When a substance changes directly from the solid state to the gaseous state without forming a liquid, the substance is said to

Step 1: Analyze the question The question asks for the term used when a substance goes straight from solid to gas, skipping the liquid state.

Step 2: Explain the concept Changes of state have specific names:

• Melting: solid → liquid
• Freezing: liquid → solid
• Evaporation (vaporization): liquid → gas
• Condensation: gas → liquid
• Sublimation: solid → gas directly (or gas → solid directly)

Step 3: Check each option

• A. Condense: gas to liquid. This is wrong.
• B. Evaporate: liquid to gas. This is wrong, because a liquid is involved.
• C. Sublime: solid to gas directly, with no liquid stage. This is correct.
• D. Precipitate: an insoluble solid forms from a solution during a reaction. This is wrong.

Step 4: Answer The substance is said to sublime. Common examples are ammonium chloride (NH₄Cl), iodine, camphor, naphthalene (mothballs), and dry ice (solid CO₂).

Exam tip: Remember that "sublime" means "skips the liquid." In WASSCE and JAMB, substances that sublime (NH₄Cl, iodine, solid CO₂) often appear in questions on separation techniques. If a mixture contains one substance that sublimes, such as NH₄Cl with sand, you can separate them by heating.