Class 10 Science Chapter 1, Chemical Reactions and Equations, opens the chemistry section of the NCERT Class 10 Science textbook (2026-27). Starting from everyday changes—milk turning sour, iron rusting in moist air, and magnesium ribbon burning with a dazzling white flame to form magnesium oxide—it teaches how to represent chemical changes with balanced chemical equations and classify reactions into five fundamental types.
What Class 10 Science Chapter 1 Covers
1.1 Chemical Equations shows how word-equations are turned into skeletal chemical equations and balanced using the law of conservation of mass (the hit-and-trial method, illustrated step by step with $3\text{Fe} + 4\text{H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4 + 4\text{H}_2$), together with physical state symbols $(s)$, $(l)$, $(g)$ and $(aq)$.
1.2 Types of Chemical Reactions covers combination reactions (quicklime $\text{CaO}$ reacting exothermically with water to form slaked lime $\text{Ca(OH)}_2$, and respiration as an exothermic process), thermal/electrolytic/photolytic decomposition ($\text{FeSO}_4$, $\text{CaCO}_3$, $\text{Pb(NO}_3)_2$, electrolysis of water, and $\text{AgCl}/\text{AgBr}$ in black-and-white photography), displacement reactions ($\text{Fe} + \text{CuSO}_4 \rightarrow \text{FeSO}_4 + \text{Cu}$), double displacement/precipitation ($\text{Na}_2\text{SO}_4 + \text{BaCl}_2 \rightarrow \text{BaSO}_4\downarrow + 2\text{NaCl}$), and oxidation-reduction (redox) reactions ($\text{CuO} + \text{H}_2 \rightarrow \text{Cu} + \text{H}_2\text{O}$).
1.3 Corrosion and Rancidity explains the rusting of iron, the black coating on silver and green coating on copper, and how antioxidants or nitrogen flushing prevent fats and oils from becoming rancid.
Exercises in Chapter 1
- In-text Questions cover why magnesium ribbon is cleaned with sandpaper before burning, identifying oxidised and reduced substances, and what happens when iron nails are dipped in copper sulphate solution.
- Chapter Exercises (20 Questions) test balancing equations, distinguishing exothermic and endothermic reactions, explaining why respiration is exothermic, and giving one equation each for thermal, electrolytic and photolytic decomposition.
Read Class 10 Science Chapter 1 Online
More Chapters
- Next: Chapter 2: Acids, Bases and Salts
- Hindi medium: Class 10 Science Chapter 1 PDF in Hindi (Vigyan)
- All Science chapters and the other Class 10 books: Class 10 NCERT books 2026-27
- All Class 1 to 12 NCERT Textbooks: NCERT Books PDF (Class 1–12)
FAQ
Why should a magnesium ribbon be cleaned before burning in air?
A magnesium ribbon forms a protective layer of basic magnesium carbonate/oxide on its surface when exposed to moist air. Rubbing it with sandpaper removes this layer so the metal burns readily in oxygen.
Why is respiration considered an exothermic reaction?
During digestion, carbohydrates are broken down into glucose ($\text{C}_6\text{H}_{12}\text{O}_6$). In cells, glucose combines with oxygen to form carbon dioxide and water while releasing energy ($\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{energy}$).