Class 10th || Science || Notes || Chapter 4: Carbon and Its Compounds

 


Chapter 4: 

Carbon is one of the most fascinating elements on the periodic table. Its versatility allows it to form millions of compounds, far more than all other elements combined. This chapter explores the unique nature of carbon, the wide variety of compounds it forms, and its significance in our daily lives.

1. Bonding in Carbon: Covalent Bond

  • Covalent Bond:
    Carbon does not lose or gain electrons to form bonds because it requires a large amount of energy to do so. Instead, it shares its valence electrons with other atoms to form covalent bonds, leading to stable compounds.
    Example: Methane (CH₄), where carbon shares electrons with four hydrogen atoms.

  • Types of Covalent Bonds:

    • Single Bond: One pair of shared electrons (e.g., H–H in hydrogen gas).
    • Double Bond: Two pairs of shared electrons (e.g., O=O in oxygen gas).
    • Triple Bond: Three pairs of shared electrons (e.g., N≡N in nitrogen gas).

  • Properties of Covalent Compounds:

    • Low melting and boiling points.
    • Poor conductors of electricity due to the absence of free ions.
    • Generally insoluble in water but soluble in organic solvents.

2. Versatile Nature of Carbon

Carbon owes its versatility to two key properties:

  1. Catenation:
    The ability of carbon atoms to bond with each other to form chains, branched structures, and rings. These structures can vary greatly in length and complexity.

    • Example: Chains in hydrocarbons like methane (CH₄), ethane (C₂H₆), and propane (C₃H₈).

  2. Tetravalency:
    Carbon has four valence electrons and can form bonds with up to four other atoms. This enables it to bond with elements such as hydrogen, oxygen, nitrogen, sulfur, and even other carbon atoms.

  • Diversity in Bonding:
    Carbon forms single, double, and triple bonds, creating an infinite variety of compounds. Examples include:
    • Single Bond: Ethane (C₂H₆)
    • Double Bond: Ethene (C₂H₄)
    • Triple Bond: Ethyne (C₂H₂)

3. Saturated and Unsaturated Compounds

  • Saturated Compounds:
    These compounds contain only single bonds between carbon atoms. They are generally less reactive.
    Example: Alkanes (Methane - CH₄, Ethane - C₂H₆).

  • Unsaturated Compounds:
    These compounds contain one or more double or triple bonds between carbon atoms, making them more reactive.
    Example: Alkenes (Ethene - C₂H₄), Alkynes (Ethyne - C₂H₂).

4. Functional Groups

Functional groups are specific atoms or groups of atoms within a molecule that determine its chemical properties. They are like the "active sites" of a molecule.

  • Common Functional Groups:
    1. Alcohol (-OH): Found in ethanol (C₂H₅OH), used in beverages and sanitizers.
    2. Aldehyde (-CHO): Found in formaldehyde (HCHO), used as a preservative.
    3. Ketone (-CO-): Found in acetone (CH₃COCH₃), used as a solvent.
    4. Carboxylic Acid (-COOH): Found in acetic acid (CH₃COOH), the main component of vinegar.

Each functional group has distinct chemical properties, making organic chemistry incredibly diverse.

5. Homologous Series

A homologous series is a group of organic compounds with the same functional group but differing by a CH₂ unit.

  • Characteristics of a Homologous Series:
    1. All members have a similar general formula.
    2. They exhibit a gradual change in physical properties (e.g., boiling point, melting point).
    3. They have similar chemical properties.

Example of Alkanes:

  • Methane (CH₄)
  • Ethane (C₂H₆)
  • Propane (C₃H₈)

6. Chemical Properties of Carbon Compounds

Carbon compounds undergo various chemical reactions that make them highly useful.

  1. Combustion:
    Carbon compounds burn in oxygen to produce carbon dioxide, water, heat, and light.

    • Example: CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
      This property makes hydrocarbons excellent fuels.

  2. Oxidation:
    Alcohols can be oxidized to aldehydes and then to carboxylic acids using oxidizing agents like potassium permanganate (KMnO₄).

    • Example: Ethanol → Ethanal → Acetic Acid

  3. Addition Reactions:
    Unsaturated hydrocarbons react with hydrogen in the presence of a catalyst (e.g., nickel) to form saturated hydrocarbons.

    • Example: C₂H₄ + H₂ → C₂H₆

  4. Substitution Reactions:
    In saturated hydrocarbons, hydrogen atoms are replaced by other atoms (e.g., halogens).

    • Example: CH₄ + Cl₂ → CH₃Cl + HCl (in the presence of sunlight)

7. Soaps and Detergents

  • Soap:
    Soaps are sodium or potassium salts of fatty acids. They clean by forming micelles, which trap dirt and grease in their hydrophobic tails and wash them away with water.

  • Detergents:
    Synthetic cleansing agents that work in both soft and hard water. Unlike soaps, detergents do not form scum in hard water.

8. Importance of Carbon Compounds

Carbon compounds are essential in everyday life:

  • Fuels: Hydrocarbons like petrol, diesel, and LPG.
  • Food: Carbohydrates, proteins, and fats are all organic compounds.
  • Medicines: Many drugs are carbon-based compounds.
  • Materials: Plastics, fibers, and synthetic rubber are products of carbon chemistry.

Key Learning Outcomes

  • Understand the structure and bonding of carbon compounds.
  • Differentiate between saturated and unsaturated compounds.
  • Recognize the role of functional groups and homologous series in organic chemistry.
  • Apply knowledge of the chemical properties of carbon compounds in real life.
  • Appreciate the importance of carbon compounds in industry and daily life.

Suggested Student Activities:

  1. Create a model of carbon compounds using sticks and balls to represent bonds and atoms.
  2. Perform an experiment to observe the cleansing action of soap in hard and soft water.
  3. Research and present the uses of any two carbon compounds in daily life.

This chapter gives us a glimpse of the endless possibilities created by the tiny yet powerful element carbon, forming the backbone of organic chemistry and life itself.

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