaped upon repeated heating gives them their name. This quality makes thermoplastics recyclable. The plastics used for pop bottles are a common example of thermoplastics that can be recycled.


What properties make plastics, the material of choice?

Plastics have the following properties which make them a material of choice:
a. Plastics are lightweight.
b. They have good strength.
c. Are easy to handle.
d. Are low priced
e. Are durable.


Match the terms of Column A correctly with the phrases given in Column B.

$$\rightarrow$$ Polyster used in not wrinkle easily.
$$\rightarrow$$ Teflon is used in non-stick cookware.
$$\rightarrow$$ Rayon is prepared by wood pulp.
$$\rightarrow$$ Nylon is used in parachutes, stocking.


Give examples to show that plastics do not corrode easily.

Plastics are non-corrosive, they do not react or do not have a chemical reaction with the material contained in them. Many containers like a bucket, mug, water bottles, and food containers are made up of plastics. Plastic does not react with the chemical or other items stored in the containers made of it, It does not get rusted when exposed to moisture and air and It does not decompose when left in open for a long period.



Why plastics are used as insulating material in electrical appliances?

Plastics do not conduct electricity and are therefore used in a variety of applications where their insulating properties are needed. Plastics are especially suited to housings for goods such as hairdryers, electric razors and food mixers as they protect the consumer from the risk of electric shock.


What are the contribution of plastics in the field of medicine?

The incorporation of plastics into modern medicine has steadily increased. Plastics have contributed to a reduction in medical costs, infectious disease and pain management. High-tech polymers are used to create new and improved artificial limbs and have succeeded in reducing the risk of infection to patients. 


Why it is dangerous to leave plastic bags near fire?

Plastic, when burnt, sends numerous hazardous chemicals into the air and causes air pollution. Hence, we should not leave plastics near the fire. 


What are the hazards of disposal of plastic into water?

Chemicals present in plastics make water unfit for drinking. Also, plastics take a long time to decompose. They stay in the water for a long time and cause harm to water animals. Birds get it stuck in their throats and fish in the ocean can get wrapped and trapped in it. Bigger fishes can ingest it unknowingly along with the water. Plastics in water can also clog drains and obstruct the flow of water.


Why plastic in known as polymer ?

Plastics are synthetic chemicals extracted mainly from petroleum and composed of hydrocarbons (compounds made from chains of hydrogen and carbon atoms). 
Plastics are polymers a large number of molecules of ethylene can be joined end to end into a familiar polymer called polyethylene (or polythene).



Explain how polybags thrown away carelessly are responsible for the deaths of animals, especially cows?

Polybags that are carelessly thrown are eaten by animals like cows. They choke the respiratory system of these animals or form a lining in their stomach and hence become the cause of their death.


Why accumulation of plastic is considered a serious problem ?

It takes a long time for the plastic to decompose in the environment. Plastic is also harmful to animals. Birds get it stuck in their throats and fish in the ocean can get it wrapped around their body and can't swim.
In addition to the waste created by plastic, the production of plastic is harmful to the environment. Plastic is made from petroleum and the refining process of petroleum puts a lot of toxins into the earth's atmosphere.


Fill in the blanks with appropriate words:

(a) Synthetic fibres are also called_____ or ____ fibres.

(b) Synthetic fibres are synthesised from raw material called _____ .

(c) Like synthetic fibres, plastic is also a ____ .

(a) Synthetic fibres are also called $$\underline {man-made}$$ or $$\underline {artificial\ fibres}$$.

(b) Synthetic fibres are synthesised from raw materials called $$\underline {petrochemicals}$$.

(c) Like synthetic fibres, plastic is also a $$\underline {polymer}$$.


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.

Rayon is a manufactured regenerated cellulose fibre. It is made from purified cellulose, primarily from wood pulp, which is chemically converted into a soluble compound.

Hence.option ($$B$$) is correct.


Explain why plastic containers are favoured for storing food?

Plastic containers are favored for storing food for the following reasons:
1. Plastic containers do not react with food.
2. Plastic containers are lightweight so they are easy to handle.
3. The price of plastic containers is very less as compared to other containers.
4. They have strong strength.
5.. Plastic containers are durable.


Fill in the blanks given below:

______________ doesn't stick to the materials and can be easily used in non-stick pans and other cookware.

Teflon is a special plastic on which oil and water do not stick. It is used as a non-stick coating in pans and other cookware.



Fill in the blank.

