我在教学《水在自然界里的循环》一课之前,复习已经学过的知识。提出:我们用湿布在桌面上擦一片水迹,一会儿不见了,把湿东西放在太阳下晒一会儿水干了等关于水蒸发的例子。学生都懂得这是水受热变成水蒸气飞散到空中去了。接着复习水凝结的实验:在两个同样的玻璃杯内倒入同样多 I am reviewing what I have learned before teaching “The Cycle of Water in Nature.” Put forward: We use a damp cloth to wipe a trace of water on the desktop, while disappearing, the wet things in the sun for a while drying in the water on the water evaporation example. Students know that it is water heated into water vapor to fly into the air. Then review the experiment of water condensation: pour in as much as two in the same glass