this will be helpfull

1. SCIENCE PROJECT
MADE BY:-
AJAY KUMAR
10th C
20

2. Chemical Reactions & Equations
Chemical reaction are the processes in which new substances with
new properties are formed . chemical reaction involve breaking of
old chemical bonds which exist between the atoms of reaction
substances ,and then making of new chemical bonds between the
rearranged atoms of new substances . During a chemical reaction,
atoms of one element do not change in to those element. only a
rearrangement of atoms takes place in a chemical reaction .

3. Characteristics of chemical reaction
In a chemical reaction the substance known as reactants are
converted into new substance called products . The conversion of
reactants into product in a chemical reaction is often
accompanied by some features which can be observed easily .
The easily observable features which take place as a result of
chemical reaction are known as characteristics of chemical
reaction . The important characteristics of chemical reaction are ;
1. Evolution of a gas ,
2. Formation of a precipitate ,
3. Change in colour ,
4. Change in temperature , and
5. Change in state

4. Chemical Equation
Chemical equation can be made more concise and useful if we
use chemical formulae instead of words. A chemical equation
Represents a chemical reaction . If you recall formulae of
magnesium , oxygen and magnesium oxide , the above word
Equation can be written as –
Mg + O2 MgO
Count and compare the number of atoms of each element on
the LHS and RHS of the arrow . Is the number of atoms of each
element the same on both the side ? If not , then the equation is
Unbalanced because the mass is not the same on both sides of
the equation . Such a chemical equation is a skeletal chemical
equation for a reaction .

5. Balanced chemical equation
The total mass of the element of the element present in the
product of a chemical reaction has to be equal to the total mass
of the element present in the reactants . The number of atoms
of each element remains the same , before and after a chemical
reaction . Let us learn about skeletal chemical equation .
The word equation for represent as –
Zinc + sulphuric acid -> zinc sulphate + Hydrogen
the above word –equation may be represent by the following
Chemical equation –
Zn + H2SO4 + H2
The number of atom of different element on both sides of the arrow .

6. Element No.of atoms in No. of atom in products
reactants (LHS) (RHS)
reactants (LHS)
Zn
Zn 1 1 1 1
HH 2 2 2 2
SS 1 1 1 1
O 4 4
O 4 4
As the number of atoms of each element is the same on both
sides of the arrow is a balanced chemical equation .