CBSE Class 12 Chemistry Chapter 15: Polymers NCERT Solutions

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 12 PDF

This resource provides detailed NCERT Solutions for Chapter 15 on Polymers, designed for CBSE Class 12 Chemistry students. It covers fundamental concepts such as the definitions of polymers and monomers, distinguishing between natural and synthetic polymers with examples, and explaining the functionality of monomers. The solutions also clarify the process of polymerization and differentiate between homopolymers and copolymers. Furthermore, it details the classification of polymers based on intermolecular forces, including elastomers, fibres, and thermoplastic polymers. These solutions offer step-by-step explanations to help students grasp complex topics, aiding in effective exam preparation and revision by reinforcing key concepts and problem-solving techniques.

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Board	CBSE
Class	Class 12
Subject	Chemiry
Session	2026
Language	English
Type	NCERT Solutions
Chapter	Chapter 15: Polymers - NCERT Exercises Solutions

Chapter summary

This chapter focuses on the fundamental concepts of polymers. The NCERT Solutions cover definitions of polymers and monomers, classification based on origin (natural/synthetic) and structure (homopolymer/copolymer), and the concept of monomer functionality. It also explains the polymerization process and classifies polymers based on intermolecular forces into elastomers, fibres, and thermoplastics. The exercises are designed to build a strong understanding of polymer chemistry.

Learning outcomes

Understand the definitions of polymer and monomer.
Differentiate between natural and synthetic polymers.
Distinguish between homopolymers and copolymers with examples.
Explain the concept of monomer functionality.
Define the polymerization process.
Classify polymers based on intermolecular forces.

Topics covered

Paper topics

Polymer definition
Monomer definition
Natural polymers
Synthetic polymers
Homopolymers
Copolymers
Monomer functionality
Polymerization
Classification of polymers
Intermolecular forces in polymers
Elastomers
Fibres
Thermoplastic polymers

Important topics

Definitions of Polymer and Monomer
Classification of Polymers (Natural/Synthetic, Homopolymer/Copolymer)
Monomer Functionality
Polymerization Process
Classification based on Intermolecular Forces

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Questions and Solutions

Question 15.1

Explain the terms polymer and monomer.

Solution: A polymer is a large, complex molecule, also known as a macromolecule, which is composed of many repeating structural units. These repeating units are derived from smaller molecules called monomers. Polymers typically have very high molecular masses, ranging from

10^3

10^7

atomic mass units (u). The monomer units within a polymer are linked together by strong covalent bonds. Polymers can occur naturally (like proteins and cellulose) or be synthesized artificially (like polythene and nylon 6,6). A monomer, on the other hand, is a simple, reactive molecule that serves as the building block for polymers. Monomers undergo a process called polymerization, where they join together in large numbers to form long chains or networks, creating polymers. Examples of monomers include ethene (which forms polythene), propene, styrene, and vinyl chloride.

Question 15.2

What are natural and synthetic polymers? Give two examples of each type.

Solution: Polymers can be broadly classified based on their origin into natural and synthetic types. Natural polymers are those that are found in nature and are typically produced by plants and animals. They are essential components of living organisms. Examples of natural polymers include:

Proteins: Found in hair, wool, silk, and enzymes.
Cellulose: A major structural component of plant cell walls.
Starch: A carbohydrate used for energy storage in plants.
Natural rubber: Obtained from the latex of rubber trees.

Synthetic polymers are man-made polymers, produced through artificial chemical processes. They are designed to have specific properties for various applications. Examples of synthetic polymers include:

Plastics: Such as polythene (polyethylene), PVC (polyvinyl chloride).
Synthetic fibres: Like nylon 6,6 and polyester.
Synthetic rubbers: Such as Buna-S (styrene-butadiene rubber) and neoprene.

Question 15.3

Distinguish between the terms homopolymer and copolymer and give an example of each.

Solution: Polymers can be classified based on the type of monomers they are composed of. The two main categories are homopolymers and copolymers. Homopolymer: A homopolymer is a polymer whose repeating structural units are all derived from a single type of monomer. In simpler terms, it is made up of only one kind of repeating building block. Example: Polythene is a homopolymer because it is formed solely from the polymerization of the monomer ethene (

CH_2=CH_2

). Copolymer: A copolymer is a polymer whose repeating structural units are derived from two or more different types of monomers. These different monomers are incorporated into the polymer chain, often in an alternating or random fashion. Example: Buna-S is a copolymer. It is synthesized from the polymerization of two different monomers: 1,3-butadiene and styrene.

Question 15.4

How do you explain the functionality of a monomer?

