Polymers Class 12 Notes CBSE Chemistry Chapter 15 (Free PDF Download)

Section–A (1 Mark Questions)

1. Arrange the following polymers in the increasing order of their intermolecular forces : Polystyrene, Terylene, Buna-S.

Ans. The intermolecular forces are least in case of elastomers like Buna-S while strongest in case of fibres like terylene and in case of thermoplastics like polystyrene the intermolecular forces are intermediate in between elastomers and fibres.

Thus, the increasing order of their intermolecular forces is Terylene > Polystyrene > Buna-S.

2. Write the name and structure of the monomers of the following polymer : Buna-S

Ans. Buna-S:

3. Which of the following is a natural polymer? Buna-S, Proteins.

Ans. Proteins are natural polymers.

4. What does the part ‘6,6’ mean in the name nylon-6,6?

Ans. In nylon 6, 6, designation ‘6, 6’ mean that both the monomers hexamethylene diamine and adipic acid contain six carbon atoms each.

5. Name a synthetic polymer which is an amide.

Ans. Nylon-6, 6.

6. What is the commercial name of PMMA?

Ans. The commercial name of PMMA (polymethylmethacrylate) is Perspex.

7. What is the trade name of polyacrylonitrile?

Ans. Orlon.

8. What is the primary structural feature necessary for a molecule to make it useful in a condensation polymerisation reaction ?

Ans. The monomers must be bifunctional i.e. contain two functional groups.

9. What are polymers?

Ans. Polymers are high molecular mass substances formed by the combination of a large number of simple molecules. They are also called macromolecules. For example, polythene, bakelite, etc.

10. Can enzyme be called a polymer?

Ans. Enzymes are biocatalysts which are proteins and are thus polymers.

Section–B (2 Marks Questions)

11. Define thermoplastics and thermosetting polymers with two examples of each.

Ans. Thermoplastics are the polymers which can be easily softened repeatedly on heating and hardened on cooling. Therefore, it can be used again and again. For example, 

(i) Polythene 

(ii) Polyvinyl chloride 

Thermosetting polymers are those which undergo permanent change on heating. They become hard and infusible on heating and cannot be softened again. For example, (i) Bakelite (ii) Urea formaldehyde resin.

12. What is the difference between elastomers and fibres ? Give one example of each.

Ans. (i) In elastomers polymer chains are held together by weakest intermolecular forces. These have elastic properties. e.g. Buna-N, Buna-S. 

(ii) In fibres polymer chains are held together by strong intermolecular forces like hydrogen bonding. These have high tensile strength. e.g., Terylene, Nylon 6,6, etc.

13. (i) What is the role of sulphur in the vulcanisation of rubber?

(ii) Identify the monomers in the following polymer:

Ans. (i) Vulcanisation is a process of heating natural rubber with sulphur and an appropriate additive to modify its properties.

It gives greater elasticity and ductility. Sulphur forms cross linked network which gives mechanical strength to the rubber.

(ii) Terephthalic acid and ethylene glycol.

14. Write the name of monomers used for getting Bakelite and give a use of Bakelite.

Ans. Bakelite: Formaldehyde (HCHO) and Phenol (C6H5OH). Bakelite is used in making combs, electrical switches etc.

15. How is dacron obtained from ethylene glycol and terephthalic acid?

Ans. Dacron is obtained by the polymerisation of ethylene glycol and terephthalic acid:

16. Why are rubbers called elastomers?

Ans. When force is applied, rubbers are stretched and these regain original state after the force is removed. Therefore these are called elastomers.

17. Can nucleic acids, proteins and starch be considered as step growth polymers?

Ans. Yes, step growth polymers are condensation polymers and they are formed by the loss of simple molecule like water leading to the formation of high molecular mass polymers.

18. To have practical applications why are cross links required in rubber?

Ans. The cross-links make the rubber hard, tough with greater tensile strength. The vulcanised rubber has excellent elasticity, low water absorption tendency, resistance to oxidation and organic solvents.

19. Differentiate the following pair of polymer based on the property mentioned: 

Novolac and bakelite (structure).

Ans. Novolac is a straight chain linear polymer but bakelite is cross linked.

