在标准大气压下，将少量固态碘放入密闭的玻璃容器中，微热后观察到紫色蒸气充满容器，容器底部无液态碘出现。该过程主要属于下列哪种变化？
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Correct answer
B. 升华
Principle or equation
固态物质不经过液态直接变为气态的过程称为升华。碘在加热时易升华，由固态直接变为气态。
Why this answer is correct
微热固态碘，紫色蒸气出现且无液态碘，说明碘由固态直接变为气态，属于升华。熔化是固态变为液态，蒸发和沸腾是液态变为气态。
Example
干冰（固态二氧化碳）在常温下直接变为二氧化碳气体，也是升华现象。
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