NCERT BOOK Class 10 Science | Chemical Reactions and Equations

Chemical Reactions and Equations is the first chapter of NCERT Science Class 10 and serves as the foundation of Chemistry. In this chapter, students learn how substances undergo chemical changes to form new products. Understanding chemical reactions helps students explain many everyday phenomena such as rusting of iron, digestion of food, burning of fuels, and photosynthesis.

This chapter is important for CBSE Board Exams and various competitive examinations because it introduces the fundamental concepts of chemical transformations and balancing chemical equations.

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What is a Chemical Reaction?

A chemical reaction is a process in which one or more substances (reactants) are converted into new substances (products) with different chemical properties.

Examples of Chemical Reactions

Burning of magnesium ribbon in air.
Rusting of iron.
Digestion of food.
Formation of curd from milk.
Respiration in living organisms.

Characteristics of a Chemical Reaction

The following observations indicate that a chemical reaction has occurred:

Change in colour
Evolution of gas
Change in temperature
Formation of a precipitate
Change in state

Chemical Equations

A chemical equation is a symbolic representation of a chemical reaction using chemical formulas.

Example

Word Equation:

Magnesium + Oxygen → Magnesium Oxide

Chemical Equation:

Mg + O? → MgO

This equation shows the reactants and products involved in the reaction.

Balanced Chemical Equations

According to the Law of Conservation of Mass, mass can neither be created nor destroyed during a chemical reaction. Therefore, the number of atoms of each element must be equal on both sides of a chemical equation.

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