Some reactions are irreversible due to the energy changes involved and the stability of the products. For example, combustion reactions release a large amount of energy, which results in the complete breakdown of reactants into simpler products that are very stable and cannot easily revert back to the original reactants. Other reactions, such as the formation of insoluble precipitates or the release of gases, may also be irreversible because they go to completion, and the products are not easily converted back to the reactants.