Acids and Bases

Acids and bases are important chemical substances that we use in our daily life. They have different properties and reactions.

🔹 What is an Acid?

An acid is a substance that tastes sour.

Examples:

  • Lemon juice

  • Vinegar

  • Curd

🔹 What is a Base?

A base is a substance that tastes bitter and feels soapy.

Examples:

  • Soap solution

  • Baking soda

  • Lime water

🔹 Indicators

Indicators help us to identify acids and bases.

  • Litmus paper

    • Red litmus → Turns blue in base

    • Blue litmus → Turns red in acid

🔹 Properties of Acids

  • Sour in taste

  • Turn blue litmus red

  • React with metals to produce hydrogen gas

Example:

Acid + Metal → Salt + Hydrogen gas

🔹 Properties of Bases

  • Bitter in taste

  • Soapy touch

  • Turn red litmus blue

🔹 Neutralization Reaction

When acid reacts with base, it forms salt and water.

Acid + Base → Salt + Water

Example:

HCl + NaOH → NaCl + H₂O

Uses:

  • Antacids reduce stomach acidity

  • Farmers treat acidic soil with lime

🔹 Strength of Acids and Bases (pH Scale)

The pH scale ranges from 0 to 14:

  • pH < 7 → Acid

  • pH = 7 → Neutral

  • pH > 7 → Base

Lower pH = Strong acid

Higher pH = Strong base

Examples:

  • Lemon juice (pH ~2)

  • Water (pH 7)

  • Soap solution (pH ~10)

🔹 Types of Acids

  1. Natural Acids

    • Citric acid (lemon)

    • Acetic acid (vinegar)

  2. Mineral Acids

    • Hydrochloric acid (HCl)

    • Sulphuric acid (H₂SO₄)

    • Nitric acid (HNO₃)

🔹 Arrhenius Concept

  • Acid produces H⁺ ions in water.

  • Base produces OH⁻ ions in water.

🔹 Chemical Properties of Acids

  1. Reaction with Metals

    Zn + HCl → ZnCl₂ + H₂

  2. Reaction with Carbonates

    Acid + Carbonate → Salt + Water + CO₂

  3. Reaction with Bases (Neutralization)

🔹 Common Salts

  • Sodium chloride (NaCl) – Common salt

  • Washing soda (Na₂CO₃)

  • Baking soda (NaHCO₃)

🏭 Uses of Acids and Bases

✔ Manufacturing fertilizers

✔ Cleaning agents

✔ Food industry

✔ Medicines

✔ Laboratory experiments

⚠ Safety Rules

  • Never taste chemicals in the lab

  • Wear gloves and goggles

  • Add acid to water slowly (never water to acid)

📌 Conclusion

Acids and bases are essential chemicals used in everyday life and industries. Understanding their properties and reactions helps students learn chemistry effectively.