CBSE Class 10 Science Chapter 4 PDF Notes – Carbon and its Compounds 2026-27

These Class 10 Science Chapter 4 PDF Notes explain Carbon and its Compounds in simple steps: covalent bonding, allotropes of carbon, versatile nature of carbon, homologous series, naming of compounds, chemical properties, ethanol, ethanoic acid, and how soaps and detergents clean.

This is the longest chemistry chapter and carries good weightage. Electron-dot structures, IUPAC names, esterification and the cleansing action of soap are asked regularly, so practise drawing and naming as you revise.

Use the table of contents below to jump to the part you need, or read top to bottom for a complete revision of the chapter.

Table of Contents

• Chapter Overview
• Important Topics and Concepts
• Homologous Series: First Members
• Important Definitions and Terms
• Short Answer Questions
• Long Answer Questions
• MCQs with Answers
• Quick Revision Points
• Chapter Summary
• Exam Tips and PYQ Pattern
• Frequently Asked Questions
• Conclusion

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Chapter Overview

Carbon forms a huge number of compounds, from fuels and plastics to the molecules of life. It does this by sharing electrons, forming strong covalent bonds with itself and with other elements.

The chapter covers why carbon bonds covalently, its allotropes (diamond, graphite, fullerenes), saturated and unsaturated hydrocarbons, functional groups, homologous series and nomenclature, then the reactions of carbon compounds and two important compounds: ethanol and ethanoic acid. It ends with soaps and detergents.

Important Topics and Concepts

Covalent bonding

Carbon (2,4) has four valence electrons. Gaining or losing four electrons needs too much energy, so carbon shares electrons, forming covalent bonds. Examples: H₂ (single bond), O₂ (double bond), N₂ (triple bond), CH₄ (four C–H single bonds). Covalent compounds have low melting and boiling points and are poor conductors because no ions form.

Allotropes of carbon

• Diamond: each carbon bonded to four others in a rigid 3D network; hardest natural substance; does not conduct electricity.
• Graphite: each carbon bonded to three others in hexagonal layers; layers slide over each other; smooth, slippery and a good conductor.
• Fullerenes: C-60 (buckminsterfullerene), carbon atoms arranged like a football.

Versatile nature of carbon

Catenation: carbon forms long chains, branched chains and rings by bonding with other carbon atoms. Tetravalency: carbon can bond with four other atoms such as H, O, N, S and halogens. Its small size makes these bonds strong and stable.

Saturated and unsaturated compounds

Saturated hydrocarbons (alkanes) have only single bonds, e.g. ethane C₂H₆. Unsaturated hydrocarbons have double bonds (alkenes, e.g. ethene C₂H₄) or triple bonds (alkynes, e.g. ethyne C₂H₂). Carbon compounds can be straight chains, branched chains or rings (cyclohexane, benzene). Compounds with the same formula but different structures are isomers, e.g. butane and isobutane (C₄H₁₀).

Functional groups

An atom or group that gives a compound its characteristic properties: halo (–Cl, –Br), alcohol (–OH), aldehyde (–CHO), ketone (>C=O), carboxylic acid (–COOH).

Homologous series

A series of compounds with the same functional group, where successive members differ by a –CH₂– unit (14 u). Members have similar chemical properties and a gradual change in physical properties such as melting and boiling points. Example: CH₃OH, C₂H₅OH, C₃H₇OH.

Nomenclature

• Count the carbon atoms for the stem: meth (1), eth (2), prop (3), but (4), pent (5).
• Add the suffix for the functional group: -ol (alcohol), -al (aldehyde), -one (ketone), -oic acid (carboxylic acid), -ene (double bond), -yne (triple bond).
• Halogens are prefixes: chloropropane, bromopropane.
• Examples: CH₃CH₂OH ethanol; CH₃CHO ethanal; CH₃COCH₃ propanone; CH₃COOH ethanoic acid.

Chemical properties of carbon compounds

• Combustion: carbon compounds burn in oxygen giving CO₂, water, heat and light. Saturated hydrocarbons burn with a clean blue flame; unsaturated ones give a yellow, sooty flame.
• Oxidation: alcohols are oxidised to acids by alkaline KMnO₄ or acidified K₂Cr₂O₇ (oxidising agents).
• Addition reaction: unsaturated hydrocarbons add hydrogen in the presence of a nickel catalyst (hydrogenation), used to convert vegetable oils into vanaspati ghee.
• Substitution reaction: in sunlight, chlorine replaces hydrogen atoms in saturated hydrocarbons, e.g. CH₄ + Cl₂ → CH₃Cl + HCl.

