Chapter 1 — Chemical Reactions and Equations

Chapter 1 of Class 10 Science, "Chemical Reactions and Equations", explains what chemical reactions are, how to write and balance chemical equations, the major types of chemical reactions (combination, decomposition, displacement, double displacement, and redox), and the everyday effects of oxidation such as corrosion and rancidity.

Class 10 Science Chapter 1 covers chemical reactions and how they are represented using balanced chemical equations. Students learn to write word equations and symbolic equations, balance them using the hit-and-trial method, and include physical state symbols. The chapter classifies reactions into five types: combination, decomposition, displacement, double displacement, and oxidation-reduction (redox). It also explains exothermic and endothermic reactions and connects these concepts to real-life phenomena like corrosion of metals and rancidity of fats and oils.

1. 01A chemical reaction is indicated by changes in state, colour, temperature, or evolution of a gas
2. 02Chemical equations must be balanced to satisfy the law of conservation of mass — atoms of each element are equal on both sides
3. 03Combination reactions form one product from two or more reactants; decomposition reactions are the reverse — one substance breaks into two or more
4. 04Displacement reactions occur when a more reactive element displaces a less reactive one from its compound; double displacement reactions involve exchange of ions between two compounds
5. 05Exothermic reactions release heat (e.g. respiration, burning of natural gas); endothermic reactions absorb energy (e.g. electrolysis of water, decomposition by heat or light)
6. 06Oxidation is the gain of oxygen or loss of hydrogen; reduction is the loss of oxygen or gain of hydrogen — both occur simultaneously in redox reactions; corrosion and rancidity are everyday oxidation effects