______________ is a natural fibre, with continuous filaments which can stretch upto $$1 \ km$$.

Silk is a natural protein fiber, some forms of which can be woven into textiles. 
The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. 
The fibrils/filaments can stretch up to $$1 \ km$$ in length.


Explain the difference between the thermoplastic and thermosetting plastics.

There are two types of plastics: Thermosetting plastics and Thermoplastics. The difference between thermoplastic and thermosetting plastics are:

                            Thermoplastics                  Thermosetting plastics
Plastics that can be easily deformed and bend easily on heating are known as thermoplastics.Plastics once moulded cannot be bent or deformed are known as thermosetting plastics.
They are used for making toys, containers.They are used for making switches, handles of utensils, etc.
Examples are PVC, PolytheneExamples are Bakelite, Melamine


Match the polymers given, in column I correctly with their respective properties or uses given in column II.

1. Polyester-Fabrics that do not wrinkle easily.
2. Teflon-Used to make non-stick cookware.
3. Rayon-Prepared by using wood pulp.
4. Nylon-Used for making parachutes and stockings.


Should the handle and bristles of a tooth brush be made of the same material? Explain your answer.

No, the handle and bristles of a toothbrush should be made of different materials than the handle of the toothbrush. The bristles of a toothbrush are made up of very soft nylon fibres to protect our gums from any harm so they are long, elastic, lightweight, lustrous and easy to use while the handle is made up of strong, hard and durable plastic to give a firm grip to the toothbrush.


'Avoid plastics as far as possible.' Comment on this advice.



Describe an activity to show that thermoplastic is a poor conductor of electricity.

We can prove the thermoplastic is a poor conductor of electricity by following experiment:

$$Requirements:$$ Battery, few wires as connectors, bulb, switch, metal rod, thermoplastic rod/piece.

$$Procedure:$$

 $$(i)$$ Connect the battery, switch, bulb and metal rod through wires and on the switch and observe the bulb is glowing or not.

$$(i)$$ Replace the metal rod by thermoplastic rod in a circuit and on the switch and observe the bulb is glowing or not.

$$Observation:$$ 

 $$(i)$$ when metal rod is connected in a circuit, bulb is glowing.

$$(ii)$$ when thermoplastic rod is connected in a circuit bulb is not glowing.

$$Conclusion:$$ Thermoplastic is bad/poor conductor of electricity.


Explain why the following are made of thermosetting plastics.
(a) Saucepan handles
(b) Electric plugs/switches/plug boards

(a) Saucepan handles-They are made from thermosetting plastics because they are bad conductors of heat and electricity. They do not bend or deform on heating.
(b) Electric plugs/switches/plug boards-They are made from thermosetting plastics because they are bad conductors of heat and electricity. It does not allow the current to pass through it.


Give examples to show that plastics don't corrode easily.

Pickles usually come packed in plastic sachets or glass bottles. Pickles contain acids, yet no harm is done to the plastic sachet.
Sanitary cleaners and some acids; which are used as bathroom cleaners are sold in plastic bottles. These examples show the non-corrosive nature of plastic.


Plastics which get deformed easily on heating and can be bent easily are known as ___________.

Plastics that get deformed easily on heating and can be bent easily are known as thermoplastics. Polythene and PVC are some of the examples of thermoplastics.



State True or False.
 
PVC is mainly used for electrical and sanitary fittings.

PVC is used as the insulation on electrical cables. PVC pipes are used in water and sanitary sewer applications.
So, the given statement is true.



True or False 
A nylon thread is actually stronger than a steel wire.

$$True$$

Nylon is a man-made fibre. it is made without using any natural raw materials (from plants or animals). It is prepared from coal, water and air. It is the first fully synthetic fibre. Nylon fibre is very strong, elastic and light. it is used for making parachutes and ropes for rock climbing. A nylon thread is actually stronger than a steel wire.



State True or False.
 
Cooking pans have plastic handles.

Cooking pans have plastics handles. A metal handle would get almost as hot as the pot while cooking something for an extended time. Plastic does not conduct heat well, so a plastic handle would not burn your hands even if it's on the gas stove for an extended time.

Hence, the given statement is true.



State True or False.
Plastics are eco-friendly.

The given statement is $$\text{False}$$ because plastic causes pollution. 

Plastics are non-biodegradable material and hence they fill up landfills, end up as litter on land or in water, also toxic to many animals. So it is not eco-friendly. 


State the difference between natural and synthetic fibres.

Natural fibres are obtained from plants and animals, for example, cotton, wool, silk, etc.

Synthetic fibres are man-made and obtained by chemical processing, for example, PVC, polyethene, nylon etc. 



