10 Science - Chemical Reactions and Equations

🔹 1. Chemical Reaction

A chemical reaction is a process in which substances undergo change to form new substances.

📌 Example:
Burning of magnesium ribbon → Magnesium Oxide is formed

🔹 2. Chemical Equation

A chemical equation represents a reaction using symbols and formulas.

👉 Example:
Mg + O₂ → MgO

🔹 3. Balanced Chemical Equation (VERY IMPORTANT)

According to the Law of Conservation of Mass, atoms must be equal on both sides.

✅ Step-by-Step Example:

Unbalanced:
Fe + H₂O → Fe₃O₄ + H₂

Balanced:
3Fe + 4H₂O → Fe₃O₄ + 4H₂

👉 Always ensure:
✔ Same number of atoms
✔ Same elements on both sides

🔹 4. Types of Chemical Reactions

🔹 5. Oxidation & Reduction (IMPORTANT)

👉 Trick to remember:

✔ OIL RIG

Oxidation = Loss

Reduction = Gain

🔹 6. Corrosion

Slow damage of metals due to air and moisture.

📌 Example:
Rusting of iron

🔹 7. Rancidity

Oxidation of food causing bad smell and taste.

👉 Prevention:
✔ Use airtight containers
✔ Refrigeration

Rusting of iron

🔹 8. Balancing Chemical Equation

🔹 Question:

Balance the following chemical equation:

👉 Al + Fe₂O₃ → Al₂O₃ + Fe

🔹 Step 1: Write the unbalanced equation

Al + Fe₂O₃ → Al₂O₃ + Fe

🔹 Step 2: Count atoms on both sides

🔹 Step 3: Balance Aluminium (Al)

👉 Put 2 before Al:

2Al + Fe₂O₃ → Al₂O₃ + Fe

🔹 Step 4: Balance Iron (Fe)

👉 Put 2 before Fe:

2Al + Fe₂O₃ → Al₂O₃ + 2Fe

🔹 Step 5: Check Oxygen (O)

✔ Already balanced (3 on both sides)

✅ Final Balanced Equation:

👉 2Al + Fe₂O₃ → Al₂O₃ + 2Fe