NCERT Class 10 Science Chapter 4 – Carbon and its Compounds

NCERT Class 10 Science Chapter 4 introduces students to the versatile nature of carbon and the basics of organic chemistry. In NCERT Class 10 Science Chapter 4, learners understand covalent bonding, hydrocarbons, functional groups, and important carbon compounds used in daily life.

The chapter begins with bonding in carbon. Since carbon has four valence electrons (electronic configuration 2,4), it forms covalent bonds by sharing electrons. Carbon forms single, double, and triple bonds, leading to a vast number of compounds.

A major theme of NCERT Class 10 Science Chapter 4 is the versatile nature of carbon, mainly due to:

• Catenation – ability to form long chains
• Tetravalency – ability to form four covalent bonds

Carbon compounds are classified as:

• Saturated hydrocarbons (Alkanes) – only single bonds
• Unsaturated hydrocarbons (Alkenes & Alkynes) – double or triple bonds

The chapter introduces homologous series, where consecutive members differ by –CH₂ (14 u), and explains the IUPAC nomenclature system for naming carbon compounds.

Another important section of NCERT Class 10 Science Chapter 4 covers chemical properties like:

• Combustion (burning in oxygen)
• Oxidation
• Addition reactions (hydrogenation using Ni catalyst)
• Substitution reactions

The chapter also explains important compounds like ethanol (C₂H₅OH) and ethanoic acid (CH₃COOH). Ethanoic acid is found in vinegar (5–8%) and pure acetic acid freezes at 289 K. The process of esterification forms esters with fruity smell.

The final section discusses soaps and detergents, including saponification, micelle formation, and why soaps do not work effectively in hard water.

For board exams, NCERT Class 10 Science Chapter 4 is essential as it forms the base of organic chemistry for higher studies. Students should refer to the official NCERT website at for authentic textbooks and syllabus updates.

For structured preparation of NCERT Class 9–12 for UPSC, BPSC and State PCS examinations, strengthen your basics with our complete NCERT Book Notes PDF for Class 9-12, available inside the NCERT foundation course level-2.

Access Complete NCERT Book Notes PDF

4.1 Bonding in Carbon – The Covalent Bond

• Carbon (Atomic number 6) has electronic configuration 2,4, so it has four electrons in its valence shell
• Carbon needs to gain or lose four electrons to achieve noble gas configuration, but gaining or losing four electrons is energetically unfavourable
• Therefore, carbon achieves stability by sharing electrons with other atoms; this type of bond is called a covalent bond
• A covalent bond is formed by the sharing of one or more pairs of electrons between atoms
• For example, in a hydrogen molecule (H₂), each hydrogen atom shares one electron to complete its duplet configuration
• In oxygen (O₂), two pairs of electrons are shared forming a double covalent bond
• In nitrogen (N₂), three pairs of electrons are shared forming a triple covalent bond
• In methane (CH₄), carbon shares one electron each with four hydrogen atoms forming four single covalent bonds
• Covalent compounds generally have low melting and boiling points and are usually poor conductors of electricity

4.2 Versatile Nature of Carbon

• Carbon forms a very large number of compounds due to its unique properties; this is called the versatile nature of carbon
• One important property is catenation, the ability of carbon atoms to form strong covalent bonds with other carbon atoms, leading to long chains
• The C–C bond is very strong and stable, allowing formation of straight chains, branched chains, and ring structures
• Carbon has a valency of four, so it can form bonds with four other atoms, including carbon, hydrogen, oxygen, nitrogen, etc.
• The small size of carbon atoms enables the formation of stable covalent bonds
• Carbon compounds containing only carbon and hydrogen are called hydrocarbons
• The versatility of carbon results in the formation of millions of organic compounds, which form the basis of life

