Class 10 Science - Chapter 1
Chemical Reactions and Equations (Detailed
Notes)
1. Chemical Reaction
A chemical reaction is a process in which one or more substances (reactants) are converted into
new substances (products) with different properties.
Example: Burning magnesium ribbon forms magnesium oxide.
Example Equation:
2Mg + O■ → 2MgO
Mg ribbon + O■ (air)
↓ (burning)
Bright white flame
↓
MgO (ash)
2. Characteristics of Chemical Reactions
• Change in colour (e.g., CuSO■ → FeSO■)
• Evolution of gas (e.g., Zn + HCl → H■ gas)
• Formation of precipitate (e.g., Pb(NO■)■ + KI → PbI■↓)
• Change in temperature (exothermic/endothermic)
3. Chemical Equations
A chemical equation represents a reaction using symbols and formulae.
Types:
• Word Equation: Hydrogen + Oxygen → Water
• Skeletal Equation: H■ + O■ → H■O
4. Balanced Chemical Equation
A balanced equation has equal number of atoms on both sides (Law of Conservation of Mass).
Example:
Unbalanced: H■ + O■ → H■O
Balanced: 2H■ + O■ → 2H■O
5. Types of Chemical Reactions
a) Combination Reaction
Two or more substances combine to form a single product.
CaO + H■O → Ca(OH)■
Chemical Reactions and Equations (Detailed
Notes)
1. Chemical Reaction
A chemical reaction is a process in which one or more substances (reactants) are converted into
new substances (products) with different properties.
Example: Burning magnesium ribbon forms magnesium oxide.
Example Equation:
2Mg + O■ → 2MgO
Mg ribbon + O■ (air)
↓ (burning)
Bright white flame
↓
MgO (ash)
2. Characteristics of Chemical Reactions
• Change in colour (e.g., CuSO■ → FeSO■)
• Evolution of gas (e.g., Zn + HCl → H■ gas)
• Formation of precipitate (e.g., Pb(NO■)■ + KI → PbI■↓)
• Change in temperature (exothermic/endothermic)
3. Chemical Equations
A chemical equation represents a reaction using symbols and formulae.
Types:
• Word Equation: Hydrogen + Oxygen → Water
• Skeletal Equation: H■ + O■ → H■O
4. Balanced Chemical Equation
A balanced equation has equal number of atoms on both sides (Law of Conservation of Mass).
Example:
Unbalanced: H■ + O■ → H■O
Balanced: 2H■ + O■ → 2H■O
5. Types of Chemical Reactions
a) Combination Reaction
Two or more substances combine to form a single product.
CaO + H■O → Ca(OH)■
