10th Class Science Chemical Reactions and Equations

Chemical Reactions and Equations

Category : 10th Class

 Chemical Reactions and Equations



  • Chemical reactions


A chemical reaction is a process in which substances undergo change to produce new substances with new properties. The substances which take part in a chemical reaction are known as reactants. The new substances formed during a chemical reaction are known as products.


  • The important characteristics of chemical reactions are: evolution of a gas, formation of a precipitate, change in colour, change in temperature, and change in state.


  • Chemical equations

A chemical equation is a short hand representation of a chemical reaction using symbols and formulae of the substances involved in the reaction.


  • A balanced chemical equation is the one which contains equal number of atoms of each element on both sides of the equation.


  • Types of chemical reactions

The reaction in which two or more substances combine to produce a single substance is known as synthesis reaction or combination reaction.


  • The reaction in which a compound is broken down into two or more simpler substances is known as decomposition reaction.


  • A reaction in which an atom or a group of atoms present in a molecule is displaced by another atom is known as displacement reaction.


  • A reaction in which two compounds exchange their ions to form two new compounds is known as double displacement reaction.


  • Double displacement reactions are also called double decomposition reactions or metathesis reactions.


  • Reactions in which heat is given out along with the products are called exothermic reactions.


  • Reactions in which heat is absorbed by reactants to form products are called endothermic reactions.


  • Oxidation and reduction reactions

Oxidation is defined as the addition of oxygen or removal of hydrogen to a substance.


  • Oxidation is also defined in terms of metals and non-metals as the addition of non-metallic element (or removal of metallic element).


  • Reduction is addition of hydrogen or removal of oxygen to a substance.


  • Reduction is also defined in terms of metals and non-metals as the addition of metallic element (or removal of non-metallic element).


  • The substance which oxidizes substances is known as an oxidizing agent.


  • The substance which reduces substances is known as a reducing agent.


  • In redox reactions, oxidation and reduction reactions occur simultaneously.

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