Samacheer Kalvi 7th Science Term 3 Solutions Chapter 3 Pdf

Samacheer Kalvi 7th Science Term 3 Solutions Chapter 3 Pdf

Tamilnadu Board Samacheer Kalvi 7th Science Term 3 Solutions Chapter 3: Tamilnadu State Board Solution Class 7 Science Term 3 Chapter 3 – Polymer Chemistry.

Samacheer Kalvi 7th Science Term 3 Solutions Chapter 3: Overview


Samacheer Kalvi





Chapter Name

Polymer Chemistry

Samacheer Kalvi 7th Science Term 3 Solutions Chapter 3 Pdf

I.) Choose the correct answers

1.) The first man-made fibre is ___

a) Nylon

b) Polyester

c) Rayon

d) Cotton

Answer : c) Rayon

Solution : Rayon is the first man made fibre. It was made as a substitute for silk in the late 19th century.

2.) Which of the following is the strongest?

a) Rayon

b) Nylon

c) Acrylic

d) Polyester

Answer : b) Nylon

Solution : Nylon is much stronger than Rayon, acrylic and polyester. Nylon thread is actually stronger than a steel wire.

3.) When you place a natural fibre in a flame it______

a) melts

b) burns

c) gets nothing

d) explodes

Answer : b) burns

Solution : Natural fibres are flammable in nature. They will burn when placed in a flame.

4.) A synthetic fibre which has similar properties to wool is ____

a) Nylon

b) Polyester

c) Acrylic

d) PVC

Answer : c) Acrylic

Solution : Acrylic has similar properties as that of wool. It is soft and gives warmth like wool but doesn’t absorb water.

5.) A good application of plastic is the use of ____

a) Blood bags

b) Plastic cutlery

c) Plastic straws

d) Plastic carry bag

Answer : a) Blood bags

Solution : Separation of blood is much easier in plastic bags. Therefore blood bags are made of plastic.

6.) ____ is a non-biodegradable material


b) A plastic bottle

c) Cotton cloth

d) Wool

Answer : b) A plastic bottle

Solution :Non- biodegradable materials are those that cannot be decomposed through natural processes or by microorganisms. Plastic products are non- biodegradable materials.

7.) PET is the acronym for ____

a) Polyester

b) Polyester and terylene

c) Polyethylene terephthalate

d) Polyetheneterylene

Answer : c) Polyethylene terephthalate

Solution :Polyethylene terephthalate (PET) is considered to be the most common thermoplastic polymer resin that is usually used in the making of fibres and containers.

II.) Fill in The Blanks

1.) _Raincoat ____ is an example of polyester fabric.

2.) _Resin codes__ are used to identify different types of plastics.

3.) A_Polymer__ is a long chain made up of many repeated small units called monomers.

4.) A natural fibre is called _Plant fibres___

5.) A natural fibre obtained by boiling cocoons is called___silk__

III.) True or False

1.) A lot of plastic pollutes our environment.

Answer : True

2.) Refuse (avoid) is the best way to manage plastic.

Answer : True

3.) It is good to wear clothes made of synthetic fibres while cooking.

Answer : False

Correct Statement : It is good to wear clothes made of natural fibres while cooking.

4.) Degradable plastics break down into tiny pieces called microplastics.

Answer : True

5.) Cotton is a natural polymer.

Answer : True

IV.) Match the Following

Nylon Fibre
PVC Thermoplastic
Bakelite plastic Thermosetting
Teflon cockware Non stick
Rayon Wood pulp


V.) Arrange in Correct Sequence

1.) Mix water, starch, vinegar and glycerin in a cooking pot.

2.) Let the article cool for 24 hours before we use it.

3.) Shape material to form a cup or bowl.

4.) Continuously mix on medium heat until the liquid turns clear.

5.) When the liquid begins to bubble it is ready to be taken off the stove.

6) Spread the gel onto aluminium foil and cool.

 Answer : 1, 4, 5, 6, 3, 2.

VI.) Analogy

1.) Cotton: natural : Polyester: __synthetic__

2.) PLA spoon : compostable : Plastic spoon : __disposable ____

3.) Nylon :melts on heating : Silk: __burns on heating ___

VII.) Assertion and Reason

1.) A: Vegetable peels buried in the soil disappear within two weeks.

R: Vegetable peels are compostable.

Answer : (a) Both A and R are true and R is the correct explanation of A

2.) A: It takes a very long time for nylon clothes to breakdown into microfibers but cotton clothes need only six months to decompose.

R: Nylon made out of petrochemicals isnon-biodegradable and cotton cloth is biodegradable.

Answer : (a) Both A and R are true and R is the correct explanation of A

3.) A: It is good to avoid plastics.

R: Plastics end up polluting the environment.

Answer : (a) Both A and R are true and R is the correct explanation of A

VIII.) Crossword


1) Acrylic

2) Polyethene

3) Polymer

4) Rayon


5) Silky

6) Terycot

7) Nylon


IX.) Very Short Answer

1.) What is the chemical name of the polymers that make up cotton?

