Chemical change is a change in which a new substance is formed.
INDICATION OF A CHEMICAL CHANGE ARE AS FOLLOWS
- change in state
- change in color
- evolution of a gas
- change in temperature.
Symbolic representation of a chemical change is called chemical equation.
TYPES OF CHEMICAL REACTION
1 Combination reaction– A reaction in which two or more substances combine to form a new single substance.
2 Decomposition reaction– A reaction in which a single substance decomposes to give two or more substances.
3 Displacement reaction– When an element displaces another element from its compound a displacement reaction occurs.
4 Double Displacement reaction– A reaction in which exchange of ions takes place between the reactants.
5 Oxidation And Reduction reaction– Reactions which involve the gain or loss of oxygen or hydrogen by reactants were come under this category. Oxidation is the gain of oxygen or loss of hydrogen and Reduction is the loss of oxygen or gain of hydrogen.
When a metal is attacked by substances around it such as moisture, acids etc. it is said to corrode and the process is called corrosion.
Those reaction in which energy is absorbed are known as endothermic reaction.
Reaction in which heat is given out along with the products are called exothermic reaction.