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Types of Chemical Reactions
Master Chemical Reactions in Minutes
Understand how atoms rearrange themselves to form new substances. Learn the five core types of chemical reactions through clear definitions, real-world examples, and exam-focused explanations.
1.0Learning Outcomes
- After completing this lesson, you will be able to:
- Identify and define the five main types of chemical reactions.
- Write balanced chemical equations for each type of reaction.
- Differentiate between exothermic and endothermic reactions.
- Predict the products of a reaction based on the reactants.
- Solve NCERT and board-level questions confidently.
2.0Introduction
Chemical reactions occur all around us, from rusting of iron and digestion of food to burning fuels and photosynthesis. Based on how reactants transform into products, chemical reactions can be classified into different categories.
Understanding these reaction types helps students predict products, balance equations, and solve chemistry problems effectively. NCERT Class 10 Science introduces five major types of chemical reactions: Combination, Decomposition, Displacement, Double Displacement, and Redox Reactions.
3.0What are Chemical Reactions?
A chemical reaction is a process in which one or more substances (reactants) are converted into new substances (products) with different chemical properties.
Indicators of a Chemical Reaction
- Change in colour
- Evolution of gas
- Formation of precipitate
- Change in temperature
- Change in state
These observations indicate that a chemical change has occurred.
4.0Combination Reaction
The reactions in which two or more substances combine to form a single new substance are called combination reactions.
Some more examples of combination reactions
(a) Between element - element
(i) Burning of Coal
C(s) + O2(g) ⎯→ CO2(g)
Carbon Oxygen Carbon dioxide
(ii) Formation of Water
2H2(g) + O2(g) ⎯→ 2H2O()
Hydrogen Oxygen Water
(iii) Burning of Magnesium in air
2Mg(s) + O2(g) ⎯→ 2MgO(s)
Magnesium Oxygen Magnesium oxide
(iv) Formation of Iron sulphide
Fe(s) + S(s) ⎯→ FeS(s)
Iron Sulphur Iron sulphide
(b) Between compound - compound
(v) Formation of Ammonium chloride
NH3(g) + HCl(g) ⎯→ NH4Cl(s)
Ammonia Hydrogen Ammonium
Chloride Chloride
(vi) Formation of Calcium Carbonate
CaO(s) + CO2(g) ⎯→ CaCO3(s)
Calcium oxide Carbon Calcium
(Quick lime) dioxide carbonate
(c) Between compound- element
(vii) Reaction of carbon monoxide with oxygen
2CO(g) + O2 (g) ⎯→ 2CO2(g)
This is also an exothermic reaction.
(viii) 2NO(g) + O2(g) ⎯→ 2NO2(g)
5.0Decomposition Reaction
The reaction in which a single compound breaks up into two or more simpler substances is known as decomposition reaction. The decomposition reaction generally takes place when energy in some form such as heat, electricity or light is supplied to the reactants.
Types of Decomposition Reaction
(a) Thermal decomposition: The reaction in which a single compound breaks up into two or more simpler substances by the action of heat is called thermal decomposition reaction.
(b) Electric Decomposition: The reaction in which a single compound breaks up into two or more simpler substances by the action of electricity is called electric decomposition reaction.
(c) Photo decomposition: The reaction in which a single compound breaks up into two or more simpler substances by the action of light is called photo decomposition reaction.
Note: Photolysis of AgBr is used in black and white photography.
6.0Displacement Reactions
A reaction in which a more reactive element displaces a less reactive element from its compounds is called displacement reaction. The elements involved may be metals or non-metals.
Relative reactivity of metals
Different metals possess different reactivities. The arrangement of metals in a vertical column in order of their decreasing reactivity from top to bottom is called reactivity series or activity series of metals.
Note : A suggested way of remembering reactivity series
Relative reactivity of some non-metals
Among halogens, fluorine is most reactive, and iodine is least reactive.
F2 > Cl2 > Br2 > I2
Some more examples of displacement reactions.
(i)Zn(s) + CuSO4 (aq) ⎯→ ZnSO4(aq) + Cu(s)
Zinc Copper sulphate Zinc sulphate Copper
(Bluish-Silver) (Blue) (Colourless) (Reddish Brown)
(ii) Cu(s) + 2AgNO3(aq) ⎯→ Cu(NO3)2(aq) + 2Ag(s)
Copper Silver nitrate Copper nitrate Silver
(Dark blue)
7.0Double Displacement Reactions
Those reactions in which two different atoms or groups of atoms are exchanged are called double displacement reactions or double decomposition reactions or metathesis reactions.
8.0Oxidation and Reduction Reactions
The reaction which involves addition of oxygen or removal of hydrogen from a substance is called oxidation reaction.
The reaction which involves addition of hydrogen or removal of oxygen from a substance is called reduction reaction.
Note : According to the electronic concept, Oxidation Is Loss of electrons. Reduction Is Gain of electrons.
9.0Memory map
10.0 EUREKA by ALLEN - Learn Smarter for Class 10 Exams
EUREKA by ALLEN is an advanced online learning platform designed for Class 10 students preparing for CBSE and State Board exams. With interactive story-based lessons, expert faculty guidance, AI-powered doubt-solving, and board-focused practice, EUREKA helps students strengthen concepts, improve retention, and score higher in class 10 board examinations.
11.0Supporting Study Materials
This study material CBSE Notes and NCERT Solutions for the Chapter "Chemical Reactions and Equations" on Oxidation and Reduction Topics is designed according to the latest CBSE Class 10 Science syllabus and NCERT guidelines. It provides clear explanations of key concepts, definitions, examples, and important questions to help students understand redox reactions, corrosion, and rancidity, and prepare effectively for examinations.
12.0Previous Year Questions (PYQs)
Q1. A student takes 2(g) of lead nitrate powder in a boiling tube and heats it over a flame. State the colour change observed and name the brown gas evolved. (CBSE Board)
Answer:
- Observation: The colourless/white powder turns yellow (due to the formation of Lead Oxide).
- Brown Gas: Nitrogen Dioxide NO2.
- Chemical Equation:
- Type of Reaction: Thermal Decomposition Reaction.
13.030-Second Review
- Combination: Two or more reactants form 1 product (A + B —> AB).
- Decomposition: 1 reactant breaks down into multiple products (AB —> A + B). Requires heat (thermal), light (photolytic), or electricity (electrolytic).
- Displacement: A more reactive metal displaces a less reactive metal from its salt solution (A + BC —> AC + B).
- Double Displacement: Two compounds exchange ions to form new products (AB + CD —>AD + CB). Often forms an insoluble solid called a precipitate.
- Oxidation: Gain of oxygen or loss of hydrogen.
- Reduction: Loss of oxygen or gain of hydrogen.
- Redox: Both oxidation and reduction happen simultaneously.
- Oxidising Agent: Gives oxygen or removes hydrogen (gets reduced itself).
- Reducing Agent: Removes oxygen or gives hydrogen (gets oxidised itself).
14.0Recommended Next Topics
- Balancing Chemical Equations
- Oxidation and Reduction (Redox Deep Dive)
- Corrosion and Rancidity
- Acids, Bases and Salts