 PDF Summary - Class 12 Chemistry Polymers Notes (Chapter 15)

1. Introduction

A polymer is a high molecular weight molecule made up of a large number of one or more different types of tiny molecular weight components.

Monomer refers to the tiny unit(s) from which polymer is formed.

A chemical combining of a number of similar or distinct molecules to produce a single big molecule is known as polymerization.

Homopolymer refers to a polymer that is made up of only one type of monomer molecule. Polyethene, PVC, PAN, Teflon, Buna rubber, and other materials are examples.

A copolymer is a polymer that is made up of more than one type of monomer. Buna-S, Dacron, Nylon-6,6, Bakelite, and so forth.

2. Classification

We can classify the polymers into two types and this is based on the origin of the polymer. These are natural polymers and synthetic polymers. These are explained below:

2.1 Natural Polymer

These come from nature or can be found in plants and animals. Natural polymers, commonly known as biopolymers, are a type of natural polymer.

Proteins (Polymers of amino acids), Polysaccharides (Polymers of monosaccharides), rubber (Polymers of isoprene), silk, wool, starch, cellulose, enzymes, natural rubber, haemoglobin, and so on are all examples of polymers.

2.2 Synthetic Polymer

These are man-made polymers. Polythene, nylon, PVC, bakelite, and dacron are among examples.

3. Synthesis

Polymers can be synthesized by two processes, i.e., Addition and Condensation.

3.1 Addition Polymerization

When the monomers are added without the loss of any molecule, then the polymer is called Addition Polymer. Example, Polyethene, PAN, etc. The production of addition polymers is referred to as addition polymerization.

3.2 Condensation Polymerization

When the monomers are added and there is loss of small molecules like water, then the polymer is called Condensed Polymer. The process by which Condensed polymers are formed is known as Condensation Polymerization. Example, Nylon-6,6, Bakelite, etc.

4. Mechanism of Polymerization

4.1 Chain Growth Polymerization

These polymers are made by adding monomer units one by one to a developing chain using a reactive intermediate (Free radical, carbocation or carbanion). Alkenes and conjugated dienes undergo chain growth polymerization, which is a common process.

Chain growth polymers include polythene, polypropylene, Teflon, PVC, and polystyrene.

We can also call Chain Growth Polymerization as Addition Polymerization.

4.2 Step Growth Polymerization

A variety of separate processes are used to create these polymers. Each step entails the condensation of two monomers, which results in the creation of a smaller polymer.

Nylon, terylene, Bakelite, and other synthetic materials are examples.

We can also call Step Growth Polymerization as Condensation Polymerization.

5. Copolymerization

A polymer made up of two or more monomer species is known as a copolymer. Copolymers make up a large number of economically significant polymers. Polyethylene-vinyl acetate (PEVA), nitrile rubber, and acrylonitrile butadiene styrene are among examples (ABS). Copolymerization refers to the process of creating a copolymer from several monomer species. It's frequently used to improve or change the characteristics of plastics.

6. Some Important Polymers

6.1 Polyethene

Polyethene is a polymer which is made up of only one type of monomer known as Ethene. The formula of ethene is $\text{C}{{\text{H}}_{\text{2}}}\text{=C}{{\text{H}}_{\text{2}}}$. Polyethene is formed by Addition Polymerization or Chain growth Polymerization. The reaction is given below:

\[\text{n C}{{\text{H}}_{\text{2}}}\text{=C}{{\text{H}}_{\text{2}}}\text{ }\xrightarrow{\text{Polymerization}}\text{ }{{\left( \text{-C}{{\text{H}}_{\text{2}}}\text{-C}{{\text{H}}_{\text{2}}}\text{-} \right)}_{\text{n}}}\] 

Polyethene is slightly flexible, inert, a poor conductor of electricity, and a strong material. It is used for making buckets, toys, packing materials, etc.

6.2 Nylon 6,6

Nylon 6,6 is a polymer which is formed by two types of monomers, i.e., adipic acid and hexamethylenediamine. It comes under the category of Polyamides. It is formed by Condensation Polymerization. The reaction is given below:

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6.3 Polyester

Polyesters are those classes of polymers in which two monomers are formed by an ester bond. An ester is shown as –O–. It forms when one of the monomers is an alcohol and the second one is an acid. Terylene or Dacron is an example of Polyester. It is used for making fiber of high crease-resistant, durable, and having low moisture content.

