What does gunpowder convert to when it burns?

When gunpowder burns, it undergoes a rapid chemical reaction that produces an expanding gas. This gas is primarily made up of carbon dioxide, nitrogen, and water vapor, resulting from the combustion of the solid components in gunpowder. The generation of this gas is crucial because it creates the pressure needed to propel a projectile out of a firearm.

The rapid expansion of gas is what makes gunpowder an effective propellant, as it can rapidly fill the confines of a gun barrel and exert force on the bullet. The transformation from solid gunpowder into a large volume of gas is also what explains the loud bang and recoil experienced when a firearm is discharged.

While gunpowder does produce smoke and some solid residue (like unburned particles from incomplete combustion), the primary change that occurs during its burning is the formation of gas, making it a key characteristic of firearm operation.