Full handwritten-style NCERT notes — every activity, every in-text question and all 20 exercise solutions, explained like your favourite teacher's copy. Tap, flip, reveal and actually enjoy chemistry!
Prepared by expert faculty of Brain Booster Academy • Aligned with rationalised NCERT syllabus
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Signs, observations & burning magnesium
ReadWord equations, hit-&-trial method, state symbols
ReadCombination, decomposition, displacement & more
ReadCorrosion & rancidity — chips packet secrets
ReadAll 8 NCERT questions — tap to flip answers
ReadAll 20 questions with reveal-to-check answers
ReadEquation bank + memory tricks + mistakes to avoid
Read6 quick MCQs with instant feedback & score
PlayNCERT Section 1.1 • read time ~6 min
Look around — milk turning into curd, iron gates getting rusty, grapes fermenting into wine, food being digested in your stomach. In every case, the original substance disappears and a completely new substance appears. That's the heart of this chapter!
A chemical reaction is a process in which one or more substances (reactants) undergo a chemical change to form one or more new substances (products) having entirely different properties.
Tap each card to flip it and see the example.
Zinc + dilute sulphuric acid — bubbles of hydrogen gas rise out. You can even burn it — it gives a pop! sound.
Zn + H2SO4 → ZnSO4 + H2 ↑
A shiny iron nail dipped in blue copper sulphate solution slowly gets a brown coat of copper and the blue colour fades.
Fe + CuSO4 → FeSO4 + Cu
Drop water on quick lime (CaO) — the test tube becomes so hot you can feel it! Slaked lime is formed.
CaO + H2O → Ca(OH)2 + Heat
Burn a candle — solid wax melts and burns to give CO₂ gas + water vapour. New state, new substance!
solid/liquid → gases
Mg combines with oxygen of the air → a new white substance forms. Hence, a chemical reaction!
Magnesium + Oxygen → Magnesium oxide | 2Mg + O2 → 2MgO
Mix the two solutions → a bright yellow precipitate of lead iodide appears instantly. Colour change proves a reaction!
Pb(NO3)2 + 2KI → PbI2 ↓ + 2KNO3
Add dilute H₂SO₄ (or HCl) to zinc granules in a conical flask — bubbles of hydrogen form AND the flask gets warm. Gas + temperature change = reaction!
Zn + H2SO4 → ZnSO4 + H2 ↑
NCERT Section 1.1 (continued) • The most scoring part of this chapter, promise!
A chemical equation is just a shorthand way of writing a reaction using symbols and formulae instead of full names.
Magnesium + Oxygen
substances that react (left side)
Magnesium oxide
new substance formed (right side)
2Mg + O2 → 2MgO
reads: "2 magnesium + 1 oxygen molecule gives 2 magnesium oxide"
GOLDEN RULE: To balance, you may only put numbers (coefficients) in FRONT of formulas — like 2H₂O, 3Fe. Never ever change the small subscripts (H₂O ✗ H₂O₂). That would change the substance itself!
The hit-and-trial method from NCERT — press Next and watch each step.
Write the formula equation (it will be unbalanced). Draw a box around each formula — we only touch the outside of boxes!
Fe + H2O → Fe3O4 + H2
| Element | Left (reactants) | Right (products) | Balanced? |
|---|---|---|---|
| Fe | 1 | 3 | ✗ |
| H | 2 | 2 | ✓ |
| O | 1 | 4 | ✗ |
Start with the element that appears in the greatest number of atoms — that's oxygen (4 on right). Make oxygen on the left equal 4 → put 4 in front of H₂O.
Fe + 4H2O → Fe3O4 + H2
| Element | Left | Right | Balanced? |
|---|---|---|---|
| Fe | 1 | 3 | ✗ |
| H | 8 | 2 | ✗ |
| O | 4 | 4 | ✓ fixed! |
Now fix hydrogen. Left side has 8 H, right has only 2 → put 4 in front of H₂ so the right side also has 8.
Fe + 4H2O → Fe3O4 + 4H2
| Element | Left | Right | Balanced? |
|---|---|---|---|
| Fe | 1 | 3 | ✗ |
| H | 8 | 8 | ✓ |
| O | 4 | 4 | ✓ |
Last one — iron. Right side needs 3 Fe, so put 3 in front of Fe on the left.
