📘Class 10 Science – Chapter: Carbon and Its Compounds Notes
🔹 Introduction to Carbon
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Carbon is a versatile element due to its ability to form strong covalent bonds.
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It is tetravalent (can form 4 bonds).
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Shows catenation – ability to form long chains.
Example: Diamond, graphite, methane.
🔹 Covalent Bonding in Carbon
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Carbon forms covalent bonds by sharing electrons.
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Types of covalent bonds:
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Single bond: e.g., CHâ‚„ (methane)
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Double bond: e.g., Câ‚‚Hâ‚„ (ethene)
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Triple bond: e.g., Câ‚‚Hâ‚‚ (ethyne)
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Representation:
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CH₄: H–C–H (each line represents a shared electron pair)
🔹 Allotropes of Carbon
| Allotrope | Structure | Properties | Uses |
|---|---|---|---|
| Diamond | 3D tetrahedral | Hardest substance, non-conductor | Cutting tools |
| Graphite | Hexagonal layers | Soft, conductor of electricity | Lubricants, electrodes |
| Fullerene | Spherical (C₆₀) | Hollow molecules, antioxidant use | Nanotechnology |
🔹 Hydrocarbons
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Compounds made of hydrogen and carbon.
Types:
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Saturated hydrocarbons (alkanes): single bonds only
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General formula: CₙH₂ₙ₊₂
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Example: Methane (CH₄), Ethane (C₂H₆)
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Unsaturated hydrocarbons (alkenes & alkynes):
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Alkenes: CₙH₂ₙ → Ethene (C₂H₄)
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Alkynes: CₙH₂ₙ₋₂ → Ethyne (C₂H₂)
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🔹 Functional Groups
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Atoms or groups replacing hydrogen in hydrocarbons.
| Functional Group | Symbol | Example |
|---|---|---|
| Alcohol | –OH | C₂H₅OH (ethanol) |
| Aldehyde | –CHO | HCHO (formaldehyde) |
| Ketone | –CO– | CH₃COCH₃ (acetone) |
| Carboxylic acid | –COOH | CH₃COOH (acetic acid) |
🔹 Nomenclature of Carbon Compounds
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Prefixes (meth-, eth-, prop-, but-, etc.) depend on number of carbon atoms.
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Suffix based on functional group.
Example:
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CHâ‚„ = Methane
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CH₃OH = Methanol
🔹 Chemical Properties of Carbon Compounds
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Combustion: Carbon compounds burn in air to form COâ‚‚ and water.
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CH₄ + 2O₂ → CO₂ + 2H₂O + heat
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Oxidation: Alcohols can be oxidised to acids.
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CH₃CH₂OH → CH₃COOH
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Addition Reaction: Unsaturated hydrocarbons react with hydrogen in the presence of catalyst (e.g., Ni).
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C₂H₄ + H₂ → C₂H₆
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Substitution Reaction: In alkanes, hydrogen atoms can be replaced by halogens.
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CH₄ + Cl₂ → CH₃Cl + HCl
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🔹 Important Carbon Compounds
1. Ethanol (Câ‚‚Hâ‚…OH)
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Colourless liquid, good solvent.
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Used in alcoholic drinks (not advisable to consume in excess).
Reactions:
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Combustion: C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O
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Reaction with sodium: 2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂
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Dehydration: C₂H₅OH → C₂H₄ + H₂O (in presence of H₂SO₄)
2. Ethanoic Acid (CH₃COOH)
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Commonly known as acetic acid (vinegar = 5–8% solution).
Properties:
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Weak acid
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Reacts with base to form salt and water (neutralisation)
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Reacts with alcohol to form ester (sweet-smelling compounds)
Reaction:
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CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O (Esterification)
🔹 Soaps and Detergents
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Soap molecules have a hydrophilic (water-attracting) head and a hydrophobic (water-repelling) tail.
Mechanism:
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Soap molecules are arranged in spherical structures called micelles.
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The hydrophobic tails attach to oil or grease particles (the dirt or stain), while the hydrophilic heads remain in contact with water.
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The hydrophobic tails break the oil and grease into tiny droplets, which are then surrounded by the soap molecules.
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The micelles (containing grease) are suspended in water and can be easily rinsed away, leaving the surface clean.
Example: When you wash your hands with soap and water, the soap molecules trap the grease or dirt in the micelles, and the dirt gets washed away.
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Soaps: Sodium or potassium salts of fatty acids.
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Made by reaction of oil/fat with NaOH (saponification).
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Work better in soft water.
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Detergents: Synthetic cleaning agents; work even in hard water.
Example Table:
| Type | Composition | Uses |
|---|---|---|
| Soap | Na/K salts of fatty acids | Washing, bathing |
| Detergent | Sulphonates or sulphates | Laundry, hard water usage |