Chemical Reactions and Equations Class 10th notes- Free NCERT Class 10 Science Chapter 1 Notes - Download PDF (2023)

Chemical reactions and equations are one of the important chapters of Class 10 Science. This chapter focused on the importance of chemical equations and their representation by using various symbols and notations. Chemical Reactions and Equations Class 10 notes will help students to get basic pieces of information about chemicals and their reactions.

Understanding chemical reactions is always a base for science students. CBSE Class 10 Science chapter 1 notes also contain some very common reactions taking place in our surroundings. Class 10 Science chapter 1 notes help the student to get a quick revision before going to attempt the examination. NCERT Class 10 Science chapter 1 notes also help in getting good marks in the board examination.

Also Read:

• NCERT Notes Class 10 Science
• NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equation
• NCERT Exemplar Class 10 Science Chapter 1 Chemical Reactions and Equation

NCERT Notes for Class 10 Science Chapter 1

Chemical Reactions and Equations

This chapter focuses on the balanced and unbalanced chemical reactions and how to balance them.

Chemical Reaction

The conversion of chemical substances into another chemical substance is known as a chemical reaction. Some of the chemical reactions are rusting of the iron setting of milk into curd respiration etc. The new chemical substance formed will be completely different from the parent substance and only then it can be called a chemical reaction. And the change taking place on them can be called a chemical change. In a chemical reaction, the rearrangement of atoms is taking place.

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 Equation

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)

NCERT notes for Class 10 science Chapter 1; Topic 9

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.

Neutralization Reaction

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

Significance of NCERT Notes for Class 10 Science Chapter 1

Notes for Class 10 Science chapter 1 focus on the important points regarding the chemical reaction and equations. The notes for Class 10 Science chapter 1 helps students to perform better in their examinations and also provide a complete revision before they are going to attempt the examination. Class 10 Science chapter 1 notes pdf download is also very helpful for students who wishes to write and crack NEET and JEE MAIN examinations. Chemical Reactions and Equations Class 10 notes help students in getting good marks while learning in the offline mode.

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