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NCERT Class 10 Science Chapter 1 Notes Chemical Reactions and Equations- Download PDF Notes

NCERT Class 10 Science Chapter 1 Notes Chemical Reactions and Equations- Download PDF Notes

Edited By Shivani Poonia | Updated on Mar 16, 2025 08:15 PM IST

Chemical Reactions and Equations is an important chapter in NCERT Class 10 Science for exam preparation. The Chapter 1 notes provide a comprehensive understanding of the topic, which covers important topics such as definitions, examples, chemical equations, balancing them, types of chemical reactions, and the impact of oxidation reactions in everyday life.

This Story also Contains
  1. NCERT Class 10 Chapter 1 Class Notes
  2. Chemical Reactions and Equations
  3. Chemical Reaction
  4. Characteristics of Chemical Reaction
  5. Chemical Equations
  6. Types of Chemical Reactions

Students should go through each topic in these notes for a quick revision. The NCERT class 10 science chapter 1 notes pdf download is also available for download in PDF format, which makes it easy to study offline anytime and anywhere. These notes are prepared to help students learn the concepts efficiently and prepare well for exams.

Background wave

Class 10 Science Chapter 1 notes cover all the important concepts from the chapter, which are also significant for various competitive exams. These NCERT Notes for Chemical Reactions and Equations help you revise key topics from the NCERT textbook during CBSE Board exam preparation. The notes include important examples that are frequently asked in exams, making them perfect for quick revision.

Revision notes and NCERT Solutions for Chapter 1 become handy and save time of students ensuring better learning outcomes. The NCERT class 10 science chapter 1 is available for download in PDF format through the link provided.

NCERT Class 10 Chapter 1 Class Notes

Chemical Reactions and Equations

This chapter discusses in detail the balanced and unbalanced chemical reactions, along with explaining the process of balancing these reactions. This chapter discusses the significance of chemical equations and their representation using various symbols. Understanding chemical reactions is important to grasp the fundamental concept for science students. Also, NCERT notes Class 10 Science Chapter 1 Chemical Reactions and Equations discuss in detail the common chemical reactions that occur in our daily surroundings.

Chemical Reaction

The change of one chemical substance into another is known as a chemical reaction. Rusting of iron, curdling of milk, and respiration are examples of chemical reactions. The formed substance in a chemical reaction is completely different from its original substance, this process is an indication of a complete chemical reaction. Also, a chemical reaction is a process in which the rearrangement of atoms takes place, which leads to the formation of new compounds.

Reactants-

The one that is taking part in a chemical reaction is a reactant.

Products-

The new substance that is formed after a chemical reaction is called a product.

Example-

Magnesium burns in the air to form magnesium oxide is a type of chemical reaction.

Mg+O2 Heat →2MgO(s)

In this reaction, the reactants are magnesium and oxygen while the new substance MgO is the product.

Characteristics of Chemical Reaction

  • Evolution of gas: In some reactions, there is an evolution of gas for example the reaction between zinc and dilute sulphuric acid is followed by the evolution of hydrogen gas. It can be represented as

Zn+H2SO4→ZnSO4+H2

  • Change in color: In some other reactions, there may be a change in color. For example, when citric acid and purple color potassium permanganate solution undergo a chemical reaction there is a change in color from purple to colorless. And also the chemical reaction between sulfur dioxide and acidified potassium dichromate solution is also followed by a change in color from orange to green.

  • Change in-state: For some chemical reactions, there is a change in the state of the substance. For example, when candle wax undergoes a combustion reaction there is a change of state from solid to liquid and gas. And the gas formed in this type of reaction is carbon dioxide.

  • Change in temperature: For some reactions, there is a change in temperature that is a rise in temperature or a fall in temperature occurs. For example, the reaction between quicklime and water to form slaked lime is followed by a rise in temperature. And also the reaction taking place between zinc granules and dilute sulphuric acid is also followed by a rise in temperature.

  • Formation of the precipitate: In the reaction between a sulphuric acid and barium chloride solution, it occurs the formation of a white precipitate of barium sulfate.

BaCl2+H2SO4→BaSO4(s )+2HCl

Chemical Equations

For representing a chemical reaction some simple and formulas can be used and this representation is called a chemical equation. For example, when A and B are a reactant and C and D are the products formed after a reaction the following representation can be used to represent reaction.

A+B→C+D

  • When hydrogen undergoes a reaction with oxygen water is formed. In which the hydrogen and oxygen is the reactant and the water obtained is the product can be represented as

H2+O2→ H2O

  • So with the help of a chemical equation we can represent it in a concise and informative way. It can also be divided into two types of balance the chemical equation and unbalanced chemical equation.

Balanced Chemical Equation

When the number of atoms of each element in a chemical reaction is equal on both sides it is called a balanced chemical equation.

Zn+H2SO4→ ZnSO4+H2

Unbalanced the Chemical Equation

When the number of atoms of each element in the reactant and product side is not equal it is called an unbalanced chemical equation.

Fe+H2O→ Fe3O4+H2

In this reaction the number of atoms of the element iron is not equal and also oxygen is also not equal. So we need to balance that unbalanced equation to its balanced form.

In this chemical equation, 3 iron is formed at the product side so we need to multiply iron with 3 on the reactant side. And also the oxygen atom formed at the product is four so the water is also multiplied by 4. So to balance both sides hydrogen evolved should also be multiplied by 4.

3Fe+4H2O→ Fe3O4+4H2

So the unbalanced equation becomes a balanced equation. In the representation of the chemical equation, the state can also be mentioned that is whether it is in the gaseous form or liquid form or solid form can be given by descending with brackets.

