Why do Chemical equations need to be Balanced?
Chemical equations have reactants to its left and products to its right. It is natural that number of atoms of each element in the reactants must be balanced with the number of atoms of those elements in the products also. This is called balancing of the chemical equation. Balancing of a chemical equation determines how many molecules of the reactants are required to react and form the resulting number of molecules of the product. This is very necessary for us to know as it will be useful in further applications of that chemical reaction.
The reason behind the balancing of a chemical equation is according to law of conservation of matter. In the physical laws, law of conservation of matter states that the initial matter will get converted to the products or gets rearranged into some other particles of different kind. But the amount of reactant matter equals to that of the products. This can be defined as, matter can neither be created nor destroyed. The meaning of this law is that matter gets converted into products after a chemical reaction. But, it results in the formation of same amount of a single product or rearrangement of the same amount into various types of matter. For example, when the wood is burnt it releases many gases like carbon-dioxide, carbon monoxide and various hydrocarbons along with ash and smoke. Even in the reactants section wood combines with oxygen in the air to get burnt. So the resulting atoms in the products are rearranged into different forms. But they remain as the same number of atoms that were present in the reactants.
This is the law followed by nature and hence it is also used by the chemical reactions that are occurring in nature. Einstein discovered that the sum of matter and energy in the Universe remains constant. The matter may get transformed into energy and vice versa. He combined the two laws of conservation of energy and mass as single law of conservation of mass-energy. This law forms the basis for the formulation of an equation by Einstein as E=m*c2.