3Fe + 4H2O → Fe3O4 + 4H2
| Element | Left | Right | Balanced? |
|---|---|---|---|
| Fe | 3 | 3 | ✓ |
| H | 8 | 8 | ✓ |
| O | 4 | 4 | ✓ |
All elements balanced — equation complete! Finally, add state symbols to make it informative. Remember: a coefficient multiplies the whole box in front of it (4H₂O = 4×H and 4×O).
3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)
Example: 3Fe(s) + 4H₂O(g) → steam is a gas, iron is a solid!
CaCO3(s) →Δ CaO(s) + CO2(g)↑
Balance these in your notebook first, then tap the eye to check.
Hydrogen + Chlorine → Hydrogen chloride
H2 + Cl2 → HCl
H2 + Cl2 → 2HCl
Barium chloride + Aluminium sulphate → Aluminium chloride + Barium sulphate
BaCl2 + Al2(SO4)3 → AlCl3 + BaSO4
3BaCl2 + Al2(SO4)3 → 2AlCl3 + 3BaSO4
Sodium + Water → Sodium hydroxide + Hydrogen
Na + H2O → NaOH + H2
2Na + 2H2O → 2NaOH + H2
NCERT Section 1.2 • Click a tab — each has a mini animation, plain-language explanation and every NCERT example.
Two or more reactants combine to form a single product. Like two friends bringing their toys together to build one big castle.
Reactions in which heat is released along with the products are called exothermic reactions. Most combination reactions are exothermic!
Calcium oxide (quick lime) reacts vigorously with water releasing loads of heat → forms slaked lime Ca(OH)₂, used for whitewashing walls.
CaO(s) + H2O(l) → Ca(OH)2(aq) + Heat
Bonus: walls get shiny white after 2–3 days because slaked lime slowly reacts with CO₂ in air: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O
Anything burning = combining with oxygen. Burning of natural gas (CH₄) is exothermic — that's how your kitchen stove heats food!
C + O2 → CO2 + Heat • CH4 + 2O2 → CO2 + 2H2O + Heat
Glucose (from digested food) combines with inhaled oxygen in our cells and releases energy to keep us alive. So respiration is an exothermic process!
C6H12O6(aq) + 6O2(aq) → 6CO2(aq) + 6H2O(l) + Energy
A single reactant breaks down into two or more simpler products. It is the exact opposite of a combination reaction.
Breaking things needs energy! Decomposition reactions need heat (Δ), light or electricity — so they are usually endothermic (energy absorbed).
Green crystals lose water, turn brown, and smell of burning sulphur (SO₂ + SO₃ gases).
2FeSO4(s) →Δ Fe2O3(s) + SO2(g) + SO3(g)
Limestone breaks for the cement industry. Lead nitrate gives brown fumes of NO₂ (very pungent!).
CaCO3(s) →Δ CaO(s) + CO2(g)
2Pb(NO3)2(s) →Δ 2PbO(s) + 4NO2(g) + O2(g)
Pass current through water (with a few acid drops) — gas collects in both test tubes; one gets twice the other. That gas is hydrogen (collected at the cathode), because water is H₂O — H:O = 2:1!
2H2O(l) →electricity 2H2(g) + O2(g)
White silver chloride turns grey in sunlight. Same reaction with silver bromide is used in black & white photography!
2AgCl(s) →sunlight 2Ag(s) + Cl2(g) • 2AgBr(s) → 2Ag(s) + Br2(g)
A more reactive element pushes out (displaces) a less reactive element from its compound — like a stronger player taking someone's seat on the team.
Reactivity ladder to remember: Fe, Zn, Pb are all more reactive than Cu — so each can steal copper's partner!
Dip an iron nail in blue CuSO₄ solution for ~20 min → nail gets a brown coating of copper and the blue colour fades to green (FeSO₄). Iron is more reactive than copper!
Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)
Pb(s) + CuCl2(aq) → PbCl2(aq) + Cu(s)
Both zinc and lead are more reactive than copper, so they displace it from its salts.
Aluminium (more reactive) snatches oxygen from iron oxide — used to weld railway tracks: Fe2O3 + 2Al → Al2O3 + 2Fe
Two compounds exchange their ions to form two new compounds — like four dancers swapping partners mid-song.