State True or False.
Polystyrene and PVC are thermoplastics.

True.

Thermoplastics can soften upon heating and return to their original form on cooling. They are easily molded and extruded into films, fibers and packaging. Examples include polyethylene (PE),polystyrene, polypropylene (PP) and polyvinyl chloride (PVC).



Match the following:

A thermoplastic is a plastic material, a polymer, that becomes pliable or moldable above a specific temperature and solidifies upon cooling and is not biodegradable.
Example: PVC, polystyrene

Thermosetting plastics are synthetic materials that strengthen when heated, but cannot be successfully remolded or reheated after their initial heat-forming and these polymers are not biodegradable.
Example: Bakelite.

Animals and plants: They are biodegradable in nature.

Plastics are not at all biodegradable.

Hence, A-2, B-1, C-4, D-3 is the correct answer.


Sita and Geeta went shopping to buy clothes to keep warm in winter. Sita wanted to buy either silk or polyester clothes while Geeta wanted woollen. Who is correct among them? Give reason.

Geeta is right. Woolen clothes are thick and keep us warmer, when compared to silk and polyester clothes.


What does the term non-biodegradable mean?

Biodegradable: Breaks down or decays without any special scientific treatment and can be thrown away without causing pollution.

Non-biodegradable: They are not capable of being broken down by the action of the living organism.
Examples of non-biodegradable polymers: Nylon, PVC, polystyrene, etc.


What are fabrics?

Fabrics mean a woven material, textile or other materials resembling woven cloth made from synthetic or natural fibres.


Plastic pollution is a major threat to solid waste management. Give two suggestions to avoid the threat :

Plastic pollution is a big threat to solid waste management. Plastic pollution can be controlled in the following ways:
i. Plastic should be used for a longer period of time.
ii. Instead of throwing plastic materials away, we should try to reuse them.
iii. Trying to use ink pens instead of ballpoint pens.
iv. Use fibres, paper or cloth for making carry bags.
In this way, we can avoid the threat.


Discuss biodegradable waste by giving examples.

  • The waste materials which are broken down by the action of decomposing microorganisms are called biodegradable waste.
  • Kitchen wastes such as vegetables and fruits, twigs, and other plant products are examples of biodegradable wastes.


What do you observe when you are visiting a nearby tailoring shop?

In a tailoring shop, we observe that there are many cuttings of fabrics leftover after stitching. We see that some cuttings are of cotton, some are of silk or wool and some are of synthetic fibres. Thus we can find fabrics made of different materials and colour in the shop.


Which material is generally used for making pens?

$$\textbf{Concept: }$$Plastics are a group of materials, either synthetic or naturally occurring, that contains as an essential ingredient an organic substance of large molecular weight.
  • Plastics are used for making pens as they are cheaper in price and have a good strength.


When we burn nylon, why we do not get the smell of burning paper or burning hair?

Nylon is a synthetic fiber made from chemicals. On burning nylon, these chemicals don't produce the smell of burning paper or hair which are natural substances.


"Use of plastic brings down deforestation". How?

Today, articles of daily use are made of plastic. If articles of daily use like chairs, tables, baskets, etc. are obtained from wood then that wood needs to be obtained from forest plants and trees. This would ultimately result in a decrease in forest wealth cover. This means deforestation takes place to fulfill our daily needs. In this way, plastic brings down deforestation.


What are natural fibres? Explain with examples.

  • Natural fibres are those fibres that is obtained from natural sources such as animals, plants.
  • Following are natural fibres obtained from:
  1. Plants: Cotton are obtained from cotton balls and jute from the jute plant.
  2. Animals: Silk are obtained from the cocoon of the silkworm and wool from the hair of animals like sheep or goats.


What is a biodegradable polymer?

A polymer that gets decomposed through natural processes, such as action by bacteria is called biodegradable polymer.
It helps in solving the problem of environmental pollution. Natural polymers are biodegradable but synthetic polymers are non-biodegradable. 
Some biodegradable materials are paper, wool, wood, etc.


What are some of the uses of plastics?

Plastic refers to its ability to deform without breaking. Plastics are versatile, hygienic, lightweight, flexible and highly durable. They are used in numerous packaging applications including containers, bottles, drums, trays, boxes, cups and vending packaging, baby products and protective packaging. 


What are bended fiber? Give any two examples.

