, Chemical reactions
Chemical reactions are the processes in which new substances with new properties are formed.
• Only a rearrangement of atoms takes place in a chemical reaction.
• The substances which take part in a chemical reaction are called reactants.
• The new substances produced as a result of chemical reaction are called products.
• In a chemical reaction, reactants are transformed into products.
• The burning of magnesium in air to form magnesium oxide is an example of a chemical reaction
• A large number of chemical reactions keep on occurring in our daily life. Souring of milk , Formation of curd
from milk, Cooking of food, Digestion of food in our body, Process of respiration, Fermentation of grapes,
Rusting of iron
Characteristics of Chemical reactions
The conversion of reactants into products in a chemical reaction is often accompanied by some
features which can be easily observed easily.
The important characteristics of chemical reactions are:
• Evolution of a gas
• Formation of a precipitate
• Change in colour
• Change in temperature
• Change in state
Evolution of a Gas:
• Some chemical reactions are characterized by the evolution of a gas.
The chemical reaction between zinc and dilute sulphuric acid is characterized by the evolution of hydrogen
gas.
Formation of a precipitate:
Some chemical reactions are characterized by the formation of precipitate. A precipitate is a ‘solid product’
which separates out from the solution during a chemical reaction.
The chemical between potassium iodide and lead nitrate is characterized by the formation of a yellow
precipitate of lead iodide.
Chemical reactions are the processes in which new substances with new properties are formed.
• Only a rearrangement of atoms takes place in a chemical reaction.
• The substances which take part in a chemical reaction are called reactants.
• The new substances produced as a result of chemical reaction are called products.
• In a chemical reaction, reactants are transformed into products.
• The burning of magnesium in air to form magnesium oxide is an example of a chemical reaction
• A large number of chemical reactions keep on occurring in our daily life. Souring of milk , Formation of curd
from milk, Cooking of food, Digestion of food in our body, Process of respiration, Fermentation of grapes,
Rusting of iron
Characteristics of Chemical reactions
The conversion of reactants into products in a chemical reaction is often accompanied by some
features which can be easily observed easily.
The important characteristics of chemical reactions are:
• Evolution of a gas
• Formation of a precipitate
• Change in colour
• Change in temperature
• Change in state
Evolution of a Gas:
• Some chemical reactions are characterized by the evolution of a gas.
The chemical reaction between zinc and dilute sulphuric acid is characterized by the evolution of hydrogen
gas.
Formation of a precipitate:
Some chemical reactions are characterized by the formation of precipitate. A precipitate is a ‘solid product’
which separates out from the solution during a chemical reaction.
The chemical between potassium iodide and lead nitrate is characterized by the formation of a yellow
precipitate of lead iodide.
