1. Conservation of mass: The total mass of the products in a chemical reaction is equal to the total mass of the reactants. This is because matter cannot be created or destroyed in a chemical reaction.

2. Conservation of energy: The total energy of the products in a chemical reaction is equal to the total energy of the reactants. This is because energy cannot be created or destroyed in a chemical reaction.

3. Stoichiometry: The stoichiometry of a chemical reaction refers to the quantitative relationship between the reactants and products. Balanced chemical equations allow us to determine the stoichiometry of a reaction, which is important for understanding the reaction and making predictions about the amounts of reactants and products involved.

For example, consider the following balanced chemical equation:

$$2H_2 + O_2 → 2H_2O$$

This equation demonstrates that two molecules of hydrogen gas react with one molecule of oxygen gas to produce two molecules of water. The stoichiometry of this reaction is 2:1:2, which means that for every two molecules of hydrogen gas that react, one molecule of oxygen gas reacts, and two molecules of water are produced.