Blended fabrics $$\rightarrow$$
Blended fabrics are made by mixing two different kinds of fibres. These blended fabrics have combined properties of each component fibre. 
Blended fabrics have good appearance and comfort and also available at low cost.
Examples: 
  1. Polycot - a mixture of polyester and cotton.
  2. Polywool - a mixture of polyester and wool.


The following is an answer given by Boojho to a question asked by his teacher - "Cotton, wool, silk, and jute are classified as natural fibres".
Can you predict, what question the teacher may have asked?

The teacher must have asked the students to classify the following fibres into natural and synthetic fibres-
Silk, Jute, Cotton, Polyester, Wool, Nylon.


Once, Paheli visited a tailor shop and brought home some cuttings of fabric to study their properties. She took two pieces and found that one of the pieces was shrinking when it was burnt with a candle. However the other did not shrink on burning. Can you help her to find out which of the two was cotton and which was silk fabric?

Cotton burns but do not shrink or melt. 
Whereas, silk shrinks away from the flame and burns but does not melt.
Hence, the fabric which shrinks is silk and the fabric that doesn't shrink when brought near a flame is cotton.


Select the articles from the following list which are biodegradable.
(a) paper                     (c) wood
(b) woolen clothes      (d) aluminium can 
(e) plastic bag              (f) peels of vegetables

The list of biodegradable articles are mentioned
below - 
(a) paper
(b) woollen clothes
(c) wood
(f) peels of vegetables.


Plastic articles are available in all possible shapes and sizes. Can you tell why?

Plastic is easily moldable and can be transformed into large or small objects of different sizes. So plastic articles are available in all possible shapes and sizes.


Plastic is used for making a large variety of articles of daily use and these articles are very attractive. But it is advised to avoid the use of plastic as far as possible. Why?

Plastic is a non-degradable substance. That is why it is causing a major problem to the environment and cause
environmental problems. We should avoid using plastic as much as possible.


Why is it not advisable to burn plastic and synthetic fabrics?

Burning plastic and synthetic fibers cause environmental pollution. When plastic burns, it produces toxic and poisonous gases which harm every kind of living being.


A synthetic fiber that looks like silk is obtained by the chemical treatment of wood pulp. It is, therefore, known as artificial silk. What is its common name?

A synthetic fiber that looks like silk is obtained by the chemical treatment of wood pup. This synthetic fiber is $$\text{rayon}$$ which looks like artificial silk. The common name for rayon is $$\text{cellular fiber.}$$


Unscramble the jumbled words given below, related to synthetic materials.
(a) anory               (b) lopmery
(b) relyteen           (d) laspict
(e) yespolter          (f) felton

Synthetic materials are:
(a) rayon
(b) polymer
(c) terylene
(d) plastic
(e) polyester
(f) teflon


PVC (polyvinyl chloride) is a thermoplastic and is used for making toys, chappals, etc. Bakelite is a thermosetting plastic and is used for making electrical switches, handles of various utensils, etc. Can you write the major difference between these two types of plastic?

The major difference is that $$\text{thermosetting plastics if once molded cannot be softened on heating. On the other}$$ $$\text{hand, thermoplastics while heated get deformed.}$$
Examples of the plastic are given below-
Thermoplastic - PVC and polyethylene 
Thermosetting plastic - Melamine and Bakelite.


A fiber similar to wool is ______ .

Acrylic is a synthetic fiber that feels like wool and is used as a substitute for wool. It is a man-made fiber that resembles wool and hence, it is also known as artificial wool or synthetic wool. In commercial use acrylic is cheaper than natural wool and can be dyed in various colors.


The first fully synthetic fibre was ________ .

The first fully synthetic fibre was nylon. It was prepared from coal, water, and air.


Rohit took with him some nylon ropes, when he was going for rock climbing. Can you tell why he selected nylon ropes instead of ropes made of cotton of jute?

Rope made of nylon is stronger than ropes made of jute or cotton. Nylon ropes are stronger than steel rope of the same thickness. That's why Rohit took nylon rope with him for hill climbing.


A lady went to the market to buy a blanket. The shopkeeper showed her blankets made of acrylic fibres as well as made of wool. She preferred to buy an acrylic blanket. Can you guess why?

Acrylic blankets are lightweight and cheap. These are more durable and also available in many colors. It's easily washable.


The synthetic fibers are also known as ______ fibres.

Synthetic fibres are made by human beings and therefore are also called as man-made fibres.


match items in List A with the items of list B.
List A list B

(a) nylon     -         (iii) parachutes
(b) PET      -         (iv) polyester
(c) Rayon   -         (v) artificial silk
(d) thermosetting plastic   -  (ii) electric switches
(e) Teflon  -           (i) non-stick coating


A polymer is a chain of many small units joined together which are called ______ .

