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Carbon and its Compounds — Class 10 Science Notes & Practice

July 31, 2026
Carbon and its Compounds — Class 10 Science Notes & Practice

Carbon and its Compounds is one of the biggest scoring chapters in Class 10 Science — carbon is the element of life, and its chemistry runs from cooking gas to vinegar to soap. This page teaches the whole chapter in plain language, with a plan and an original practice set (with answers you can reveal) at the end.

What This Chapter Covers

Your Game Plan for This Chapter

  1. First — Understand covalent bonding and why carbon forms so many compounds.
  2. Next — Learn hydrocarbons, functional groups and homologous series.
  3. Last — Cover the reactions, ethanol and ethanoic acid, and soaps — then attempt the practice set.

Study Notes

1. Covalent Bonding and the Versatile Nature of Carbon

Carbon has four electrons in its outer shell, so instead of gaining or losing electrons it shares them, forming covalent bonds. Two properties make carbon extraordinarily versatile: tetravalency (it can form four strong bonds) and catenation (carbon atoms link to one another in long chains, branches and rings). Together, these let carbon form millions of stable compounds.

Diagram showing that carbon forms millions of compounds because of tetravalency, which lets one carbon atom make four bonds, and catenation, which lets carbon atoms link into chains, branches and rings.
Figure: Tetravalency and catenation explain carbon’s versatility · चित्र: टेट्रावैलेन्सी और कैटेनेशन
Key Idea
Tetravalency + catenation = the two reasons carbon forms more compounds than every other element combined. If a question asks “why so many carbon compounds,” these are the two words to write.

2. Hydrocarbons: Saturated and Unsaturated

Hydrocarbons contain only carbon and hydrogen. Saturated hydrocarbons (alkanes) have only single bonds; unsaturated ones have double bonds (alkenes) or triple bonds (alkynes).

FamilyBondGeneral formula & example
AlkanesSingle (C–C)CnH2n+2 — e.g. CH4, C2H6
AlkenesDouble (C=C)CnH2n — e.g. C2H4
AlkynesTriple (C≡C)CnH2n−2 — e.g. C2H2

3. Functional Groups and Homologous Series

A functional group is an atom or group of atoms that gives a compound its characteristic properties — for example, –OH (alcohol) and –COOH (carboxylic acid). A homologous series is a family of compounds with the same functional group in which each member differs from the next by a –CH2– unit. Members of a series show similar chemical properties and a gradual change in physical properties.

Diagram showing the OH functional group giving alcohols and the COOH functional group giving carboxylic acids, alongside the homologous series methanol, ethanol, propanol and butanol where each member differs from the next by one CH2 unit.
Figure: Functional groups and a homologous series · चित्र: क्रियात्मक समूह और समजातीय श्रेणी

4. Chemical Reactions; Ethanol and Ethanoic Acid; Soaps

  • Combustion: carbon compounds burn in air to give carbon dioxide, water, heat and light.
  • Addition: unsaturated hydrocarbons add hydrogen (with a nickel catalyst) to become saturated.
  • Substitution: saturated hydrocarbons (alkanes) react with chlorine in sunlight, where hydrogen atoms are replaced by chlorine.

Ethanol reacts with sodium to give hydrogen gas, and on oxidation it becomes ethanoic acid (acetic acid, the acid in vinegar). Ethanoic acid reacts with carbonates to release CO2, and with an alcohol to form a sweet-smelling ester. Soap cleans because each molecule has a water-hating tail and a water-loving head: in water the tails surround the oily dirt while the heads face outward, forming clusters called micelles that carry the dirt away.

Common Mistake
Addition reactions belong to unsaturated hydrocarbons; substitution reactions belong to saturated ones. Swapping these is a frequent slip.

Practice Worksheet

Try each question fully on your own first, then click Show Answer to check yourself.

Q1. Why does carbon form a very large number of compounds? Give two reasons.

Show Answer
(i) Tetravalency — carbon has four valence electrons and forms four strong covalent bonds. (ii) Catenation — carbon atoms link to one another to form long chains, branches and rings. Together these allow a huge variety of stable compounds.

Q2. What is a homologous series? Give one example.

Show Answer
A family of compounds with the same functional group, in which each member differs from the next by a –CH2– unit; members have similar chemical properties and a gradual change in physical properties. Example: the alkanes — CH4, C2H6, C3H8, and so on.

Q3. Distinguish between an addition reaction and a substitution reaction.

Show Answer
Addition reactions occur in unsaturated hydrocarbons — e.g. hydrogenation of ethene to ethane using a nickel catalyst. Substitution reactions occur in saturated hydrocarbons (alkanes) — e.g. methane reacting with chlorine in sunlight, where hydrogen atoms are replaced by chlorine.

Q4. How does ethanol react with (a) sodium and (b) on oxidation?

Show Answer
(a) Ethanol reacts with sodium to give sodium ethoxide and hydrogen gas. (b) On oxidation (using an oxidising agent such as alkaline KMnO4 or acidified K2Cr2O7), ethanol is oxidised to ethanoic acid.

Q5. Explain the cleansing action of soap and the role of micelles.

Show Answer
A soap molecule has a water-hating (hydrophobic) tail and a water-loving (hydrophilic) head. In water, the tails surround the oil and dirt while the heads face the water, forming clusters called micelles. The dirt is trapped inside the micelle and rinsed away with the water.

Once these feel easy, you have genuinely finished this chapter. Do not aim for perfect on the first try — aim for one more correct question than yesterday.

Written & reviewed by Team Principal Saab — Meet the team →