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Chemistry · Class 12 Science

Ch 6Polymers — Class 12 Chemistry, concept-first.

A polymer is a very large molecule (a macromolecule) built by covalently joining together a large number of small, repeating structural units called monomers. The number of monomer units joined in one polymer chain is called the degree of polymerisation, and it commonly runs into the hundreds or thousands.

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Key concepts

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Classification by Source

Polymers are classified by where they come from.

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Chapter contents

The NCERT structure, section by section. Open a section to see its questions, then read the concept-first solution.

19.1

Classification of Polymers

A polymer is a very large molecule (a macromolecule) built by covalently joining together a large number of small, repeating structural units called monomers.

19.2

Addition Polymerisation and Polythene (LDPE, HDPE)

Addition polymerisation (also called chain-growth polymerisation) builds a polymer by repeatedly adding molecules of an unsaturated monomer -- one containing a reactive double bond -- to a single grow…

19.3

Condensation Polymerisation and Nylon-6,6

Condensation polymerisation (also called step-growth polymerisation) builds a polymer by repeatedly reacting together two bifunctional (or polyfunctional) monomers -- each carrying two reactive functi…

19.4

Copolymerisation: Buna-S and Buna-N

Copolymerisation is addition polymerisation carried out with TWO (or occasionally more) different monomers together in the same reaction, so that the resulting chain -- a copolymer -- contains both ki…

19.5

Polyester: Terylene (Dacron)

Polyesters are condensation polymers in which the repeating linkage joining the monomer units is an ester group, , formed by the reaction of a carboxylic acid group with a hydroxyl (alcohol) group, re…

19.6

Bakelite: Phenol-Formaldehyde Resin

Bakelite, the first fully synthetic polymer ever commercialised (developed by Leo Baekeland in 1907), is a condensation polymer of phenol, , and formaldehyde, (methanal), and is the syllabus's represe…

19.7

Natural Rubber and Vulcanisation

Natural rubber is a natural, addition polymer of the monomer isoprene (2-methylbuta-1,3-diene, ), obtained as a milky colloidal suspension called latex tapped from the bark of the rubber tree, Hevea b…

19.8

Biodegradable and Non-Biodegradable Polymers

A polymer is called biodegradable if micro-organisms present in soil or water (bacteria, fungi) can break its long chains down into small, harmless molecules -- typically carbon dioxide, water and bio…

Important Polymers at a Glance

Summary

This chapter covered polymers -- the giant, repeating-unit macromolecules central to modern materials -- along two classification threads.

Sample & Board Papers

Sample papers and previous-year board questions for this subject.

+Show 14 questions14 questions
  1. Q1(i) Identify the two monomers in the following polymer: —[NH–(CH2)6–NH–C(=O)–(CH2)4–C(=O)–]n. (ii) What is condensation polymerisation react…Preview
  2. Q2Which of the following is a natural polymer? (a) Polyethylene (b) Nylon (c) Protein (d) TerylenePreview
  3. Q3Write the name of the monomer unit(s) of Dacron and mention one use of it. (1+1)Preview
  4. Q4Which of the following is not a condensation polymer? (a) Bakelite (b) Nylon (c) Melamine-formaldehyde resin (d) TeflonPreview
  5. Q5Which of the following is/are biodegradable polymer(s)? (a) PHBV (b) Nylon-2-Nylon-6 (c) Nylon-6,6 (d) Both (a) and (b)Preview
  6. Q6(i) Write the names of monomers of the following polymer (see figure). (ii) Give an example of thermoplastic polymer and thermosetting polym…Preview
  7. Q7Which of the following is a polyamide polymer? (a) Bakelite (b) Terylene (c) Teflon (d) Nylon-6,6Preview
  8. Q8(i) How does vulcanisation change the nature of natural rubber? (ii) Write the names of the monomers each of Terylene and Dacron. [1+1]Preview
  9. Q9Vulcanisation of rubber makes it (a) soft (b) hard (c) less elastic (d) soluble in waterPreview
  10. Q10Write the names of monomer units of Nylon-6,6. Mention one use of Nylon-6,6. [1+1]Preview
  11. Q11Which one of the following polymers is prepared by condensation polymerization? (a) Teflon (b) PAN (c) Nylon-6, 6 (d) LDPEPreview
  12. Q12The catalyst used in addition polymerization of olefins is (a) Ziegler-Natta catalyst (b) Zeolite (c) Wilkinson catalyst (d) Pd-BaSO4Preview
  13. Q13Which of the following polymers contains acrylonitrile as monomer? (a) Orlon (b) Dacron (c) Teflon (d) NylonPreview
  14. Q14Match Column-I with Column-II and select the correct option: Column-I: (i) P-F Resin, (ii) Neoprene, (iii) Natural rubber, (iv) Nylon-6. Col…Preview

