Which substance is in the solid state at room conditions according to the material?

• A. Chlorine
• B. Sodium Chloride
• C. ANFO
• D. Sodium

Answer: (B)

At room temperature, the state a substance is in depends on how strongly its particles are held together. Ionic compounds form rigid crystal lattices with strong electrostatic bonds, so they stay solid and have high melting points. Sodium chloride fits this pattern: its ions are locked into a stable lattice, making it a solid at room conditions.

Chlorine, on the other hand, is a diatomic molecule held together by relatively weak forces between molecules, so it exists as a gas at room temperature. ANFO is a mixture, not a single pure substance, and its components behave differently under ordinary conditions, so its overall state isn’t described the same way as a pure solid. Sodium is a metal and is also solid at room temperature, but the example given aligns with the common solid salt form described in the material.