The law of conservation of mass 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. A balanced chemical reaction demonstrates this principle by:

* Representing the chemical formulas: The chemical formulas in a balanced equation accurately represent the atoms and molecules involved in the reaction.

* Maintaining equal numbers of each type of atom: The coefficients in front of each chemical formula ensure that the same number of atoms of each element are present on both sides of the equation.

Here's a simple example:

The combustion of methane (CH4) with oxygen (O2) produces carbon dioxide (CO2) and water (H2O).

Unbalanced Equation:

CH4 + O2 → CO2 + H2O

Balanced Equation:

CH4 + 2O2 → CO2 + 2H2O

Explanation:

* Reactants: On the left side, we have one carbon atom (C), four hydrogen atoms (H), and two oxygen atoms (O).

* Products: On the right side, we also have one carbon atom (C), four hydrogen atoms (H), and four oxygen atoms (O).

By balancing the equation, we ensure that the same number of each atom type exists on both sides. This means that the total mass of the reactants (methane and oxygen) must equal the total mass of the products (carbon dioxide and water). No atoms are lost or gained during the reaction, only rearranged, confirming the law of conservation of mass.