🧪 CBSE · Class 12 · Chemistry · Chapter 15

Chapter 15:
Polymers

Complete chapter resources for CBSE Class 12 Chemistry — classification, addition and condensation polymerisation, important synthetic and natural polymers, biodegradable materials, and instant AI question paper generation.

3Topics
4–5Board marks
8Sample questions
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Key Concepts — Chapter 15
  • Addition polymer: nCH₂=CH₂ → (−CH₂−CH₂−)ₙ (polyethylene)
  • Condensation polymer: monomers react → polymer + small molecule (H₂O, HCl)
  • Nylon-6,6: hexamethylenediamine + adipic acid; amide (−CO−NH−) linkage
  • Dacron (Terylene): ethylene glycol + terephthalic acid; ester linkage
  • Bakelite: phenol + formaldehyde; cross-linked thermosetting
  • PHBV: biodegradable co-polymer; β-hydroxybutyrate + β-hydroxyvalerate
Chapter Overview

What this chapter covers

Polymers are large macromolecules formed by the repetitive bonding of small structural units called monomers. Chapter 15 of NCERT Class 12 Chemistry classifies polymers on the basis of source (natural, semi-synthetic, synthetic), structure (linear, branched, cross-linked), and mode of polymerisation (addition vs. condensation). Understanding these classification axes is essential for answering definition-based board questions and for connecting polymer properties to their industrial uses.

The two central reaction mechanisms are addition polymerisation — where unsaturated monomers link together without eliminating any atom (e.g., polyethylene, PVC, Teflon, Buna-S) — and condensation polymerisation — where bifunctional monomers react repeatedly, releasing a small molecule such as water or HCl at each step (e.g., Nylon-6,6, Nylon-6, Dacron, Bakelite). Board questions frequently ask students to identify the monomer(s), type of polymerisation, and functional linkage (amide, ester, peptide) for a named polymer.

A growing area of the chapter is biodegradable and specialty polymers. PHBV (poly-β-hydroxybutyrate-co-β-hydroxyvalerate) is the key NCERT example of an eco-friendly polymer used in packaging and surgical sutures. Students are also expected to know about rubber — both natural rubber and synthetic elastomers (Buna-S, Buna-N, neoprene) — as well as the distinction between thermoplastic and thermosetting polymers (Bakelite, melamine-formaldehyde resin). These application-oriented details are common in the 2–3 mark short-answer questions seen in recent board papers.

Topics

What's inside Chapter 15

As per NCERT Class 12 Chemistry (CBSE syllabus)

Topic 1
Classification of Polymers
Classification by source (natural, semi-synthetic, synthetic), by structure (linear, branched, cross-linked), by mode of synthesis (addition, condensation), and by molecular forces (elastomers, fibres, thermoplastics, thermosetting plastics).
Topic 2
Polymerisation Reactions
Addition polymerisation (free-radical, cationic, anionic mechanisms) of alkene monomers producing polyethylene, PVC, Teflon, polystyrene, Buna-S, Buna-N, and neoprene. Condensation polymerisation producing Nylon-6,6, Nylon-6, Dacron, Bakelite, and melamine-formaldehyde resin — with monomer names, linkages, and reaction conditions.
Topic 3
Important Polymers & Biodegradable Polymers
Properties and uses of natural rubber, vulcanised rubber, and key synthetic polymers. Biodegradable polymers — PHBV structure, synthesis, and applications in packaging and medicine. Environmental impact of non-biodegradable polymers vs. eco-friendly alternatives.
Connections

How this chapter fits in

Useful for setting question difficulty and cross-chapter papers.

Builds on
Ch 11 · Alcohols, Phenols & Ethers
Functional groups in polymer monomers; condensation reactions
Ch 12 · Aldehydes, Ketones & Carboxylic Acids
Ester and amide bond formation; Bakelite synthesis mechanism
Chapter 15 Polymers
Leads to
Ch 14 · Biomolecules
Proteins and nucleic acids as natural condensation polymers
Materials Science (Higher Studies)
Polymer composites, nanotechnology, and smart materials
Board Blueprint

Marks & question-type breakdown

Typical pattern based on CBSE Class 12 Chemistry board papers from the last five years.

Question type Marks Typical count What's usually tested
MCQ / Objective 1 1 Identify polymer type, monomer, or linkage from a list
Very Short Answer 2 1 Name monomer(s), classify as addition/condensation, or state one use
Short Answer 3 1 Explain polymerisation with structure, compare two polymers, or describe PHBV
Total (approximate) 4–5 3 Weightage varies across paper sets and years
Sample Questions

8 sample questions — generated by MarksZen AI

Aligned to CBSE Class 12 Chemistry Chapter 15. Covers all question types across Easy, Medium, and Hard difficulty.

