加热致使水汽蒸发,而玻璃又是冷的,水汽遇冷之后凝华成水.初中物理讲的~I want English answer . Thankswhen the water is boiled, the water begins to evaporate. And when the water vapor reaches the glass which is cold, the water vapor changes into the form of water again. This whole process is called the Sublimation in Physics.When the water reach its boiled piont , it will evaporates into hot water vapur . And when the hot water vapour touches the cooler surface of the glass , it will condences into water droplets .your answer is much better...well.since you've already know the answer, why did you bring it up~Emm ... Sorry . Well..can we be friends .Bytheway , thanks for your answer .fine~are you a Chinese or a foreigner?I am Singaporean but i was born at Chinaso ,you still cannot speak Chinese？