Chemical Reactions and Equations

Introduction

A chemical reaction is a process in which one or more substances (called reactants) change to form new substances (called products). These changes may involve color change, gas formation, temperature change, or formation of a solid.

1. Chemical Equation
A chemical equation is the symbolic representation of a chemical reaction using chemical formulas.

Example:
Magnesium + Oxygen → Magnesium oxide
Mg + O₂ → MgO

This is a chemical equation showing the reactants and the product.

2. Balanced Chemical Equation
The law of conservation of mass says that mass is neither created nor destroyed in a chemical reaction.
So, the number of atoms of each element must be the same on both sides of the equation.

Balanced example:
2Mg + O₂ → 2MgO

3. Types of Chemical Reactions
        Combination Reaction:--
             Two substances combine to form one compound.
              Example: CaO + H₂O → Ca(OH)₂

         Decomposition Reaction:--
              A single compound breaks down into simpler substances.
              Example: 2H₂O₂ → 2H₂O + O₂

          Displacement Reaction:--
               One element replaces another in a compound.
               Example: Zn + CuSO₄ → ZnSO₄ + Cu

         Double Displacement Reaction:
               Two compounds exchange their ions.
               Example: Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl

4. Effects of a Chemical Reaction
       Chemical reactions may show:

• Change in color
• Evolution of gas
• Formation of a precipitate
• Change in temperature