A polymer is a chain of many small units joined together which are called $$Monomer.$$


State whether the following statements are true or false. Also, write the false statements in their correct form.
The fabric terywool is obtained by mixing terylene and wool.

The given statement is true because the fabric terywool is made by mixing terylene and wool.


Complete the crossword given below with the help of clues.

The substance is made up of a large number of smaller molecules(7).

1790995_fa30cc8cf10f41c49228bfe5fd9d2781.png


Polymer

1649585_1790995_ans_92b1317218f4470d94ebd9363f0aff58.png


Across:
First row: Substance used as synthetic wool.
Second row: A plastic used for making containers and carry bags.
Third row: Substance made up of a large number of smaller molecules. 
Fourth row: This fabric is also known as artificial silk.

Down:
First column:  A type of fibre obtained naturally from the cocoon.
Second column: A synthetic fibre classified as a polyester.
Third column: A polymer used for making ropes.

1790997_d2f48ecad1a442569aad87c54fdb5ceb.png


Across
1.ACRYLIC
2.POLYETHENE
3.POLYMER
4.RAYON
Down
1.SILK
2.TERYLENE
3.NYLON

1649588_1790997_ans_d60a5ff1e13b45c1a0486f8fe08aa14a.png


Complete the crossword given below with the help of clues.
Across
Subtance used as synthetic wool (7)
1790989_e40e09a808ff441296277cfa1e3f0034.png


$$Acrylic$$

1649551_1790989_ans_75aaed157c944082845f403dfd495d78.png


State some of the uses of synthetic polymers.

Uses of some of the synthetic polymers are given below:
(1) Nylon is a very strong synthetic polymer and hence is used in making ropes for climbing, fishing ropes, parachutes, and raincoats.
(2) Sweaters, linings, tracksuits, gloves and lining for boots are made from acrylic.
(3) Textile companies use terylene to make tapestry and other clothes like sarees.
(4) Plastic are strong, lightweight and durable, that's why they are used in making packets of pickles, dry food, milk water, and many other items.


Complete the crossword given below with the help of the clues.

$$Across:$$
First row: Substance used as synthetic wool 
Second row: A plastic used for making containers and carry bags 
Third row: Substance made up of large number of smaller molecules 
Fourth row: Another name for this compound is artificial silk 

$$Down:$$
First column:  A type of fibre obtained naturally from cocoon
Second column: A synthetic fibre classified as polyester 
Third column: A polymer used for making rope

1790993_48d3da5387f242548a7702c5276108cc.png

$$Across:$$
First row: Substance used as synthetic wool - Acrylic
Second row: A plastic used for making containers and carry bags - Polythene
Third row: Substance made up of large number of smaller molecules - Polymer
Fourth row: Another name for this compound is artificial silk - Rayon

$$Down:$$
First column:  A type of fibre obtained naturally from cocoon - Silk
Second column: A synthetic fibre classified as polyester - Terylene
Third column: A polymer used for making rope - Nylon

1649565_1790993_ans_21f5b18e8f8b4a5eb2c9bb1607ed77c3.png


Complete the crossword given below with the help of clues.
Across
(7) A polymer used for making ropes
1791001_54c58467f647463db58ed8292a3f596c.png

$$\text{Nylon}$$

1649598_1791001_ans_b3734a834b504d628b5f929e5bafe789.png


Despite being very useful, it is advised to restrict the use of plastic. Why is it so?

Items made out of plastic never completely degrade. This means the more we use plastic; we add lot of plastic to the environment.
Therefore, the more the amount of plastic, the more there is plastic pollution and its effects. Restricting the use of plastic will help reduce this to a  great effect. Hence even though plastics are very useful, the harm they cause to the environment, outweighs their utility and therefore their use should be restricted.


Complete the crossword given below with the help of clues.
Across
A synthetic fiber classified as polyester (8)
1791000_b5f2d638d52c4417bd216f0155e7f6a3.PNG

$$Terylene$$


Is it risky to wear synthetic clothes while working in the kitchen?

Yes, it is risky to wear synthetic clothes in kitchen. That's because synthetic fibres like polyester catch fire very easily and melt. After melting, they stick to the body of the person wearing them, causing severe burns. Hence, it is advised not wear synthetic clothes while working in the kitchen.