Ethanol (C₂H₅OH)

A liquid at room temperature, active ingredient of alcoholic drinks and a good solvent (tincture of iodine, cough syrups). Reactions: 2Na + 2CH₃CH₂OH → 2CH₃CH₂ONa + H₂; heating with excess concentrated H₂SO₄ at 443 K gives ethene (dehydration). Denatured alcohol is ethanol made unfit for drinking by adding methanol and a dye. Ethanol is also used as a cleaner fuel when mixed with petrol.

Ethanoic acid (CH₃COOH)

Called acetic acid; a 5-8% solution is vinegar. Pure ethanoic acid freezes in cold climates and is called glacial acetic acid. Reactions: esterification (CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O with an acid catalyst), with a base (NaOH → sodium ethanoate + water) and with carbonates and hydrogencarbonates (releases CO₂). Esters smell sweet and are used in perfumes; saponification is the reverse reaction with NaOH, giving soap.

Soaps and detergents

Soap molecules are sodium or potassium salts of long-chain carboxylic acids. One end is ionic and hydrophilic (water-loving); the other is a long hydrocarbon tail that is hydrophobic (oil-loving). In water, they form clusters called micelles with the tails inside trapping oily dirt, which is then rinsed away. In hard water, soaps form an insoluble scum with calcium and magnesium salts. Detergents (sulphonic acid or ammonium salts) do not form scum, so they work in hard water too.

Homologous Series: First Members

Important Definitions and Terms

Short Answer Questions

Q1. Why does carbon form covalent bonds and not ionic bonds?

Carbon has four valence electrons. Gaining four electrons (C⁴⁻) or losing four (C⁴⁺) needs a lot of energy and the ions would be unstable, so carbon shares electrons instead.

Q2. Why are covalent compounds poor conductors of electricity?

Covalent bonds are formed by sharing electrons, so no ions are formed. Without charged particles free to move, these compounds do not conduct electricity.

Q3. Why does a yellow sooty flame appear when unsaturated compounds burn?

Unsaturated hydrocarbons have a higher proportion of carbon and do not burn completely in air. Unburnt carbon particles make the flame yellow and sooty.

Q4. Why do we use a nickel catalyst while converting vegetable oil to vanaspati ghee?

The catalyst speeds up the addition of hydrogen to the unsaturated fats in vegetable oil without being used up itself.

Q5. What is the difference between soaps and detergents?

Soaps are sodium/potassium salts of long-chain carboxylic acids and form scum in hard water. Detergents are ammonium or sulphonate salts of long-chain acids and work well even in hard water.

Q6. How would you distinguish experimentally between an alcohol and a carboxylic acid?

Add sodium hydrogencarbonate. A carboxylic acid gives brisk effervescence of CO₂ (turns lime water milky); an alcohol shows no reaction.

Q7. Why is graphite used as a lubricant while diamond is used in cutting tools?

Graphite has layers that slide over one another, making it slippery. Diamond has a rigid 3D network of strong bonds, making it extremely hard.

Q8. What are isomers? Give an example.

Compounds with the same molecular formula but different structures are isomers. Butane and isobutane (2-methylpropane) both have the formula C₄H₁₀.

Long Answer Questions

Q1. Explain the cleansing action of soap with the help of micelles.

A soap molecule has a long hydrocarbon tail that dissolves in oil (hydrophobic) and an ionic head that dissolves in water (hydrophilic).

When soap is added to water containing oily dirt, the tails of soap molecules point into the oil droplet while the ionic heads face outward into the water. This cluster is called a micelle.

The micelles stay suspended in water because of their charged surfaces, and the oily dirt they hold is washed away when we rinse. Mechanical action like scrubbing helps lift the dirt off.

Q2. Describe esterification and saponification with equations.

Esterification: when ethanoic acid is warmed with ethanol in the presence of an acid catalyst (conc. H₂SO₄), a sweet-smelling ester forms.

Equation: CH₃COOH + CH₃CH₂OH → CH₃COOCH₂CH₃ + H₂O

Saponification: when an ester is treated with sodium hydroxide, it converts back to an alcohol and the sodium salt of the acid. This reaction is used to make soap.

Equation: CH₃COOC₂H₅ + NaOH → C₂H₅OH + CH₃COONa

Q3. What is a homologous series? Give its characteristics with an example.

A homologous series is a family of carbon compounds with the same functional group in which successive members differ by a –CH₂– group.

Characteristics: (i) same general formula; (ii) successive members differ by –CH₂– and 14 u in molecular mass; (iii) similar chemical properties because of the same functional group; (iv) gradual change in physical properties such as melting point, boiling point and solubility as molecular mass increases.

Example: the alcohols methanol (CH₃OH), ethanol (C₂H₅OH) and propanol (C₃H₇OH).

