What is a primary explosive?

A primary explosive is defined as a relatively easy to initiate explosive that is highly sensitive to heat, shock, or friction. These materials are often used to initiate secondary explosives, which require a larger amount of energy for detonation. Due to their sensitivity, primary explosives can be activated by relatively low-energy triggers, making them essential in various applications, including in military ordnance and in blasting caps.

In contrast, the other options do not accurately describe primary explosives. For instance, a substance that is difficult to initiate does not fit the definition of a primary explosive since such materials require a more intense stimulus to detonate. Likewise, an explosive with lower power would refer to a sensitivity or energy output level not characteristic of primary explosives, which are designed to provide a significant amount of energy upon initiation. Lastly, a mixture of different chemicals does not specifically define what makes a primary explosive; while some primary explosives can be mixtures, the essence of being classified as a primary explosive lies in its sensitivity and ease of initiation rather than just its composition.