单选题老师在实验室给同学们演示了如下实验：在插有小树枝的封闭烧瓶中放有一些卫生球粉末，然后在酒精灯上微微加热烧瓶，可以看到粉末越来越少，停止加热后，一会儿烧瓶内的树枝上出现了洁白玲珑的人造“雪景”。对于以上实验现象，以下说法正确的是（）。A“雪景”是卫生球升华而形成的B“雪景”是卫生球凝华而形成的C“雪景”经历了先凝华后升华两个物态变化过程D“雪景”经历了先升华后凝华两个物态变化过程
单选题
老师在实验室给同学们演示了如下实验：在插有小树枝的封闭烧瓶中放有一些卫生球粉末，然后在酒精灯上微微加热烧瓶，可以看到粉末越来越少，停止加热后，一会儿烧瓶内的树枝上出现了洁白玲珑的人造“雪景”。对于以上实验现象，以下说法正确的是（）。
A
“雪景”是卫生球升华而形成的
B
“雪景”是卫生球凝华而形成的
C
“雪景”经历了先凝华后升华两个物态变化过程
D
“雪景”经历了先升华后凝华两个物态变化过程
参考解析
解析：
加热后，卫生球粉末由固态变成气态充斥在烧瓶中，发生了升华现象.停止加热冷却后，气体放热又变成了固态的卫生球粉末附在烧瓶内的树枝上，是凝华现象。
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