Complete the crossword given below with the help of clues.
Across
A type of fiber obtained naturally from cocoon (4)
1790999_e40852276d6549cea81667ed7aece513.png



$$Silk$$

1649592_1790999_ans_4aa3b36018274f6382d2f428093a8ede.png


Unscramble the jumbled words given below, related to synthetic materials.
(a) anory

$$\text{anory}\Rightarrow\text{ rayon}$$ 
rayon is a synthetic material.


Unscramble the jumbled words given below, related to synthetic materials
(c) relyteen

$$ relyteen \Rightarrow \text{ Terylene}$$


Unscramble the jumbled words given below, related to synthetic materials.
  • laspict
  • teresolpy

$$laspict\Rightarrow \text{Plastic}$$
$$teresolpy\Rightarrow \text{Polyester}$$


List some objects made from plastic.

Some of the objects made using plastic are:
  • Soft drink bottles.
  • Juice bottles.
  • Water bottles.
  • Shampoo/conditioner bottles.
  • Liquid hand soap bottles.
  • Carry-home food containers.


List a substance made by using cloth

Shirt or bag


Unscramble the jumbled words given below to find a term related to synthetic materials:

yespolter

Yespolter $$\Rightarrow$$ Polyester

Polyester is a synthetic fibre.


Unscramble the jumbled word given below, related to synthetic materials.
(a) lopmery

$$ lopmery\Rightarrow \text{polymer}$$
Polymers are those which consists of repeated structural units known as monomers. All these are said to be synthetic polymers.


Unscramble the jumbled words given below, related to synthetic materials.
felton

$$felton\Rightarrow\text{Telfon}$$
Teflon is a plastic, which is a synthetic material.


Plastic shows______ property, hence it can be molded to any shape.

Plastic shows the malleable property, hence it can be molded to any shape.


Rayon is also called ............. 

Rayon is also called $$\underline{artificial\ silk}$$ . rayon fiber but possesses shine like that of natural silk. That is why rayon is known as artificial silk. 


What are the natural and artificial fibers ? Give examples of each.

1.Natural Fibers - Those fibers which are obtained from plants and animals are called natural fibers .
Example - wool , cotton , jute , moonj , etc.
2. Artificial Fibers - Those fibers which are made by human with chemicals are called artificial fibers.
Example - rayon , dacron , nylon , etc.


Plastic is also a type of ......

Plastic is also type of $$\underline{synthesised\ polymer}$$, like synthetic fibres (e.g. acrylic and nylon). It is made artificially from many units of chemical substances linked together as chains or in the form of cross-links.


Give examples of natural fibres obtained from plants and animals and the objects made from them.

$$Source$$
$$Natural\ fibre$$$$Objects$$ 
$$Plants$$JuteBags
 Cotton
Clothes
$$Animals$$WoolSweaters

SilkSareers


Explain the difference between natural fibers and synthetic fibers.

1. Natural Fibers - Those fibers which are obtained from plants and animals are called natural fibers. Example: wool, cotton, jute, silk, etc.
2. Synthetic Fibers - Those fibers which are made by human with chemicals are called artificial fibers. Example: rayon, nylon, etc.


What are thermoplastics? Give example.

Plastics that get deformed easily on heating are thermoplastics. They turn liquid when heated and freeze to a very glassy state when cooled sufficiently. They can be recycled.

Example: Polythene and PVC


What is nylon used for?

Nylon is used in making canopies of parachutes, tents, sleeping bags, sails, rope, tennis strings, fishing poles and lines, cookware etc.


With the help of an activity, show the properties of two types of plastics.

Put some hot water in a plastic bottle and try to press it. You will feel that the bottle has become comparatively softer than it was before. Now at the time of cooking try to press the handle of the pressure cooker. You observe that the handle neither becomes hot nor soft. Both the bottle and handle are made of plastic but show different properties because the internal structures of both of them are different. 

$$\text{Thus plastics are of two types }$$.

(a)Thermoplastic (thermally soft): they become soft on heating.
(b)Thermosetting plastic (thermally strong ) remain hard and retain their properties even on heating


Why is polyester quite suitable for making dress material ?

$$\text{Polyester is synthetic fibre}$$. 
$$\text{Fabric made from polyester does not get wrinkled easily .}$$
$$\text{It remain crisp and is easy  to wash, so it is quite suitable for making dress materials .}$$ 
$$\text{Terylene  is a type of popular polyester,}$$ $$\text{It can be Drawn into very fine fibres that can be woven like any yam .}$$ 
$$\text{PET is also popular polyester .}$$
$$\text{It is used for making bottles .utensils, tiles, wires and many other useful products. }$$


Rayon is not considered as a synthetic fibre completely. Justify the statement. 

$$\text{In the true sense or literally rayon is not considered as a synthetic fibre completely because}$$, it involves the regeneration of cellulose from natural resources, in the synthetic, to improve the quality of fibre. Hence it is also called modified natural fibres.


