Write it, balance it, and recognise what kind it is — then see why iron rusts and chips go stale. The chapter that makes the whole of chemistry click.
Play with it
Tap − and + to change each coefficient and watch the H and O atom counts line up on both sides — that's exactly what "balanced" means.
Not balanced yet — make H and O equal on both sides.
Learn
A chemical reaction is written as an equation: reactants → products. A word equation names them; a symbol equation uses formulae. Extra symbols add information: (s) solid, (l) liquid, (g) gas, (aq) dissolved in water; ↑ a gas given off and ↓ a precipitate.
Zinc + sulphuric acid → zinc sulphate + hydrogen, i.e. Zn + H₂SO₄ → ZnSO₄ + H₂↑
Atoms are never created or destroyed in a reaction (law of conservation of mass), so every element must have the same number of atoms on both sides. We balance by adjusting the coefficients — never the formulae.
Try the interactive at the top of the page — adjust the coefficients until H and O balance on both sides.
Most Class 10 reactions fall into four families. Tap each to see its shape and a real example.
A + B → AB
2Mg + O₂ → 2MgO
Two or more substances combine to form a single product.
Oxidation = gain of oxygen (or loss of hydrogen). Reduction = loss of oxygen (or gain of hydrogen). In any redox reaction one substance is oxidised while another is reduced — together.
In CuO + H₂ → Cu + H₂O: CuO loses oxygen (reduced) and H₂ gains oxygen (oxidised).
Corrosion: metals are slowly eaten away by air and moisture — iron rusts (needs both oxygen and water), silver blackens, copper goes green. Prevented by painting, oiling, galvanising, or alloying.
Rancidity: fats and oils in food get oxidised, giving a bad smell and taste. Slowed by antioxidants, airtight packing, refrigeration, or flushing packets with nitrogen.
Check yourself
Modelled on CBSE's competency-based pattern — MCQ, assertion–reason and case-study items, the kind that now make up about half your board paper.
Interactive explainers inspired by OpenMAIC (THU-MAIC, MIT). Content from NCERT Class 10 Science.
Buffyyour study buddy Buffy is an AI helper and can be wrong — always check your NCERT textbook.