Acids, Bases and Salts

Acids:
An acid is a substance that releases hydrogen ions (H⁺) when dissolved in water. Acids have a sour taste, turn blue litmus paper red, and have a pH less than 7.

Examples:
Hydrochloric acid (HCl) — found in stomach
Sulphuric acid (H₂SO₄) — used in car batteries
Citric acid — found in lemons
Acetic acid — found in vinegar

Bases:
A base is a substance that releases hydroxide ions (OH⁻) when dissolved in water. Bases have a bitter taste, feel slippery, turn red litmus paper blue, and have a pH greater than 7. Bases that dissolve in water are called alkalis.

Examples:
Sodium hydroxide (NaOH) — used in soap making
Ammonia (NH₃) — used in cleaning products
Calcium hydroxide (Ca(OH)₂) — used in cement

pH Scale:
The pH scale measures how acidic or basic a solution is, ranging from 0 to 14.
pH 0–6 = Acidic (lower number = stronger acid)
pH 7 = Neutral (pure water)
pH 8–14 = Basic/Alkaline (higher number = stronger base)

Salts:
A salt is formed when an acid and a base react together in a process called neutralization. In this reaction, the H⁺ from the acid and the OH⁻ from the base combine to form water, while the remaining ions form a salt.

Reaction:
Acid + Base → Salt + Water

Example:
HCl + NaOH → NaCl (salt) + H₂O (water)

Common Salts:
Sodium chloride (NaCl) — table salt
Calcium carbonate (CaCO₃) — limestone and chalk
Potassium nitrate (KNO₃) — used in fertilizers