If one product is an insoluble solid that settles down, it's called a precipitate (↓) and the reaction is a precipitation reaction.
Mixing the two solutions instantly forms a white precipitate of barium sulphate (insoluble in water). Classic precipitation reaction!
Na2SO4(aq) + BaCl2(aq) → BaSO4(s)↓ + 2NaCl(aq)
AgNO3(aq) + NaCl(aq) → AgCl↓ + NaNO3
Pb(NO3)2 + 2KI → PbI2↓(yellow) + 2KNO3
Spot the pattern every time: the ions simply trade partners!
Oxidation = substance gains oxygen (or loses hydrogen). Reduction = substance loses oxygen (or gains hydrogen).
When oxidation and reduction happen together in the same reaction (they always do!), it's called a redox reaction.
Heat brown copper powder in a china dish — its surface turns black! That's copper(II) oxide forming on top.
2Cu + O2 →heat 2CuO (Cu is OXIDISED)
Pass hydrogen gas over hot CuO — the black coating turns brown again (copper is back!) and steam forms.
CuO + H2 →heat Cu + H2O
CuO → Cu: loses O, REDUCED. H₂ → H₂O: gains O, OXIDISED. Both together = redox!
ZnO + C → Zn + CO (ZnO reduced, C oxidised)
MnO2 + 4HCl → MnCl2 + 2H2O + Cl2 (MnO₂ reduced, HCl oxidised)
NCERT Section 1.3 • The chapter's favourite "reasoning" questions come from here!
When a metal is slowly attacked by substances around it like moisture or acids, it's called corrosion. The metal gets eaten away layer by layer!
Damage: weakens car bodies, bridges, iron railings, ships — costs crores every year!
How we fight it:
That's exactly why we paint iron articles — the paint blocks air + moisture (Exercise Q18!).
When fats and oils in food get oxidised, their smell and taste change — the food becomes rancid. Ever smelled old ghee or stale chips? That's rancidity.
How to prevent it:
All 8 questions from inside the chapter. Try each in your head, then tap the card to flip the answer.
Answers stay blurred — write your own first, then hit the eye to check. That's how toppers study!
Read this on the morning of your exam. Seriously.
Combination
2Mg + O2 → 2MgO
CaO + H2O → Ca(OH)2 + Heat
C + O2 → CO2
H2 + Cl2 → 2HCl
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
Decomposition
2FeSO4 →Δ Fe2O3 + SO2 + SO3
CaCO3 →Δ CaO + CO2
2Pb(NO3)2 →Δ 2PbO + 4NO2 + O2
2H2O →electricity 2H2 + O2
2AgCl →sunlight 2Ag + Cl2
ZnCO3 → ZnO + CO2
Displacement
Fe + CuSO4 → FeSO4 + Cu
Zn + CuSO4 → ZnSO4 + Cu
Pb + CuCl2 → PbCl2 + Cu
Fe2O3 + 2Al → Al2O3 + 2Fe
2AgNO3 + Cu → Cu(NO3)2 + 2Ag
Fe + 2HCl → FeCl2 + H2↑
Double displacement
Na2SO4 + BaCl2 → BaSO4↓ + 2NaCl
AgNO3 + NaCl → AgCl↓ + NaNO3
Pb(NO3)2 + 2KI → PbI2↓ + 2KNO3
2KBr + BaI2 → 2KI + BaBr2
Ca(OH)2 + Na2CO3 → CaCO3↓ + 2NaOH
Oxidation–Reduction
2Cu + O2 → 2CuO (Cu oxidised)
CuO + H2 → Cu + H2O (CuO reduced)
ZnO + C → Zn + CO
MnO2 + 4HCl → MnCl2 + 2H2O + Cl2
2PbO + C → 2Pb + CO2
Balancing practice set
N2 + 3H2 → 2NH3
2H2S + 3O2 → 2H2O + 2SO2
3BaCl2 + Al2(SO4)3 → 3BaSO4 + 2AlCl3
2Na + 2H2O → 2NaOH + H2
2NaOH + H2SO4 → Na2SO4 + 2H2O
Mistakes that cost marks!
Memory tricks
6 quick questions • instant feedback • score at the end. No peeking at the notes!