Kidz Olympiad🎉

Science Class 10 - Chemical Reactions-And-Equations Notes

Comprehensive study notes for Class 10 - Chemical Reactions-And-Equations olympiad preparation

Chemical Reactions and Equations

Welcome to the chapter on Chemical Reactions and Equations for Class 10. In this chapter, you will learn what chemical reactions are, how to write and balance chemical equations, and understand the different types of chemical reactions. By the end of this chapter, you will be able to identify, represent, and explain chemical changes using equations.

Introduction

Chemical reactions are changes in which one or more substances are converted into new substances. These changes are represented using chemical equations.

What is a Chemical Reaction?

  • A chemical reaction involves the breaking and making of bonds between atoms to produce new substances.
  • The substances you start with are called reactants.
  • The new substances formed are called products.

Example: When magnesium burns in air, it forms magnesium oxide.
Magnesium + Oxygen → Magnesium oxide

Chemical Equations

A chemical equation is a short way to show a chemical reaction using symbols and formulas.

  • Word equation: Magnesium + Oxygen → Magnesium oxide
  • Symbolic equation: Mg + O2 → MgO

Balancing Chemical Equations

The number of atoms of each element must be the same on both sides of the equation. This is called balancing the equation.

  • Unbalanced: H2 + O2 → H2O
  • Balanced: 2H2 + O2 → 2H2O

Types of Chemical Reactions

  • Combination Reaction: Two or more substances combine to form a single product.
    Example: 2H2 + O2 → 2H2O
  • Decomposition Reaction: A single compound breaks down into two or more simpler substances.
    Example: 2H2O2 → 2H2O + O2
  • Displacement Reaction: One element replaces another in a compound.
    Example: Zn + CuSO4 → ZnSO4 + Cu
  • Double Displacement Reaction: Exchange of ions between two compounds.
    Example: AgNO3 + NaCl → AgCl + NaNO3

Observing Chemical Reactions

  • Change in color
  • Change in temperature
  • Formation of a gas
  • Formation of a precipitate (solid)

Fun Activity: Try This at Home!

Mix vinegar and baking soda in a cup. What do you observe? (Bubbles form—this is a chemical reaction producing carbon dioxide gas!)

Summary

  • Chemical reactions change reactants into products.
  • Chemical equations show these changes using symbols.
  • Equations must be balanced.
  • There are different types of chemical reactions.

Practice Questions

  1. What is a chemical reaction? Give one example.
  2. Write the balanced equation for the reaction of hydrogen and oxygen to form water.
  3. Name two types of chemical reactions and give examples.
  4. What are reactants and products?
  5. List two observations that show a chemical reaction has taken place.

Challenge Yourself

  • Balance the following equation: Fe + O2 → Fe2O3
  • Classify the following reactions as combination, decomposition, displacement, or double displacement:
    a) CaCO3 → CaO + CO2
    b) Na2SO4 + BaCl2 → BaSO4 + 2NaCl

Did You Know?

  • Photosynthesis in plants is a chemical reaction that makes food using sunlight!
  • Rusting of iron is a slow chemical reaction with air and water.

Glossary

  • Reactant: A substance that takes part in a chemical reaction.
  • Product: A new substance formed in a chemical reaction.
  • Precipitate: A solid formed from a solution during a chemical reaction.
  • Balanced Equation: An equation with equal numbers of each atom on both sides.

Answers to Practice Questions

  1. A chemical reaction is a process where substances change to form new substances. Example: Burning of magnesium in air.
  2. 2H2 + O2 → 2H2O
  3. Combination: H2 + Cl2 → 2HCl; Decomposition: 2H2O2 → 2H2O + O2
  4. Reactants are starting substances; products are new substances formed.
  5. Change in color, formation of gas (any two observations).

Practice writing and balancing equations to master chemical reactions!

Quick Navigation