Gunpowder before being set on fire is a solid mixture composed mainly of potassium nitrate (KNO3), sulfur (S), and charcoal (carbon, C). When gunpowder is ignited, it undergoes a chemical reaction where these components react to form new substances. The potassium nitrate breaks down to release oxygen, which combines with the charcoal to form carbon dioxide (CO2) gas, while the nitrogen from potassium nitrate forms nitrogen gas (N2). The potassium reacts with sulfur to form potassium sulfide (K2S) or potassium sulfate, depending on the reaction conditions. After being set on fire, the gunpowder is chemically and physically very different:
- The original solid mixture no longer exists.
- Gas products (N2 and CO2) are released, which rapidly expand and cause the explosive effect.
- The solid residues are new compounds such as potassium sulfide and potassium carbonate.
- The reaction releases a significant amount of heat (exothermic reaction) and increases entropy, making it irreversible and impossible to revert to the original powder without external energy and complex chemical processes.
In summary, before ignition, gunpowder is a solid mixture with high potential chemical energy, and after ignition, it becomes a mixture of gases and new solid chemical compounds, with a large release of energy in the form of heat and expanding gases.