Here's why:

* Conservation of Mass: This fundamental law states that in a closed system, the total mass of the reactants before a chemical reaction must equal the total mass of the products after the reaction.

* Balancing Equations: By balancing the equation, we ensure that the number of atoms of each element on the reactant side (left side) is equal to the number of atoms of that element on the product side (right side). This ensures that no atoms are "lost" or "created" during the reaction, upholding the law of conservation of mass.

Example:

The unbalanced equation for the combustion of methane is:

CH4 + O2 → CO2 + H2O

This equation is unbalanced because:

* There is 1 carbon atom on the left but 1 on the right.

* There are 4 hydrogen atoms on the left but 2 on the right.

* There are 2 oxygen atoms on the left but 3 on the right.

The balanced equation is:

CH4 + 2O2 → CO2 + 2H2O

Now, the number of atoms of each element is the same on both sides, satisfying the law of conservation of mass.