Explain the statement $$\text{''reduce the use plastics in daily life as far as possible''}$$.

Extensive use of synthetic polymers has led to certain environmental hazards, making with a matter of global concern. Plastics proved to be a magical material for the world because of their properties but they have a negative side too.

1. Plastic cause health hazards and are very harmful to the environment, as they are non-biodegradable and cannot be decomposed by microorganism.

2.They prevent rainwater from seeping into the earth and affect plant growth.

3.Plastics lying on roadsides and floating in lakes and streams provide shelter for germs and animals causing diseases.

4.Toxic to aquatic life when placed in water.

5.Produce toxic gases when burned, causing air pollution.

6.Take several years to decompose.

We can avoid these problems by

1.recycling involved collecting, sorting and processing plastic.

2.following $$4R$$ $$principal$$ - reduce , reuse , recycle and recover.

3.making use of cotton, jute bags while shopping.

4.dividing the garbage into biodegradable and non-biodegradable wastes and hence recycling the non-biodegradable wastes.   


Name the two types of plastics based on their behaviour under heat.

Plastic are of two types:-
$$(a)$$ $$Thermoplastic $$, which turn soft on heating.
$$(b)$$ $$Thermosetting$$ $$plastic $$, which do not turn soft even on heating.


Thread made up of different fibers are stretched. What do you observe?

We observed that it is difficult to stretch nylon, polyester, rayon thread than cotton thread. They are more strong. 
Therefore, We can say that synthetic fibers are strong and durable for a long time.


How rayon or artificial silk produced ? Write its uses?

We know that silk discovered in China and was kept a closely guarded secret for a long time. Fabric made from the silk were very costly. However , the beautiful texture or silk fascinated everybody attempts where made by the chemists to make artificial silk, and they were successful by the end of the nineteenth century. 

The product they developed is called rayon and has similar properties to the silk. The raw material for the production of rayon is pure cotton or wood cellulose. Rayon is sometimes cellulose. Rayon us sometimes called regenerated fibre, because it is produced by modifying the natural fibre. Rayon is not truly an artificial fibre because its raw material is a natural fibre. However for all practical purposes it is included in to man - made fibre or synthetic fibre.

$$\text{Uses of Rayon}$$ :

The filament of rayon can be woven like any other natural fibre. They have a feel and texture of natural silk.
1. Rayon filament are blended with wool in the manufacture of carpet
2. Rayon filaments are blended with cotton to make smooth silk cloth which can be used for making bed sheets.
3. long filaments of rayon are used for making reinforced automobile tyres.


What are natural fibres ?

$$\text{Natural fibres are synthetic are obtained from natural sources like plants or animals}$$.


Define plastic .

$$Plastic$$ is a polymer that is easily mouded or set into any disired  shape when heated . It hardens on cooling to makes a durable object . 


What are plastics? Give examples of some plastics.

Plastics are polymers of chemical substances (units) linked together as a straight chain or as cross-links. They can be molded into solid objects. PVC, polythene, and melamine are examples of plastics.


Write differences between thermosetting and thermoplastic polymers.

Thermoplastic polymers: These are linear or slightly branched long-chain molecules capable of repeatedly softening on heating and hardening on cooling. These polymers possess intermolecular forces of attraction intermediate between those in elastomers and fibers. Polythene and polystyrene are examples of thermoplastic polymers.

Thermosetting polymers: These polymers are cross-linked or heavily branched molecules that on heating undergo extensive cross-linking in molds and become infusible. These cannot be reused. Bakelite, urea-formaldehyde, resins are examples of thermosetting polymers.


Name some modern clothes that are unstitched pieces of fabric.

Saree, dhoti, lungi and turban are unstitched pieces of fabric that are used as clothing in modern times.


List the constituent elements of some plastics?

$$\text{PVC}$$: Carbon, hydrogen, chlorine
$$\text{polythene}$$: Carbon, hydrogen


What thermoplastic and thermosetting polymers ?

Thermoplastics are linear polymers which can be repeatedly softened on heating and hardened on cooling and hence can be repeatedly used. ex: polythene, polypropene etc.
Thermosetting polymers are on the other hand permanently setting polymers. On heating, they harden and can't be softened again.
ex: bakelite, urea-formaldehyde resin.