Types of Chemical Reactions

Combination Reaction

the chemical reaction in which two or more reactance are combined to form another product is a combination reaction. That is,

A+B→ AB

Magnesium reacts with oxygen to form magnesium oxide is a typical example of this reaction.

2Mg+O2 Heat→2MgO(s)

Decomposition reaction

When one compounder decomposes into two or more compounds it is called a decomposition reaction. That is,

AB→ A+B

A typical example of a decomposition reaction is the formation of calcium oxide and carbon dioxide by the decomposition of calcium carbonate.

CaCO3(s) Heat→ CaO+CO2(g)

Thermal decomposition is when a substance undergoes a decomposition reaction by heating it is thermal decomposition.

CaCO3(s) Heat→ CaO+CO2(g)

Electrolytic decomposition is the reaction signature a compound decomposes into another component by the supply of electricity is electrolytic decomposition. Electrolysis is a type of electrolytic decomposition.

For example, when electricity is passed in water it will decompose into oxygen and hydrogen. That is,

2H2O→2H2+O2

Photolysis or Photodecomposition

The decomposition reaction performed in the presence of sunlight is known as photolysis. For example, when silver chloride is put in the sunlight it will decompose to produce the metal silver and chlorine gas. The reaction is,

2AgCl sunlight→ 2Ag+Cl2

Displacement Reaction

A chemical reaction in which a reactive element is replaced with a less reactive element is a displacement reaction. It can be represented as,

A+BC→ AC+B

The reaction taking place between Zinc and hydrochloric acid is an example of a displacement reaction.

Zn+2HCl→ ZnCl2+H2

Precipitation Reaction

The reaction in which a precipitate is formed after the chemical reaction is called a precipitation reaction. An example for it is,

AgNO3+NaCl→ AgCl(s)+NaNO3

AgCl is the precipitate.

Neutralisation Reaction

A chemical reaction in which acid and a base undergo a reaction to form a neutral product that is water is called a neutralisation reaction.

NaOH+HCl→ NaCl+H2O

Oxidation Reaction

The removal of hydrogen or metallic element and the addition of oxygen or nonmetallic element from a compound is known as oxidation. The element in which the nonmetallic element or oxygen is added and hydrogen or metallic element is removed is said to be oxidized.

Example: Rusting iron.

Reduction Reaction

Removal of oxygen or nonmetallic element and addition of hydrogen or metallic element from any compound is called reduction. And the element in which it will undergo A reduction process is said to be reduced.

Redox Reaction

When the process of reduction and oxidation takes place simultaneously it is said to be a redox reaction. And the substance which removes hydrogen or gives oxygen is said to be an oxidizing agent. And the one which gives hydrogen or removes oxygen is said to be a reducing agent.

CuO+H2→ Cu+H2O

In this reaction oxygen is removed from CuO therefore it is said to be a reduction process. While oxygen is added to H2 so it is an oxidation process.

Exothermic Reaction

The reaction in which energy is produced is called an exothermic reaction. And the energy is produced in the form of heat.

CaO+H2O→ Ca(OH)2+Energy

Endothermic Reaction

When heat energy is absorbed or consumed to undergo a chemical reaction it is an endothermic reaction.

CaCO3 Heat→ CaO+CO2

Also Read:

Chapter-Wise NCERT Class 10 Notes Science


Significance of NCERT Notes for Class 10 Science Chapter 1

Ncert class 10 science chapter 1 notes give a detailed write-up to understand the first chemistry chapter. These notes are important for covering the important concepts mentioned in the CBSE Class 10 Syllabus 2025 PDF. These notes are also important for the competitive exams like AIPMT, AIIMS, NEET, etc. The NCERT class 10 science chapter 1 notes pdf is available for download, which can help students in faster revision of the topics.

Important topics of Chemical Reactions and Equations are discussed here, hence these notes help students grasp fundamental concepts effectively. Also, these notes are very good for students preparing for competitive exams like NEET and JEE Main.

Also read,


Books and Syllabus

NCERT Books for Class 10NCERT Syllabus for Class 10


Frequently Asked Questions (FAQs)

1. What is the importance of studying chemical reactions and equations?

Studying chemical reactions and equations is fundamental to understanding chemistry. It allows us to: 

1. Understand how matter changes and interacts. 

2. Predict the products of a reaction. 

3. Balance chemical equations to satisfy the law of conservation of mass. 

4. Apply this knowledge to everyday life, like cooking, medicine, and industry.

2. Why is the use of chemical equations important?

Chemical equations clearly explain what are the chemicals involved and also what are the products obtained after a reaction has been completed.

3. What are the key concepts covered in this chapter?

The key concepts covered in this chapter are: Chemical Reactions, Chemical Equations, Balancing Chemical Equations, Types of Chemical Reactions (Combination, Decomposition, Displacement, Double Displacement, Redox), Corrosion, Rancidity

4. What's the difference between a physical change and a chemical change?

Physical Change: A change in the form or appearance of a substance, but not in its chemical composition. No new substance is formed. Examples: melting ice, boiling water. 

Chemical Change: A change that results in the formation of a new substance (or substances) with different chemical properties. Examples: burning wood, rusting iron.

5. Why is it necessary to balance a chemical equation?

It is necessary to balance a chemical equation to satisfy the Law of Conservation of Mass. This law states that matter cannot be created or destroyed in a chemical reaction. Therefore, the number of atoms of each element must be the same on both the reactant and product sides of the equation.

6. What is a precipitation reaction? What kind of reaction is it?

A precipitation reaction is a type of double displacement reaction where two aqueous solutions react to form an insoluble solid called a precipitate.

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