Class 10 Science – Chemical Reactions and Equations | Interactive Visual Revision Notes

📚 Section 1 — Classroom Notes

Real-World Connection: Think about baking a cake — the flour, sugar, and eggs (reactants) transform into something completely new: a cake (products). Chemical reactions work exactly the same way. Every time you see iron rust, a candle burn, or milk turn sour, a chemical reaction is happening all around you!

🔥 Topic 1: What Is a Chemical Reaction?

A chemical reaction changes one thing into another.
Old things are called reactants.
New things made are called products.
Bonds break and new bonds form.
Energy may be taken in or given out.

🔍 Topic 2: Signs of a Chemical Reaction

Color change shows a reaction happened.
Gas bubbles may come out.
The mix may get hot or cold.
A solid may form in a liquid.
Smell change can also be a sign.

✍️ Topic 3: Writing Chemical Equations

We use symbols to write reactions short.
Reactants go on the left side.
Products go on the right side.
An arrow shows the direction of change.
We write (s), (l), (g), (aq) for states.

⚖️ Topic 4: Balancing Chemical Equations

Atoms must be equal on both sides.
We add numbers before formulas to balance.
Never change the formula of a substance.
Start with the biggest molecule first.
Check all atoms match at the end.

🤝 Topic 5: Combination Reaction

Two or more things join to make one.
Example: calcium oxide + water makes lime.
Burning coal is a combination reaction.
These reactions often give out heat.
A + B makes AB is the pattern.

💥 Topic 6: Decomposition Reaction

One thing breaks into two or more.
Heat can cause decomposition to happen.
Sunlight breaks silver chloride into silver.
Electricity can also break water apart.
AB breaks into A + B pattern.

🔄 Topic 7: Displacement Reaction

A stronger element pushes a weaker one out.
Iron nail in copper sulfate turns brown.
Iron replaces copper in the solution.
More reactive metals displace less reactive ones.
A + BC gives AC + B pattern.

🔀 Topic 8: Double Displacement Reaction

Two compounds swap their parts with each other.
A solid often forms in the liquid.
This solid is called a precipitate.
AB + CD gives AD + CB pattern.
Example: sodium sulfate and barium chloride react.

🔋 Topic 9: Oxidation and Reduction

Oxidation means gaining oxygen or losing hydrogen.
Reduction means losing oxygen or gaining hydrogen.
Both happen together in a redox reaction.
Rusting of iron is an oxidation example.
The substance reduced is the oxidizing agent.

🍫 Topic 10: Corrosion and Rancidity

Corrosion happens when metals react with air.
Iron gets a brown coating called rust.
Silver turns black when exposed to air.
Rancidity is when food fats taste bad.
Keep food in airtight jars to prevent rancidity.

✏️ Section 3 — Worked Examples

📝 Example 1: Balance This Equation

Balance: Fe + O₂ → Fe₂O₃

Count Fe: Left = 1, Right = 2.

Count O: Left = 2, Right = 3.

Put 4 before Fe, 3 before O₂.

Put 2 before Fe₂O₃ on right side.

Check: Fe = 4, O = 6 both sides.

Answer: 4Fe + 3O₂ → 2Fe₂O₃

📝 Example 2: Name the Reaction Type

CaO + H₂O → Ca(OH)₂

Count substances on the left: two things.

Count substances on the right: one thing.

Two things join to make one thing.

Answer: This is a Combination Reaction.

📝 Example 3: Oxidation or Reduction?

CuO + H₂ → Cu + H₂O

CuO lost oxygen. It became Cu.

Losing oxygen means reduction.

H₂ gained oxygen. It became H₂O.

Gaining oxygen means oxidation.

Answer: CuO is reduced. H₂ is oxidized. This is a redox reaction.

📋 Section 4 — Cheat Sheet

Word	Meaning
Reactant	The starting substance in a reaction.
Product	The new substance made after reaction.
Precipitate	A solid that forms inside a liquid.
Combination	Two things join to make one thing.
Decomposition	One thing breaks into two or more.
Displacement	A stronger element pushes a weaker one out.
Oxidation	Gaining oxygen or losing hydrogen.
Reduction	Losing oxygen or gaining hydrogen.
Corrosion	Metal surface damaged by air and water.
Rancidity	Fats go bad and smell foul.
Exothermic	Reaction that gives out heat energy.
Endothermic	Reaction that takes in heat energy.

🏠 Section 5 — Take-Home Handout

Part A: Fill in the Blanks

1. Old substances in a reaction are called ________.

2. A solid formed in liquid is called a ________.

3. Two things joining to make one is a ________ reaction.

4. Gaining oxygen is called ________.

5. Fats going bad is called ________.

Part B: True or False

1. Atoms can be created in a chemical reaction. ________

2. Rusting is a type of corrosion. ________

3. Decomposition means two things join together. ________

4. A balanced equation has equal atoms both sides. ________

5. Rancidity can be stopped using airtight jars. ________

Part C: Solve

1. Balance this equation: Mg + O₂ → MgO

2. Balance this equation: Na + H₂O → NaOH + H₂

Part D: Match the Columns

Column A	Column B
1. Combination	a. AB → A + B
2. Decomposition	b. A + B → AB
3. Displacement	c. AB + CD → AD + CB
4. Double Displacement	d. A + BC → AC + B

Part E: Draw and Label

Draw what happens when iron reacts with oxygen and water to form rust.