4.2.1 Saturated and Unsaturated Carbon Compounds

• Carbon compounds in which all carbon–carbon bonds are single covalent bonds are called saturated compounds
• Saturated hydrocarbons are known as alkanes, for example methane (CH₄) and ethane (C₂H₆)
• Carbon compounds that contain one or more double or triple bonds between carbon atoms are called unsaturated compounds
• Unsaturated hydrocarbons with a double bond are called alkenes, such as ethene (C₂H₄)
• Unsaturated hydrocarbons with a triple bond are called alkynes, such as ethyne (C₂H₂)
• Saturated compounds generally undergo substitution reactions, while unsaturated compounds undergo addition reactions
• The presence of double or triple bonds makes unsaturated compounds more reactive than saturated compounds

4.2.2 Chains, Branches and Rings

• Carbon atoms can form long straight chains by bonding with each other, for example propane (C₃H₈) and butane (C₄H₁₀)
• Carbon compounds may also form branched chains, where one or more carbon atoms are attached as side branches
• For example, isobutane is a branched form of butane having a different arrangement of carbon atoms
• Carbon atoms can join to form closed ring structures, such as cyclohexane (C₆H₁₂)
• Different arrangements of the same molecular formula give rise to isomers, which have similar chemical formulae but different structures
• The ability to form chains, branches, and rings increases the diversity of carbon compounds

4.2.3 Will You Be My Friend?

• Carbon compounds may contain elements other than carbon and hydrogen, such as oxygen, nitrogen, sulphur, chlorine, etc.
• Atoms or groups of atoms that replace a hydrogen atom in a hydrocarbon and determine its chemical properties are called functional groups
• Some common functional groups include –OH (alcohol group), –COOH (carboxylic acid group), –Cl (chloro group), and –CHO (aldehyde group)
• The presence of a functional group gives specific characteristic properties to the compound
• For example, compounds containing the –OH group are called alcohols, while those containing –COOH are called carboxylic acids
• Functional groups help classify organic compounds into different families with similar chemical behaviour

4.2.4 Homologous Series

• A homologous series is a group of carbon compounds having the same functional group and similar chemical properties
• Successive members of a homologous series differ by a –CH₂ group
• All members of a series have the same general formula, for example alkanes: CₙH₂ₙ₊₂
• The difference in molecular mass between consecutive members is 14 u (mass of –CH₂)
• Members of a homologous series show a gradual change in physical properties such as boiling point and melting point
• Chemical properties remain similar because all members contain the same functional group
• Examples include the alkane series (methane, ethane, propane, butane)

4.2.5 Nomenclature of Carbon Compounds

• The naming of carbon compounds follows the IUPAC (International Union of Pure and Applied Chemistry) system
• The longest carbon chain in the compound is identified first, and its name forms the base name
• The number of carbon atoms determines the prefix:
  Meth- (1), Eth- (2), Prop- (3), But- (4), Pent- (5), Hex- (6)
• The type of bond determines the suffix:
  –ane (single bond), –ene (double bond), –yne (triple bond)
• If a functional group is present, it is indicated by a specific suffix such as –ol (alcohol), –oic acid (carboxylic acid)
• The carbon chain is numbered to give the lowest possible number to the functional group or double/triple bond
• Branches or substituents are named and numbered according to their position in the carbon chain

4.3 Chemical Properties of Carbon Compounds

• Carbon compounds mainly undergo reactions such as combustion, oxidation, addition, and substitution
• Most carbon compounds are combustible and burn in air to produce carbon dioxide (CO₂) and water (H₂O) along with heat and light
• In limited supply of oxygen, carbon compounds may produce carbon monoxide (CO), which is a poisonous gas
• Unsaturated hydrocarbons undergo addition reactions, where atoms are added across double or triple bonds
• Saturated hydrocarbons generally undergo substitution reactions, where one atom is replaced by another
• Some carbon compounds can be oxidised using oxidising agents like alkaline potassium permanganate (KMnO₄) or acidified potassium dichromate (K₂Cr₂O₇)
• The chemical behaviour of carbon compounds largely depends on the presence of functional groups

