Chemical Reactions and Equations

Introduction

• Leaving fruit or vegetables at room temperature for a long time causes them to rot.
• Chemical reactions occur that produce a foul smell.

Importance of Chemical Reactions

• Medicine in diseases and oxidation in the body.
• Digestion of food and burning of fuel.
• Photosynthesis in plants.
• Rusting of iron.

Chemical Reactions and Chemical Equations

• Chemical Reaction: A process where one substance turns into another.
• Chemical Equation: A symbolic representation of a chemical reaction.
• Example: Magnesium + Oxygen → Magnesium Oxide.

Signs of Chemical Changes

• Change in state: From gas to solid.
• Change in color: Iron's color in rusting.
• Evolution of gas: Burning of fuel.
• Change in temperature: Cooking of an egg.

Benefits of Chemical Equations

• Short names, easy to write, easy to balance.

Balancing Chemical Equations

• Magnesium + Oxygen → Magnesium Oxide.
• Balancing the atoms of each element.

Types of Chemical Reactions

Combination Reaction

• Two or more reactants combine to form one product.
• Example: H2 + O2 → H2O.

Decomposition Reaction

• A compound breaks down into two or more substances.
• Example: 2H2O → 2H2 + O2.

Displacement Reaction

• One element displaces another element in a compound.
• Example: Zn + H2SO4 → ZnSO4 + H2.

Double Displacement Reaction

• Exchange of ions between two compounds.
• Example: Na2SO4 + BaCl2 → BaSO4 + 2NaCl.

Neutralization Reaction

• Acid and base combine to form salt and water.
• Example: HCl + NaOH → NaCl + H2O.

Special Types of Reactions

Oxidation and Reduction (Redox Reactions)

• Oxidation: Gain of oxygen or loss of hydrogen.
• Reduction: Loss of oxygen or gain of hydrogen.
• Example: Fe + O2 → Fe2O3 (oxidation) and CuO + H2 → Cu + H2O (reduction).

Rusting of Iron

• Iron reacts with oxygen and water.
• Prevention: Coating with paint.

Rancidification

• Spoiling of oily food.
• Prevention: Airtight containers.

Conclusion

• Importance and types of chemical reactions and equations.
• Balancing equations and special types of reactions.