✅ Detailed Solutions — Section 5 Take-Home Handout

Part A: Fill in the Blanks

1. Old substances in a reaction are called reactants.

2. A solid formed in liquid is called a precipitate.

3. Two things joining to make one is a combination reaction.

4. Gaining oxygen is called oxidation.

5. Fats going bad is called rancidity.

Part B: True or False

1. Atoms can be created in a chemical reaction. → False — Atoms are neither created nor destroyed (Law of Conservation of Mass).

2. Rusting is a type of corrosion. → True — Rusting is the slow corrosion of iron when it reacts with oxygen and water.

3. Decomposition means two things join together. → False — Decomposition breaks one compound into two or more simpler substances.

4. A balanced equation has equal atoms both sides. → True — A balanced equation obeys the Law of Conservation of Mass.

5. Rancidity can be stopped using airtight jars. → True — Keeping fats away from oxygen prevents oxidation and rancidity.

Part C: Solve

1. Balance: Mg + O₂ → MgO

Count atoms: Left has 1 Mg and 2 O; Right has 1 Mg and 1 O — oxygen is unbalanced.

Add coefficient 2 in front of MgO: Mg + O₂ → 2MgO. Now O is balanced but Mg is not.

Add coefficient 2 in front of Mg: 2Mg + O₂ → 2MgO ✅

2. Balance: Na + H₂O → NaOH + H₂

Count atoms: Left: 1 Na, 2 H, 1 O. Right: 1 Na, 1 O, 3 H — hydrogen is unbalanced.

Add coefficient 2 to Na, NaOH, and H₂O: 2Na + 2H₂O → 2NaOH + H₂

Check: Left: 2 Na, 4 H, 2 O. Right: 2 Na, 2 O, 4 H. Balanced ✅

Part D: Match the Columns

1. Combination → b. A + B → AB (two reactants combine into one product)

2. Decomposition → a. AB → A + B (one compound breaks into simpler substances)

3. Displacement → d. A + BC → AC + B (a more reactive element displaces a less reactive one)

4. Double Displacement → c. AB + CD → AD + CB (exchange of ions between two compounds)

Part E: Draw and Label — Rust Formation

Your diagram should show:

An iron nail in the centre
Arrows pointing to it from O₂ (oxygen from air) and H₂O (water)
A reddish-brown layer forming on the nail surface labelled Fe₂O₃ (Rust / Hydrated Iron Oxide)
Overall equation below: 4Fe + 3O₂ + xH₂O → 2Fe₂O₃·xH₂O

🧪 Class 10 Science — Chemical Reactions and Equations
Original Visual Revision Notes Aligned with the Class 10 Science syllabus. Independently created study material. Not affiliated with or endorsed by NCERT.

📖 Table of Contents

📚 Section 1 — Classroom Notes

🔥 Topic 1: What Is a Chemical Reaction?

🔍 Topic 2: Signs of a Chemical Reaction

✍️ Topic 3: Writing Chemical Equations

⚖️ Topic 4: Balancing Chemical Equations

🤝 Topic 5: Combination Reaction

💥 Topic 6: Decomposition Reaction

🔄 Topic 7: Displacement Reaction

🔀 Topic 8: Double Displacement Reaction

🔋 Topic 9: Oxidation and Reduction

🍫 Topic 10: Corrosion and Rancidity

🎨 Section 2 — Easy Illustrations

✏️ Section 3 — Worked Examples

📝 Example 1: Balance This Equation

📝 Example 2: Name the Reaction Type

📝 Example 3: Oxidation or Reduction?

📋 Section 4 — Cheat Sheet

🏠 Section 5 — Take-Home Handout

Part A: Fill in the Blanks

Part B: True or False

Part C: Solve

Part D: Match the Columns

Part E: Draw and Label

✅ Detailed Solutions — Section 5 Take-Home Handout

Part A: Fill in the Blanks

Part B: True or False

Part C: Solve

Part D: Match the Columns

Part E: Draw and Label — Rust Formation

🎴 Section 6 — Revision Flashcards

🧠 Section 7 — Mind Map

🧪 Class 10 Science — Chemical Reactions and EquationsOriginal Visual Revision Notes Aligned with the Class 10 Science syllabus. Independently created study material. Not affiliated with or endorsed by NCERT.

📖 Table of Contents

📚 Section 1 — Classroom Notes

🔥 Topic 1: What Is a Chemical Reaction?

🔍 Topic 2: Signs of a Chemical Reaction

✍️ Topic 3: Writing Chemical Equations

⚖️ Topic 4: Balancing Chemical Equations

🤝 Topic 5: Combination Reaction

💥 Topic 6: Decomposition Reaction

🔄 Topic 7: Displacement Reaction

🔀 Topic 8: Double Displacement Reaction

🔋 Topic 9: Oxidation and Reduction

🍫 Topic 10: Corrosion and Rancidity

🎨 Section 2 — Easy Illustrations

✏️ Section 3 — Worked Examples

📝 Example 1: Balance This Equation

📝 Example 2: Name the Reaction Type

📝 Example 3: Oxidation or Reduction?

📋 Section 4 — Cheat Sheet

🏠 Section 5 — Take-Home Handout

Part A: Fill in the Blanks

Part B: True or False

Part C: Solve

Part D: Match the Columns

Part E: Draw and Label

✅ Detailed Solutions — Section 5 Take-Home Handout

Part A: Fill in the Blanks

Part B: True or False

Part C: Solve

Part D: Match the Columns

Part E: Draw and Label — Rust Formation

🎴 Section 6 — Revision Flashcards

🧠 Section 7 — Mind Map

🧪 Class 10 Science — Chemical Reactions and Equations
Original Visual Revision Notes Aligned with the Class 10 Science syllabus. Independently created study material. Not affiliated with or endorsed by NCERT.