6.4 Bakelite

Bakelite is a phenol-formaldehyde polymer because the monomers of Bakelite are phenol and formaldehyde. Bakelite is a cross-linked polymer and it is also a thermosetting polymer. It is used for making computer discs, phonograph records, fountain pen barrels, etc.

6.5 Natural Rubber

Natural rubber is a polymer as it has elasticity and long range reversible extension it is also called an elastomer. The monomer of natural rubber is isoprene or 2-Methyl-1,3-Butadiene. Natural rubber is also known as Polyisoprene. The reaction is given below:

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7. Biodegradable and Non-Biodegradable Polymer

7.1 Biodegradable Polymer

Biodegradable polymers are natural polymers (cellulose, starch, proteins, nucleic acids, and so on) that dissolve on their own after a given amount of time. 

7.2 Non-Biodegradable Polymer

Synthetic polymers, on the other hand, do not degrade over time and are thus referred to as Non-Biodegradable Polymers.

8. Some Synthetic Biodegradable Polymer

There are some Synthetic polymers which are biodegradable and these are given below:

• Poly-$\text{ }\!\!\beta\!\!\text{ }$-hydroxybutyrate-Co-$\text{ }\!\!\beta\!\!\text{ }$-hydroxyvalerate (PHBV): It is a copolymer of 3-Hydroxybutanoic acid and 3-Hydroxypentanoic acid.

• Dextron: Poly(glycolic acid) Poly(lactic acid) is the other name of dextron and it is also a Synthetic Biodegradable Polymer.

• Nylon-2-Nylon-6: It is a polymer of Glycine and 6-Aminohexanoic acid.

9. Some Important Polymers with Monomers are Given Below:

Polymers: Class 12 Chemistry Chapter 15 Summary

If you study this chapter, you will find the meaning of the word ‘polymer’. Here, ‘poly’ means more than one. polymers are bigger molecules produced due to the bonding between the monomers (single molecule). Polymers can be natural or prepared synthetically. Proceed to study the chapter and find out what new concepts you can learn. Here, you will need Class 12 Chemistry Polymers Revision Notes as a reference.

In this chapter, you will find out the proper explanation of all the sections. The first section describes the different classifications of polymers. Here, you will find out what linear, branched/chain, or cross-linked polymers. This classification is done based on the chemical structure of a polymer molecule. Similarly, if you consider the origin of polymers, you will find three distinct classes. They are synthetic, semi-synthetic, and natural. Every class of the polymers will be properly explained with apt examples and descriptions. Follow Polymers Class 12 Chemistry Revision Notes so that you can grab hold of the concepts well and quickly answer the questions.

On proceeding further, you will understand that polymerization is of different types. The nature of the reactions will also determine the chemical structure of the polymers. In addition reaction, the monomer molecules are attached one after the other in a simpler way. The monomers are small molecules with double or triple bonds. For instance, polypropylene forms when propene monomers join one after the other. Check the Revision Notes Class 12 Chapter 15 for a better description of addition polymers along with examples.

Another type of polymers is formed by conducting a condensation reaction. When the condensation reaction is repeated, the monomers connect to each other to form a macromolecule. The monomers can either be bi-functional or tri-functional. The best example, in this case, is nylon. Refer to the Class 12 Revision Notes Chapter 15 to understand condensation reaction better and find a proper explanation of the examples too.

Why Use the Revision Notes for Polymers Class 12 Chemistry?

Polymers are typically used almost every day in our daily life. We find them in packaging materials, utensils, furniture, electronic devices, etc. High-quality polymers are even used for industrial and medical purposes. To learn polymers, you will need the assistance of the Revision Notes Class 12 Chemistry Chapter 15. In these notes, the experts have perfectly explained how polymers are formed. Natural polymers are also defined and explained in such a way that you can resolve your queries on your own.

The revision notes for this chapter are designed in such a way that you can organize your study schedule and give a better output. You can easily revise and prepare the chapter before an exam to score better. Study the chapter and use these revision notes to prepare more efficiently. Add these revision notes to your chemistry study material and prepare the chapter better to stay ahead of the competition.