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Grade 10/ Science/ Chemistry/ Chemical Reactions
Chapter 1 · NCERT Science 086

Chemical Reactions
& Equations

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.

⚗️ 5 topics⏱ ~34 min📝 20-question quiz
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Play with it

Balance a chemical equation

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.

Explore · Balance the equationuse − / +
1 H₂+ 1 O₂ 1 H₂O
H — left 2 · right 2 O — left 2 · right 1

Not balanced yet — make H and O equal on both sides.

Learn

The five ideas in this chapter

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.

Example

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.

Explore · Four types of reactions

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.

Example

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

Competency quiz

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.

Score 0/20

Interactive explainers inspired by OpenMAIC (THU-MAIC, MIT-licensed). Content from NCERT Class 10 Science.

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