Ready
Your guide has been resting for a day
Turn the avatar back on if you want help with doubts, hints, and step-by-step guidance.
1
Lesson
Chemical Reactions and Equations — Complete Lesson
?? What is a Chemical Reaction?
A chemical reaction is a process in which one or more substances (called reactants) are transformed into one or more different substances (called products). Unlike physical changes, chemical changes are usually irreversible.
Real-Life Example: When you burn a piece of paper, it cannot be turned back into paper. That's a chemical reaction! ??
?? Signs of a Chemical Reaction
- ??? Change in state — solid to gas
- ?? Change in colour — iron turning red-brown when it rusts
- ?? Formation of gas — fizzing when baking soda + vinegar
- ?? Formation of precipitate — white solid appears when solutions mix
- ??? Change in temperature — heat released or absorbed
?? Writing and Balancing Chemical Equations
The Law of Conservation of Mass states: matter is neither created nor destroyed. So atoms on both sides of the equation must be equal.
Unbalanced: H2 + O2 ? H2O
Balanced: 2H2 + O2 ? 2H2O
Left: 4H + 2O = Right: 4H + 2O ?
?? Types of Chemical Reactions
| Type | Description | Example |
|---|---|---|
| Combination | A + B ? AB | 2Mg + O2 ? 2MgO |
| Decomposition | AB ? A + B | 2H2O ? 2H2 + O2 |
| Displacement | A + BC ? AC + B | Zn + CuSO4 ? ZnSO4 + Cu |
| Double Displacement | AB + CD ? AD + CB | Na2SO4 + BaCl2 ? BaSO4? + 2NaCl |
| Oxidation/Reduction | Gain/loss of oxygen or electrons | 4Fe + 3O2 ? 2Fe2O3 (rusting) |
?? Did You Know? The word equation for burning magnesium in air:
Magnesium + Oxygen ? Magnesium oxide
Magnesium burns with a dazzling white light — that's why it was used in old camera flash bulbs!
Magnesium + Oxygen ? Magnesium oxide
Magnesium burns with a dazzling white light — that's why it was used in old camera flash bulbs!
2
MCQ Practice
Chemical Reactions — MCQ Practice (10 Questions)
3
Memory Trick
Memory Trick: Types of Chemical Reactions
Remember the 5 types of chemical reactions with the mnemonic:
C.D.D.D.O
"Can Dogs Drink Dirty Orange juice?"
- ?? Combination — A + B ? AB (things combine)
- ?? Decomposition — AB ? A + B (things break down)
- ?? Displacement — A + BC ? AC + B (one displaces another)
- ?? Double Displacement — AB + CD ? AD + CB (both swap)
- ?? Oxidation/Reduction — gain or loss of oxygen/electrons
Bonus Trick for Balancing:
"Left = Right, Always Fight!"
Atoms on left side must always equal atoms on right side. Balance H and O last!
"Left = Right, Always Fight!"
Atoms on left side must always equal atoms on right side. Balance H and O last!
Interactive
Mission: Master This Topic!
Reinforce what you learned with fun activities
🎯
Ready to Battle? Test Your Knowledge!
Practice MCQs, build combos, climb the leaderboard!
Start Practice