A sample of solid carbon dioxide (dry ice) is placed in an open container at room temperature and atmospheric pressure. It gradually disappears without forming a liquid. Which term best describes this change of state?
Show the answer and explanation
Correct answer
B. Sublimation
Principle or equation
Sublimation is the direct transition from solid to gas without passing through the liquid phase. Dry ice (solid CO2) sublimes at atmospheric pressure because its triple point is above 1 atm.
Why this answer is correct
At room temperature and 1 atm, solid CO2 cannot exist as a liquid; it transitions directly to gas. This is sublimation. Evaporation is liquid to gas, condensation is gas to liquid, and melting is solid to liquid.
Example
Solid iodine also sublimes when heated gently, producing purple vapor without melting.
This published item includes a stored explanation and passed the platform’s publication workflow. It is independent preparation material, not a claim of an official or recalled examination question.