What are the characteristics of a chemical reaction?

 What are the characteristics of a chemical reaction?         

 Important characteristics of a chemical reaction are

                

(i)     Change in temperature

(ii)    Change in color

(iii)   Change in state

(iv)   Formation of precipitate

(v)    Evaluation of gas

Change in temperature:- If mixing two substances there is a change in temperature then we can say that chemical reaction is taking place.

Example:-

1. If we add water to quick lime then a lot of heat is produce  and the temperature of the reaction mixture become very high .This is an exothermic reaction .

2. If we add barium oxide and aluminum chloride is an exothermic so it can produce a lot of heat then mixture becomes very hot.

Change in color:-  If on reducing two substances change in colour taking place then we can say that chemical reaction is taken place.

Example :- 

 when citric acid react with potassium paramagnet then purple color of  potassium paramagnet

Change in state:- Some chemical reaction are characterized by the change in state

Example:-

 When wax is burned then carbon dioxide and hydrogen are formed.

                      In this reaction the state changes from solid to liquid.

Formation of the precipitate:- If on adding two substances a precipitate is formed then we can say  than we can say a chemical reaction is taken place.

Example:-
white precipitate of silver chloride is formed.

Evaluation of gas:-If on mixing reactants a gas is produced

Example:- 
when we heated the CaCO3 , CO2 gas is evolved .