An acid is a substance that donates protons (H⁺ ions) in a chemical reaction. This is known as the Brønsted–Lowry definition. In simple terms, acids are proton donors.

🧪 Types of Acids:

1. Based on Strength:

Strong Acids: Completely ionize in water.

Examples:

Hydrochloric acid (HCl)

Nitric acid (HNO₃)

Sulfuric acid (H₂SO₄)

Weak Acids: Partially ionize in water.

Examples:

Acetic acid (CH₃COOH)

Carbonic acid (H₂CO₃)

Citric acid

2. Based on Source:

Organic Acids: Found in living things.

Examples: Citric acid, Acetic acid

Inorganic Acids (Mineral Acids): Made from minerals.

Examples: HCl, H₂SO₄, HNO₃

⚗️ Physical and Chemical Properties of Acids:

Taste: Sour (Never taste in labs!)

Feel: Corrosive (can burn skin)

pH: Less than 7 (lower pH = stronger acid)

Color Change: Turns blue litmus red

Reacts with Metals: Produces hydrogen gas

Acid + Metal → Salt + H₂ (gas)

Acid + Metal → Salt + H₂ (gas)

Reacts with Bases (Alkalis): Forms salt and water

Acid + Base → Salt + Water

Acid + Base → Salt + Water (Neutralization)

🌍 Uses of Acids in Daily Life:

Hydrochloric acid: Digestion (stomach acid)

Sulfuric acid: Car batteries, fertilizers

Nitric acid: Explosives, fertilizers

Acetic acid: Food (vinegar)

Citric acid: Preservative, flavoring in food

Ascorbic acid (Vitamin C): Nutrition

💡 Fun Facts:

Lemon juice has a pH around 2.

Stomach acid is strong enough to dissolve metal.

Acid rain is caused by sulfuric and nitric acids in the atmosphere.