Final answer:
The statement is context-dependent; in the mechanism of a percussion cap firearm, true ignition requires a percussion cap, but gunpowder can also be ignited by other means.
Step-by-step explanation:
The statement that “Only the percussion cap or powder will ignite” can be both true and false depending on the context. When discussing firearms, specifically those from the 19th century, such as during the Civil War, the percussion cap was indeed the primary method for igniting the powder inside the firearm's barrel.
However, the powder can also ignite due to other external sources of flame or spark, though in the context of firearms, this would be less controlled and potentially dangerous.
In a percussion cap firearm, the percussion cap contains a small amount of a shock-sensitive explosive compound that, when struck by the hammer of the gun, detonates and causes a flame to shoot through a small hole to ignite the main charge of gunpowder within the barrel.
Without the percussion cap, the gunpowder in the barrel will not ignite from the hammer’s strike alone. Nonetheless, gunpowder itself is an explosive and can be ignited if exposed to an open flame or a spark outside of this system.