CBSE Class 10 Science Revision Notes Chapter 4 Carbon and Its Compounds 2026–27

CBSE Class 10 Science Revision Notes Chapter 4 cover carbon bonding, hydrocarbons, reactions, ethanol, ethanoic acid and cleansing agents. Carbon and Its Compounds explains why carbon forms many compounds through covalent bonding, tetravalency and catenation in the CBSE Class 10 Science syllabus.

Carbon and Its Compounds studies the bonding, structure and chemical behaviour of carbon compounds. Carbon forms covalent bonds and can join with itself to form long chains, branches and rings. This makes carbon a major element in fuels, food, medicines, soaps, detergents and many daily-use substances.

Use these CBSE Class 10 Science Revision Notes Chapter 4 for the 2026–27 exams to revise definitions, formulas, reactions and important differences. Start with covalent bonding and the versatile nature of carbon, then revise hydrocarbons, functional groups, ethanol, ethanoic acid, soaps and detergents.

Key Takeaways

• Carbon: It has four valence electrons and forms covalent bonds by sharing electrons.
• Tetravalency: Carbon can form four bonds with carbon, hydrogen, oxygen, chlorine and other atoms.
• Catenation: Carbon atoms join together to form straight chains, branched chains and rings.
• Reaction types: Combustion, oxidation, addition and substitution are key chemical reactions in this chapter.

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CBSE Class 10 Science Revision Notes Chapter 4 at a Glance

Carbon and Its Compounds is a chemistry chapter based on bonding, structure and reactions. The chapter connects simple molecular structures with daily-use substances such as fuels, vinegar, soaps and detergents.

What are Carbon Compounds?

Carbon compounds are chemical compounds that contain carbon. Most fuels, food materials, medicines, plastics, fibres, soaps and detergents contain carbon.

Carbon forms a large number of compounds because it bonds with itself and other elements. It can form single, double and triple covalent bonds.

Bonding in Carbon

Carbon has atomic number 6. Its electronic configuration is 2, 4. It has four electrons in its outermost shell.

Carbon cannot easily lose four electrons because that requires high energy. It also cannot easily gain four electrons because the nucleus cannot hold ten electrons strongly. So, carbon shares electrons and forms covalent bonds.

Covalent Bonding in Carbon

A covalent bond is formed when atoms share one or more pairs of electrons. Carbon mainly forms covalent bonds because it needs four more electrons to complete its octet.

Covalent bonding in carbon helps form stable molecules such as methane, ethane, ethene and ethyne.

Formation of Covalent Bonds in Common Molecules

Covalent bond formation becomes easier to revise through simple molecules. These examples show how atoms complete their outermost shells by sharing electrons.

Hydrogen Molecule

Each hydrogen atom has one electron. Two hydrogen atoms share one pair of electrons and form H₂.

H - H

Oxygen Molecule

Each oxygen atom has six valence electrons. Two oxygen atoms share two pairs of electrons and form O₂.

O = O

Nitrogen Molecule

Each nitrogen atom has five valence electrons. Two nitrogen atoms share three pairs of electrons and form N₂.

N ≡ N

Methane Molecule

Carbon shares one electron each with four hydrogen atoms. This forms four single covalent bonds in methane.

Formula: CH₄

Properties of Covalent Compounds

Covalent compounds are formed by sharing electrons. They usually have low melting and boiling points because the forces between their molecules are weak.

Covalent compounds do not conduct electricity because they do not contain free ions.

Versatile Nature of Carbon

The versatile nature of carbon means carbon can form a wide variety of compounds. This happens mainly because of tetravalency and catenation.

Carbon can form bonds with hydrogen, oxygen, nitrogen, sulphur, chlorine and other carbon atoms. It can also form different structures with the same atoms.

Tetravalency of Carbon

Carbon has four valence electrons. It can share all four electrons with other atoms. This property is called tetravalency.

Due to tetravalency, carbon forms four covalent bonds. In methane, one carbon atom forms four single bonds with four hydrogen atoms.

CH₄

Catenation

Catenation is the ability of carbon atoms to bond with other carbon atoms. Carbon shows catenation because carbon-carbon bonds are stable.

Carbon can form straight chains, branched chains and ring structures.

Catenation explains why carbon compounds exist in large numbers.

Saturated and Unsaturated Hydrocarbons

Hydrocarbons are compounds made of carbon and hydrogen. They are classified based on the type of bond between carbon atoms.

Saturated and unsaturated hydrocarbons are important in Carbon and Its Compounds Class 10 Notes because their reactions are different.

Alkanes, Alkenes and Alkynes

Alkanes, alkenes and alkynes are three main groups of hydrocarbons. Their names and formulas depend on the bonds present between carbon atoms.

Alkanes are saturated hydrocarbons. Alkenes and alkynes are unsaturated hydrocarbons.

Chains, Branches and Rings

Carbon atoms can arrange themselves in different ways. This creates different compounds with different structures.

