Class 10th: CHEMICAL REACTIONS AND
EQUATIONS
● Chemical changes are called chemical reactions
- The substances that take part in the chemical reaction
are called reactants
- The new substance that is formed as a result of the
chemical reaction known as product
● Characteristic features of a chemical reaction
- 1.Physical state changes
2.Change of colour
3.formation of a new solid (precipitate)
4.Evolution of a new gas
5. Change in temperature
● Chemical equation
- Word equation
A word equation shows the change of reactants to
products through an arrow.
The reactants are written on the LHS with a plus sign
between them and the products are written on the RHS
with a plus sign between them.
The arrow head points towards the products and thus, it
shows the direction of the reaction
- Chemical equation
It is a symbolic notation that uses symbols and formulae
instead of words to represent substances of a chemical
reaction
- Balanced chemical equation
An equation in which the number of atoms of each
element on the reactants side and the products side is
equal to that on the products side is called a balanced
equation
, Need For A Balanced Equation
The law of conservation of mass states that matter can neither be
created nor be destroyed.Therefore the number of atoms of each
element in the reaction must be equal to that in the products. Such
a chemical equation is called a balanced equation
● Making a chemical equation more informative
1.Physical state of the reactants and products:
(s)-------> this ‘s’ in an equation stands for the solid state of an
element
(l)--------> this ‘l’ in an equation stands for the liquid state of an
element
(g)-------> this ‘g’ in an equation stands for the gaseous state of an
element
(aq)--------> this sign stands for a solution
2.Reaction condition:-
The reaction conditions such as pressure, temperature and
presence of catalyst are indicated above and/or below the arrow in
the equation
3.Heat change during the reaction:-
The heat evolved in an exothermic reaction is shown by a plus(+)
sign on the product side and the heat absorbed in an endothermic
reaction by a plus(+) sign on the reactant side or by a negative
sign(-) on the product side
4.Concentration of reactants and products:-
EQUATIONS
● Chemical changes are called chemical reactions
- The substances that take part in the chemical reaction
are called reactants
- The new substance that is formed as a result of the
chemical reaction known as product
● Characteristic features of a chemical reaction
- 1.Physical state changes
2.Change of colour
3.formation of a new solid (precipitate)
4.Evolution of a new gas
5. Change in temperature
● Chemical equation
- Word equation
A word equation shows the change of reactants to
products through an arrow.
The reactants are written on the LHS with a plus sign
between them and the products are written on the RHS
with a plus sign between them.
The arrow head points towards the products and thus, it
shows the direction of the reaction
- Chemical equation
It is a symbolic notation that uses symbols and formulae
instead of words to represent substances of a chemical
reaction
- Balanced chemical equation
An equation in which the number of atoms of each
element on the reactants side and the products side is
equal to that on the products side is called a balanced
equation
, Need For A Balanced Equation
The law of conservation of mass states that matter can neither be
created nor be destroyed.Therefore the number of atoms of each
element in the reaction must be equal to that in the products. Such
a chemical equation is called a balanced equation
● Making a chemical equation more informative
1.Physical state of the reactants and products:
(s)-------> this ‘s’ in an equation stands for the solid state of an
element
(l)--------> this ‘l’ in an equation stands for the liquid state of an
element
(g)-------> this ‘g’ in an equation stands for the gaseous state of an
element
(aq)--------> this sign stands for a solution
2.Reaction condition:-
The reaction conditions such as pressure, temperature and
presence of catalyst are indicated above and/or below the arrow in
the equation
3.Heat change during the reaction:-
The heat evolved in an exothermic reaction is shown by a plus(+)
sign on the product side and the heat absorbed in an endothermic
reaction by a plus(+) sign on the reactant side or by a negative
sign(-) on the product side
4.Concentration of reactants and products:-
