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买一瓶纯净水放到冰箱的冷冻室(-18℃左右)中,两个小时之后把它拿出来,你会发现水的温度已经低于0℃,但是水并没有结冰!为什么?是不是冻的时间不够长?把它小心地放回冷冻室,轻轻地关上冰箱的门,再冷冻一个小时,然后取出来.你会发现水的温度已经远远低于0℃,但仍然没有结冰!这时拿起瓶子用力摇晃或在桌子上用力磕一下,你会观察到水迅速结冰,在数秒内,整瓶的水都结冰了!(安全提示:如果同学们有兴趣做这个实验,请千万不要用玻璃瓶,并且要敞开瓶口.)
Buy a bottle of purified water and put it in the freezer (about -18°C) of the refrigerator. After two hours, take it out. You will find that the temperature of the water is already below 0°C, but the water is not frozen! Why? Not frozen for long enough? Put it carefully back in the freezer, gently close the refrigerator door, freeze for an additional hour, and then remove it. You will find that the temperature of the water is already well below 0°C but still not Icy! Now pick up the bottle and shake it hard or slam it on the table. You will see the water freezing quickly. Within seconds, the whole bottle of water is freezing! (Safety Tip: If the students are interested in doing it For this experiment, please do not use glass bottles and open the bottle.)