4.3.1 Combustion

• Most carbon compounds are combustible and burn in air to produce carbon dioxide (CO₂) and water (H₂O) along with release of heat and light
• For example, methane (CH₄) burns in oxygen to form carbon dioxide and water:
  CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
• Combustion reactions are exothermic, meaning they release a large amount of energy
• When oxygen supply is sufficient, combustion is complete and produces a clean blue flame
• In limited supply of oxygen, incomplete combustion occurs and produces carbon monoxide (CO), which is a poisonous gas
• Incomplete combustion may also produce soot (carbon particles), resulting in a yellow flame
• Fuels like LPG, CNG, petrol, and diesel are carbon compounds used for combustion to obtain energy

4.3.2 Oxidation

• Oxidation of carbon compounds involves the addition of oxygen or removal of hydrogen
• Alcohols can be oxidised to form carboxylic acids using oxidising agents such as alkaline potassium permanganate (KMnO₄) or acidified potassium dichromate (K₂Cr₂O₇)
• For example, ethanol (C₂H₅OH) can be oxidised to form ethanoic acid (CH₃COOH)
• Mild oxidising agents can convert alcohols to aldehydes, while stronger oxidising agents convert them further to acids
• Oxidation reactions are important in industrial processes and in daily life applications
• Controlled oxidation helps in producing useful products, while uncontrolled oxidation may lead to spoilage or damage

4.3.3 Addition Reaction

• Addition reactions occur mainly in unsaturated hydrocarbons that contain double or triple bonds
• In an addition reaction, atoms such as hydrogen or halogens are added across the double or triple bond, converting it into a single bond
• For example, ethene (C₂H₄) reacts with hydrogen in the presence of a nickel (Ni) catalyst to form ethane (C₂H₆):
  C₂H₄ + H₂ → C₂H₆
• This process of adding hydrogen is called hydrogenation
• Hydrogenation of vegetable oils is used to produce vanaspati ghee, converting unsaturated oils into saturated fats
• Addition of hydrogen increases the saturation level of the compound
• The presence of double or triple bonds makes unsaturated compounds more reactive toward addition reactions

4.3.4 Substitution Reaction

• Substitution reactions are characteristic of saturated hydrocarbons (alkanes)
• In a substitution reaction, one atom (usually hydrogen) is replaced by another atom such as chlorine or bromine
• For example, methane (CH₄) reacts with chlorine (Cl₂) in the presence of sunlight to form chloromethane (CH₃Cl) and hydrogen chloride:
  CH₄ + Cl₂ → CH₃Cl + HCl
• Further substitution may replace more hydrogen atoms, forming compounds like CH₂Cl₂, CHCl₃, and CCl₄
• These reactions require ultraviolet light or sunlight to initiate the reaction
• Substitution reactions are important in the manufacture of various organic chemicals

4.4 Some Important Carbon Compounds – Ethanol and Ethanoic Acid

• Ethanol (C₂H₅OH) and ethanoic acid (CH₃COOH) are two important carbon compounds widely used in daily life and industry
• Ethanol belongs to the alcohol family and contains the functional group –OH (hydroxyl group)
• Ethanoic acid belongs to the carboxylic acid family and contains the functional group –COOH (carboxyl group)
• Ethanol is a colourless liquid with a characteristic smell and is used in medicines, perfumes, and as a solvent
• Ethanoic acid is commonly known as acetic acid and is responsible for the sour taste of vinegar
• These compounds show characteristic chemical reactions based on their functional groups
• The study of ethanol and ethanoic acid helps understand the properties of alcohols and carboxylic acids

4.4.1 Properties of Ethanol

• Ethanol (C₂H₅OH) is a colourless liquid with a characteristic smell and is commonly called alcohol
• Ethanol is soluble in water due to the presence of the –OH (hydroxyl) functional group
• Ethanol reacts with sodium metal to form sodium ethoxide and hydrogen gas:
  2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂
• On heating with concentrated sulphuric acid (H₂SO₄) at about 443 K, ethanol undergoes dehydration to form ethene (C₂H₄)
• Ethanol is widely used as a solvent in medicines, varnishes, and perfumes
• Excessive consumption of ethanol affects the central nervous system and may cause serious health problems
• Ethanol is also used as a fuel and in blending with petrol

