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为了使学生了解到分子之间是有空隙的,浙教版科学七年级上册第四章第一节“物质的构成”设计了一个酒精和水混合的实验活动,具体操作及相应现象如下:第一,往一端封闭的细径玻璃管内注入近一半的清水,再沿内管壁缓缓注入酒精,使酒精上液面距离管口约5 cm,标出酒精上液面的位置。第二,用手指封住管口,将玻璃管反复颠倒几次,使酒精和水充分混合。此时混合液的液面将低于原先所标的液面位置。实验表明,水和酒精混合后的总体积小于水和酒精各自的体积之和。这是因为水分子、酒精分子进入
In order to make students understand that there is a gap between the molecules, the Zhejiang PEP Edition 7, Volume 4, Chapter 4, “Composition of Matter”, designed a mixed experiment of alcohol and water. The specific operation and the corresponding phenomena are as follows : First, inject nearly half of the clear water into a closed-end glass tube of one end, and slowly inject the alcohol along the inner wall of the tube to make the upper surface of alcohol be about 5 cm away from the orifice of the tube. Second, with a finger to seal the nozzle, the glass tube repeatedly reversed several times, so that full mixing of alcohol and water. At this point the liquid level of the mixture will be lower than the original level of the liquid level. Experiments show that the combined volume of water and alcohol is less than the sum of the volumes of water and alcohol. This is because water molecules, alcohol molecules enter