More questions

26 Q
+Show 10 questions10 questions
  1. Example 1Classify the following as natural or synthetic polymers, giving a reason for each: (a) starch, (b) nylon-6,6, (c) natural rubber, (d) polyth…Free
  2. Example 2Explain, with equations, the free-radical addition polymerization mechanism by which ethene is converted into polythene, naming the three st…Free
  3. Example 3Explain condensation polymerization using the formation of nylon-6,6 from hexamethylenediamine and adipic acid as an example, and write the…Free
  4. Example 4What is copolymerization? Illustrate your answer with the formation of Buna-S from buta-1,3-diene and styrene.Preview
  5. Example 5Distinguish between low density polythene (LDPE) and high density polythene (HDPE) in terms of the polymerization conditions used, chain str…Preview
  6. Example 6Draw the repeat unit of nylon-6,6 and identify the type of linkage that joins successive monomer units.Preview
  7. Example 7Describe how terylene (Dacron) is manufactured from ethylene glycol and terephthalic acid, and state what type of polymer it is.Preview
  8. Example 8Describe the structure of bakelite and explain how a three-dimensional cross-linked network is built up from phenol and formaldehyde.Preview
  9. Example 9What is the structural repeat unit of natural rubber? Explain the process of vulcanization and how it changes the polymer's properties.Preview
  10. Example 10Differentiate between biodegradable and non-biodegradable polymers, giving one example of each and explaining the chemical reason for the di…Preview
+Show 16 questions16 questions
  1. Q11Give two examples each of natural polymers and synthetic polymers.Free
  2. Q12What is the fundamental difference between addition polymerization and condensation polymerization? Give one example of a polymer formed by…Free
  3. Q13Vinyl chloride, $\text{CH}_2{=}\text{CHCl}$, undergoes free-radical addition polymerization to form PVC. Write equations for the initiation,…Free
  4. Q14Nylon-6,6 is formed from hexamethylenediamine and adipic acid. (a) What small molecule is eliminated at each linking step? (b) Why is the po…Preview
  5. Q15What is Buna-N? How does its structure and monomer composition differ from Buna-S?Preview
  6. Q16Explain, in terms of chain structure (branching), why LDPE is a soft, flexible plastic used for bags while HDPE is a rigid, tough plastic us…Preview
  7. Q17Write the structure of the repeat unit of terylene (polyethylene terephthalate), naming the type of linkage present.Preview
  8. Q18Bakelite is prepared by the condensation of phenol with formaldehyde. Name the linear intermediate formed before cross-linking, and describe…Preview
  9. Q19Why is untreated natural rubber soft, tacky and of low tensile strength, while vulcanized rubber is much harder, stronger and more elastic?…Preview
  10. Q20Classify each of the following as biodegradable or non-biodegradable, giving a reason: (a) PHBV, (b) polythene, (c) nylon-6,6, (d) PVC.Preview
  11. Q21What structural feature in a polymer's backbone generally makes it susceptible to microbial (biodegradable) breakdown?Preview
  12. Q22Distinguish between a homopolymer and a copolymer, giving one example of each.Preview
  13. Q23Explain why addition polymers formed from vinyl-type monomers typically have a purely carbon backbone, while condensation polymers contain h…Preview
  14. Q24What role does sulfur play in the vulcanization of rubber, and why does vulcanized rubber not become sticky in hot weather the way raw rubbe…Preview
  15. Q25Give the monomer(s) used to prepare each of the following polymers: (a) polythene, (b) nylon-6,6, (c) terylene, (d) bakelite, (e) natural ru…Preview
  16. Q26Explain why non-biodegradable polymers such as polythene persist in the environment for a very long time, and why this is considered an envi…Preview