NCERT Class 11 Chemistry Chemistry Part II: Chapter 3 — Hydrocarbons
This chapter introduces hydrocarbons, compounds of carbon and hydrogen, which are vital energy sources and industrial materials. It covers their classification into saturated (alkanes, cycloalkanes), unsaturated (alkenes, alkynes), and aromatic hydrocarbons based on carbon-carbon bond types. The chapter details the general formula for alkanes (CnH2n+2) and discusses methane's tetrahedral structure. It also touches upon nomenclature, isomerism in alkanes, and the inert nature of these compounds, previously known as paraffins. The importance of hydrocarbons in daily life, from fuels like LPG and CNG to materials like polymers and solvents, is highlighted, setting the stage for further exploration of their properties and reactions.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 11 |
| Subject | Chemistry |
| Book | Chemistry Part II |
| Chapter | Chapter 3 — Hydrocarbons |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 6 minutes |
| Word count | 1001 |
Learning outcomes
- Name hydrocarbons according to IUPAC nomenclature.
- Recognize and write structures of isomers of alkanes, alkenes, alkynes, and aromatic hydrocarbons.
- Learn various methods for preparing hydrocarbons.
- Distinguish between alkanes, alkenes, alkynes, and aromatic hydrocarbons based on properties.
- Appreciate the role of hydrocarbons as energy sources and in industrial applications.
Vocabulary
| Word | Meaning |
|---|---|
| Hydrocarbons | Compounds containing only carbon and hydrogen. |
| LPG | Liquefied Petroleum Gas, a fuel. |
| CNG | Compressed Natural Gas, a fuel. |
| Saturated hydrocarbons | Hydrocarbons with only single bonds between carbon atoms. |
| Unsaturated hydrocarbons | Hydrocarbons with at least one double or triple bond between carbon atoms. |
| Aromatic hydrocarbons | A special class of cyclic hydrocarbons, like benzene. |
| Alkanes | Saturated open-chain hydrocarbons (e.g., methane, ethane). |
| Cycloalkanes | Saturated hydrocarbons forming a closed ring. |
| Alkenes | Unsaturated hydrocarbons with at least one carbon-carbon double bond. |
| Alkynes | Unsaturated hydrocarbons with at least one carbon-carbon triple bond. |
| Paraffins | An older term for alkanes, meaning 'little affinity'. |
| Isomerism | The phenomenon where compounds have the same molecular formula but different structural formulas. |
The complete chapter text is read in the official NCERT PDF viewer below (streamed from ncert.nic.in). This page provides NCERT Help study material — summary, vocabulary, practice questions, and FAQs — not a full reproduction of the textbook.
Read chapter online
This PDF is loaded from the official NCERT website (ncert.nic.in). Use the page buttons below to read — download is disabled on NCERT Help.
Read page by page below. PDF is streamed from the official NCERT website — no download button on this page.
Practice questions
- What are hydrocarbons? Answer: Hydrocarbons are compounds composed solely of carbon and hydrogen atoms.
- Name the three main categories of hydrocarbons. Answer: The three main categories are saturated, unsaturated, and aromatic hydrocarbons.
- What is the general formula for alkanes? Answer: The general formula for alkanes is CnH2n+2.
- Why were alkanes once called paraffins? Answer: Alkanes were called paraffins because they are relatively inert and do not react easily with most reagents.
- Give examples of fuels that are mixtures of hydrocarbons. Answer: Examples include LPG, CNG, petrol, diesel, and coal gas.
Frequently asked questions
What are hydrocarbons and why are they important?
Hydrocarbons are compounds made only of carbon and hydrogen. They are crucial as sources of energy (like LPG, CNG, petrol) and are used in manufacturing polymers, dyes, and drugs.
How are hydrocarbons classified?
They are classified based on carbon-carbon bonds into saturated (single bonds, e.g., alkanes), unsaturated (double/triple bonds, e.g., alkenes, alkynes), and aromatic hydrocarbons.
What is the general formula for alkanes?
The general formula for alkanes is CnH2n+2, where 'n' represents the number of carbon atoms.
What is the structure of methane according to VSEPR theory?
Methane (CH4) has a tetrahedral structure with the carbon atom at the center and hydrogen atoms at the corners, with H-C-H bond angles of 109.5°.
What is the difference between n-butane and its isomer?
n-butane has a continuous chain of four carbon atoms, while its isomer, isobutane (or 2-methylpropane), has a branched chain.
Why were alkanes called paraffins?
Alkanes were called paraffins because they are chemically unreactive ('little affinity') under normal conditions.
Related resources
Important topics
Topics covered
NCERT Class 11 Chemistry — Chemistry Part II — Chapter 3 — Hydrocarbons. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.