MCQs with Answers

1. The number of covalent bonds in ethane (C₂H₆) is
(a) 6 (b) 7 (c) 8 (d) 10
Answer: (b) 7 – 1 C–C + 6 C–H.

2. Which allotrope of carbon conducts electricity?
(a) Diamond (b) Graphite (c) Fullerene (d) Charcoal
Answer: (b) Graphite

3. The functional group in propanone is
(a) –OH (b) –CHO (c) >C=O (d) –COOH
Answer: (c) >C=O

4. Vinegar is a solution of
(a) Methanoic acid (b) Ethanoic acid (c) Citric acid (d) Lactic acid
Answer: (b) Ethanoic acid

5. Conversion of vegetable oil to ghee is an example of
(a) Substitution (b) Addition (hydrogenation) (c) Oxidation (d) Esterification
Answer: (b) Addition (hydrogenation)

6. Which burns with a sooty flame?
(a) Methane (b) Ethane (c) Ethyne (d) Propane
Answer: (c) Ethyne – It is unsaturated.

7. The next homologue of C₂H₅OH is
(a) CH₃OH (b) C₃H₇OH (c) C₄H₉OH (d) C₂H₄
Answer: (b) C₃H₇OH

8. Soap molecules form micelles because they have
(a) Only hydrophobic parts (b) Only hydrophilic parts (c) Both hydrophobic and hydrophilic parts (d) No charge
Answer: (c) Both hydrophobic and hydrophilic parts

9. Substitution reaction of methane with chlorine requires
(a) Darkness (b) Sunlight (c) Nickel catalyst (d) Water
Answer: (b) Sunlight

10. Ethanol on heating with excess conc. H₂SO₄ at 443 K gives
(a) Ethane (b) Ethene (c) Ethanal (d) Ethanoic acid
Answer: (b) Ethene – Dehydration.

Quick Revision Points

• Carbon forms covalent bonds by sharing electrons; tetravalency + catenation make it versatile.
• Diamond is hard and non-conducting; graphite is slippery and conducting; C-60 is a fullerene.
• Alkanes CₙH₂ₙ₊₂, alkenes CₙH₂ₙ, alkynes CₙH₂ₙ₋₂.
• Homologues differ by –CH₂– (14 u).
• Combustion, oxidation, addition (Ni catalyst), substitution (sunlight).
• Esterification: acid + alcohol → ester + water; saponification gives soap.
• Soap fails in hard water (scum); detergents work in hard water.

Chapter Summary

Carbon shares electrons to form covalent bonds, and its tetravalency and catenation allow chains, branches and rings of many sizes. Diamond, graphite and fullerenes are its allotropes. Hydrocarbons can be saturated or unsaturated, and functional groups create families called homologous series, which are named using standard rules.

Carbon compounds undergo combustion, oxidation, addition and substitution reactions. Ethanol and ethanoic acid are two important compounds whose reaction forms esters. Soaps clean by forming micelles, while detergents also work in hard water.

Exam Tips and PYQ Pattern

• Draw electron-dot structures of CH₄, C₂H₆, C₂H₄, CO₂ and N₂ neatly; they are common 2-3 mark questions.
• IUPAC naming and identifying functional groups appear as MCQs and short answers.
• Micelle formation is a frequent 3- or 5-mark question; include a labelled diagram.
• Learn the conditions for each reaction (sunlight, Ni catalyst, conc. H₂SO₄, 443 K).

Frequently Asked Questions

What is catenation?

Catenation is carbon’s ability to bond with other carbon atoms to form long chains, branched chains and rings.

Why do soaps not work in hard water?

Hard water contains calcium and magnesium salts that react with soap to form an insoluble scum, so much soap is wasted.

What is the difference between ethanol and ethanoic acid?

Ethanol is an alcohol (–OH group); ethanoic acid is a carboxylic acid (–COOH group) that turns blue litmus red and reacts with carbonates to release CO₂.

Conclusion

Carbon and its Compounds is large but very logical. Master covalent bonding, the naming rules and four reaction types, then learn ethanol, ethanoic acid and soaps carefully. Regular practice of structures and equations is the fastest route to full marks here.

More Notes: Class 10 Science Chapter 3: Metals and Non-metals notes | Class 10 Science Chapter 5: Life Processes notes | All Class 10 Science notes

Author Bio: Written and reviewed by the Nextoper Editorial Team, a group of CBSE science educators who build chapter notes directly from the NCERT textbook and past board paper patterns.

Freshness Note: These notes follow the NCERT Class 10 Science textbook (Reprint 2026-27) and the CBSE syllabus for the 2026-27 session. Last checked on 7 November 2026.