Self reacting solids are characterized by which of the following?

• A. Solids that burn only in the presence of oxygen.
• B. Solids that must be exposed to water to ignite.
• C. Solids that require heat to ignite but not decompose.
• D. Thermally unstable materials that may decompose exothermically without oxygen.

Answer: (D)

Self-reacting solids are materials that are thermally unstable and can decompose on their own, releasing heat in an exothermic process. That internal heat can drive further decomposition and may lead to ignition or even explosion without any external source of oxygen. In storage, a small amount of heat or contamination can trigger this runaway reaction. This description fits best because it captures both the self-sustaining heat from decomposition and the possibility of ignition without relying on ambient air. The other ideas describe burning only in the presence of oxygen, needing water to ignite, or needing heat to ignite without any decomposition, which don’t describe the self-driven, exothermic decomposition that characterizes self-reacting solids.