1. What is a Chemical Reaction?
A process where original substances change their nature and identity to form entirely new substances with new properties. The starting substances are Reactants, and the newly formed substances are Products.
2. Types of Chemical Reactions
- Combination Reaction: Two or more reactants combine to form a single product.
CaO(s) + H2O(l) → Ca(OH)2(aq) + Heat [Slaking of Lime]
- Decomposition Reaction: A single reactant breaks down into multiple simpler products. (Requires Heat, Light, or Electricity).
2FeSO4(s) + Heat → Fe2O3(s) + SO2(g) + SO3(g)
- Displacement Reaction: A more reactive element pushes out a less reactive element from its salt solution.
Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
- Double Displacement Reaction: Mutual exchange of ions between two compounds to form a solid precipitate.
Na2SO4(aq) + BaCl2(aq) → BaSO4(s)↓ + 2NaClaq)
3. Oxidation and Reduction (Redox)
Oxidation: Gain of oxygen or loss of hydrogen.
Reduction: Loss of oxygen or gain of hydrogen.
CBSE Board Exam Favorite Question
Why do we paint iron grills? Iron reacts with moisture and oxygen in the air to undergo Corrosion (Rusting). Applying paint cuts off the metal's direct contact with air and moisture, keeping it safe from degradation.