在教学“绿叶在光下制造淀粉”实验时,学生按照相应实验步骤进行,在最后一步“滴加碘液”时,笔者向学生解释了淀粉遇碘变蓝的特性,当滴上碘液,每个小组的叶片都相应变了色。一个学生突然问:“老师,碘液滴在叶片上是棕黑色,为什么不是蓝色?”其他学生也附和着:“不是老师说淀粉遇碘液变蓝色吗?为什么叶片上不是蓝色呢?”叶片的确是棕黑色,面对学生的提问,笔者不知所措,因为从 In teaching “green leaves in the light of the starch ” experiment, the students in accordance with the corresponding experimental steps, in the final step “drip iodine ”, I explained to the students the characteristics of iodine turns blue, when the drop On the iodine solution, each group of leaves have changed color accordingly. Suddenly a student asks: “Teacher, iodine droplets are brownish black on the leaves and why is not blue?” Other students also echoed: “Is not the teacher saying that starch turns blue in iodine solution and why leaves are not Blue it? ”Leaf is indeed brown black, the face of students' questions, I know what to do, because from