Substances that ignite when combined create a what?

Substances that ignite when combined create a what?

• A. Endothermic reaction
• B. Exothermic reaction
• C. Combustion reaction
• D. A hypergolic reaction

Answer: (D)

Substances that ignite when they meet ignite on contact. This is known as a hypergolic reaction: a fuel and an oxidizer designed to ignite spontaneously when they come into contact, without any external spark, flame, or heater. This property is why hypergolic pairs are used in some rocket engines, but it also means they pose serious handling hazards—any accidental mixing or leakage can cause immediate ignition. This differs from a general exothermic reaction, which simply releases heat and may still require an ignition source to start. It also differs from combustion as a broad category, which is rapid oxidation producing heat and light; hypergolic ignition specifically describes the spontaneous ignition that occurs upon the two reactants touching, not just any rapid oxidation.

Substances that ignite when they meet ignite on contact. This is known as a hypergolic reaction: a fuel and an oxidizer designed to ignite spontaneously when they come into contact, without any external spark, flame, or heater. This property is why hypergolic pairs are used in some rocket engines, but it also means they pose serious handling hazards—any accidental mixing or leakage can cause immediate ignition.

This differs from a general exothermic reaction, which simply releases heat and may still require an ignition source to start. It also differs from combustion as a broad category, which is rapid oxidation producing heat and light; hypergolic ignition specifically describes the spontaneous ignition that occurs upon the two reactants touching, not just any rapid oxidation.