What are the five main types of chemical reactions?

1. Synthesis (Combination): Two or more substances combine to form one product.
A + B → AB | Example: 2H₂ + O₂ → 2H₂O

2. Decomposition: One compound breaks into simpler substances.
AB → A + B | Example: 2H₂O → 2H₂ + O₂

3. Single Replacement: One element replaces another in a compound.
A + BC → AC + B | Example: Zn + CuSO₄ → ZnSO₄ + Cu

4. Double Replacement: Two compounds exchange ions.
AB + CD → AD + CB | Example: NaCl + AgNO₃ → NaNO₃ + AgCl

5. Combustion: A substance reacts with O₂, producing heat, CO₂, and H₂O.
Example: CH₄ + 2O₂ → CO₂ + 2H₂O