Which of the following is not a self-reactive material?

• A. Oxygen
• B. Rearranging materials
• C. Decomposing materials
• D. Polymerizing materials

Answer: (A)

Self-reactive materials are those that can undergo a chemical reaction on their own, without needing a lot of external energy to start it. The danger comes from internal energy release that can heat up the material and sometimes trigger a runaway reaction.

Oxygen isn’t self-reactive because, by itself, it’s a stable diatomic molecule and doesn’t spontaneously transform or release energy. Its hazard is as an oxidizer that accelerates reactions with other materials, not a substance that reacts with itself.

Rearranging materials can release energy as their internal structure shifts, sometimes forming a more energy-dense or unstable configuration. Decomposing materials break down and release heat or gas, which can continue without additional input once started. Polymerizing materials can begin to link monomers into polymers on their own or with minimal initiation, often generating heat in the process.

So, oxygen is the one that does not fit the pattern of self-reactive behavior, while rearranging, decomposing, and polymerizing materials can exhibit self-reactive tendencies under the right conditions.