Q1 Easy 1 mark MCQ
Which of the following is an addition polymer? (a) Nylon-6,6 (b) Dacron (c) Teflon (d) Bakelite
Q2 Easy 2 marks Short Answer
Name the monomers used to prepare Nylon-6,6 and identify the type of linkage present in it.
Q3 Medium 2 marks Short Answer
Distinguish between thermoplastic and thermosetting polymers. Give one example of each.
Q4 Medium 3 marks Short Answer
Write the names and structures of the monomers of Dacron (Terylene). What type of polymerisation is involved and what linkage is formed?
Q5 Medium 3 marks Short Answer
What is vulcanisation of rubber? How does it change the properties of natural rubber? Why is vulcanised rubber preferred over natural rubber?
Q6 Hard 4 marks Short Answer
(a) What is PHBV? Name its constituent monomers. (b) Why is PHBV considered a better alternative to conventional plastics? (c) Give two applications of PHBV in medicine and everyday life.
Q7 Hard 4 marks Word Problem
Classify the following polymers under (i) addition or condensation, (ii) linear, branched or cross-linked structure, and (iii) thermoplastic or thermosetting — giving a reason for each classification: (a) Bakelite (b) Nylon-6 (c) Low-density polythene (d) Buna-N
Q8 Hard 5 marks Case-Based
A polymer manufacturer produces two products: Product A is made from caprolactam (a single monomer) and Product B from hexamethylenediamine and adipic acid (two monomers). (i) Identify Products A and B. (ii) Name the type of polymerisation for each. (iii) Draw the repeating structural unit of Product A. (iv) State one industrial use of each product. (v) Product B contains a linkage found in proteins — name this linkage.
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Previous Year Questions

From CBSE board examinations

Actual questions from past Class 12 Chemistry board papers — Polymers chapter.

Board 20222 marks
Write the names and structures of the monomers of Nylon-6,6. What type of polymerisation is involved in its formation? (CBSE All India 2022)
Board 20232 marks
What are biodegradable polymers? Give one example and state its application. (CBSE Delhi 2023)
Board 20203 marks
Explain the following terms with one suitable example each: (i) Addition polymerisation (ii) Condensation polymerisation (iii) Co-polymerisation. (CBSE 2020)
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FAQ

Questions teachers ask

How many marks does Polymers carry in the CBSE Class 12 Chemistry board exam? +
Polymers typically carries 4–5 marks in the CBSE Class 12 Chemistry board exam, usually split across one 2-mark short answer and one 2–3 mark question on classification or a specific polymer's properties and uses. The chapter appears consistently in board papers and is considered a high-scoring, definition-heavy chapter.
What is the difference between addition polymerisation and condensation polymerisation? +
In addition polymerisation, monomers with double or triple bonds repeatedly add to each other without eliminating any small molecule — examples include polyethylene, PVC, and Teflon. In condensation polymerisation, two different bifunctional monomers react repeatedly and a small molecule such as water or HCl is eliminated at each step — examples include Nylon-6,6, Dacron (Terylene), and Bakelite.
Which polymers are most important for the CBSE Class 12 board exam? +
The highest-frequency polymers in CBSE board papers are: Nylon-6,6 (condensation, amide linkage), Dacron/Terylene (condensation, ester linkage), Bakelite (cross-linked condensation), PHBV (biodegradable), Buna-S and Buna-N (synthetic rubbers), and Teflon (addition). Students should know the monomer(s), type of polymerisation, linkage, and at least one use for each.
What are biodegradable polymers and which ones are in the NCERT Class 12 syllabus? +
Biodegradable polymers can be decomposed by microorganisms in the environment, making them eco-friendly alternatives to conventional plastics. The NCERT Class 12 syllabus covers PHBV (poly-β-hydroxybutyrate-co-β-hydroxyvalerate) as the main example. It is a co-polymer used in packaging, drug delivery, and surgical sutures. Board questions often ask for its full name, structure, or why it is preferred over non-biodegradable polymers.
How do I generate a custom question paper for Polymers using MarksZen? +
Sign up for a free MarksZen account, choose CBSE Class 12 Chemistry, select Chapter 15 (Polymers), set your preferred question-type mix (MCQ, short answer, case-based) and total marks — the AI generates a complete board-aligned paper with answer key in under 2 minutes, ready for PDF export.