一杯温水、一杯冷水、一杯热水。先将手放在冷水中，再放到温水中，会感到温水热；先将手放到热水中，再放到温水中，会感到温水凉。同一杯温水，出现两种不同的感觉，这就是冷热水效应。教师在教学活动中，善于运用这种冷热水效应可赢得某种心理优势，进而获得主动，增添教学 A cup of warm water, a glass of cold water, a cup of hot water. Put your hands in cold water first, and then put it in warm water, you will feel warm and hot water; put your hands into hot water first, then put into warm water, you will feel warm and cool. The same cup of warm water, there are two different feelings, this is the effect of hot and cold water. In teaching activities, teachers are good at using this hot and cold water effect to win certain psychological advantages and gain initiative and increase teaching.