Which term best describes materials that react with water, including elements like lithium and sodium?

• A. Hypergolic
• B. Pyrophoric
• C. Water reactive
• D. Inhibitors

Answer: (C)

The main idea here is identifying substances that pose hazards specifically when they come into contact with water. Lithium and sodium are classic examples: they react vigorously with water, producing heat and hydrogen gas, which can ignite or explode. That direct reactivity with water is what the term “water reactive” captures.

For example, with lithium: 2 Li + 2 H2O → 2 LiOH + H2. With sodium: 2 Na + 2 H2O → 2 NaOH + H2. In both cases, the key feature is the reaction with water itself, not necessarily ignition in air or contact with another chemical.

Hypergolic is about spontaneous ignition when a fuel meets an oxidizer, not specifically about water. Pyrophoric describes materials that ignite in air, which is a different trigger than water. Inhibitors are substances that slow or stop reactions, not about reacting with water. So the best term for materials that react with water, including these alkali metals, is water reactive.