Straight-chain compounds have carbon atoms joined in a continuous line. Branched compounds have side chains attached to the main chain. Ring compounds have carbon atoms joined in a closed structure.

Structural Isomerism

Structural isomerism occurs when compounds have the same molecular formula but different structures.

Example: Butane and isobutane both have the formula C₄H₁₀. Their carbon atoms are arranged differently.

Structural isomerism happens because carbon can form different chains and branches.

Functional Groups

A functional group is an atom or group of atoms that gives a carbon compound its characteristic properties. It decides how the compound reacts.

Functional groups help classify organic compounds in Class 10 Science Chapter 4 Carbon and Its Compounds.

Homologous Series

A homologous series is a group of organic compounds with the same functional group and similar chemical properties. Two successive members differ by a -CH₂ unit.

Example: Alkane series

Members of a homologous series have similar chemical properties because they contain the same functional group.

Features of a Homologous Series

Homologous series helps organise carbon compounds. It also helps predict formulas and properties of related compounds.

• Members have the same functional group.
• Members have the same general formula.
• Successive members differ by -CH₂.
• Chemical properties are similar.
• Physical properties change gradually with molecular mass.

Nomenclature of Carbon Compounds

Nomenclature means naming carbon compounds using fixed rules. The name depends on the number of carbon atoms, bond type and functional group.

Suffix Based on Bond Type

The suffix tells the type of bond present in the carbon chain.

Suffix Based on Functional Group

The functional group changes the ending of the compound name.

Chemical Properties of Carbon Compounds

Carbon compounds show different reactions based on their bonding and functional groups. The main reactions are combustion, oxidation, addition and substitution.

These reactions are important in Class 10 Chemistry Chapter 4 Notes because they often appear in reasoning questions.

Combustion

Combustion is the burning of a substance in oxygen to produce heat and light. Carbon compounds burn in oxygen to form carbon dioxide and water.

General reaction:
Carbon compound + O₂ → CO₂ + H₂O + Heat + Light

Example:
CH₄ + 2O₂ → CO₂ + 2H₂O + Heat

Saturated hydrocarbons usually burn with a clean flame. Unsaturated hydrocarbons often burn with a yellow, smoky flame.

Oxidation

Oxidation is a reaction in which oxygen is added to a substance. Ethanol can be oxidised to ethanoic acid.

CH₃CH₂OH + Oxygen → CH₃COOH + H₂O

Oxidising agents such as alkaline potassium permanganate or acidified potassium dichromate are used for this reaction.

Addition Reaction

Addition reactions occur in unsaturated hydrocarbons. In these reactions, atoms are added across a double or triple bond.

Example:
Ethene + Hydrogen → Ethane

C₂H₄ + H₂ → C₂H₆

This reaction takes place in the presence of a catalyst such as nickel.

Substitution Reaction

Substitution reaction occurs when one atom replaces another atom in a compound. Alkanes usually show substitution reactions.

Example:
CH₄ + Cl₂ → CH₃Cl + HCl

Condition: Sunlight

In this reaction, chlorine replaces one hydrogen atom of methane.

Combustion, Oxidation, Addition and Substitution Reactions

Reactions of Ethanol and Ethanoic Acid

Ethanol and ethanoic acid are two important carbon compounds. Their formulas, properties and reactions are frequently asked in CBSE Notes Class 10 Science Chapter 4.

Ethanol

Ethanol is an alcohol with the formula C₂H₅OH. It is a colourless liquid with a pleasant smell.

Uses of Ethanol

Ethanol is used as a solvent in medicines, paints and perfumes. It is also used in tincture iodine and as a fuel mixture with petrol.

Ethanol is present in alcoholic drinks. Large amounts affect the nervous system and damage health.

Reaction of Ethanol with Sodium

Ethanol reacts with sodium to form sodium ethoxide and hydrogen gas.

2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂

Hydrogen gas is released during this reaction.

Dehydration of Ethanol

When ethanol is heated with concentrated sulphuric acid at 443 K, it forms ethene.

CH₃CH₂OH → CH₂=CH₂ + H₂O

Condition: Concentrated H₂SO₄, 443 K

This reaction is called dehydration because water is removed.

Ethanoic Acid

Ethanoic acid is a carboxylic acid with the formula CH₃COOH. Its common name is acetic acid.

A 5-8% solution of ethanoic acid in water is called vinegar.

Pure ethanoic acid freezes in cold weather and forms ice-like crystals.

Reactions of Ethanoic Acid

Ethanoic acid reacts with bases, carbonates and bicarbonates. These reactions help identify carboxylic acids.

Reaction with Sodium Hydroxide

CH₃COOH + NaOH → CH₃COONa + H₂O

This is a neutralisation reaction.

Reaction with Sodium Carbonate

2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂

Carbon dioxide gas is released.

Reaction with Sodium Bicarbonate

CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂

The brisk effervescence shows the release of carbon dioxide gas.

Esterification

Esterification is the reaction between an alcohol and a carboxylic acid to form an ester. Esters have a pleasant smell.

CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O

Condition: Concentrated H₂SO₄

Ethanoic acid and ethanol form ethyl ethanoate during esterification.

Saponification

Saponification is the alkaline hydrolysis of an ester to form soap and alcohol.

General reaction:
Ester + Sodium hydroxide → Sodium salt of carboxylic acid + Alcohol

This reaction is used in soap-making.

Soaps and Detergents

Soaps and detergents are cleansing agents. They remove dirt and grease from surfaces such as skin and clothes.

Soap is a sodium or potassium salt of a long-chain carboxylic acid. Detergents are cleansing agents that work better in hard water.

Structure of Soap Molecule

A soap molecule has two parts. One part dissolves in oil, while the other dissolves in water.

The hydrophobic tail attaches to oily dirt. The hydrophilic head remains attached to water.

Cleansing Action of Soap

When soap is added to water, soap molecules arrange around oily dirt. Their tails move into oil, while their heads face water.

This forms a spherical structure called a micelle. On rinsing, micelles carry dirt and grease away with water.

What is a Micelle?

A micelle is a cluster of soap molecules formed around oily dirt in water. The hydrophobic tails stay inside, while the hydrophilic heads stay outside.

Micelles help remove oil and grease from clothes and skin.

Why Soap Does Not Work Well in Hard Water

Hard water contains calcium and magnesium salts. These salts react with soap and form an insoluble substance called scum.

2C₁₇H₃₅COONa + CaCl₂ → (C₁₇H₃₅COO)₂Ca + 2NaCl

Scum reduces lather and wastes soap. It also makes cleaning less effective.

Difference Between Soaps and Detergents

Soaps and detergents both clean surfaces, but they behave differently in hard water.

Important Formulas from CBSE Notes Class 10 Science Chapter 4

These formulas are useful for quick revision before solving chapter questions.

Important Reactions from Class 10 Science Chapter 4

These equations cover the main reaction types in Carbon and Its Compounds Notes.

How to Identify Reaction Types in Carbon Compounds

Questions in this chapter often give a condition or product. Use the clue to identify the reaction type.

Difference Between Key Concepts in Carbon and Its Compounds

Difference-based questions are common in Class 10 Science Chapter 4 Notes. Revise these pairs before practising answers.

Common Exam Questions from Carbon and Its Compounds

These question types help revise the scoring parts of Class 10 Science Chapter 4 Carbon and Its Compounds.

Q1. Why does carbon form covalent bonds?

Carbon has four valence electrons. It cannot easily lose or gain four electrons. So, it shares electrons with other atoms and forms covalent bonds.

Q2. What are tetravalency and catenation?

Tetravalency is the ability of carbon to form four covalent bonds. Catenation is the ability of carbon to bond with itself and form chains, branches and rings.

Q3. What is the difference between saturated and unsaturated hydrocarbons?

Saturated hydrocarbons contain only single bonds between carbon atoms. Unsaturated hydrocarbons contain double or triple bonds between carbon atoms.

Q4. What is a homologous series?

A homologous series is a group of organic compounds with the same functional group and similar chemical properties. Two successive members differ by -CH₂.

Q5. Why are detergents more effective than soaps in hard water?

Detergents do not form scum with calcium and magnesium ions in hard water. So, they clean better than soaps in hard water.

Solved Questions from Carbon and Its Compounds Class 10 

Solved examples help connect definitions with reactions and exam-style answers.

Example 1: Why does carbon form a large number of compounds?

Carbon forms a large number of compounds because it shows tetravalency and catenation. It can form four covalent bonds and can join with other carbon atoms. This allows carbon to form chains, branches and rings.

Example 2: Write the reaction of ethanol with sodium.

Ethanol reacts with sodium to form sodium ethoxide and hydrogen gas.

2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂

Example 3: Why are unsaturated hydrocarbons more reactive?

Unsaturated hydrocarbons contain double or triple bonds. These bonds can open up during addition reactions. So, unsaturated hydrocarbons are more reactive than saturated hydrocarbons.

Example 4: What happens when ethanoic acid reacts with sodium bicarbonate?

Ethanoic acid reacts with sodium bicarbonate to form sodium ethanoate, water and carbon dioxide.

CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂

Brisk effervescence occurs due to carbon dioxide gas.

Example 5: Why does soap form scum in hard water?

Hard water contains calcium and magnesium ions. These ions react with soap and form insoluble salts called scum. Scum reduces lather and cleaning action.

CBSE Class 10 Science Chapter 4 Carbon and Its Compounds Summary

Carbon and Its Compounds explains how carbon forms covalent bonds through electron sharing. Carbon shows tetravalency and catenation, which help it form many compounds.

The chapter covers saturated and unsaturated hydrocarbons, functional groups, homologous series and nomenclature. It also explains chemical reactions such as combustion, oxidation, addition and substitution.

Ethanol, ethanoic acid, esterification, saponification, soaps and detergents are important scoring areas. Students can revise formulas, equations, differences and definitions from these notes before practising NCERT questions.

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