Chemical reactions and equations class 10th. Science chapter1

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CHEMICAL REACTION AND EQUATIONS


PHYSICAL CHANGE:

 Those processes in which no new chemical substances are obtained.

CHEMICAL CHANGES:

Those processes in which the original substances lose their nature and identify and form new chemical substances with different properties.

 REACTANTS AND PRODUCTS:

In chemical reaction, the original substances that undergo chemical change in the reaction are called reactants.

The new chemical substances formed during the reaction are called products.

Ex. A  +   B   ➡   C  +   D.

           (Reactants).                   (Products)


Characteristics of chemical reactions:

• change in state.
• Evolution of a gas.
• Change in colour.
• Formation of precipitate.
• Change in temperature.

    CHEMICAL EQUATIONS


 • WORD EQUATION: A chemical reaction can be represented in terms of words.

Ex.

Magnesium + oxide  ➡  magnesium oxide


• CHEMICAL EQUATIONS: A Chemical equation is a representation of a chemical reaction with the help of symbols and formulae of different substances involved in reaction.

Ex.   Mg  +  O2    ➡   MgO.

 

BALANCED AND UNBALANCED EQUATIONS:

•Balanced Equation:

 An equation in which the number of atoms of each other element on the both sides of the equation are equal.

 Ex.   Zn + H2SO4   ➡  ZnSO4 + H2


•Unbalanced Equation:

An equation in which number of atoms different elements is not equal on the both sides of equation.

      Ex.       H2O   ➡  H2  +  O2


Balancing of chemical equation:

For Ex.    Fe + H2O   ➡   Fe3O4   +H2



Element.        No. of atoms.      No. of atoms 

                (Reactants).           (Products)

Fe             1            3

H                 2                2

O                 1                4



Balanced eq:

  3Fe + 4H2O   ➡   Fe3O4 + 4H2

               LHS.           RHS

Fe.           3.                  3
H.            8.                  8
O.            4.                  4

No. of atoms are equal in both sides of equation hence equation Balanced.

   TYPES OF CHEMICAL REACTIONS:

• COMBINATION REACTION.
• DECOMPOSITION REACTION.
• DISPLACEMENT REACTION.
• DOUBLE DISPLACEMENT REACTION.
• OXIDATION AND REDUCTION.


                          

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