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Chemical Reactions and Types of Chemical Reaction


Physical and Chemical Changes

Physical Changes

  • The changes in which the physical properties and state of matter change but there is no change in its chemical properties are called physical changes.
  • Water is in a liquid state and on heating, it turns into vapor state. This is an example of physical change.

Chemical Changes

  • The changes in which the chemical properties and organization of a substance change are called chemical changes. A new substance is formed after a chemical change.
  • An example of a chemical change is the carbon dioxide gas produced when coal is burnt.
  • Other examples of chemical changes are curdling of milk, rusting of iron, etc.


Chemical Equations

  • In any chemical reaction, substances are represented by atoms and symbols, the same is called a chemical equation.
  • The substances participating in the chemical reaction are written to the left before the arrow marks are called actuators or reactants. 
  • The arrow marks indicate the direction of the reaction.
  • The product on the right side of the arrow mark is the substance formed by the reaction.

Chemical Reaction

  • When a chemical changes in any substance, it differs from the original substance in chemical properties and organization. This phenomenon is called a chemical reaction.
  • In a chemical reaction, products are formed from the possessors but the total mass of the substance remains the same. 


  1. Combination reaction

A chemical reaction in which two or more reactants combine to form a single product is called a reaction.

2. Dissociation Reaction (Decompensation Reaction)

The reaction in which a reactant decomposes and forms two or more products is called a decomposition reaction.


Electrical decomposition

The reactions in which decomposition occurs by the electric current are called electrolytic reactions.

Thermal decomposition

The reaction in which decomposition occurs by heating.

Optical decomposition

The reaction in which the energy you get from the cut light is called.

3. Displacement Reaction


The reaction in which the atom or group of atoms present in one reactor is displaced by the atom or group of atoms of another reactant is called displacement reaction.

4. Double Displacement Reaction

In this type of reaction, atoms or groups of atoms of both reactants are displaced. 

5. Exothermic Reactions

Reactions that emit/release energy are known as Exothermic reactions.

6. Endothermic Reaction

Reactions in which heat is absorbed are called endothermic reactions.


7. Oxidation-Reduction


Oxidation reaction 

The addition of oxygen or removal of hydrogen is called an oxidation reaction.

Reduction Reaction

Reactions in which the addition of hydrogen or removal of oxygen are called reduction reactions.


Based on the Exchange of Electrons

Oxidation Reaction

Reactions in which the element, atom, ion, or molecule release any number of electrons is called an oxidation reaction.

Reduction reaction

The reaction in which an element, atom, ion, or molecule accepts electron is called a reduction reaction.

Redox Reaction

Reactions that involve both oxidation and reduction are called redox reactions or oxidative reactions.

The substance that is oxidized is called the reducing agent and the substance that is reduced is called oxidizers.

Reductive electron donor reactant oxidizing electron




Any reactive substances which change the velocity of a chemical reaction but remain unchanged are called catalysts.

Positive Catalysts

Substances that increase reaction velocity are called positive catalysts.

Negative Catalysts

Substances that reduce the velocity of the reaction are called negative catalysts.

Homogeneous Catalyst

When a catalyst, reactant and product are in the same physical state in a chemical reaction, the catalyst is called a homogeneous catalyst.

Heterogeneous Catalytic

When the physical state of the reactants and catalysts in a chemical reaction is different is called a Heterogeneous catalyst.


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