Solution: The functionality of a monomer refers to the number of specific, reactive sites or binding positions within that monomer molecule that are capable of participating in the polymerization reaction. These sites are where the monomer can form covalent bonds with other monomers to build the polymer chain. For instance:

Monomers like ethene ( $CH_2=CH_2$ ) and propene ( $CH_3-CH=CH_2$ ) have a functionality of one. This is because they typically react through their double bond, which acts as a single reactive site for addition polymerization.
Monomers like 1,3-butadiene ( $CH_2=CH-CH=CH_2$ ) and adipic acid ( $HOOC-(CH_2)_4-COOH$ ) have a functionality of two. 1,3-butadiene can react at its double bonds, and adipic acid has two carboxyl groups ( $-COOH$ ) that can react, allowing them to form linear polymer chains by linking at two points.

The functionality of a monomer is crucial in determining the type of polymer formed (linear, branched, or cross-linked).

Question 15.5

Define the term polymerisation.

Solution: Polymerization is the fundamental chemical process by which small, reactive molecules known as monomers combine chemically to produce a large chain-like molecule, or macromolecule, called a polymer. This process involves the formation of new covalent bonds between the monomer units. During polymerization, a large number of monomer molecules link together to form a polymer chain. The resulting polymer has a very high molecular mass, typically in the range of

10^3

10^7

atomic mass units (u). The structure of the polymer consists of repeating structural units that are derived from the original monomers. The specific way monomers join depends on the type of polymerization reaction (e.g., addition or condensation polymerization).

Question 15.6

Is $+NH-CHR-CO)_n$ , a homopolymer or copolymer?

Solution: The polymer represented by the formula

+NH-CHR-CO)_n

is a homopolymer. This is because the repeating unit

(-NH-CHR-CO-)

is derived from a single type of monomer. This monomer is an amino acid, which has the general structure

NH_2-CHR-COOH

. In the polymerization process, the amino group (

-NH_2

) of one amino acid molecule reacts with the carboxyl group (

-COOH

) of another, forming an amide linkage (

-NH-CO-

) and releasing a molecule of water. Since only one type of monomer (an amino acid) is involved in forming the polymer chain, it is classified as a homopolymer.

Question 15.7

In which classes, the polymers are classified on the basis of molecular forces?

Solution: Polymers can be classified into different classes based on the strength and type of intermolecular forces that exist between their long molecular chains. These forces significantly influence the physical properties of the polymer. On the basis of the magnitude of intermolecular forces, polymers are primarily classified into the following three groups:

Elastomers: These polymers have weak intermolecular forces between their chains, allowing them to be stretched considerably and return to their original shape upon release of the stress. Examples include natural rubber and Buna-S.
Fibres: These polymers possess strong intermolecular forces, such as hydrogen bonds or dipole-dipole interactions, which hold the chains tightly together. This results in a high tensile strength and a thread-like structure. Examples include nylon and silk.
Thermoplastic polymers: These polymers have intermediate intermolecular forces. They soften upon heating and can be molded into different shapes, and they solidify upon cooling. This process can be repeated. Examples include polythene and polystyrene.

Common mistakes

Confusing homopolymers with copolymers.
Misunderstanding the concept of monomer functionality.
Incorrectly classifying polymers based on intermolecular forces.

Revision tips

Clearly define and differentiate between polymers and monomers.
Memorize examples of natural, synthetic, homopolymers, and copolymers.
Understand the basis for classifying polymers (origin, structure, intermolecular forces).
Review the concept of monomer functionality and its role in polymerization.

Practice MCQs

Q1. What is a polymer?

Q2. Which of the following is an example of a natural polymer?

Q3. A polymer formed from only one type of monomer is called a:

Q4. What does the functionality of a monomer refer to?

Q5. Which class of polymers exhibits strong intermolecular forces and can be drawn into long threads?

Frequently asked questions

What is the difference between a polymer and a monomer?

A monomer is a small, simple molecule that can react with other monomers. A polymer is a large molecule, or macromolecule, formed by the chemical combination of many monomers.

Can you give examples of natural and synthetic polymers?

Natural polymers include proteins, cellulose, and starch. Synthetic polymers are man-made, such as polythene, nylon 6,6, and synthetic rubber (Buna-S).

What is a homopolymer versus a copolymer?

A homopolymer is made from only one type of monomer, like polythene from ethene. A copolymer is made from two or more different types of monomers, such as Buna-S from butadiene and styrene.

How are polymers classified based on intermolecular forces?

Polymers are classified into elastomers (weak forces, rubber-like elasticity), fibres (strong forces, thread-like structure), and thermoplastic polymers (intermediate forces, soften on heating).

What is monomer functionality?

Monomer functionality refers to the number of binding or reactive sites a monomer has, which dictates how it can link with other monomers to form a polymer chain.

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