Answer : Cellulose

2.) What gives plastic different qualities and characteristics?

Answer : In the production of plastics different additives or chemicals are used that give them various qualities and characteristics like waterproof, lightweight, strong, flexible etc.

3.) It is not advisable to burn plastic and synthetic fabrics. Why?

Answer : On burning plastics form toxic chemicals that do not dispose easily. This causes serious effects. Therefore it is not advisable to burn synthetic fabrics and plastic.

4.) A bucket made of plastic does not rust like a bucket made of iron. Why?

Answer : Because plastic does not react with moist air whereas iron reacts with moist air (oxgen + water) to form rust.

5.) Why is it better to avoid the use of plastic products?

Answer :It is better to avoid the use of plastic products because they do not decompose or destroy easily. Use of plastic products is one of the main cause of pollution that lead to diseases and it also impact animal lives.

6.) Give two examples of thermosetting plastics.

Answer : 1)Bakelite


7.) What is the 5 R principle?

Answer :  5R Principle – Refuse, Reduce, Reuse, Recycle and  Recover.

X.) Short Answer

1.) What does the term biodegradable mean?

Answer :The term biodegradable refers to those materials that get easily decompose through natural process or by the help of bacteria and other microorganisms.

2.) What kind of fabric is suitable to dress-up and play in the summer?

Answer : During summer it is favorable to wear light coloured cotton clothes as cotton fabric absorbs sweat and helps in circulation of air. Also light colour clothes reflects sun rays more.

3.) How do plastics impact animals and the environment?

Answer :

Plastic cause serious problems to animals and environment .

People usually throw left over food wrapped in plastic bags. When animals eat the food from them they accidentally eat the plastic along with the food. This causes serious health issues and sometimes animal also die due to this.

Accumulation of large amount of plastic wastes in landfills or dumping of plastics in open area pollute the environment. Often thrown away plastic bags and food packaging or other one time use plastics are responsible for clogging drains. Diseases such as malaria and dengue are spread through mosquitoes that breeds in standing water. This also leads to flooding.


XI.) Long Answer

1.) List the advantages and disadvantages of synthetic fibres.

Advantages :

  1. As compared to natural fibres, synthetic fibres are much stronger and durable.
  2. They are easier to maintain and wash.
  3. They take less time to dry and also absorb less water. This is the reason why swimming costumes are made of synthetic fibres.
  4. They have similar shine and lustre as natural fibres but are more affordable than natural fibres.
  5. Synthetic fibres never shrink.
  6. Resistant to insect and moth.
  7. Unlike natural fibres,  yielding of synthetic fibres does not depend upon crops or Animals.


Disadvantages :

  1. Synthetic fibres are flame resistant. While some are ignite, they will melt easily upon heating.
  2. Synthetic clothes are not favorable to wear during humid and summer season as they do not absorb water or sweat.
  3. We may cause skin allergies due to deposition of sweat if we wear synthetic clothes in humid or summer season.
  4. They are not environmental friendly.
  5. In the production of synthetic fibres a huge amount of exhautible resources like petrochemicals are used.


2.) Suggest safe methods of disposing plastics.

Answer :

Various methods of disposing plastics are:

Refuse : Try avoiding the use of one-time use throwaway plastics

Reduce : The amount of plastics we use should be reduce and this should be considered important.

Reuse : It refers to reusing of plastic products as much as possible.

Recycle: Recycle refers to recycling of plastic wastes. Instead of dumping or throwing plastic wastes in landfills, it should be Separated based on the resin code and can be recycled into something new that is useful.

Recover (Compost and Incinerate): This involves converting of solid wastes into resources such as electricity and compost using thermal or biological means.



1.) The Tamil Nadu Government has banned the use of one-time use throwaway plastics.Why do you think this is important?

Answer :The use of one-time use plastics like plastic bags and food packaging are one of the main cause of pollution as they cannot be destroyed completely. So banning them is important.

2.) A plastic bag dumped in the soil stays without breaking down for 500 years. If a new generation starts in every 30 years, how many generations would it take to see the plastic bag finally broken down?

Answer : For around 500 years dumped plastic bags stays in the soil. To see these bags finally broken down it would take 16 – 17 generations.


XIII.) i) Fill in the blanks

ii) Look at the following picture and explain what is happening.

Answer : Often thrown away plastic bags and food packaging or other one time use plastics are responsible for clogging drains and polluting the environment. Diseases such as malaria and dengue are spread through mosquitoes that breeds in standing water. This also leads to flooding.

iii) Read the following information and convert them into a graph to compare the countries and the amount of plastic they use.

China contributes the highest share – that is around 28%, of the total plastic used globally. Indonesia uses 10%, both the Philippines and Vietnam use 6% each; Thailand uses 3.2%, Egypt 3%, Nigeria 2.7% and South Africa 2%.

Answer :

Updated: July 6, 2022 — 12:30 am

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