• Chemical reactions involve the transformation of substances into new substances with different properties.
• There are several types of chemical reactions, each with distinct characteristics.

1. Combination Reactions:

• The chemical reactions in which two or more substances (reactants) combine together to form single substance (product) are called combination reactions.

• Also known as synthesis reactions.
• A majority of the combination reactions are Exothermic in nature.
• General form:

A + B → AB.

2. Decomposition Reactions:

• The chemical reactions in which a single compound breaks into smaller or simpler substances or units are called decomposition reactions.

• A majority of the combination reactions are Endothermic in nature.
• General form:

AB → A + B.

3. Displacement Reactions:

• Involves the replacement of one element in a compound by another element.

• Single displacement:

AB + C → A+ BC.

4 . Double displacement:

• The chemical reactions in which exchange of ions takes place when the aqueous solutions of two ionic compounds are mixed together.

AB + CD → AD + CB.

5. Precipitation Reactions:

• A type of double displacement reaction where two soluble compounds react to form an insoluble product (precipitate).

• Example: AgNO3 + NaCl → AgCl ↓ + NaNO3.

6. Redox Reactions (Oxidation-Reduction Reactions):

• Involves the transfer of electrons from one substance to another.
• Oxidation: Loss of electrons.
• Reduction: Gain of electrons.
• Redox reactions always occur simultaneously.
• Example: 2Na + Cl2 → 2NaCl.

6. Combustion Reactions:

• A type of redox reaction where a substance reacts with oxygen to produce heat, light, and often carbon dioxide and water.
• Common in the burning of fuels.

• Example: CH4 + 2O2 → CO2 + 2H2O.

7. Acid-Base (Neutralization) Reactions:

• Involves the reaction between an acid and a base to produce salt and water.
• Example: HCl + NaOH → NaCl + H2O.

8. Precipitation, Acid-Base, and Redox Reactions in Daily Life:

• Precipitation: Formation of scale in kettles due to the reaction between calcium and carbonate ions in hard water.
• Acid-Base: Antacid tablets neutralize excess stomach acid.
• Redox: Rusting of iron is a common redox process.