1. Acids
Definition
Acids are substances that produce hydrogen ions (H⁺) when dissolved in water. They generally have a
sour taste and turn blue litmus paper red.
Examples
Hydrochloric acid (HCl)
Sulphuric acid (H₂SO₄)
Nitric acid (HNO₃)
Acetic acid (CH₃COOH) — present in vinegar
Citric acid — present in citrus fruits
Properties of Acids
1. They have a sour taste.
2. They turn blue litmus red.
3. Their aqueous solutions conduct electricity.
4. They react with some metals to produce hydrogen gas.
5. They react with bases to form salt and water.
6. Strong acids can be corrosive.
2. Bases
Definition
Bases are substances that produce hydroxide ions (OH⁻) in water. They generally have a bitter taste
and feel soapy or slippery.
Examples
Sodium hydroxide (NaOH)
Potassium hydroxide (KOH)
Calcium hydroxide [Ca(OH)₂]
Magnesium hydroxide [Mg(OH)₂]
Ammonium hydroxide (NH₄OH)
Properties of Bases
1. They usually have a bitter taste.
2. They turn red litmus blue.