A solid substance turns directly into a gas. Which term describes this change?

• A. Melting
• B. Sublimation
• C. Condensation
• D. Deposition

Answer: (B)

Verified step by step guidance

1. Identify the phase change described: a solid turning directly into a gas without passing through the liquid phase.
2. Recall the common phase changes: melting (solid to liquid), vaporization (liquid to gas), condensation (gas to liquid), freezing (liquid to solid), sublimation (solid to gas), and deposition (gas to solid).
3. Match the description to the correct term: since the substance goes from solid directly to gas, this process is called sublimation.
4. Understand that sublimation occurs when molecules in a solid gain enough energy to enter the gas phase directly, bypassing the liquid state.
5. Confirm that the other options do not fit: melting involves solid to liquid, condensation is gas to liquid, and deposition is gas to solid.