A sample of solid naphthalene is heated in an open container. It melts at 80°C to form a clear liquid, and further heating at 218°C produces a vapor. Which of the following correctly describes the changes of state that occur?
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Correct answer
A. Melting followed by evaporation
Principle or equation
Melting is the change from solid to liquid; evaporation is the change from liquid to gas. Sublimation is solid directly to gas, which does not occur here because the liquid phase is observed.
Why this answer is correct
The solid naphthalene first melts to a liquid (melting), then the liquid evaporates to a vapor (evaporation). The sequence is melting then evaporation.
Example
Ice melts to water and then water evaporates to steam.
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