Classify the following fibres as 'natural' or 'synthetic':
Nylon, Wool, Cotton, Silk, Polyester, Jute.

Natural fibres: Cotton, Jute, Silk, Wool- obtained from natural sources like plants and animals.

Synthetic fibres: Nylon, Polyester- obtained from chemical processes by man-made efforts.


Why cotton clothes are preferred over synthetic fibre?

Cotton clothes are preferred over synthetic fiber because they are natural fiber and are biodegradable. They do not cause any pollution and are also good for our skin as they have natural ventilation.


The school science club has decided to conduct poster propaganda for creating awareness about pollution due to plastics. Prepare some posters for it.

Posters can be made using the quotes:
  • Avoid disposable plastic products use glass, ceramic utensils or natural substances
  • Use paper or natural materials for decorations
  • Don't dump plastic materials in soil. 


Some argue that plastics are to be completely banned as they cause environmental pollution. What is your view? 

No, Without plastic, we cannot manage daily life. 
We should control the usage of plastic, avoid disposable plastic products and use thermoplastic materials.


What suggestions can you propose to realise the concept of plastic waste-free school'? List your findings. 

Reduce: Buy only what you need because a better way to reduce waste is by not creating it. Reuse: Instead of throwing out the plastic products you no longer think you need, try repurposing them because plastics exist for a long time. Eg. use refill in ball pens, use thick plastics which can be reused, reuse plastic bottles. The banning of plastics below the thickness of 30 microns aims at this. When thickness increases a tendency will arise to use it again. 

Recycling-. Is the process by which the plastics which is rendered useless are heated and subjected to certain processes to produces new materials. 
Recycling the rate of environmental pollution.

Refuse: We can avoid the use of plastic when it is not necessary. Avoid thin plastic covers when things are bought. Use cloth bag paper bag or thick plastic covers which can be used for a long time 


Write 4 activity due to which plastic is harmful to daily life.

1. Environmental pollution when it is thrown without any control. 
2. When burning, it causes air pollution. 
3. Hindrance in drainages.
4. The water absorption property of soil decreases when plastics are dumped in soil. 


What are looms?

The devices on which weaving of fabrics takes place are called looms. The looms are either hand operated or power operated.


When we burn nylon, why we do not get the smell of burning paper or burning hair?

Nylon is a synthetic fibre made from chemicals. On burning nylon these chemicals don’t produce the smell of burning paper or hair which are natural substances.


Given some occasions of using plastic. Find the peculiarity of plastic used and fill the table. Answer:     
OccasionPeculiarity
As the covering of the conductor
To make the handles of cooking vessels
To keep chemicals 
To make water tanks
To make household materials

OccasionPeculiarity
As the covering of conductorPlastics are insulators
To make the handles of cooking vessels  Not conducting heat
To keep chemicals Do not react with chemical 
To make water tanksNo rusting. Less weight 
To make household materialsEasy to use. Less weight 


What are natural fibres? Explain with example.

The fibres obtained from plants and animals are called natural fibres. 
For example Cotton from cotton balls, jute from the jute plant, silk from cocoon of silkworm and from the hair of animals like sheep or goats.


Name some items that are made from coir, jute, hemp, silk, and cotton.

Some items that are made from coir: Ropes, floor covering, stuffing in mattresses, and pillows.

Some items that are made from Jute: Jute bags, hat, slipper, rope, mat, and sack.

Some items that are made from hemp: Ropes, carpets, nets, clothes, and paper.

Some items that are made from flax: Used to make a fabric called linen, rope, and quality paper.


What is the use of plastic in the field of human health?

To produce heart valves is the major use of  plastics in human health.


Give examples for natural fibres.

Examples for natural fibres are coconut husk, cotton, hemp, silk etc.


List the peculiarities of plastic.

Peculiarities of plastic are it can be molded in any shape, it is long-lasting, itis insulator, does not conduct heat, does not react with chemicals and water, will burn. 


A plastic used for making crockery is ______ .

Answer: melamine

A plastic used for making crockery is melamine. That's because melamine resists fire and can tolerate heat better than other plastics.


Classify the following into thermoplastic and thermosetting plastics. 
Bakelite, polyvinyl chloride, nylon, celluloid, urea-formaldehyde, Teflon, polyester, polythene. 

ThermoplasticsThermosetting
Nylonplastics
Polyvinyl chloride                     Bakelite
polythene urea formaldehyde
celluloidpolyester
Teflon


Class 8 Chemistry Extra Questions