4.4.2 Properties of Ethanoic Acid

• Ethanoic acid (CH₃COOH) is a colourless liquid with a pungent smell and is commonly known as acetic acid
• A dilute solution of ethanoic acid in water is called vinegar, which contains about 5–8% acetic acid
• Pure ethanoic acid freezes at around 289 K forming ice-like crystals, hence it is called glacial acetic acid
• Ethanoic acid reacts with metals such as sodium to produce sodium ethanoate and hydrogen gas
• It reacts with metal carbonates and hydrogencarbonates to produce salt, water, and carbon dioxide gas
• Ethanoic acid reacts with alcohols in the presence of concentrated sulphuric acid to form esters; this reaction is called esterification
• Esters have a pleasant fruity smell and are used in perfumes and flavouring agents

4.5 Soaps and Detergents

• Soaps are sodium or potassium salts of long-chain fatty acids, prepared by the process of saponification
• During saponification, fats or oils react with sodium hydroxide (NaOH) to form soap and glycerol
• A soap molecule has two parts: a hydrophobic (water-repelling) hydrocarbon tail and a hydrophilic (water-attracting) ionic head
• In water, soap molecules form structures called micelles, where the tails trap oily dirt and the heads remain in contact with water
• Soaps do not work well in hard water because they form insoluble scum with calcium and magnesium salts
• Detergents are synthetic cleansing agents that work effectively in both soft and hard water
• Detergents do not form scum and are widely used in household and industrial cleaning

Exam Oriented Facts

• Atomic number of carbon = 6, electronic configuration 2,4
• Carbon forms covalent bonds by sharing electrons
• Single bond (–), Double bond (=), Triple bond (≡) represent sharing of 1, 2, and 3 pairs of electrons
• Catenation is the ability of carbon to form long chains
• Alkanes (CₙH₂ₙ₊₂) are saturated hydrocarbons
• Alkenes contain double bonds; Alkynes contain triple bonds
• Consecutive members of a homologous series differ by –CH₂ (14 u)
• Functional groups:–OH (Alcohol), –COOH (Carboxylic acid), –CHO (Aldehyde), –Cl (Halo group)
• Hydrogenation of unsaturated compounds is done using Nickel (Ni) catalyst
• Ethanol formula: C₂H₅OH
• Dehydration of ethanol occurs at about 443 K with concentrated H₂SO₄
• Ethanoic acid formula: CH₃COOH
• Vinegar contains 5–8% acetic acid
• Pure ethanoic acid freezes at 289 K (Glacial acetic acid)
• Esterification reaction: Alcohol + Carboxylic acid → Ester + Water
• Soap formation process: Saponification
• Soaps form micelles; detergents work in hard water

Understanding NCERT Class 10 Science Chapter 4 – Carbon and its Compounds helps students master covalent bonding, hydrocarbons, and organic reactions.

NCERT Class 10 Science Chapter 4 builds the foundation for advanced organic chemistry topics in Class 11 and 12.

Continue reading NCERT Class 10 Science Chapter 5 – Life Processes to understand biological systems and metabolism.

FAQs

Q1. What is NCERT Class 10 Science Chapter 4 about?
It explains covalent bonding, hydrocarbons, homologous series, ethanol, ethanoic acid, and soaps.

Q2. What is catenation?
It is the ability of carbon to form long chains by bonding with itself.

Q3. What is a homologous series?
A group of compounds with the same functional group and general formula, differing by –CH₂.

Q4. What is hydrogenation?
It is the addition of hydrogen to unsaturated hydrocarbons using a nickel catalyst.

Q5. Why is Chapter 4 important for exams?
It forms the foundation of organic chemistry and functional group reactions.

---